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Amputation of a limb may have a negative impact on the psychological and physical well-being, mobility and social life of individuals with limb amputations. Participation in sports and/or regular physical activity has a positive effect on the above mentioned areas in able-bodied individuals. Data concerning participation in sports or regular physical activity together with its benefits and risks for individuals with limb amputations are scarce. No systematic review exists that addresses a wide range of outcomes such as biomechanics, cardiopulmonary function, psychology, sport participation and sport injuries. Therefore, the aim of this article is to systematically review the literature about individuals with limb amputations and sport participation. MEDLINE (PubMed), EMBASE, CINAHL® and SportDiscus® were searched without time or language restrictions using free text words and MeSH terms. The last search date was 31 March 2010. Books, internet sites and references of included papers were checked for papers relevant to the topic under review. Papers were included if the research topic concerned sports and a minimum of ten individuals with limb amputations were part of the study population. Papers were excluded if they included individuals with amputations of body parts other than upper or lower limbs or more distal than the wrist or ankle, or if they consisted of case reports, narrative reviews, books, notes or letters to the editor. Title, abstract and full-text assessments were performed by two independent observers following a list of preset criteria. Of the 3689 papers originally identified, 47 were included in the review. Most of the included studies were older than 10 years and had cross-sectional designs. Study participants were generally younger and often had more traumatic amputations than the general population of individuals with limb amputations. Heterogeneity in population characteristics, intervention types and main outcomes made data pooling impossible. In general, sports were associated with a beneficial effect on the cardiopulmonary system, psychological well-being, social reintegration and physical functioning. Younger individuals with unilateral transtibial amputations achieve better athletic performance and encounter fewer problems when participating in sports compared with older individuals with bilateral transfemoral amputations. Regardless of their amputation level, individuals with limb amputations participate in a wide range of recreational activities. The majority of them were not aware of the sport facilities in their area and were not informed about available recreational activities. Sport prosthetic devices were used mostly by competitive athletes. For football, the injury rate and pattern of the players with an amputation were similar to those of able-bodied players. Individuals with limb amputations appear to benefit both physically and psychologically from participation in sports and/or regular physical activity. Therefore, sports should be included in rehabilitation programmes, and individuals with limb amputations should be encouraged to pursue a physically active life following hospital discharge. [ABSTRACT FROM AUTHOR]

It is important to optimise the functional recovery process to enhance patient outcomes after major injury such as anterior cruciate ligament reconstruction (ACLR). Restoring movement quality during sporting-type movements is important prior to return-to-sport (RTS) after ACLR. Alterations in movement quality during an array of functional tasks are common amongst ACLR patients at or near the time of RTS and are associated with worse outcomes after ACLR. The inability to correct movement issues prior to RTS is likely due to the use of incomplete programmes or a lack of volume and intensity of movement re-training programmes. Although most clinicians and researchers understand that re-training movement after ACLR is important (e.g., the 'why'), there is often a disconnect with understanding the 'how' and 'what' of movement re-training post ACLR. The aim of this paper was to discuss factors relevant to movement dysfunction and re-training after ACLR and provide recommendations for clinicians to restore movement quality of patients after ACLR, prior to RTS. The paper recommends: (i) considering the factors which influence the expression of movement quality, which revolve around individual (e.g., neuromuscular, biomechanical, sensorimotor and neurocognitive factors), task-specific and environmental constraints; (ii) incorporating a three-staged movement re-training approach aligned to the ACLR functional recovery process: (1) addressing the neuromuscular and biomechanical and sensorimotor control factors which affect movement quality and motor learning, (2) including a progressive movement re-training approach to re-learn an array of functional tasks optimising coordination and motor learning (3) performing the final aspect of rehabilitation and movement training on the field, in realistic environments progressively simulating the sporting movement demands and environmental constraints; and (iii) effectively designing the movement programme for optimal load management, employing effective coach and feedback techniques and utilising qualitative movement analysis for transition between exercises, stages and for RTS. [ABSTRACT FROM AUTHOR]

Background: Running overuse injuries (ROIs) occur within a complex, partly injury-specific interplay between training loads and extrinsic and intrinsic risk factors. Biomechanical risk factors (BRFs) are related to the individual running style. While BRFs have been reviewed regarding general ROI risk, no systematic review has addressed BRFs for specific ROIs using a standardized methodology. Objective: To identify and evaluate the evidence for the most relevant BRFs for ROIs determined during running and to suggest future research directions. Design: Systematic review considering prospective and retrospective studies. (PROSPERO_ID: 236,832). Data Sources: PubMed. Connected Papers. The search was performed in February 2021. Eligibility Criteria: English language. Studies on participants whose primary sport is running addressing the risk for the seven most common ROIs and at least one kinematic, kinetic (including pressure measurements), or electromyographic BRF. A BRF needed to be identified in at least one prospective or two independent retrospective studies. BRFs needed to be determined during running. Results: Sixty-six articles fulfilled our eligibility criteria. Levels of evidence for specific ROIs ranged from conflicting to moderate evidence. Running populations and methods applied varied considerably between studies. While some BRFs appeared for several ROIs, most BRFs were specific for a particular ROI. Most BRFs derived from lower-extremity joint kinematics and kinetics were located in the frontal and transverse planes of motion. Further, plantar pressure, vertical ground reaction force loading rate and free moment-related parameters were identified as kinetic BRFs. Conclusion: This study offers a comprehensive overview of BRFs for the most common ROIs, which might serve as a starting point to develop ROI-specific risk profiles of individual runners. We identified limited evidence for most ROI-specific risk factors, highlighting the need for performing further high-quality studies in the future. However, consensus on data collection standards (including the quantification of workload and stress tolerance variables and the reporting of injuries) is warranted. [ABSTRACT FROM AUTHOR]

Adolescent cricket pace bowlers are prone to non-contact shoulder, low back and lower-limb injuries. Exercise-based injury prevention programmes (IPPs) are effective for reducing non-contact injuries in athletes; however, a specific programme for adolescent pace bowlers has not been published. This paper therefore seeks to provide a rationale for the development of an exercise-based IPP specific for adolescent pace bowlers. It also outlines design principles and provides an example exercise programme that can be implemented at the community level. In addition, the paper addresses other injury prevention techniques concerned with the prescription of appropriate bowling loads and the modification of poor bowling biomechanics. Performing an exercise-based IPP before cricket training could reduce injury rates in adolescent pace bowlers. Eccentric strengthening exercises can be employed to target injuries to the posterior shoulder muscles, hip adductors and hamstring muscles. The risk of low back, knee and ankle injury could also be reduced with the inclusion of dynamic neuromuscular control exercises and trunk extensor endurance exercises. Other prevention strategies that need to be considered include the modification of poor bowling biomechanics, such as shoulder counter-rotation and lateral trunk flexion. Coaches and players should also aim to quantify bowling load accurately and coaches should use this information to prescribe appropriate individualised bowling loads. Specifically, players would benefit from avoiding both long periods of low load and acute periods when load is excessively high. Future evidence is needed to determine the effectiveness of the example programme outlined in this paper. It would also be beneficial to investigate whether the modification of bowling biomechanics is achievable at the non-elite level and if bowling load can be accurately measured and manipulated within a community-level population. [ABSTRACT FROM AUTHOR]

Background: Patellar tendinopathy (PT) is common and debilitating for jumping athletes. Intriguingly, despite its high prevalence and many research studies, a causal explanation for PT presence remains elusive. Objective: Our objective was to investigate whether landing biomechanics among jumping athletes are associated with PT and can predict onset. Methods: We conducted a systematic review with evidence gap map and meta-analysis. We searched three databases from inception to May 2021 for observational studies or trials evaluating landing biomechanics in jumping athletes with PT (JPTs). We assessed quality with a modified Downs and Black checklist, risk of bias with the Quality Assessment of Diagnostic Accuracy Studies (QUADAS-2) tool, and evidence levels with van Tulder's criteria and provided an evidence gap map. Results: One prospective cohort (moderate quality), one cross-sectional cohort (moderate quality), and 14 case–control (four high-, seven moderate-, and three low-quality) studies, including 104 JPTs, 14 with previous PT, 45 with asymptomatic patellar tendon abnormality (PTA), and 190 controls were retained. All studies had a high risk of bias. Meta-analysis showed an association between lower ankle dorsiflexion and the presence of tendinopathy during drop and spike landings, and JPTs had reduced knee joint power and work during volleyball approach or drop landings (moderate evidence). Limited evidence suggested that JPTs had lower patellar tendon loads during drop landings. Strong or moderate evidence showed no relation between PT and sagittal plane peak knee and hip angles or range of motion; hip, knee, or ankle angles at initial contact (IC); knee angular velocities, peak trunk kinematics, or trunk angles at IC; sagittal plane hip, knee, or ankle moments; and peak vertical ground reaction force (vGRF) and vGRF impulse. Identified gaps were that no study simultaneously investigated athletes with previous PT, current PT, and PTA, and studies of joint angular velocities at IC, ankle and hip angular velocities after touchdown, leg stiffness, loading rate of forces, and muscle activation are lacking. Conclusion: Despite the voluminous literature, large number of participants, multitude of investigated parameters, and consistent research focus on landing biomechanics, only a few associations can be identified, such as reduced ankle dorsiflexion–plantarflexion range. Further, the quality of the existing literature is inadequate to draw strong conclusions, with only four high-quality papers being found. We were unable to determine biomechanical factors that predicted PT onset, as longitudinal/prospective studies enabling causal inference are absent. The identified gaps indicate useful areas in which to explore causal relationships to inform intervention development. Therefore, high-quality prospective studies are essential to definitively determine whether landing biomechanics play a part in the development, recurrence, or management of PT and represent a potential therapeutic or preventive target alongside non-biomechanical factors. [ABSTRACT FROM AUTHOR]

Football codes (rugby union, soccer, American football) train and play matches on natural and artificial turfs. A review of injuries on different turfs was needed to inform practitioners and sporting bodies on turf-related injury mechanisms and risk factors. Therefore, the aim of this review was to compare the incidence, nature and mechanisms of injuries sustained on newer generation artificial turfs and natural turfs. Electronic databases were searched using the keywords 'artificial turf', 'natural turf', 'grass' and 'inj*'. Delimitation of 120 articles sourced to those addressing injuries in football codes and those using third and fourth generation artificial turfs or natural turfs resulted in 11 experimental papers. These 11 papers provided 20 cohorts that could be assessed using magnitude-based inferences for injury incidence rate ratio calculations pertaining to differences between surfaces. Analysis showed that 16 of the 20 cohorts showed trivial effects for overall incidence rate ratios between surfaces. There was increased risk of ankle injury playing on artificial turf in eight cohorts, with incidence rate ratios from 0.7 to 5.2. Evidence concerning risk of knee injuries on the two surfaces was inconsistent, with incidence rate ratios from 0.4 to 2.8. Two cohorts showed beneficial inferences over the 90% likelihood value for effects of artificial surface on muscle injuries for soccer players; however, there were also two harmful, four unclear and five trivial inferences across the three football codes. Inferences relating to injury severity were inconsistent, with the exception that artificial turf was very likely to have harmful effects for minor injuries in rugby union training and severe injuries in young female soccer players. No clear differences between surfaces were evident in relation to training versus match injuries. Potential mechanisms for differing injury patterns on artificial turf compared with natural turf include increased peak torque and rotational stiffness properties of shoe-surface interfaces, decreased impact attenuation properties of surfaces, differing foot loading patterns and detrimental physiological responses. Changing between surfaces may be a precursor for injury in soccer. In conclusion, studies have provided strong evidence for comparable rates of injury between new generation artificial turfs and natural turfs. An exception is the likely increased risk of ankle injury on third and fourth generation artificial turfs. Therefore, ankle injury prevention strategies must be a priority for athletes who play on artificial turf regularly. Clarification of effects of artificial surfaces on muscle and knee injuries are required given inconsistencies in incidence rate ratios depending on the football code, athlete, gender or match versus training. [ABSTRACT FROM AUTHOR]

Background: The high prevalence of injury amongst cricket fast bowlers exposes a great need for research into the risk factors associated with injury. Both extrinsic (environment-related) and intrinsic (person-related) risk factors are likely to be implicated within the high prevalence of non-contact injury amongst fast bowlers in cricket. Identifying and defining the relative importance of these risk factors is necessary in order to optimize injury prevention efforts. Objective: The objective of this review was to assess and summarize the scientific literature related to the extrinsic and intrinsic factors associated with non-contact injury inherent to adult cricket fast bowlers. Method: A systematic review was performed in compliance with the PRISMA guidelines. This review considered both experimental and epidemiological study designs. Studies that included male cricket fast bowlers aged 18 years or above, from all levels of play, evaluating the association between extrinsic/intrinsic factors and injury in fast bowlers were considered for inclusion. The three-step search strategy aimed at finding both published and unpublished studies from all languages. The searched databases included MEDLINE via PubMed, Cumulative Index to Nursing and Allied Health Literature (CINAHL), the Cochrane Controlled Trials Register in the Cochrane Library, Physiotherapy Evidence Database (PEDro), ProQuest 5000 International, ProQuest Health and Medical Complete, EBSCO MegaFile Premier, Science Direct, SPORTDiscus with Full Text and SCOPUS (prior to 28 April 2015). Initial keywords used were 'cricket', 'pace', 'fast', 'bowler', and 'injury'. Papers which fitted the inclusion criteria were assessed by two independent reviewers for methodological validity prior to inclusion in the review using standardized critical appraisal instruments from the Joanna Briggs Institute Meta Analysis of Statistics Assessment and Review Instrument (JBI-MAStARI). Results: A total of 16 studies were determined to be suitable for inclusion in this systematic review. The mean critical appraisal score of the papers included in this study was 6.88 (SD 1.15) out of a maximum of 9. The following factors were found to be associated with injury: bowling shoulder internal rotation strength deficit, compromised dynamic balance and lumbar proprioception (joint position sense), the appearance of lumbar posterior element bone stress, degeneration of the lumbar disc on magnetic resonance imaging (MRI), and previous injury. Conflicting results were found for the association of quadratus lumborum (QL) muscle asymmetry with injury. Technique-related factors associated with injury included shoulder-pelvis flexion-extension angle, shoulder counter-rotation, knee angle, and the proportion of side-flexion during bowling. Bowling workload was the only extrinsic factor associated with injury in adult cricket fast bowlers. A high bowling workload (particularly if it represented a sudden upgrade from a lower workload) increased the subsequent risk to sustaining an injury 1, 3 or 4 weeks later. Conclusion: Identifying the factors associated with injury is a crucial step which should precede the development of, and research into, the effectiveness of injury prevention programs. Once identified, risk factors may be included in pre-participation screening tools and injury prevention programs, and may also be incorporated in future research projects. Overall, the current review highlights the clear lack of research on factors associated with non-contact injury, specifically in adult cricket fast bowlers. Systematic review registration number Johanna Briggs Institute Database of Systematic Reviews and Implementation Reports 1387 (Olivier et al., JBI Database Syst Rev Implement Rep 13(1):3-13. doi:, ). [ABSTRACT FROM AUTHOR]

Background: A return to running after anterior cruciate ligament reconstruction (ACL-R) is critical to the clinical success of any cutting and pivoting athlete who wishes to return to sport. Knowledge of specific alterations during running after ACL-R is required to optimise rehabilitation for improving outcomes and long-term disability. Objective: The objective of this systematic review was to summarise kinematic, kinetic and muscle activation data during running after ACL-R and the intrinsic factors (e.g. surgical technique and strength asymmetries) affecting running biomechanics. Methods: MEDLINE, EMBASE, SPORTDiscus and CINAHL databases were searched from inception to 10 December, 2018. The search identified studies comparing kinematic, kinetic or muscle activation data during running between the involved limb and contralateral or control limbs. Studies analysing the effect of intrinsic factors in the ACL-R group were also included. Risk of bias was assessed, qualitative and quantitative analyses performed, and levels of evidence determined. Results: A total of 1993 papers were identified and 25 were included for analysis. Pooled analyses reported a deficit of knee flexion motion and internal knee extension moment, compared with both contralateral or control limbs, during the stance phase of running from 3 months to 5 years after ACL-R (strong evidence). Inconsistent results were found for both peak vertical ground reaction force and impact forces after ACL-R. Patellofemoral and tibiofemoral joint contact forces differed from both contralateral or control limbs up until at least 2.5 years after ACL-R and moderate evidence indicated no difference for muscle activations during moderate speed running. Quadriceps and hamstring strength asymmetries, and knee function, but not surgical techniques, were likely to be associated with both knee kinematics and kinetics during running after ACL-R. Conclusion: After ACL-R, knee flexion motion and internal knee extension moment are the most affected variables and are consistently smaller in the injured limb during running when pooling evidence. Clinicians should be aware that these deficits do not appear to resolve with time and, thus, specific clinical interventions may be needed to reduce long-term disability. Systematic review registration: Registered in PROSPERO 2017, CRD42017077130. [ABSTRACT FROM AUTHOR]

This paper evaluates the effectiveness of, and highlights issues with, conventional paradigms in applied sports biomechanics research and comments on their capacity to optimise techniques of individual athletes. In empirical studies, group-based analyses often mask variability between athletes and only permit probabilistic 'in general' or 'on average' statements that may not be applicable to specific athletes. In individual-based analyses, performance parameters typically exhibit a small range and a flat response over iterative performance trials, making establishing associations between performance parameters and the performance criterion problematic. In theoretical studies, computer simulation modelling putatively enables athlete-specific optimum techniques to be identified, but given each athlete's unique intrinsic dynamics, it is far from certain that these optimum techniques will be attainable, particularly under the often intense psychological pressures of competition, irrespective of the volume of practice undertaken. Sports biomechanists and coaching practitioners are advised to be more circumspect with regard to interpreting the results of applied sports biomechanics research and have greater awareness of their assumptions and limitations, as inappropriate interpretation of results may have adverse consequences for performance and injury. [ABSTRACT FROM AUTHOR]

Background: To date, athletic performance has been extensively assessed in youth soccer players through laboratory and field testing. Only recently has running performance via time-motion analysis been assessed during match play. Match running data are often useful in a practical context to aid game understanding and decision making regarding training content and prescriptions. A plethora of previous reviews have collated and appraised the literature on time-motion analysis in professional senior players, but none have solely examined youth players.Objective: The aim of the present systematic review was to provide a critical appraisal and summary of the original research articles that have evaluated match running performance in young male soccer players.Methods: Following the Preferred Reporting Items for Systematic Reviews and Meta-analyses (PRISMA) statement, literature searches were performed in four databases: PubMed, ISI Web of Science, SPORTDiscus and SciELO. We used the following descriptors: soccer, football, young, youth, junior, physical performance, running performance, match running performance, movement patterns, time-motion analysis, distances covered, activity profile, work rate, match analysis, and match performance. Articles were included only if they were original articles written in the English language, studied populations of male children and/or adolescents (aged ≤ 20 years), were published/ahead of print on or before 31 December 2017 and showed at least one outcome measure regarding match running performance, such as total distance covered, peak game speed or indicators of activities performed at established speed thresholds.Results: A total of 5801 records were found. After duplicates were removed and exclusion and inclusion criteria applied, 50 articles were included (n = 2615 participants). Their outcome measures were extracted and findings were synthesized. The majority of the reviewed papers covered the European continent (62%) and used global positioning systems (GPS) (64%). Measurement error of the tools used to obtain position data and running metrics was systematically overlooked among the studies. The main aims of studies were to examine differences across playing positions (20%), age groups (26%) and match halves (36%). Consistent findings pointed to the existence of positional role and age effects on match running output (using fixed running speed thresholds), but there was no clear consensus about reductions in activity over the course of match play. Congested schedules negatively affected players' running performance. While over 32% of all studies assessed the relationships between match running performance and physical capacity, biochemical markers and body composition, ~ 70% of these did not account for playing position.Conclusions: This review collated scientific evidence that can aid soccer conditioning professionals in understanding external match loads across youth categories. Coaches working with youth development programs should consider that data derived from a given population may not be relevant for other populations, since game rules, match format and configuration are essentially unstandardized among studies for age-matched players. Despite limited evidence, periodization training emphasizing technical-tactical content can improve match running performance. Occurrence of acute and residual impairments in the running performance of young soccer players is common. Prescription of postmatch recovery strategies, such as cold water immersion and spa treatment, can potentially help reduce these declines, although additional research is warranted. This review also highlighted areas requiring further investigation, such as the possible influence of environmental and contextual constraints and a more integrative approach combining tactical and technical data. [ABSTRACT FROM AUTHOR]

Anti-pronation taping is a treatment technique commonly used by clinicians in the management of lower extremity musculoskeletal pain and injury. The clinical efficacy of anti-pronation tape is described anecdotally and has some support through clinical trials for some foot conditions. However, the mechanism(s) underlying its clinical efficacy is unknown, but are broadly categorized under mechanical, neurophysiological and psychological hypotheses. This article explores these hypotheses and contributes to the understanding of the technique. A computer database search was conducted to identify relevant experimental studies using an a priori defined search strategy. Data were extracted from reviewed articles and wherever possible mean differences between baseline and taped condition and the 95% confidence interval, as well as percentage change scores and effect size statistics were calculated. Articles were organized pertaining to the hypothetical mechanism investigated and presented accordingly into biomechanical, neurophysiological or psychological paradigms. Overall, the research to date has focused predominantly on the mechanical paradigm with far fewer papers being found for the neurophysiological and psychological paradigms. The literature provides evidence that anti-pronation tape has a biomechanical effect, which has been demonstrated by increases in navicular height and medial longitudinal arch height, reductions in tibial internal rotation and calcaneal eversion and alteration of plantar pressure patterns, under both static (i.e. standing) and dynamic (i.e. walking, jogging, running) conditions. The reduction in pronation was dependent on the surrogate measure of pronation used, but generally ranged from as little as 5% increase in longitudinal arch height during jogging to as much as a 33% change in calcaneal eversion during walking. Preliminary evidence from few studies suggests that anti-pronation tape has a neurophysiological effect as it has been shown to reduce the activity of several muscles of the leg during dynamic tasks such as walking, hopping, cutting, back pedalling and drop jumps. Data were difficult to extract from these papers, but it would appear from a small study that the reduction is in the order of about 45% for tibialis posterior. To date, there has been limited investigation of the psychological effects of anti-pronation tape. A main issue, as with most placebo or sham interventions for physical therapy research, is that of an appropriate comparator in this regard. Consequently, these effects are currently not well understood. This article reports of evidence in support of anti-pronation tape exerting a biomechanical effect. As its name suggests, it does reduce pronation. There is emerging evidence of a neurophysiological effect, which is generally one of reduction in muscle activity, but caution is urged in over-interpreting a few studies on small sample sizes. Further research is required in this paradigm before sports medicine practitioners can utilize these findings in day-to-day clinical practice. Due to insufficient evidence, this article was unable to draw any conclusions as to the psychological effects of the tape, but the article does prompt the need for further exploration into the possible role of placebo in the clinical effects of antipronation taping. [ABSTRACT FROM AUTHOR]

Since it was first observed, and especially so in recent years, the phenomenon of the so-called 'sticking point' in resistance training has attracted a substantial amount of sports and exercise science research. Broadly speaking, the sticking point is understood as the position in the range of motion of a lift at which a disproportionately large increase in the difficulty associated with continuing the lift is experienced. Hence the sticking point is inherently the performance bottleneck, and is also associated with an increased chance of exercise form deterioration or breakdown. Understanding the aspects of lifting performance which should be analysed in order to pinpoint the cause of a specific sticking point and therefore devise an effective training strategy to overcome it is of pervasive importance to strength practitioners, and is conducive to injury avoidance and continued progress. In this paper, we survey a range of physiological and biomechanical mechanisms which contribute to the development of sticking points, and then, led by this insight, review and analyse the findings of the existing observational research on the occurrence of sticking points in three ubiquitous exercises: the bench press, the squat, and the deadlift. The findings of our analysis should be used to inform future research and current resistance training practice. [ABSTRACT FROM AUTHOR]

Background: The adolescent 'growth spurt' results in rapid growth of the skeletal system. It has been theorised that absence of a concomitant increase in muscular adaptations in female athletes may predispose them to an increased risk of anterior cruciate ligament injuries. Objectives: To determine if sex differences exist in landing biomechanics and postural stability of adolescent athletes; with a further objective of determining if such differences are propagated during adolescence. Data sources: The following databases were searched: MEDLINE, EMBASE, CINAHL, PEDro, PubMed, SPORTDiscus and Web of Science. Research papers were identified by including search terms for neuromuscular control, lower limb and pubertal development. Inclusion Criteria: Studies were required to be written in English; report on biomechanical analyses; include landing or postural control tasks; be cross-sectional or longitudinal; and include healthy adolescent/pubertal subjects. Study Appraisal and Synthesis Methods: A modified version of the Strengthening the Reporting of Observational studies in Epidemiology checklist was used to rate methodological quality. Meta-analyses were performed when more than one study reported on an outcome measure. Results: Sixteen articles were included. The overall methodological quality of evaluated studies was low (mean score = 5.75/10 points). Adolescent females exhibited increased knee valgus with increasing maturity. There was no consensus on sex differences in postural stability. Conclusions: With increasing maturation, females are characterized by increased knee valgus during landing tasks. To date, no research has longitudinally investigated postural stability development during adolescence in females, despite the importance of postural control training in injury prevention programmes. Therefore, further research on this topic is warranted. [ABSTRACT FROM AUTHOR]

Background: Patellofemoral pain (PFP) is highly prevalent within both sporting and recreationally active populations. Multiple treatment approaches have been advocated for the management of PFP, attempting to address both intrinsic and extrinsic factors thought to contribute to the development and persistence of pain. A number of predictors of treatment success have been proposed, and evaluated, for directing intervention choice. Objective: Our aim was to systematically review the literature that identifies outcome predictors of specific conservative interventions in the management of PFP, including quality of the current evidence, to guide clinical practice and future studies investigating outcome predictors within this population. Data Sources: The AMED, CINAHL, EMBASE, MEDLINE and Web of Science databases were searched from inception to April 2013. Study Selection: Randomized controlled trials (RCTs) and cohort studies. Study Appraisal and Synthesis Methods: Following initial searching, all potential papers were assessed by two independent reviewers for inclusion using a checklist developed from the inclusion criteria. Cited, and citing, references were also searched in Google Scholar, but unpublished work was not sought. Methodological quality was assessed using a previously designed quality assessment scale. Definitions for levels of evidence were guided by recommendations made by van Tulder et al. Results: Fifteen low-quality (LQ) cohort studies were included. No RCTs were found. This systematic review identified the evaluation of 205 conservative management outcome predictor variables. Of this large number of variables that have been assessed, 19 (9 %) were found to significantly predict a successful outcome. Where two or more outcome predictors and success determinants were consistent between studies, data were pooled. Within these studies, the low number of participants per output variable, and absence of controls, is likely to compromise the validity of the predictor's accuracy. Very limited evidence identified higher functional index questionnaire scores (mean 0.82, 95 % confidence interval [CI] 0.18-1.46), greater forefoot valgus (mean 0.67, 95 % CI 0.05-1.28) and greater rearfoot eversion magnitude peak (mean −0.93, 95 % CI −1.84 to −0.01) to significantly predict improved outcomes with orthoses interventions. Shorter symptom duration ( p = 0.019), lower frequency of pain ( p = 0.012), younger age, faster vastus medialis oblique reflex response time ( p = 0.026), negative patella apprehension, absence of chondromalacia patella, tibial tubercle deviation of <14.6 mm and greater total quadriceps cross-sectional area on magnetic resonance imaging ( p = 0.01), and reduced eccentric average quadriceps peak torque ( p = 0.015) significantly predicted exercise intervention success following multivariate statistical analysis. Limited evidence identified increased Q-angle (mean 0.38, 95 % CI 0.05-0.72) and very limited evidence identified greater usual pain (mean 0.43, 95 % CI 0.01-0.85) to predict taping intervention success. Conclusions: This systematic review provides a comprehensive summary of current derivation level studies identifying indicators of prediction for conservative PFP management. The overall strength of evidence was low. With appropriate caution, clinicians should consider taping for those with greater usual pain, orthoses for older individuals and exercise for younger individuals, and orthoses intervention for patients with greater forefoot valgus and rearfoot eversion magnitude peak. RCTs with evaluation of outcome prediction as a primary aim are clearly warranted to provide clinicians with robust evidence and facilitate evidence-informed, tailored intervention to this heterogeneous patient population. [ABSTRACT FROM AUTHOR]

Background: Alpine ski racing is a popular international winter sport that is complex and challenging from physical, technical, and tactical perspectives. Despite the vast amount of scientific literature focusing on this sport, including topical reviews on physiology, ski-snow friction, and injuries, no review has yet addressed the biomechanics of elite alpine ski racers and which factors influence performance. In World Cup events, winning margins are often mere fractions of a second and biomechanics may well be a determining factor in podium place finishes. Objective: The aim of this paper was to systematically review the scientific literature to identify the biomechanical factors that influence the performance of elite alpine ski racers, with an emphasis on slalom, giant slalom, super-G, and downhill events. Methods: Four electronic databases were searched using relevant medical subject headings and key words, with an additional manual search of reference lists, relevant journals, and key authors in the field. Articles were included if they addressed human biomechanics, elite alpine skiing, and performance. Only original research articles published in peer-reviewed journals and in the English language were reviewed. Articles that focused on skiing disciplines other than the four of primary interest were excluded (e.g., mogul, ski-cross and freestyle skiing). The articles subsequently included for review were quality assessed using a modified version of a validated quality assessment checklist. Data on the study population, design, location, and findings relating biomechanics to performance in alpine ski racers were extracted from each article using a standard data extraction form. Results: A total of 12 articles met the inclusion criteria, were reviewed, and scored an average of 69 ± 13 % (range 40-89 %) upon quality assessment. Five of the studies focused on giant slalom, four on slalom, and three on downhill disciplines, although these latter three articles were also relevant to super-G events. Investigations on speed skiing (i.e., downhill and super-G) primarily examined the effect of aerodynamic drag on performance, whereas the others examined turn characteristics, energetic principles, technical and tactical skills, and individual traits of high-performing skiers. The range of biomechanical factors reported to influence performance included energy dissipation and conservation, aerodynamic drag and frictional forces, ground reaction force, turn radius, and trajectory of the skis and/or centre of mass. The biomechanical differences between turn techniques, inter-dependency of turns, and abilities of individuals were also identified as influential factors in skiing performance. In the case of slalom and giant slalom events, performance could be enhanced by steering the skis in such a manner to reduce the ski-snow friction and thereby energy dissipated. This was accomplished by earlier initiation of turns, longer path length and trajectory, earlier and smoother application of ground reaction forces, and carving (rather than skidding). During speed skiing, minimizing the exposed frontal area and positioning the arms close to the body were shown to reduce the energy loss due to aerodynamic drag and thereby decrease run times. In actual races, a consistently good performance (i.e., fast time) on different sections of the course, terrains, and snow conditions was a characteristic feature of winners during technical events because these skiers could maximize gains from their individual strengths and minimize losses from their respective weaknesses. Limitations: Most of the articles reviewed were limited to investigating a relatively small sample size, which is a usual limitation in research on elite athletes. Of further concern was the low number of females studied, representing less than 4 % of all the subjects examined in the articles reviewed. In addition, although overall run time is the ultimate measure of performance in alpine ski racing, several other measures of instantaneous performance were also employed to compare skiers, including the aerodynamic drag coefficient, velocity, section time, time lost per change in elevation, and mechanical energy behaviours, which makes cross-study inferences problematic. Moreover, most studies examined performance through a limited number of gates (i.e., 2-4 gates), presumably because the most commonly used measurement systems can only capture small volumes on a ski field with a reasonable accuracy for positional data. Whether the biomechanical measures defining high instantaneous performance can be maintained throughout an entire race course remains to be determined for both male and female skiers. Conclusions: Effective alpine skiing performance involves the efficient use of potential energy, the ability to minimize ski-snow friction and aerodynamic drag, maintain high velocities, and choose the optimal trajectory. Individual tactics and techniques should also be considered in both training and competition. To achieve better run times, consistency in performance across numerous sections and varied terrains should be emphasized over excellence in individual sections and specific conditions. [ABSTRACT FROM AUTHOR]

Kitesurfing is a relatively new extreme water sport that is considered a high-risk sport and has rising popularity. Kitesurfing combines aspects of several water sports, including surfing, windsurfing, and wakeboarding. With a large controllable kite and a small board, kitesurfers travel over the water surface with speeds of up to 35 knots. The vertical lift of the kite makes it possible to perform jumps up to 15 m high and 30 m long, while doing different manoeuvres in the air. Few scientific data are available concerning the biomechanical and physiological demands of kitesurfing and the epidemiology of kitesurfing injury, and research methods used are often questionable. During kitesurfing, considerable stress is placed on the musculoskeletal and physiological systems, and the possibility of injury or fatality is an inherent part of participation. The lower back and thigh muscles are often perceived as being highly stressed, while abdominal muscles, knees, and feet are common sites of pain or discomfort. During kitesurfing, both aerobic and anaerobic metabolism contribute to energy delivery. It is reported in the literature that kitesurfing injuries are mainly acute, due to accidents or trauma. Non-competitive kitesurfing resulted in an overall injury rate of 5.9-7.0 injuries per 1,000 kitesurfing hours. It seems that the risk of injury increases dramatically in competitive kitesurfing. However, contradictory results have been found. Lower extremities were the most common major site of injuries, followed by upper extremities, trunk, and head. Most accidents during kitesurfing reported in the literature were attributed to the inability to detach the kite from the harness. Due to technical innovations, recent studies report uncontrolled actions and unsuccessful tricks and jumps with poor landings as the main mechanisms of injuries. The main purpose of the present paper is to critically analyse the current relevant scientific literature on the biomechanical and physiological demands of kitesurfing and the epidemiology of injury among kitesurfers, in order to obtain greater insights into (i) the stresses imposed on the musculoskeletal and physiological systems by kitesurfing, and (ii) the rate, pattern, and mechanisms of kitesurfing injuries. [ABSTRACT FROM AUTHOR]

There have been different approaches to studying penalty-kick performance in association football and in this paper we synthesize key findings within an ecological dynamics theoretical framework. According to this theoretical perspective, information is the cornerstone for understanding the dynamics of action regulation in penalty-kick performance. Research suggests that investigators need to identify the information sources that are most relevant to penalty-kick performance. An important task is to understand how constraints can channel (i.e. change, emphasize or mask) information sources used to regulate upcoming actions and how the influence of these constraints is expressed in players' behavioural dynamics. Due to the broad range of constraints influencing penalty-kick performance, it is recommended that future research adopts an interdisciplinary focus on performance assessment to overcome the current lack of representativeness in penalty-kick experimental designs. Such an approach would serve to capture the information-based control of action of both players as components of this dyadic system in competitive sport. [ABSTRACT FROM AUTHOR]

To date, scientific investigations into the biomechanical aspects of cricket fast bowling techniques have predominantly focused on identifying the mechanical factors that may predispose fast bowlers to lower back injury with a relative paucity of research being conducted on the technical features that underpin proficient fast bowling performance. In this review paper, we critique the scientific literature examining fast bowling performance. We argue that, although many published investigations have provided some useful insights into the biomechanical factors that contribute to a high ball release speed and, to a lesser extent, bowling accuracy, this research has not made a substantive contribution to knowledge enhancement and has only had a very minor influence on coaching practice. To significantly enhance understanding of cricket fast bowling techniques and, therefore, have greater impact on practice, we recommend that future scientific research adopts an interdisciplinary focus, integrating biomechanical measurements with the analytical tools and concepts of dynamical systems motor control theory. The use of qualitative (topological) analysis techniques, in particular, promises to increase understanding of the coordinative movement patterns that define 'technique' in cricket fast bowling and potentially help distinguish between functional and dysfunctional aspects of technique for individual fast bowlers. [ABSTRACT FROM AUTHOR]

Acromioclavicular joint (ACJ) separation injuries are common injuries among sporting populations. ACJ separations are graded according to severity from grade I being a mild sprain to grade VI, which is severe dislocation with displacement. There is consensus in the literature that grade I-III ACJ separations are managed conservatively and grades IV-VI are managed surgically. Despite conservative care being recommended for lesser grades of injury, there is very little evidence in the literature as to what constitutes conservative care. Therefore, the purpose of this paper was, first, to review the relevant anatomy and kinematics of the ACJ and, second, to review the literature relating to current evidence of conservative management of ACJ injury. Using this data, a best practice guideline for conservative rehabilitation in grade I-III ACJ separations was developed. For the conservative management, a literature search was undertaken using the following databases in the Auckland University of Technology's electronic library resources; MEDLINE, CINAHL, SPORTDiscus~" and the Cochrane Library. The following keywords or phrases were used: 'acromioclavicular joint separa- tions', 'injury', 'dislocations', 'rehabilitation', 'conservative care', 'physio- therapy' and 'exercise'. A total of 24 articles was identified. There were no randomized con- trolled trials (RCTs) that investigated conservative treatment for grade I-III ACJ sprains. Therefore, a narrative review was formulated covering the anatomy and biomechanics of the ACJ, injury mechanisms and relevant literature reviewed covering rehabilitation principles. Conservative manage- ment of grade I-III ACJ separations is still the main recommendation following this review. A best practice guideline for managing grade I-III ACJ separations is presented to help guide clinicians until well constructed RCTs are carried out to improve the conservative management of ACJ injuries. [ABSTRACT FROM AUTHOR]

Introduction: Changing running technique or equipment can alter tibial loads. The efficacy of interventions to modify tibial loads during running is yet to be synthesised and evaluated. This article reviewed the effect of running technique and footwear interventions on tibial loading during running. Methods: Electronic databases were searched using terms relevant to tibial load and running. Interventions were categorised according to their approach (i.e., footwear; barefoot running; speed; surface; overground versus treadmill; orthotics, insoles and taping; and technique); if necessary, further subgrouping was applied to these categories. Standardised mean differences (SMDs) with 95% confidence intervals (CIs) for changes in tibial loading were calculated and meta-analyses performed where possible. Results: Database searches yielded 1617 articles, with 36 meeting the inclusion criteria. Tibial loading increased with (1) barefoot running (SMD 1.16; 95% CI 0.50, 1.82); (2) minimalist shoe use by non-habitual users (SMD 0.89; 95% CI 0.40, 1.39); (3) motion control shoe use (SMD 0.46; 95% CI 0.07, 0.84); (4) increased stride length (SMD 0.86; 95% CI 0.18, 1.55); and (5) increased running speed (SMD 1.03; 95% CI 0.74, 1.32). Tibial loading decreased when (1) individuals ran on a treadmill versus overground (SMD − 0.83; 95% CI − 1.53, − 0.12); and (2) targeted biofeedback was used (SMD − 0.93; 95% CI − 1.46, − 0.41). Conclusions: Running barefoot, in motion control shoes or in unfamiliar minimalist shoes, and with an increased stride length increases tibial loads and may increase the risk of a tibial stress injury during periods of high training load. Adopting interventions such as running on a treadmill versus overground, and using targeted biofeedback during periods of high loads could reduce tibial stress injury. [ABSTRACT FROM AUTHOR]

Background: Investigators have proposed that various physical head and neck characteristics, such as neck strength and head and neck size, are associated with protection from mild traumatic brain injury (mTBI/concussion). Objectives: To systematically review the literature and investigate potential relationships between physical head and neck characteristics and mTBI risk in athletic and military populations. Methods: A comprehensive search of seven databases was conducted: MEDLINE, EMBASE, CINAHL, Scopus, SPORTDiscus, Cochrane Library, and Web of Science. Potential studies were systematically screened and reviewed. Studies on military and athletic cohorts were included if they assessed the relationship between physical head-neck characteristics and mTBI risk or proxy risk measures such as head impact kinematics. Results: The systematic search yielded a total of 11,723 original records. From these, 22 studies met our inclusion criteria (10 longitudinal, 12 cross-sectional). Relevant to our PECO (Population, Exposure, Comparator, and Outcomes) question, exposures included mTBI incidence and head impact kinematics (acceleration, velocity, displacement) for impacts during sport play and training and in controlled laboratory conditions. Outcome characteristics included head and neck size (circumference, mass, length, ratios between these measures), neck strength and endurance, and rate of force development of neck muscles. Discussion: We found mixed evidence for head and neck characteristics acting as risk factors for and protective factors against mTBI and increased susceptibility to head impacts. Head-neck strength and size variables were at times associated with protection against mTBI incidence and reduced impact kinematics (14/22 studies found one or more head-neck variable to be associated with protection); however, some studies did not find these relationships (8/22 studies found no significant associations or relationships). Interestingly, two studies found stronger and larger athletes were more at risk of sustaining high impacts during sport. Strength and size metrics may have some predictive power, but impact mitigation seems to be influenced by many other variables, such as behaviour, sex, and impact anticipation. A meta-analysis could not be performed due to heterogeneity in study design and reporting. Conclusion: There is mixed evidence in the literature for the protective capacity of head and neck characteristics. We suggest field-based mTBI research in the future should include more dynamic anthropometric metrics, such as neck stiffness and response to perturbation. In addition, laboratory-based mTBI studies should aim to standardise design and reporting to help further uncover these complicated relationships. [ABSTRACT FROM AUTHOR]

In recent years, there has been a significant expansion in female participation in endurance (road and trail) running. The often reported sex differences in maximal oxygen uptake (VO2max) are not the only differences between sexes during prolonged running. The aim of this narrative review was thus to discuss sex differences in running biomechanics, economy (both in fatigue and non-fatigue conditions), substrate utilization, muscle tissue characteristics (including ultrastructural muscle damage), neuromuscular fatigue, thermoregulation and pacing strategies. Although males and females do not differ in terms of running economy or endurance (i.e. percentage VO2max sustained), sex-specificities exist in running biomechanics (e.g. females have greater non-sagittal hip and knee joint motion compared to males) that can be partly explained by anatomical (e.g. wider pelvis, larger femur-tibia angle, shorter lower limb length relative to total height in females) differences. Compared to males, females also show greater proportional area of type I fibres, are more able to use fatty acids and preserve carbohydrates during prolonged exercise, demonstrate a more even pacing strategy and less fatigue following endurance running exercise. These differences confer an advantage to females in ultra-endurance performance, but other factors (e.g. lower O2 carrying capacity, greater body fat percentage) counterbalance these potential advantages, making females outperforming males a rare exception. The present literature review also highlights the lack of sex comparison in studies investigating running biomechanics in fatigue conditions and during the recovery process. [ABSTRACT FROM AUTHOR]

Background: Compression garments are regularly worn during exercise to improve physical performance, mitigate fatigue responses, and enhance recovery. However, evidence for their efficacy is varied and the methodological approaches and outcome measures used within the scientific literature are diverse. Objectives: The aim of this scoping review is to provide a comprehensive overview of the effects of compression garments on commonly assessed outcome measures in response to exercise, including: performance, biomechanical, neuromuscular, cardiovascular, cardiorespiratory, muscle damage, thermoregulatory, and perceptual responses. Methods: A systematic search of electronic databases (PubMed, SPORTDiscus, Web of Science and CINAHL Complete) was performed from the earliest record to 27 December, 2020. Results: In total, 183 studies were identified for qualitative analysis with the following breakdown: performance and muscle function outcomes: 115 studies (63%), biomechanical and neuromuscular: 59 (32%), blood and saliva markers: 85 (46%), cardiovascular: 76 (42%), cardiorespiratory: 39 (21%), thermoregulatory: 19 (10%) and perceptual: 98 (54%). Approximately 85% (n = 156) of studies were published between 2010 and 2020. Conclusions: Evidence is equivocal as to whether garments improve physical performance, with little evidence supporting improvements in kinetic or kinematic outcomes. Compression likely reduces muscle oscillatory properties and has a positive effect on sensorimotor systems. Findings suggest potential increases in arterial blood flow; however, it is unlikely that compression garments meaningfully change metabolic responses, blood pressure, heart rate, and cardiorespiratory measures. Compression garments increase localised skin temperature and may reduce perceptions of muscle soreness and pain following exercise; however, rating of perceived exertion during exercise is likely unchanged. It is unlikely that compression garments negatively influence exercise-related outcomes. Future research should assess wearer belief in compression garments, report pressure ranges at multiple sites as well as garment material, and finally examine individual responses and varying compression coverage areas. [ABSTRACT FROM AUTHOR]

The development of a pronounced iliotibial band (ITB) is an anatomically distinct evolution of humans. The mechanical behaviour of this "new" structure is still poorly understood and hotly debated in current literature. Iliotibial band syndrome (ITBS) is one of the leading causes of lateral knee pain injuries in runners. We currently lack a comprehensive understanding of the healthy behaviour of the ITB, and this is necessary prior to further investigating the aetiology of pathologies like ITBS. Therefore, the purpose of this narrative review was to collate the anatomical, biomechanical and clinical literature to understand how the mechanical function of the ITB is influenced by anatomical variation, posture and muscle activation. The complexity of understanding the mechanical function of the ITB is due, in part, to the presence of its two in-series muscles: gluteus maximus (GMAX) and tensor fascia latae (TFL). At present, we lack a fundamental understanding of how GMAX and TFL transmit force through the ITB and what mechanical role the ITB plays for movements like walking or running. While there is a range of proposed ITBS treatment strategies, robust evidence for effective treatments is still lacking. Interventions that directly target the running biomechanics suspected to increase either ITB strain or compression of lateral knee structures may have promise, but clinical randomised controlled trials are still required. [ABSTRACT FROM AUTHOR]

A conceptual framework has a central role in the scientific process. Its purpose is to synthesize evidence, assist in understanding phenomena, inform future research and act as a reference operational guide in practical settings. We propose an updated conceptual framework intended to facilitate the validation and interpretation of physical training measures. This revised conceptual framework was constructed through a process of qualitative analysis involving a synthesis of the literature, analysis and integration with existing frameworks (Banister and PerPot models). We identified, expanded, and integrated four constructs that are important in the conceptualization of the process and outcomes of physical training. These are: (1) formal introduction of a new measurable component 'training effects', a higher-order construct resulting from the combined effect of four possible responses (acute and chronic, positive and negative); (2) explanation, clarification and examples of training effect measures such as performance, physiological, subjective and other measures (cognitive, biomechanical, etc.); (3) integration of the sport performance outcome continuum (from performance improvements to overtraining); (4) extension and definition of the network of linkages (uni and bidirectional) between individual and contextual factors and other constructs. Additionally, we provided constitutive and operational definitions, and examples of theoretical and practical applications of the framework. These include validation and conceptualization of constructs (e.g., performance readiness), and understanding of higher-order constructs, such as training tolerance, when monitoring training to adapt it to individual responses and effects. This proposed conceptual framework provides an overarching model that may help understand and guide the development, validation, implementation and interpretation of measures used for athlete monitoring. [ABSTRACT FROM AUTHOR]

High-intensity horizontal decelerations occur frequently in team sports and are typically performed to facilitate a reduction in momentum preceding a change of direction manoeuvre or following a sprinting action. The mechanical underpinnings of horizontal deceleration are unique compared to other high-intensity locomotive patterns (e.g., acceleration, maximal sprinting speed), and are characterised by a ground reaction force profile of high impact peaks and loading rates. The high mechanical loading conditions observed when performing rapid horizontal decelerations can lead to tissue damage and neuromuscular fatigue, which may diminish co-ordinative proficiency and an individual's ability to skilfully dissipate braking loads. Furthermore, repetitive long-term deceleration loading cycles if not managed appropriately may propagate damage accumulation and offer an explanation for chronic aetiological consequences of the 'mechanical fatigue failure' phenomenon. Training strategies should look to enhance an athlete's ability to skilfully dissipate braking loads, develop mechanically robust musculoskeletal structures, and ensure frequent high-intensity horizontal deceleration exposure in order to accustom individuals to the potentially damaging effects of intense decelerations that athletes will frequently perform in competition. Given the apparent importance of horizontal decelerations, in this Current Opinion article we provide considerations for sport science and medicine practitioners around the assessment, training and monitoring of horizontal deceleration. We feel these considerations could lead to new developments in injury-mitigation and physical development strategies in team sports. [ABSTRACT FROM AUTHOR]

Running injuries are very common, and there are well-established protocols for clinicians to manage specific musculoskeletal conditions in runners. However, competitive and elite runners may experience different injuries than the average recreational runner, due to differences in training load, biomechanics, and running experience. Additionally, injury-specific rehabilitation protocols do not consider the broader goal of return to competitive running, including the unique psychosocial and cardiorespiratory fitness needs of elite athletes. This review aims to suggest a guideline for running-specific progression as part of a comprehensive rehabilitation program for injured competitive runners. Tools to evaluate an athlete's psychosocial preparedness to return to competition are presented. Recommendations are also provided for monitoring cardiorespiratory fitness of injured runners, including the nuances of interpreting these data. Finally, a six-phase training paradigm is proposed to guide clinicians as they help competitive runners transition from the early stages of injury through a full return to competition. [ABSTRACT FROM AUTHOR]

Muscle glycogen is the main substrate during high-intensity exercise and large reductions can occur after relatively short durations. Moreover, muscle glycogen is stored heterogeneously and similarly displays a heterogeneous and fiber-type specific depletion pattern with utilization in both fast- and slow-twitch fibers during high-intensity exercise, with a higher degradation rate in the former. Thus, depletion of individual fast- and slow-twitch fibers has been demonstrated despite muscle glycogen at the whole-muscle level only being moderately lowered. In addition, muscle glycogen is stored in specific subcellular compartments, which have been demonstrated to be important for muscle function and should be considered as well as global muscle glycogen availability. In the present review, we discuss the importance of glycogen metabolism for single and intermittent bouts of high-intensity exercise and outline possible underlying mechanisms for a relationship between muscle glycogen and fatigue during these types of exercise. Traditionally this relationship has been attributed to a decreased ATP resynthesis rate due to inadequate substrate availability at the whole-muscle level, but emerging evidence points to a direct coupling between muscle glycogen and steps in the excitation–contraction coupling including altered muscle excitability and calcium kinetics. [ABSTRACT FROM AUTHOR]

Background: Netball is the one of the most popular women's sports in the world. Since gaining professional status in 2008 there has been a rapid growth in research in the applied sports science and medicine of the sport. A scoping review of the area would provide practitioners and researchers with an overview of the current scientific literature to support on-court performance, player welfare and reduce injury. Objective: The primary objective was to identify the current research on the applied sports science and medicine of netball. Additionally, the article provides a brief summary of the research in each topic of sports science and medicine in netball and identifies gaps in the current research. Methods: Systematic searches of PubMed, SPORTDiscus, MEDLINE and CINAHL were undertaken from earliest record to Dec 2020 and reference lists were manually searched. The PRISMA-ScR protocol was followed. Studies were eligible for inclusion if they investigated netball as a sport or the applied sport science and medicine of netball athletes. Results: 962 studies were identified in the initial search, 150 of which met the inclusion criteria. Injury was the most highly investigated sport science and medicine topic (n = 45), followed by physical qualities (n = 37), match characteristics (n = 24), biomechanics (n = 15), psychology (n = 13), fatigue and recovery (n = 9), training load (n = 4) and nutrition (n = 3). A range of cohorts were used from school to elite and international standards. All cohorts were female netballers, except for one study. A rapid growth in studies over recent years was demonstrated with 65% of studies published in the last decade. There still remains gaps in the literature, with a low evidence base for nutrition, training load and fatigue and recovery. Conclusion: This scoping review summarises the current evidence base and key findings that can be used in practice to enhance the applied sport science and medical support to netball athletes across a range of playing standards, and support the growth of the sport. It is evident that netball as a sport is still under-researched. [ABSTRACT FROM AUTHOR]

Background: Inertial measurement units (IMUs) are used for running gait analysis in a variety of sports. These sensors have been attached at various locations to capture stride data. However, it is unclear if different placement sites affect the derived outcome measures. Objective: The aim of this systematic review and meta-analysis was to investigate the impact of placement on the validity and reliability of IMU-derived measures of running gait. Methods: Online databases SPORTDiscus with Full Text, CINAHL Complete, MEDLINE (EBSCOhost), EMBASE (Ovid) and Scopus were searched from the earliest record to 6 August 2020. Articles were included if they (1) used an IMU during running (2) reported spatiotemporal variables, peak ground reaction force (GRF) or vertical stiffness and (3) assessed validity or reliability. Meta-analyses were performed for a pooled validity estimate when (1) studies reported means and standard deviation for variables derived from the IMU and criterion (2) used the same IMU placement and (3) determined validity at a comparable running velocity (≤ 1 m·s−1 difference). Results: Thirty-nine articles were included, where placement varied between the foot, tibia, hip, sacrum, lumbar spine (LS), torso and thoracic spine (TS). Initial contact, toe-off, contact time (CT), flight time (FT), step time, stride time, swing time, step frequency (SF), step length (SL), stride length, peak vertical and resultant GRF and vertical stiffness were analysed. Four variables (CT, FT, SF and SL) were meta-analysed, where CT was compared between the foot, tibia and LS placements and SF was compared between foot and LS. Foot placement data were meta-analysed for FT and SL. All data are the mean difference (MD [95%CI]). No significant difference was observed for any site compared to the criterion for CT (foot: − 11.47 ms [− 45.68, 22.74], p = 0.43; tibia: 22.34 ms [− 18.59, 63.27], p = 0.18; LS: − 48.74 ms [− 120.33, 22.85], p = 0.12), FT (foot: 11.93 ms [− 8.88, 32.74], p = 0.13), SF (foot: 0.45 step·min−1 [− 1.75, 2.66], p = 0.47; LS: − 3.45 step·min−1 [− 16.28, 9.39], p = 0.37) and SL (foot: 0.21 cm [− 1.76, 2.18], p = 0.69). Reliable derivations of CT (coefficient of variation [CV] < 9.9%), FT (CV < 11.6%) and SF (CV < 4.4%) were shown using foot- and LS-worn IMUs, while the CV was < 7.8% for foot-determined stride time, SL and stride length. Vertical GRF was reliable from the LS (CV = 4.2%) and TS (CV = 3.3%) using a spring-mass model, while vertical stiffness was moderately (r = 0.66) and nearly perfectly (r = 0.98) correlated with criterion measures from the TS. Conclusion: Placement of IMUs on the foot, tibia and LS is suitable to derive valid and reliable stride data, suggesting measurement site may not be a critical factor. However, evidence regarding the ability to accurately detect stride events from the TS is unclear and this warrants further investigation. [ABSTRACT FROM AUTHOR]

Recent public concern over the short- and long-term effects of repetitive head impacts (RHI) associated with purposeful heading in soccer has led researchers to study a multitude of variables related to this important aspect of the game. Of particular interests are the effects of soccer heading in the youth population (≤ 13 years old) whose brains are undergoing rapid development. We conducted a review on youth soccer heading that includes purposeful heading frequency, head impact biomechanics, head injuries, clinical outcomes, and modifying factors. We have concluded that youth soccer players head the ball at a low frequency that typically increases with age and with a finding that boys head the ball more often than girls do. Interestingly, although girls head the ball less frequently than boys do, they tend to sustain higher head impact magnitudes. Head injuries are more likely to occur in girls versus boys and during games because of contact with another player. Clinical outcome measures of concussion are often utilized to study the effects of soccer heading, in both field and laboratory environments. Immediately following soccer heading, youth often report having a headache and demonstrate some deficits in balance measures. Modifying factors that may benefit soccer players participating in purposeful heading activities include stronger neck musculature, wearing headgear, and the use of mouthguards. Research involving youth soccer players needs to be expanded and funded appropriately to better understand the consequences of RHI in both the short and long term. [ABSTRACT FROM AUTHOR]

Background: Cross-education refers to increased motor output (i.e., force generation, skill) of the opposite, untrained limb following a period of unilateral exercise training. Despite extensive research, several aspects of the transfer phenomenon remain controversial. Methods: A modified two-round Delphi online survey was conducted among international experts to reach consensus on terminology, methodology, mechanisms of action, and translational potential of cross-education, and to provide a framework for future research. Results: Through purposive sampling of the literature, we identified 56 noted experts in the field, of whom 32 completed the survey, and reached consensus (75% threshold) on 17 out of 27 items. Conclusion: Our consensus-based recommendations for future studies are that (1) the term 'cross-education' should be adopted to refer to the transfer phenomenon, also specifying if transfer of strength or skill is meant; (2) functional magnetic resonance imaging, short-interval intracortical inhibition and interhemispheric inhibition appear to be promising tools to study the mechanisms of transfer; (3) strategies which maximize cross-education, such as high-intensity training, eccentric contractions, and mirror illusion, seem worth being included in the intervention plan; (4) study protocols should be designed to include at least 13–18 sessions or 4–6 weeks to produce functionally meaningful transfer of strength, and (5) cross-education could be considered as an adjuvant treatment particularly for unilateral orthopedic conditions and sports injuries. Additionally, a clear gap in views emerged between the research field and the purely clinical field. The present consensus statement clarifies relevant aspects of cross-education including neurophysiological, neuroanatomical, and methodological characteristics of the transfer phenomenon, and provides guidance on how to improve the quality and usability of future cross-education studies. [ABSTRACT FROM AUTHOR]

Coaches and athletes in elite sports are constantly seeking to use innovative and advanced training strategies to efficiently improve strength/power performance in already highly-trained individuals. In this regard, high-intensity conditioning contractions have become a popular means to induce acute improvements primarily in muscle contractile properties, which are supposed to translate to subsequent power performances. This performance-enhancing physiological mechanism has previously been called postactivation potentiation (PAP). However, in contrast to the traditional mechanistic understanding of PAP that is based on electrically-evoked twitch properties, an increasing number of studies used the term PAP while referring to acute performance enhancements, even if physiological measures of PAP were not directly assessed. In this current opinion article, we compare the two main approaches (i.e., mechanistic vs. performance) used in the literature to describe PAP effects. We additionally discuss potential misconceptions in the general use of the term PAP. Studies showed that mechanistic and performance-related PAP approaches have different characteristics in terms of the applied research field (basic vs. applied), effective conditioning contractions (e.g., stimulated vs. voluntary), verification (lab-based vs. field tests), effects (twitch peak force vs. maximal voluntary strength), occurrence (consistent vs. inconsistent), and time course (largest effect immediately after vs. ~ 7 min after the conditioning contraction). Moreover, cross-sectional studies revealed inconsistent and trivial-to-large-sized associations between selected measures of mechanistic (e.g., twitch peak force) vs. performance-related PAP approaches (e.g., jump height). In an attempt to avoid misconceptions related to the two different PAP approaches, we propose to use two different terms. Postactivation potentiation should only be used to indicate the increase in muscular force/torque production during an electrically-evoked twitch. In contrast, postactivation performance enhancement (PAPE) should be used to refer to the enhancement of measures of maximal strength, power, and speed following conditioning contractions. The implementation of this terminology would help to better differentiate between mechanistic and performance-related PAP approaches. This is important from a physiological point of view, but also when it comes to aggregating findings from PAP studies, e.g., in the form of meta-analyses, and translating these findings to the field of strength and conditioning. [ABSTRACT FROM AUTHOR]

Background: Change-of-direction (CoD) speed is a physical fitness attribute in many field-based team and individual sports. To date, no systematic review with meta-analysis available has examined the effects of resistance training (RT) on CoD speed in youth and adults. Objective: To aggregate the effects of RT on CoD speed in youth and young physically active and athletic adults, and to identify the key RT programme variables for training prescription. Data sources: A systematic literature search was conducted with PubMed, Web of Science, and Google Scholar, with no date restrictions, up to October 2019, to identify studies related to the effects of RT on CoD speed. Study Eligibility Criteria: Only controlled studies with baseline and follow-up measures were included if they examined the effects of RT (i.e., muscle actions against external resistances) on CoD speed in healthy youth (8–18 years) and young physically active/athletic male or female adults (19–28 years). Study Appraisal and Synthesis Methods: A random-effects model was used to calculate weighted standardised mean differences (SMD) between intervention and control groups. In addition, an independent single training factor analysis (i.e., RT frequency, intensity, volume) was undertaken. Further, to verify if any RT variable moderated effects on CoD speed, a multivariate random-effects meta-regression was conducted. The methodological quality of the included studies was assessed using the physiotherapy evidence database (PEDro) scale. Results: Fifteen studies, comprising 19 experimental groups, were included. The methodological quality of the studies was acceptable with a median PEDro score of 6. There was a significant large effect size of RT on CoD speed across all studies (SMD = − 0.82 [− 1.14 to − 0.49]). Subgroup analyses showed large effect sizes on CoD speed in males (SMD = − 0.95) contrasting with moderate improvements in females (SMD = − 0.60). There were large effect sizes on CoD speed in children (SMD = − 1.28) and adolescents (SMD = − 1.21) contrasting with moderate effects in adults (SMD = − 0.63). There was a moderate effect in elite athletes (SMD = − 0.69) contrasting with a large effect in subelite athletes (SMD = − 0.86). Differences between subgroups were not statistically significant. Similar improvements were observed regarding the effects of independently computed training variables. In terms of RT frequency, our results indicated that two sessions per week induced large effects on CoD speed (SMD = − 1.07) while programmes with three sessions resulted in moderate effects (SMD = − 0.53). For total training intervention duration, we observed large effects for ≤ 8 weeks (SMD = − 0.81) and > 8 weeks (SMD = − 0.85). For single session duration, we found large effects for ≤ 30 min and ≥ 45 min (both SMD = − 1.00). In terms of number of training sessions, we identified large effects for ≤ 16 sessions (SMD = − 0.83) and > 16 sessions (SMD = − 0.81). For training intensity, we found moderate effects for light-to-moderate (SMD = − 0.76) and vigorous-to-near maximal intensities (SMD = − 0.77). With regards to RT type, we observed large effects for free weights (SMD = − 0.99) and machine-based training (SMD = − 0.80). For combined free weights and machine-based training, moderate effects were identified (SMD = − 0.77). The meta-regression outcomes showed that none of the included training variables significantly predicted the effects of RT on CoD speed (R2 = 0.00). Conclusions: RT seems to be an effective means to improve CoD speed in youth and young physically active and athletic adults. Our findings indicate that the impact of RT on CoD speed may be more prominent in males than in females and in youth than in adults. Additionally, independently computed single factor analyses for different training variables showed that higher compared with lower RT intensities, frequencies, and volumes appear not to have an advantage on the magnitude of CoD speed improvements. In terms of RT type, similar improvements were observed following machine-based and free weights training. [ABSTRACT FROM AUTHOR]

Background: Running participation continues to increase. The ideal strike pattern during running is a controversial topic. Many coaches and therapists promote non-rearfoot strike (NRFS) running with a belief that it can treat and prevent injury, and improve running economy. Objective: The aims of this review were to synthesise the evidence comparing NRFS with rearfoot strike (RFS) running patterns in relation to injury and running economy (primary aim), and biomechanics (secondary aim). Design: Systematic review and meta-analysis. Consideration was given to within participant, between participant, retrospective, and prospective study designs. Data Sources: MEDLINE, EMBASE, CINAHL, and SPORTDiscus. Results: Fifty-three studies were included. Limited evidence indicated that NRFS running is retrospectively associated with lower reported rates of mild (standard mean difference (SMD), 95% CI 3.25, 2.37–4.12), moderate (3.65, 2.71–4.59) and severe (0.93, 0.32–1.55) repetitive stress injury. Studies prospectively comparing injury risk between strike patterns are lacking. Limited evidence indicated that running economy did not differ between habitual RFS and habitual NRFS runners at slow (10.8–11.0 km/h), moderate (12.6–13.5 km/h), and fast (14.0–15.0 km/h) speeds, and was reduced in the immediate term when an NRFS-running pattern was imposed on habitual RFS runners at slow (10.8 km/h; SMD = − 1.67, − 2.82 to − 0.52) and moderate (12.6 km/h; − 1.26, − 2.42 to − 0.10) speeds. Key biomechanical findings, consistently including both comparison between habitual strike patterns and following immediate transition from RFS to NRFS running, indicated that NRFS running was associated with lower average and peak vertical loading rate (limited-moderate evidence; SMDs = 0.72–2.15); lower knee flexion range of motion (moderate-strong evidence; SMDs = 0.76–0.88); reduced patellofemoral joint stress (limited evidence; SMDs = 0.63–0.68); and greater peak internal ankle plantar flexor moment (limited evidence; SMDs = 0.73–1.33). Conclusion: The relationship between strike pattern and injury risk could not be determined, as current evidence is limited to retrospective findings. Considering the lack of evidence to support any improvements in running economy, combined with the associated shift in loading profile (i.e., greater ankle and plantarflexor loading) found in this review, changing strike pattern cannot be recommended for an uninjured RFS runner. PROSPERO Registration: CRD42015024523. [ABSTRACT FROM AUTHOR]

Background: Treadmills are often used in research, clinical practice, and training. Biomechanical investigations comparing treadmill and overground running report inconsistent findings. Objective: This study aimed at comparing biomechanical outcomes between motorized treadmill and overground running. Methods: Four databases were searched until June 2019. Crossover design studies comparing lower limb biomechanics during non-inclined, non-cushioned, quasi-constant-velocity motorized treadmill running with overground running in healthy humans (18–65 years) and written in English were included. Meta-analyses and meta-regressions were performed where possible. Results: 33 studies (n = 494 participants) were included. Most outcomes did not differ between running conditions. However, during treadmill running, sagittal foot–ground angle at footstrike (mean difference (MD) − 9.8° [95% confidence interval: − 13.1 to − 6.6]; low GRADE evidence), knee flexion range of motion from footstrike to peak during stance (MD 6.3° [4.5 to 8.2]; low), vertical displacement center of mass/pelvis (MD − 1.5 cm [− 2.7 to − 0.8]; low), and peak propulsive force (MD − 0.04 body weights [− 0.06 to − 0.02]; very low) were lower, while contact time (MD 5.0 ms [0.5 to 9.5]; low), knee flexion at footstrike (MD − 2.3° [− 3.6 to − 1.1]; low), and ankle sagittal plane internal joint moment (MD − 0.4 Nm/kg [− 0.7 to − 0.2]; low) were longer/higher, when pooled across overground surfaces. Conflicting findings were reported for amplitude of muscle activity. Conclusions: Spatiotemporal, kinematic, kinetic, muscle activity, and muscle–tendon outcome measures are largely comparable between motorized treadmill and overground running. Considerations should, however, particularly be given to sagittal plane kinematic differences at footstrike when extrapolating treadmill running biomechanics to overground running. Protocol registration CRD42018083906 (PROSPERO International Prospective Register of Systematic Reviews). [ABSTRACT FROM AUTHOR]

There has been a move towards a criterion-based return to play in recent years, with 4 single-leg hop tests commonly used to assess functional performance. Despite their widespread integration, research indicates that relationships between 'passing' 'hop test criteria and successful outcomes following rehabilitation are equivocal, and, therefore, require further investigation. This critical review includes key information to examine the evolution of these tests, their reliability, relationships with other constructs, and sensitivity to change over time. Recommendations for how measurement and administration of the tests can be improved are also discussed. The evidence presented in this review shows that hop tests display good reliability and are sensitive to change over time. However, the use of more than 2 hop tests does not appear to be necessary due to high collinearity and no greater sensitivity to detect abnormality. The inclusion of other hop tests in different planes may give greater information about the current function of the knee, particularly when measured over time using both relative and absolute measures of performance. It is recommended that the contralateral limb be tested prior to surgery for a more relevant benchmark for performance, and clinicians are strongly advised to measure movement quality, as hop distance alone appears to overestimate the recovery of the knee. [ABSTRACT FROM AUTHOR]

Background: Performance analysis research in association football has recently cusped a paradigmatic shift in the way tactical behaviours are studied. Based on insights from system complexity research, a growing number of studies now analyse tactical behaviours in football based on the collective movements of team players. Objective: The aim of this systematic review is to provide a summary of empirical research on collective tactical behaviours in football, with a particular focus on organising the methods used and their key findings. Methods: A systematic search of relevant English-language articles was performed on one database (Web of Science Core Collection) and one search engine (PubMed), based on PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-analyses) guidelines. The keywords 'football' and 'soccer' were each paired with all possible combinations of the following keywords: 'collective movement behaviour', 'collective behaviour', 'tactical behaviour', 'interpersonal coordination', 'space', 'Voronoi', 'synchronisation', 'tactical analysis', 'constraints', 'ecological dynamics', and 'dynamic positioning'. Empirical studies that were related to tactical analyses of footballers' positional data were sought for inclusion and analysis. Results: Full-text articles of 77 studies were reviewed. A total of 27 tactical variables were identified, which were subsequently organised into 6 categories. In addition to conventional methods of linear analysis, 11 methods of nonlinear analysis were also used, which can be organised into measures of predictability (4 methods) and synchronisation (7 methods). The key findings of the reviewed studies were organised into two themes: levels of analysis, and levels of expertise. Conclusions: Some trends in key findings revealed the following collective behaviours as possible indicators of better tactical expertise: higher movement regularity; wider dispersion in youth players and shorter readjustment delay between teammates and opponents. Characteristic behaviours were also observed as an effect of playing position, numerical inequality, and task constraints. Future research should focus on contextualising positional data, incorporating the needs of coaching staff, to better bridge the research-practice gap. [ABSTRACT FROM AUTHOR]

Background: Concurrent strength and endurance (CSE) training improves distance running performance more than endurance training alone, but the mechanisms underpinning this phenomenon are unclear. It has been hypothesised that biomechanical or neuromuscular adaptations are responsible for improvements in running performance; however, evidence on this topic has not been synthesised in a review. Objective: To evaluate the effect of CSE training on biomechanical and neuromuscular variables in distance runners. Methods: Seven electronic databases were searched from inception to November 2018 using key terms related to running and strength training. Studies were included if the following criteria were met: (1) population: 'distance' or 'endurance' runners of any training status; (2) intervention: CSE training; (3) comparator: running-only control group; (4) outcomes: at least one biomechanical or neuromuscular variable; and, (5) study design: randomised and non-randomised comparative training studies. Biomechanical and neuromuscular variables of interest included: (1) kinematic, kinetic or electromyography outcome measures captured during running; (2) lower body muscle force, strength or power outcome measures; and (3) lower body muscle–tendon stiffness outcome measures. Methodological quality and risk of bias for each study were assessed using the PEDro scale. The level of evidence for each variable was categorised according to the quantity and PEDro rating of the included studies. Between-group standardised mean differences (SMD) with 95% confidence intervals (95% CI) were calculated for studies and meta-analyses were performed to identify the pooled effect of CSE training on biomechanical and neuromuscular variables. Results: The search resulted in 1578 potentially relevant articles, of which 25 met the inclusion criteria and were included. There was strong evidence that CSE training significantly increased knee flexion (SMD 0.89 [95% CI 0.48, 1.30], p < 0.001), ankle plantarflexion (SMD 0.74 [95% CI 0.21–1.26], p = 0.006) and squat (SMD 0.63 [95% CI 0.13, 1.12], p = 0.010) strength, but not jump height, more than endurance training alone. Moderate evidence also showed that CSE training significantly increased knee extension strength (SMD 0.69 [95% CI 0.29, 1.09], p < 0.001) more than endurance training alone. There was very limited evidence reporting changes in stride parameters and no studies examined changes in biomechanical and neuromuscular variables during running. Conclusions: Concurrent strength and endurance training improves the force-generating capacity of the ankle plantarflexors, quadriceps, hamstrings and gluteal muscles. These muscles support and propel the centre of mass and accelerate the leg during running, but there is no evidence to suggest these adaptations transfer from strength exercises to running. There is a need for research that investigates changes in biomechanical and neuromuscular variables during running to elucidate the effect of CSE training on run performance in distance runners. [ABSTRACT FROM AUTHOR]

Background: The external movement loads imposed on players during competitive team sports are commonly measured using global positioning system devices. Information gleaned from analyses is employed to calibrate physical conditioning and injury prevention strategies with the external loads imposed during match play. Intense accelerations and decelerations are considered particularly important indicators of external load. However, to date, no prior meta-analysis has compared high and very high intensity acceleration and deceleration demands in elite team sports during competitive match play. Objective: The objective of this systematic review and meta-analysis was to quantify and compare high and very high intensity acceleration vs. deceleration demands occurring during competitive match play in elite team sport contexts. Methods: A systematic review of four electronic databases (CINAHL, MEDLINE, SPORTDiscus, Web of Science) was conducted to identify peer-reviewed articles published between January 2010 and April 2018 that had reported higher intensity (> 2.5 m·s−2) accelerations and decelerations concurrently in elite team sports competitive match play. A Boolean search phrase was developed using key words synonymous to team sports (population), acceleration and deceleration (comparators) and match play (outcome). Articles only eligible for meta-analysis were those that reported either or both high (> 2.5 m·s−2) and very high (> 3.5 m·s−2) intensity accelerations and decelerations concurrently using global positioning system devices (sampling rate: ≥ 5 Hz) during elite able-bodied (mean age: ≥ 18 years) team sports competitive match play (match time: ≥ 75%). Separate inverse random-effects meta-analyses were conducted to compare: (1) standardised mean differences (SMDs) in the frequency of high and very high intensity accelerations and decelerations occurring during match play, and (2) SMDs of temporal changes in high and very high intensity accelerations and decelerations across first and second half periods of match play. Using recent guidelines recommended for the collection, processing and reporting of global positioning system data, a checklist was produced to help inform a judgement about the methodological limitations (risk of detection bias) aligned to 'data collection', 'data processing' and 'normative profile' for each eligible study. For each study, each outcome was rated as either 'low', 'unclear' or 'high' risk of bias. Results: A total of 19 studies met the eligibility criteria, comprising seven team sports including American Football (n = 1), Australian Football (n = 2), hockey (n = 1), rugby league (n = 4), rugby sevens (n = 3), rugby union (n = 2) and soccer (n = 6) with a total of 469 male participants (mean age: 18–29 years). Analysis showed only American Football reported a greater frequency of high (SMD = 1.26; 95% confidence interval [CI] 1.06–1.43) and very high (SMD = 0.19; 95% CI − 0.42 to 0.80) intensity accelerations compared to decelerations. All other sports had a greater frequency of high and very high intensity decelerations compared to accelerations, with soccer demonstrating the greatest difference for both the high (SMD = − 1.74; 95% CI − 1.28 to − 2.21) and very high (SMD = − 3.19; 95% CI − 2.05 to − 4.33) intensity categories. When examining the temporal changes from the first to the second half periods of match play, there was a small decrease in both the frequency of high and very high intensity accelerations (SMD = 0.50 and 0.49, respectively) and decelerations (SMD = 0.42 and 0.46, respectively). The greatest risk of bias (40% 'high' risk of bias) observed across studies was in the 'data collection' procedures. The lowest risk of bias (35% 'low' risk of bias) was found in the development of a 'normative profile'. Conclusions: To ensure that elite players are optimally prepared for the high-intensity accelerations and decelerations imposed during competitive match play, it is imperative that players are exposed to comparable demands under controlled training conditions. The results of this meta-analysis, accordingly, can inform practical training designs. Finally, guidelines and recommendations for conducting future research, using global positioning system devices, are suggested. [ABSTRACT FROM AUTHOR]

Background: Sensor devices have enabled estimations of head impact kinematics across contact sports. Objectives: To quantitatively report the magnitude (linear and rotational acceleration) and frequency of game-related head impacts recorded in male contact sports athletes. Methods: A systematic review was conducted in June 2017. Inclusion criteria were English-language in vivo studies published after 1990 with a study population of male athletes aged ≥ 16 years, in any sport, where athletes were instrumented with an accelerometer device for measuring head impacts. Study populations were not limited to players with a clinical diagnosis of concussion. Results: Twenty-one studies met the inclusion criteria with 12 conducted on American Football athletes. Six of these studies were included for meta-analysis. At a threshold of 10g, amateur rugby players sustained the most impacts per player per game (mean = 77, SD = 42), followed by amateur Australian Football (mean = 29, SD = 37) and collegiate lacrosse athletes (mean = 11.5, SD = 3.6). At thresholds of greater than 14.4g, high school American Football athletes sustained between 19 (SD = 19.1) and 24.4 (SD = 22.4) impacts per player per game. Statistically significant heterogeneity was observed among the included studies, and meta-analysis of impact magnitude was limited. Conclusions: The frequency of "head acceleration events" was quantified and demonstrated substantial variation in methodology and reporting of results. Future research with standardised reporting of head impacts and inclusion of non-helmeted sports is warranted to enable more robust comparisons across sports. Prospero ID: CRD42017070065. [ABSTRACT FROM AUTHOR]

The start from blocks is a fundamental component of all track and field sprint events (≤ 400 m). This narrative review focusses on biomechanical aspects of the block phase and the subsequent first flight and stance phases. We discuss specific features of technique and how they may be important for a high level of performance during the start. The need to appropriately quantify performance is discussed first; external power has recently become more frequently adopted because it provides a single measure that appropriately accounts for the requirement to increase horizontal velocity as much as possible in as little time as possible. In the "set" position, a relatively wide range of body configurations are adopted by sprinters irrespective of their ability level, and between-sprinter differences in these general positions do not appear to be directly associated with block phase performance. Greater average force production during the push against the blocks, especially from the rear leg and particularly the hip, appears to be important for performance. Immediately after exiting the blocks, shorter first flight durations and longer first stance durations (allowing more time to generate propulsive force) are found in sprinters of a higher performance level. During the first stance phase, the ankle and knee both appear to play an important role in energy generation, and higher levels of performance may be associated with a stiffer ankle joint and the ability to extend the knee throughout stance. However, the role of the sprinter's body configuration at touchdown remains unclear, and the roles of strength and anatomy in these associations between technique and performance also remain largely unexplored. Other aspects such as the sex, age and performance level of the studied sprinters, as well as issues with measurement and comparisons with athletes with amputations, are also briefly considered. [ABSTRACT FROM AUTHOR]

Background: Running is a popular form of physical activity with many health benefits. However, the incidence and prevalence of running-related injuries (RRIs) is high. Biomechanical factors may be related to the development of RRIs. Objective: This systematic review synthesizes biomechanical risk factors related to the development of RRIs in non-injured runners. Methods: PubMed, Web of Science, CINAHL, Embase, and SPORTDiscus were searched in July 2018 for original peer-reviewed prospective studies evaluating potential biomechanical factors associated with the development of RRIs. Preferred Reporting Items for Systematic Reviews and Meta-Analyses guidelines were followed. Two reviewers independently assessed articles for inclusion and methodological quality. Due to methodological heterogeneity across studies, a narrative synthesis of findings was conducted, rather than a meta-analysis. Results: Sixteen studies, including 13 of high quality and three of moderate quality, were included. A large number of biomechanical variables were evaluated, producing inconsistent evidence overall. Limited evidence indicated greater peak hip adduction in female runners developing patellofemoral pain and iliotibial band syndrome, but not for a mixed-sex population of cross-country runners sustaining an RRI. The relationship between vertical loading rate and RRIs was inconsistent. Other kinematic, kinetic and spatiotemporal factors were only studied to a limited extent. Conclusions: Current prospective evidence relating biomechanical variables to RRI risk is sparse and inconsistent, with findings largely dependent on the population and injuries being studied. Future research is needed to confirm these biomechanical risk factors and determine whether modification of these variables may assist in running injury prevention and management. [ABSTRACT FROM AUTHOR]

Lower limb external maximal power output capacity is a key physical component of performance in many sports. During squat jump and countermovement jump tests, athletes produce high amounts of mechanical work over a short duration to displace their body mass (i.e. the dimension of mechanical power). Thus, jump height has been frequently used by the sports science and medicine communities as an indicator of the power output produced during the jump and by extension, of maximal power output capacity. However, in this article, we contend that squat jump and countermovement jump height are not systematically good indicators of power output produced during the jump and maximal power output capacity. To support our opinion, we first detail why, theoretically, jump height and maximal power output capacity are not fully related. Specifically, we demonstrate that individual body mass, push-off distance, optimal loading and the force-velocity profile confound the jump height–power relationship. We also discuss the relationship between squat jump or countermovement jump height and maximal power output capacity measured with a force plate based on data reported in the literature, which added to our own experimental evidence. Finally, we discuss the limitations of existing practical solutions (regression-based estimation equations and allometric scaling), and advocate using a valid, reliable and simple field-based procedure to compute individual power output produced during the jump and maximal power output capacity directly from jump height, body mass and push-off distance. The latter may allow researchers and practitioners to reduce bias in their assessment of lower limb mechanical power output by using jump height as an input with a simple yet accurate computation method, and not as the first/only variable of interest. [ABSTRACT FROM AUTHOR]

When assessing biomechanics in a laboratory setting, task selection is critical to the production of accurate and meaningful data. The injury biomechanics of landing is commonly investigated in a laboratory setting using a drop landing task. However, why this task is so frequently chosen is unclear. Therefore, this narrative review aimed to (1) identify the justification/s provided within the published literature as to why a drop landing task was selected to investigate the injury biomechanics of landing in sport and (2) use current research evidence, supplemented by a new set of biomechanical data, to evaluate whether the justifications are supported. To achieve this, a comprehensive literature search using Scopus, PubMed, and SPORTDiscus online databases was conducted for studies that had collected biomechanical data relating to sport injuries using a drop landing task. In addition, kinematic and kinetic data were collected from female netball players during drop landings and maximum-effort countermovement jumps from the ground to grab a suspended ball. The literature search returned a total of 149 articles that were reviewed to determine the justification for selecting a drop landing task. Of these, 54% provided no explicit justification to explain why a drop landing task was chosen, and 15% stated it was selected because it had been used in previous research. Other reasons included that the drop landing provides high experimental control (16%), is a functional sports task (11%), and is a dynamic task (6%). Evidence in the literature suggests that the biomechanical data produced with drop landings may not be as externally valid as more sport-specific tasks. Biomechanical data showed that the drop landing may not control center of mass fall height any better than maximum-effort countermovement jumps from the ground. Further, the frequently used step-off technique to initiate drop landings resulted in kinematic and kinetic asymmetries between lower limbs, which would otherwise be symmetrical when performing a countermovement jump from the ground. Researchers should consider the limitations of a drop landing task and endeavor to improve the laboratory tasks used to collect biomechanical data to examine the injury biomechanics of landing. [ABSTRACT FROM AUTHOR]

The article focuses on research examining if marathon runner Eliud Kipchoge could reduce his time running the Berlin, Germany marathon to under two hours by using cooperative drafting (CD). It states on September 16, 2018 he eclipsed the previous world record for the Berlin marathon by one minute, 18 seconds for a time of 2:01:39. It utilizes mathematical models to examine how CD would benefit running speed and found three Kipchoge-like-runners could together beat the two-hour marathon barrier.

Background: During a race, competing cyclists often cooperate by alternating between leading and drafting positions. This approach allows them to maximize velocity by using the energy saved while drafting, a technique to reduce the overall drag by exploiting the leader’s slipstream. We have argued that a similar cooperative drafting approach could benefit elite marathon runners in their quest for the sub-2-hour marathon.Objective: Our aim was to model the effects of various cooperative drafting scenarios on marathon performance by applying the critical velocity concept for intermittent high-intensity running.Methods: We used the physiological characteristics of the world’s most elite long-distance runners and mathematically simulated the depletion and recovery of their distance capacity when running above and below their critical velocity throughout a marathon.Results: Our simulations showed that with four of the most elite runners in the world, a 2:00:48 (h:min:s) marathon is possible, a whopping 2 min faster than the current world record. We also explored the possibility of a sub-2-hour marathon using multiple runners with the physiological characteristics of Eliud Kipchoge, arguably the best marathon runner of our time. We found that a team of eight Kipchoge-like runners could break the sub-2-hour marathon barrier.Conclusion: In the context of cooperative drafting, we show that the best team strategy for improving marathon performance time can be optimized using a mathematical model that is based on the physiological characteristics of each athlete. [ABSTRACT FROM AUTHOR]

Background: Head/neck dynamic response to perturbation has been proposed as a risk factor for sports-related concussion.Objectives: The aim of this systematic review was to compare methodologies utilised to assess head/neck dynamic response to perturbation, report on magnitude, validity and reliability of the response, and to describe modifying factors.Methods: A systematic search of databases resulted in 19 articles that met the inclusion and exclusion criteria.Results: Perturbation methods for head/neck dynamic response included load dropping, quick release and direct impact. Magnitudes of perturbation energy varied from 0.1 to 11.8 J. Head/neck response was reported as neck muscle latency (18.6-88.0 ms), neck stiffness (147.2-721.9 N/rad, 14-1145.3 Nm/rad) and head acceleration (0.2-3.8g). Reliability was only reported in two studies. Modifying factors for head/neck response included younger and older participants presenting increased responses, females showing better muscular reactivity but similar or increased head kinematics compared with males, and bracing for impact limiting muscular activity and head kinematics.Discussion: Substantial differences in experimental and reporting methodologies limited comparison of results. Methodological factors such as impact magnitude should be considered in future research.Conclusion: Each methodology provides valuable information but their validity for anticipated and unanticipated head impacts measured in vivo needs to be addressed. Reports on head/neck response should include measurement of transmitted force, neck muscle latency, head linear and rotational accelerations, and neck stiffness. Modifying factors of anticipation, participants’ age, sex, and sport are to be considered for head/neck dynamic response.PROSPERO Registration Number: CRD42016051057 (last updated on 27 February 2017). [ABSTRACT FROM AUTHOR]

Background: Quantifying the peak match demands within the football codes is useful for the appropriate prescription of external training load. Wearable microtechnology devices can be used to identify the peak match demands, although various methodologies exist at present.Objectives: This systematic review aimed to identify the methodologies and microtechnology-derived variables used to determine the peak match demands, and to summarise current data on the peak match demands in the football codes.Methods: A systematic search of electronic databases was performed from earliest record to May 2018; keywords relating to microtechnology, peak match demands and football codes were used.Results: Twenty-seven studies met the eligibility criteria. Six football codes were reported: rugby league (n = 7), rugby union (n = 5), rugby sevens (n = 4), soccer (n = 6), Australian Football (n = 2) and Gaelic Football (n = 3). Three methodologies were identified: moving averages, segmental and ‘ball in play’. The moving averages is the most commonly used (63%) and superior method, identifying higher peak demands than other methods. The most commonly used variables were relative distance covered (63%) and external load in specified speed zones (57%).Conclusion: This systematic review has identified moving averages to be the most appropriate method for identifying the peak match demands in the football codes. Practitioners and researchers should choose the most relevant duration-specific period and microtechnology-derived variable for their specific needs. The code specific peak match demands revealed can be used for the prescription of conditioning drills and training intensity. [ABSTRACT FROM AUTHOR]