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Abstract: Dawson, L, Beato, M, Devereux, G, and McErlain-Naylor, SA. A review of the validity and reliability of accelerometer-based metrics from upper back-mounted GNSS player tracking systems for athlete training load monitoring. J Strength Cond Res 38(8): e459-e474, 2024-Athlete load monitoring using upper back-mounted global navigation satellite system (GNSS) player tracking is common within many team sports. However, accelerometer-based load monitoring may provide information that cannot be achieved with GNSS alone. This review focuses on the accelerometer-based metrics quantifying the accumulation of accelerations as an estimation of athlete training load, appraising the validity and reliability of accelerometer use in upper back-mounted GNSS player tracking systems, the accelerometer-based metrics, and their potential for application within athlete monitoring. Reliability of GNSS-housed accelerometers and accelerometer-based metrics are dependent on the equipment model, signal processing methods, and the activity being monitored. Furthermore, GNSS unit placement on the upper back may be suboptimal for accelerometer-based estimation of mechanical load. Because there are currently no feasible gold standard comparisons for field-based whole-body biomechanical load, the validity of accelerometer-based load metrics has largely been considered in relation to other measures of training load and exercise intensity. In terms of convergent validity, accelerometer-based metrics (e.g., PlayerLoad, Dynamic Stress Load, Body Load) have correlated, albeit with varying magnitudes and certainty, with measures of internal physiological load, exercise intensity, total distance, collisions and impacts, fatigue, and injury risk and incidence. Currently, comparisons of these metrics should not be made between athletes because of mass or technique differences or between manufacturers because of processing variations. Notable areas for further study include the associations between accelerometer-based metrics and other parts of biomechanical load-adaptation pathways of interest, such as internal biomechanical loads or methods of manipulating these metrics through effective training design., (Copyright © 2024 National Strength and Conditioning Association.)

Abstract: Dawson, L, McErlain-Naylor, SA, Devereux, G, and Beato, M. Practitioner usage, applications, and understanding of wearable GPS and accelerometer technology in team sports. J Strength Cond Res 38(7): e373-e382, 2024-Monitoring training load is essential for optimizing the performance of athletes, allowing practitioners to assess training programs, monitor athlete progress, and minimize the risk of injury and overtraining. However, there is no universal method for training load monitoring, and the adoption of wearable global positioning system (GPS) and accelerometer technology in team sports has increased the volume of data and, therefore, the number of possible approaches. This survey investigated the usage, applications, and understanding of this technology by team sports practitioners. Seventy-two practitioners involved in team and athlete performance monitoring using GPS and accelerometer technology completed the survey. All respondents reported supporting the use of GPS technology in their sport, with 70.8% feeling that GPS technology is important for success. Results showed that 87.5% of respondents use data from wearable technology to inform training prescription, although only 50% use the data to influence decisions in competition. In addition, results showed that GPS metrics are used more than accelerometer-derived metrics; however, both are used regularly. Discrepancies in accelerometer usage highlighted concerns about practitioners' understanding of accelerometer-derived metrics. This survey gained insight into usage, application, understanding, practitioner needs, and concerns and criticisms surrounding the use of GPS and accelerometer metrics for athlete load monitoring. Such information can be used to improve the implementation of this technology in team sport monitoring and highlight gaps in the literature that will help to design future studies to support practitioner needs., (Copyright © 2024 National Strength and Conditioning Association.)

Introduction: Return to play related research is increasing rapidly, with two recent competency-based frameworks offering conceptualised support for on-field rehabilitation (OFR) decision-making. It is still unknown, however, who is responsible for OFR and how they typically select, monitor, and progress OFR processes., Aims: The purpose of this study was to investigate current OFR practice within English professional football to support practitioners with decision-making and highlight opportunities for future research related to the design, monitoring, and progression of OFR., Methods: Sixty-nine practitioners responsible for the design and implementation of OFR at 69 clubs (75% of the English Premier League and Football League) responded to a survey containing 30 questions (14 open and 16 closed)., Results: The main findings were that therapists (physiotherapists/sports therapists) have the largest influence on OFR, followed by physical performance coaches (sports scientists/strength and conditioning coaches), technical coaches and medical doctors. There was more agreement for the ordering of specific OFR drills earlier in the process when activities are easier to control. The most frequently reported objective monitoring tool was global positioning systems (GPS), with functional/clinical experience/expertise remaining subjectively vital. GPS outputs ( e.g ., sprint metrics and accelerations/decelerations) were most used for between session decision-making, with verbal communication being key for within session decision-making., Conclusion: Future research should use evidence of current practice, such as drill design and monitoring techniques, to explore drill-level analysis and give practitioners greater insights into which stage of current OFR frameworks specific drills fall, and how they might be more objectively progressed/regressed.

High amplitudes of shock during running have been thought to be associated with an increased injury risk. This study aimed to quantify the association between dual-energy X-ray absorptiometry (DEXA) quantified body composition, and shock attenuation across the time and frequency domains. Twenty-four active adults participated. A DEXA scan was performed to quantify the fat and fat-free mass of the whole-body, trunk, dominant leg, and viscera. Linear accelerations at the tibia, pelvis, and head were collected whilst participants ran on a treadmill at a fixed dimensionless speed 1.00 Fr. Shock attenuation indices in the time- and frequency-domain (lower frequencies: 3-8 Hz; higher frequencies: 9-20 Hz) were calculated. Pearson correlation analysis was performed for all combinations of DEXA and attenuation indices. Regularised regression was performed to predict shock attenuation indices using DEXA variables. A greater power attenuation between the head and pelvis within the higher frequency range was associated with a greater trunk fat-free mass (r = 0.411, p = 0.046), leg fat-free mass (r = 0.524, p = 0.009), and whole-body fat-free mass (r = 0.480, p = 0.018). For power attenuation of the high-frequency component between the pelvis and head, the strongest predictor was visceral fat mass (β = 48.79). Passive and active tissues could represent important anatomical factors aiding in shock attenuation during running. Depending on the type and location of these masses, an increase in mass may benefit injury risk reduction. Also, our findings could implicate the injury risk potential during weight loss programs., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier Ltd.. All rights reserved.)

Background: Flywheel resistance training has become more integrated within resistance training programs in a variety of sports due to the neuromuscular, strength, and task-specific enhancements reported with this training., Objective: This paper aimed to present the consensus reached by internationally recognized experts during a meeting on current definitions and guidelines for the implementation of flywheel resistance training technology in sports., Methods: Nineteen experts from different countries took part in the consensus process; 16 of them were present at the consensus meeting (18 May 2023) while three submitted their recommendations by e-mail. Prior to the meeting, evidence summaries were developed relating to areas of priority. This paper discusses the available evidence and consensus process from which recommendations were made regarding the appropriate use of flywheel resistance training technology in sports. The process to gain consensus had five steps: (1) performing a systematic review of systematic reviews, (2) updating the most recent umbrella review published on this topic, (3) first round discussion among a sample of the research group included in this consensus statement, (4) selection of research group members-process of the consensus meeting and formulation of the recommendations, and (5) the consensus process. The systematic analysis of the literature was performed to select the most up-to-date review papers available on the topic, which resulted in nine articles; their methodological quality was assessed according to AMSTAR 2 (Assessing the Methodological Quality of Systematic Review 2) and GRADE (Grading Recommendations Assessment Development and Evaluation). Statements and recommendations scoring 7-9 were considered appropriate., Results: The recommendations were based on the evidence summary and researchers' expertise; the consensus statement included three statements and seven recommendations for the use of flywheel resistance training technology. These statements and recommendations were anonymously voted on and qualitatively analyzed. The three statements reported a score ranging from 8.1 to 8.8, and therefore, all statements included in this consensus were considered appropriate. The recommendations (1-7) had a score ranging from 7.7 to 8.6, and therefore, all recommendations were considered appropriate., Conclusions: Because of the consensus achieved among the experts in this project, it is suggested that practitioners and researchers should adopt the guidelines reported in this consensus statement regarding the use of flywheel resistance technology in sports., (© 2024. The Author(s).)

E-textiles have emerged as a fast-growing area in wearable technology for sports and fitness due to the soft and comfortable nature of textile materials and the capability for smart functionality to be integrated into familiar sports clothing. This review paper presents the roles of wearable technologies in sport and fitness in monitoring movement and biosignals used to assess performance, reduce injury risk, and motivate training/exercise. The drivers of research in e-textiles are discussed after reviewing existing non-textile and textile-based commercial wearable products. Different sensing components/materials (e.g., inertial measurement units, electrodes for biosignals, piezoresistive sensors), manufacturing processes, and their applications in sports and fitness published in the literature were reviewed and discussed. Finally, the paper presents the current challenges of e-textiles to achieve practical applications at scale and future perspectives in e-textiles research and development.

The present study investigated the post-activation performance enhancement (PAPE) of isokinetic quadriceps and hamstrings torque after flywheel (FW)-squat vs. FW-deadlift in comparison to a control condition. Fifteen male athletes were enrolled in this randomised, crossover study. Each protocol consisted of 3 sets of 6 repetitions, with an inertial load of 0.029 kg . m 2 . Isokinetic quadriceps (knee extension) and hamstrings (knee flexion) concentric peak torque (60º/s) and hamstring eccentric peak torque (-60º/s) were measured 5 min after experimental or control conditions. A significant condition (PAPE) effect was reported ( f = 4.067, p = 0.008) for isokinetic hamstrings eccentric peak torque following FW-squat and FW-deadlift, but no significant differences were found for quadriceps and hamstrings concentric peak torques. The significant difference averaged 14 Nm between FW-squat vs. control (95% CI: 2, 28; d = 0.75, moderate ; p = 0.033), and 13 Nm between FW-deadlift vs. control (95% CI: 1, 25; d = 0.68, moderate ; p = 0.038). This study reported that both FW-squat and FW-deadlift exercises are equivalently capable of generating PAPE of isokinetic hamstrings eccentric torque. Practitioners may use these findings to inform strength and power development during complex training sessions consisting of flywheel-based exercises prior to a sport-specific task.

Purpose: This preregistered trial investigated how 6 weeks of unilateral flywheel leg-curl and hip-extension training impact isokinetic, isometric, and flywheel strength and power outcomes., Methods: The study involved 11 male university athletes (age 22 [2] y; body mass 77.2 [11.3] kg; height 1.74 [0.09] m) with one leg randomly allocated to flywheel training and one leg to control. Unilateral eccentric and isometric knee-flexion torque and flywheel unilateral leg-curl and hip-extension peak power were tested. Training intensity and volume (3-4 sets of 6 + 2 repetitions) were progressively increased., Results: The intervention enhanced hip-extension concentric (P < .01, d = 1.76, large) and eccentric (P < .01, d = 1.33, large) peak power more than the control (significant interaction effect). Similarly, eccentric (P = .023, d = 1.05, moderate) peak power was enhanced for the leg curl. No statistically significant differences between conditions were found for isokinetic eccentric (P = .086, d = 0.77, moderate) and isometric (P = .431, d = 0.36, small) knee-flexor strength or leg-curl concentric peak power (P = .339, d = 0.52, small). Statistical parametric mapping analysis of torque-angle curves also revealed no significant (P > .05) time-limb interaction effect at any joint angle., Conclusion: Unilateral flywheel hamstring training improved knee-flexor eccentric peak power during unilateral flywheel exercise but not flywheel concentric, isokinetic eccentric, or isometric (long-lever) knee-flexor strength.

Differences in workload exist between netball playing positions and competition levels, but no research has compared workloads experienced by the same elite players during national and international competitions. This study collected internal (heart rate) and external (PlayerLoad·min -1 ) workload data per match quarter from 44 players during a national competition and 12 players during an international competition. Nine players played in both competitions. Linear mixed models compared percentage of match quarter in each heart rate zone and PlayerLoad·min -1 between competitions for each playing position. Workloads against low- and high-ranked international opponents were also compared. Internal workloads were greater in national compared to international competition for GD and WD positions. PlayerLoad·min -1 was significantly higher by 8-13% in the national competition for positions WD and C, and by 5-8% in the international competition for GD and GA. Positional differences may indicate a role of the team's tactical style of play. Workloads were generally greater against higher- rather than lower-ranked international opponents. These results indicate that tactical factors in combination with playing position and opposition characteristics should be considered when preparing physically for matches.

Using an expert consensus-based approach, a netball video analysis consensus (NVAC) group of researchers and practitioners was formed to develop a video analysis framework of descriptors and definitions of physical, technical and contextual aspects for netball research. The framework aims to improve the consistency of language used within netball investigations. It also aims to guide injury mechanism reporting and identification of injury risk factors. The development of the framework involved a systematic review of the literature and a Delphi process. In conjunction with commercially used descriptors and definitions, 19 studies were used to create the initial framework of key descriptors and definitions in netball. In a two round Delphi method consensus, each expert rated their level of agreement with each of the descriptors and associated definition on a 5-point Likert scale (1-strongly disagree; 2-somewhat disagree; 3-neither agree nor disagree; 4-somewhat agree; 5-strongly agree). The median (IQR) rating of agreement was 5.0 (0.0), 5.0 (0.0) and 5.0 (0.0) for physical, technical and contextual aspects, respectively. The NVAC group recommends usage of the framework when conducting video analysis research in netball. The use of descriptors and definitions will be determined by the nature of the work and can be combined to incorporate further movements and actions used in netball. The framework can be linked with additional data, such as injury surveillance and microtechnology data., Competing Interests: Competing interests: LM is part-funded by England Netball. LL and JT are employed by England Netball. PB, KD, JK and JS work for England Netball through the English Institute of Sport. JC, FH, LL and SW are employed by Leeds Rhinos Netball. DCJvR is affiliated to World Netball. SAM-N is a Vitality Netball Superleague umpire., (© Author(s) (or their employer(s)) 2023. No commercial re-use. See rights and permissions. Published by BMJ.)

Background: It remains unknown if flywheel-assisted squats can be reliably utilized to increase power outputs and if such outputs are related., Objectives: To compare assisted and unassisted flywheel squat peak power outputs, determine their reliability, and analyze the relationship of the delta difference between peak power outputs during the squats., Methods: Twenty male athletes attended the laboratory 6 times-performing 3 sets of 8 repetitions of assisted and unassisted squats during 2 familiarization sessions and then 3 sets of 8 repetitions during experimental sessions 3 to 6 (2 sessions for unassisted and assisted squat in randomized order, respectively)., Results: Concentric and eccentric peak power were significantly greater during assisted squats (both P < .001, d = 1.59, d = 1.57, respectively). Rating of perceived exertion (P = .23) and eccentric:concentric ratio (P = .094) did not differ between squat conditions. Peak power measures obtained excellent reliability, while rating of perceived exertion and eccentric:concentric ratio estimates were rated as acceptable to good, with greater uncertainty. A large to very large correlation (r = .77) was found between concentric and eccentric peak power delta difference of assisted and unassisted squats., Conclusions: Greater concentric outputs during assisted squats induce greater eccentric outputs and obtain greater mechanical load. Peak power is a reliable metric for monitoring flywheel training, whereas the eccentric:concentric ratio should be used with caution. Eccentric and concentric peak power are strongly related during flywheel squats, evidencing the need to maximize the concentric output to enhance the eccentric output.

Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Jump take-off momentum has previously been proposed as an alternative test to predict sprint momentum. This study used a data simulation to replicate and systematically investigate relationships reported in previous studies between body mass, vertical jump performance, and sprint performance. Results were averaged for 1000 simulated data sets in each condition, and the effects of various parameters on correlations between jump momentum and sprint momentum were determined. The ability of jump take-off momentum to predict sprint momentum is greatest under relatively high inter-individual variation in body mass and relatively low inter-individual variation in jump height. This is largely due to the increased emphasis on body mass in these situations. Even under zero or a small negative ( r  = -0.30) correlation between jump height and sprint velocity, the correlation between the two momenta remained very large ( r  ≥ 0.76) on average. There were no investigated conditions under which jump momentum was most frequently a significantly ( p  < 0.05) greater predictor of sprint momentum compared to simply using body mass alone. Furthermore, between-individual correlations should not be used to make inferences or predictions for within-individual applications ( e.g. predicting or evaluating the effects of a longitudinal training intervention). It is recommended that any rationale for calculating and/or monitoring jump take-off momentum should be separate from its ability to predict sprint momentum. Indeed, body mass alone may be a better predictor of sprint momentum. Highlights This study replicated and systematically perturbed relationships reported in the literature to investigate factors contributing to correlations between jump momentum and sprint momentum.The ability of jump take-off momentum to predict sprint momentum is greatest under relatively high inter-individual variation in body mass and relatively low inter-individual variation in jump height. This is largely due to the increased emphasis on body mass in these situations.Even under zero or a small negative correlation between jump height and sprint velocity, the correlation between the two momenta remained very large on average. There were no investigated conditions under which jump momentum was a better predictor of sprint momentum compared to simply using body mass alone.It is recommended that any rationale for calculating and/or monitoring jump take-off momentum should be separate from its ability to predict sprint momentum. Indeed, body mass alone may be a better inter-individual predictor of sprint momentum if such a prediction were deemed necessary.

Growing evidence supports use of eccentric methods for strength development and injury prevention within elite soccer, yet uncertainty remains regarding practitioners' application of flywheel (isoinertial) methods. The aims of this study were to investigate how the flywheel training literature is perceived and applied by elite soccer practitioners, highlight gaps in knowledge and develop industry-relevant research questions. Fifty-one practitioners completed an electronic questionnaire. Fourteen Likert scale statements were grouped into topics: strength and performance; post-activation performance enhancement and methodological considerations; chronic strength; chronic performance; injury prevention. Three general questions followed, allowing more detail about flywheel training application. A Majority of the participants reported ≥ 2 years' experience of programming flywheel training. Nearly all participants agreed that familiarisation is needed. Practitioners agree that flywheel training can improve sport performance, strength and likelihood of non-contact injury outcomes. Most practitioners prescribe 2 weekly sessions during pre- and in-season periods. Flywheel sessions mostly consist of squats but a variety of exercises (lunge, hip hinge, and open kinetic chain) are also frequently included. Practitioners are mostly unsure about differences between flywheel and traditional resistance training equipment and outcomes, practicality of flywheel equipment, and evidence-based guidelines. The investigation provides valuable insight into the perspectives and application of flywheel training within elite soccer, highlighting its perceived efficacy for strength and injury prevention., (Copyright © Biology of Sport 2022.)

This study examined 503 power-hitting strokes that resulted in the maximum of 6-runs being scored in international men's one-day and T20 cricket. Chi-Squared analyses were conducted to determine if performance and situational variables were associated with the distribution (direction) of aerial power-hitting strokes. Results revealed that bowling length, bowling line, bowler type and powerplays were all significantly ( p < 0.001) associated with ball-hitting distribution. Post-hoc analysis of the standardised residuals revealed that greater than expected 6's were scored behind square and were associated with short-pitched bowling, fast bowling and the power-play. Similarly, bowling the half-volley length and the outside off line resulted in greater than expected 6's on the off-side. The results suggest that bowlers should try to avoid offering width outside the off stump as well as bowling the half-volley and short-pitched lengths as these bowling lines and lengths present batters with greater opportunities to score maximum runs. Fast bowling is revealed to be more susceptible to power-hitting strokes than spin bowling. Conversely, batters may wish to target the areas behind square or on the off-side for opportunities to score maximum runs, and they should look to take full advantage of the powerplay field restrictions.

The effect of load on time-series data has yet to be investigated during weightlifting derivatives. This study compared the effect of load on the force-time and velocity-time curves during the countermovement shrug (CMS). Twenty-nine males performed the CMS at relative loads of 40%, 60%, 80%, 100%, 120%, and 140% one repetition maximum (1RM) power clean (PC). A force plate measured the vertical ground reaction force (VGRF), which was used to calculate the barbell-lifter system velocity. Time-series data were normalized to 100% of the movement duration and assessed via statistical parametric mapping (SPM). SPM analysis showed greater negative velocity at heavier loads early in the unweighting phase (12-38% of the movement), and greater positive velocity at lower loads during the last 16% of the movement. Relative loads of 40% 1RM PC maximised propulsion velocity, whilst 140% 1RM maximized force. At higher loads, the braking and propulsive phases commence at an earlier percentage of the time-normalized movement, and the total absolute durations increase with load. It may be more appropriate to prescribe the CMS during a maximal strength mesocycle given the ability to use supramaximal loads. Future research should assess training at different loads on the effects of performance.

This study investigated the effect of flywheel moment of inertia (0.029, 0.061, and 0.089 kg·m 2 ) on concentric and eccentric peak power and eccentric:concentric peak power ratio during unilateral flywheel leg curl and hip extension exercises. Moreover, the inter-session reliability of peak power was analyzed during both exercises. Twenty amateur male soccer athletes attended five visits-performing three sets of eight repetitions of either unilateral leg curl or hip extension (all three moments of inertias) during each visit. For the unilateral leg curl, there were no differences in any measure between moments of inertia ( p = 0.479) but a higher eccentric than concentric peak power for all moments of inertia ( p < 0.001). For the unilateral hip extension, differences between moments of inertia were reported for all measures ( p < 0.05). Specifically, the lowest moment of inertia elicited the greatest concentric peak power ( p = 0.022), there were no differences with the medium inertia ( p = 0.391), and the greatest moment of inertia obtained the greatest eccentric peak power ( p = 0.036). Peak power measures obtained acceptable to excellent reliability while the eccentric:concentric ratio reported unacceptable to good reliability for both exercises. A variety of moments of inertia can elicit high eccentric knee flexor demands during unilateral leg curls, whereas higher moments of inertia are needed to achieve an eccentric-overload in peak power during hip extensions. Different exercises may have different inertia-power relationships. Concentric and eccentric peak power measures should continue to inform training, while the eccentric:concentric ratio should not be used., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2022 de Keijzer, McErlain-Naylor and Beato.)

Organismic, task, and environmental constraints are known to differ between skilled male and female cricket batters during power hitting tasks. Despite these influences, the techniques used in such tasks have only been investigated in male cricket batters. This study compared power hitting kinematics between 15 male and 15 female batters ranging from university to international standard. General linear models were used to assess the effect of gender on kinematic parameters describing technique, with height and body mass as covariates. Male batters generated greater maximum bat speeds, ball launch speeds, and ball carry distances than female batters on average. Male batters had greater pelvis-thorax separation in the transverse plane at the commencement of the downswing (β = 1.14; p = 0.030) and extended their lead elbows more during the downswing (β = 1.28; p = 0.008) compared to female batters. The hypothesised effect of gender on the magnitude of wrist uncocking during the downswing was not observed (β = -0.14; p = 0.819). The causes of these differences are likely to be multi-factorial, involving aspects relating to the individual players, their history of training experiences and coaching practices, and the task of power hitting in male or female cricket.

Abstract: Beato, M, De Keijzer, KL, Leskauskas, Z, Allen, WJ, Dello Iacono, A, and McErlain-Naylor, SA. Effect of postactivation potentiation after medium vs. high inertia eccentric overload exercise on standing long jump, countermovement jump, and change of direction performance. J Strength Cond Res 35(9): 2616-2621, 2021-This study aimed to evaluate the postactivation potentiation (PAP) effects of an eccentric overload (EOL) exercise on vertical and horizontal jumps and change of direction (COD) performance. Twelve healthy physically active male subjects were involved in a crossover study. The subjects performed 3 sets of 6 repetitions of EOL half squats for maximal power using a flywheel ergometer. Postactivation potentiation using an EOL exercise was compared between a medium (M-EOL) vs. high inertia (H-EOL) experimental condition. Long jump (LJ) was recorded at 30 seconds, 3, and 6 minutes after both EOL exercises and compared with baseline values (control). The same procedure was used to assess countermovement jump (CMJ) height and peak power and 5-m COD test (COD-5m). A fully Bayesian statistical approach to provide probabilistic statements was used in this study. Long jump performance reported improvements after M-EOL and H-EOL exercise (Bayes factor [BF10] = 32.7, strong; BF10 = 9.2, moderate), respectively. Countermovement jump height (BF10 = 135.6, extreme; BF10 > 200, extreme), CMJ peak power (BF10 > 200, extreme; BF10 = 56.1, very strong), and COD-5m (BF10 = 55.7, very strong; BF10 = 16.4, strong) reported improvements after M-EOL and H-EOL exercise, respectively. Between analysis did not report meaningful differences in performance between M-EOL and H-EOL exercises. The present outcomes highlight that PAP using an EOL (M-EOL and H-EOL) improves LJ, CMJ height, CMJ peak power, and COD-5m in male athletes. The optimal time window for the PAP effect was found for both EOL conditions from 3 to 6 minutes. However, M-EOL and H-EOL produce similar PAP effect on LJ, CMJ, and COD-5m tasks., (Copyright © 2019 National Strength and Conditioning Association.)

The aim of this study was to determine the inter-unit reliability of IMU Step biomechanical load monitoring metrics using IMeasureU Blue Trident inertial measurement units in tasks common to running-based team sports. Knowledge of variability between units is required before researchers and practitioners can make informed decisions on "true" differences between limbs. Sixteen male college soccer players performed five running-based tasks, generating 224 trials and 17,012 steps. Data were analysed for each task and for the whole session, investigating six IMU Step metrics: step count; impact load; bone stimulus; and low, medium and high intensity steps. Inter-unit reliability was excellent (ICC ≥ 0.90) for 21 out of 26 metrics, and good (0.83 ≤ ICC ≤ 0.86) for all other metrics except for Yo-Yo impact load (ICC = 0.79) which was acceptable . These findings confirm the inter-unit reliability of IMU Step metrics using IMeasureU Blue Trident inertial measurement units for running-based team sports. Now that inter-unit variability has been quantified, researchers and practitioners can use this information when interpreting inter-limb differences for monitoring external biomechanical training load.

The aim of this study was to evaluate the effects of varying flywheel inertia on velocity and power during flywheel squats. Fifteen healthy physically active males performed 6 maximal effort flywheel half-squats at each of 0.029, 0.061, 0.089 and 0.121 kg·m 2 , with velocity recorded via 3D motion capture and power recorded via inbuilt transducer. Peak concentric velocity (χ2 = 37.9; p < 0.001), peak eccentric velocity (χ2 = 24.9; p < 0.001), mean concentric velocity ( F (3) = 52.7; p < 0.001) and mean eccentric velocity (χ2 = 16.8; p < 0.001) all tended to decrease with increases in flywheel inertia, whereas the ratio of peak eccentric to peak concentric power ( F (3) = 4.26; p = 0.010) tended to increase. Flywheel inertia had no significant effect on peak concentric or eccentric power, or the ratio of eccentric to concentric peak or mean velocities. The best fit subject-specific inertia-velocity relationships were reported for peak concentric velocity (median linear R 2  = 0.95, median logarithmic R 2  = 0.97). The results suggest that velocity, rather than power, should be used to prescribe and monitor flywheel squat exercise intensities, and that individualized linear relationships between inertia and peak concentric velocity can be used for this purpose.

The purpose of this study was to quantify the magnitude and frequency content of surface-measured accelerations at each major human body segment from foot to head during impact landings. Twelve males performed two single leg drop landings from each of 0.15 m, 0.30 m, and 0.45 m. Triaxial accelerometers (2000 Hz) were positioned over the: first metatarsophalangeal joint; distal anteromedial tibia; superior to the medial femoral condyle; L5 vertebra; and C6 vertebra. Analysis of acceleration signal power spectral densities revealed two distinct components, 2-14 Hz and 14-58 Hz, which were assumed to correspond to time domain signal joint rotations and elastic wave tissue deformation, respectively. Between each accelerometer position from the metatarsophalangeal joint to the L5 vertebra, signals exhibited decreased peak acceleration, increased time to peak acceleration, and decreased power spectral density integral of both the 2-14 Hz and 14-58 Hz components, with no further attenuation beyond the L5 vertebra. This resulted in peak accelerations close to vital organs of less than 10% of those at the foot. Following landings from greater heights, peak accelerations measured distally were greater, as was attenuation prior to the L5 position. Active and passive mechanisms within the lower limb therefore contribute to progressive attenuation of accelerations, preventing excessive accelerations from reaching the torso and head, even when distal accelerations are large., Competing Interests: Declaration of Competing Interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2021 Elsevier Ltd. All rights reserved.)

(1) Background: The aim of the study was to determine the post-activation performance enhancement (PAPE) of vertical and horizontal ground reaction force parameters during jumps and change of direction following flywheel squat exercise using two different flywheel inertias. (2) Methods: Eleven male athletes performed a countermovement jump (CMJ), standing broad jump (SBJ), and "modified 505" change of direction (COD) in a control condition and 6 minutes following three sets of six repetitions of flywheel half squats at one of two inertias (0.029 kg·m 2 and 0.061 kg·m 2 ). Peak directional ground reaction force, power, and rate of force development were calculated for each test. (3) Results: Higher inertia flywheel squats were able to acutely enhance CMJ peak vertical force (Bayes Factor (BF 10 ) = 33.5, very strong ; δ = 1.66; CI: 0.67, 2.70), whereas lower inertia flywheel squats were able to acutely enhance CMJ peak vertical power (BF 10 = 3.65, moderate ; δ = 0.93; CI: 0.11, 1.88). The vertical squat exercise induced no PAPE effect on resultant SBJ or horizontal COD ground reaction force parameters, nor were any differences observed between the inertias. (4) Conclusions: Researchers and practitioners should consider the kinetic and kinematic correspondence of a pre-load stimulus to the subsequent sport-specific activity (i.e., flywheel squat to CMJ).

A logarithmic curve fitting methodology for the calculation of badminton racket-shuttlecock impact locations from three-dimensional motion capture data was presented and validated. Median absolute differences between calculated and measured impact locations were 3.6 [IQR: 4.4] and 3.5 [IQR: 3.5] mm mediolaterally and longitudinally on the racket face, respectively. Three-dimensional kinematic data of racket and shuttlecock were recorded for 2386 smashes performed by 65 international badminton players, with racket-shuttlecock impact location assessed against instantaneous post-impact shuttlecock speed and direction. Mediolateral and longitudinal impact locations explained 26.2% (quadratic regression; 95% credible interval: 23.1%, 29.2%; BF 10  = 1.3 × 10 131 , extreme ; p < 0.001) of the variation in participant-specific shuttlecock speed. A meaningful (BF 10  = ∞, extreme ; p < 0.001) linear relationship was observed between mediolateral impact location and shuttlecock horizontal direction relative to a line normal to the racket face at impact. Impact locations within one standard deviation of the pooled mean impact location predict reductions in post-impact shuttlecock speeds of up to 5.3% of the player's maximal speed and deviations in the horizontal direction of up to 2.9° relative to a line normal to the racket face. These results highlight the margin for error available to elite badminton players during the smash.

The aim of this study was to investigate student experiences of publishing undergraduate research in biomechanics. A total of 29 former students with experience of publishing peer-reviewed undergraduate biomechanics research completed an online survey regarding their perceived benefits, level of involvement, and experiences in aspects of the research process. On average, students perceived their experiences to be "largely helpful" or greater in all aspects. Areas were identified corresponding to: the greatest perceived benefits (eg, understanding of the research process); the least perceived benefits (eg, statistical analysis skills); the greatest student involvement (eg, reading relevant literature); and the least student involvement (eg, developing hypotheses and/or methods). A thematic analysis of open question responses identified themes relating to: future career, skills, scientific process, intra- and interpersonal factors, and pedagogy. Common intended learning outcomes may be achieved through involvement in the research process independently of the level of staff involvement. Staff should be encouraged to involve students in publishable biomechanics research projects where this is possible without compromising research standards and should explore ways of recreating the publishing process internally for all students.

To compare demands of national netball umpires between levels of competition, 22 Netball New Zealand high-performance umpires participated in this investigation. These included from highest to lowest standard: 9 × semi-professional ANZ Championships (ANZC); 6 × National A Squad (NZA); and 7 × National Development Squad (DEV). Physical (global positioning system tri-axial accelerometry), physiological (heart rate) and technical (video analysis) demands were determined for 48 (16 per group) umpire match performances. Level of competition had no significant effect on physical or mean physiological demands. However, ANZC umpires spent a lower proportion of time at low heart rates compared to DEV, and a greater proportion of time at high, rather than moderate, heart rates compared to NZA. Compared to lower standard umpires, ANZC spent lesser proportions of time standing but greater proportions of time walking backwards and sideways, and turning to change direction. Furthermore, ANZC umpires spent lower proportions of time jogging, but greater proportions of time sprinting compared to DEV. Finally, ANZC umpires spent longer mean durations than DEV on the goal third side line. As such, the difference in demands experienced by national netball umpires between levels of competition is more technical than physical or physiological.

Purpose: To investigate the postactivation potentiation (PAP) effects of different eccentric overload (EOL) exercise volumes on countermovement-jump (CMJ) and standing-long-jump (LJ) performance., Methods: In total, 13 male university soccer players participated in a crossover design study following a familiarization period. Control (no PAP) CMJ and LJ performances were recorded, and 3 experimental protocols were performed in a randomized order: 1, 2, or 3 sets of 6 repetitions of flywheel EOL half-squats (inertia = 0.029 kg·m2). Performance of CMJ and LJ was measured 3 and 6 minutes after all experimental conditions. The time course and magnitude of the PAP were compared between conditions., Results: Meaningful positive PAP effects were reported for CMJ after 2 (Bayes factor [BF10] = 3.15, moderate) and 3 (BF10 = 3.25, moderate) sets but not after 1 set (BF10 = 2.10, anecdotal). Meaningful positive PAP effects were reported for LJ after 2 (BF10 = 3.05, moderate) and 3 (BF10 = 3.44, moderate) sets but not after 1 set (BF10 = 0.53, anecdotal). The 2- and 3-set protocols resulted in meaningful positive PAP effects on both CMJ and LJ after 6 minutes but not after 3 minutes., Conclusion: This study reported beneficial effects of multiset EOL exercise over a single set. A minimum of 2 sets of flywheel EOL half-squats are required to induce PAP effects on CMJ and LJ performance of male university soccer players. Rest intervals of around 6 minutes (>3 min) are required to maximize the PAP effects via multiple sets of EOL exercise. However, further research is needed to clarify the optimal EOL protocol configurations for PAP response.

Purpose: To summarize the evidence on postactivation potentiation (PAP) protocols using flywheel eccentric overload (EOL) exercises., Methods: Studies were searched using the electronic databases PubMed, Scopus, and Institute for Scientific Information Web of Knowledge., Results: In total, 7 eligible studies were identified based on the following results: First, practitioners can use different inertia intensities (eg, 0.03-0.88 kg·m2), based on the exercise selected, to enhance sport-specific performance. Second, the PAP time window following EOL exercise seems to be consistent with traditional PAP literature, where acute fatigue is dominant in the early part of the recovery period (eg, 30 s), and PAP is dominant in the second part (eg, 3 and 6 min). Third, as EOL exercises require large force and power outputs, a volume of 3 sets with the conditioning activity (eg, half-squat or lunge) seems to be a sensible approach. This could reduce the transitory muscle fatigue and thereby allow for a stronger potentiation effect compared with larger exercise volumes. Fourth, athletes should gain experience by performing EOL exercises before using the tool as part of a PAP protocol (3 or 4 sessions of familiarization). Finally, the dimensions of common flywheel devices offer useful and practical solutions to induce PAP effects outside of normal training environments and prior to competitions., Conclusions: EOL exercise can be used to stimulate PAP responses to obtain performance advantages in various sports. However, future research is needed to determine which EOL exercise modalities among intensity, volume, and rest intervals optimally induce the PAP phenomenon and facilitate transfer effects on athletic performances.

The aim of this study was to evaluate the post-activation potentiation (PAP) effects following eccentric overload (EOL) and traditional weightlifting (TW) exercise on standing long jump (SLJ), countermovement jump (CMJ), and 5 m sprint acceleration performance. Ten male athletes were involved in a randomized, crossover study. The subjects performed 3 sets of 6 repetitions of EOL or TW half squat exercise followed by SLJ, CMJ, and 5 m sprint tests at 1 min, 3 min and 7 min, in separate sessions using a randomized order. Bayes factor (BF10) was reported to show the strength of the evidence. Differences were found using EOL for SLJ distance at 3 min (BF10 = 7.24, +8%), and 7 min (BF10 = 19.5, +7%), for CMJ at 3 min (BF10 = 3.25, +9%), and 7 min (BF10 = 4.12, +10.5%). Differences were found using TW exercise for SLJ at 3 min (BF10 = 3.88, +9%), and 7 min (BF10 = 12.4, +9%), CMJ at 3 min (BF10 = 7.42, +9.5%), and 7 min (BF10 = 12.4, +12%). No meaningful differences were found between EOL and TW exercises for SLJ (BF10 = 0.33), CMJ (BF10 = 0.27), and 5 m sprint (BF10 = 0.22). In conclusion, EOL and TW exercises acutely increase SLJ and CMJ, but not 5 m sprint performance. The PAP time window was found between 3 min and 7 min using both protocols. This study did not find differences between EOL and TW exercises, and so both methodologies can be used to stimulate a PAP response., Competing Interests: The authors have declared that no competing interests exist.

The ability of a batsman to clear the boundary is a major contributor to success in modern cricket. The aim of this study was to identify technique parameters characterising those batsmen able to generate greater bat speeds, ball launch speeds, and carry distances during a range hitting task in cricket. Kinematic data were collected for 20 batsmen ranging from international to club standard, and a series of ball launch, bat-ball impact, and technique parameters were calculated for each trial. A stepwise multiple linear regression analysis found impact location on the bat face in the medio-lateral and longitudinal directions and bat speed at impact to explain 68% of the observed variation in instantaneous post-impact ball speed. A further regression analysis found the X-factor (separation between the pelvis and thorax segments in the transverse plane) at the commencement of the downswing, lead elbow extension, and wrist uncocking during the downswing to explain 78% of the observed variation in maximum bat speed during the downswing. These findings indicate that players and coaches should focus on generating central impacts with the highest possible bat speed. Training and conditioning programmes should be developed to improve the important kinematic parameters shown to generate greater bat speeds, particularly focussing on increased pelvis to upper thorax separation in the transverse plane., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Three-dimensional kinematic data of bat and ball were recorded for 239 individual shots performed by twenty batsmen ranging from club to international standard. The impact location of the ball on the bat face was determined and assessed against the resultant instantaneous post-impact ball speed and measures of post-impact bat torsion and ball direction. Significant negative linear relationships were found between post-impact ball speed and the absolute distance of impact from the midline medio-laterally and sweetspot longitudinally. Significant cubic relationships were found between the distance of impact from the midline of the bat medio-laterally and both a measure of bat torsion and the post-impact ball direction. A "sweet region" on the bat face was identified whereby impacts within 2 cm of the sweetspot in the medio-lateral direction, and 4.5 cm in the longitudinal direction, caused reductions in ball speed of less than 6% from the optimal value, and deviations in ball direction of less than 10° from the intended target. This study provides a greater understanding of the margin for error afforded to batsmen, allowing researchers to assess shot success in more detail, and highlights the importance of players generating consistently central impact locations when hitting for optimal performance.