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The study aimed to establish the test-retest reliability of detrended fluctuation analysis of heart rate variability (DFA-α1) based exercise intensity thresholds, assess its agreement with ventilatory- and lactate-derived thresholds and the moderating effect of sex and cardiorespiratory fitness (CRF) on the agreement. Intensity thresholds for thirty-seven participants (17 females) based on blood lactate (LT 1 /LT 2 ), gas-exchange (VT 1 /VT 2 ) and DFA-α1 (αTh 1 /αTh 2 ) were assessed. Heart rate (HR) at αTh 1 and αTh 2 showed good test-retest reliability (coefficient of variation [CV] < 6%), and moderate to high agreement with LTs ( r  = 0.40 - 0.57) and VTs ( r  = 0.61 - 0.66) respectively. Mixed effects models indicated bias magnitude depended on CRF, with DFA-α1 overestimating thresholds versus VTs for lower fitness levels (speed at VT 1 <8.5 km⋅hr -1 ), while underestimating for higher fitness levels (speed at VT 2 >15 km⋅hr -1 ; VO 2max >55 mL·kg -1 ·min -1 ). Controlling for CRF, sex significantly affected bias magnitude only at first threshold, with males having higher mean bias (+2.41 bpm) than females (-1.26 bpm). DFA-α1 thresholds are practical and reliable intensity measures, however it is unclear if they accurately represent LTs/VTs from the observed limits of agreement and unexplained variance. To optimise DFA-α1 threshold estimation across different populations, bias should be corrected based on sex and CRF.

The aim was to assess concurrent validity and test-retest reliability of spatiotemporal gait parameters from a thoracic-placed inertial measurement unit (IMU) in lab- (Phase One) and field-based (Phase Two) conditions. Spatiotemporal gait parameters were compared (target speeds 3, 5 and 7.5 m·s -1 ) between a 100 Hz IMU and an optical measurement system (OptoJump Next, 1000 hz) in 14 trained individuals (Phase One). Additionally, 29 English Premier League football players performed weekly 3 × 60 m runs (5 m·s -1 ; observations = 1227; Phase Two). Mixed effects modelling assessed the effect of speed on agreement between systems (Phase One) and test-retest reliability (Phase Two). IMU step time showed strong agreement (<0.3%) regardless of individual or running speed. Direction of mean biases up to 40 ms for contact and flight time depended on the running speed and individual. Step time, length and frequency were most reliable (coefficient of variation = 1.3-1.4%) but confounded by running speed. Step time, length and frequency derived from a thoracic-placed IMU can be used confidently. Contact time could be used if bias is corrected for each individual. To optimise test-retest reliability, a minimum running distance of 40 m is needed to ensure 10 constant-speed steps is gathered.

The aims were to determine the relationship(s) between match-play external load and post-match neuromuscular fatigue as latent constructs, the contribution of the specific measured variables to these latent constructs, and how these differ between forwards and backs in elite rugby union. Forty-one elite male rugby union players (22 forwards and 19 backs) from the same international rugby union team were tested, with data included from the 2020 and 2021 international seasons (11 matches; 146 player appearances). Player's match-play external loads were quantified using microtechnology (for locomotor activities) and video analysis (for collision actions). Neuromuscular fatigue was quantified using countermovement jump tests on force plates which were conducted ~ 24 to 48 hours pre- and post-match. Partial least squares correlation (PLSC) leave one variable out (LOVO) procedure established the relative variable contribution to both external load ( X matrix) and neuromuscular fatigue ( Y matrix) constructs. Linear mixed-effects models were then constructed to determine the variance explained by the latent scores applied to the variables representing these constructs. For external load, both locomotor and collision variables were identified for the forwards and the backs, although the identified variables differed between groups. For neuromuscular fatigue, jump height was identified as a high contributor for the forwards and the backs, with concentric impulse and reactive strength index high contributors only for the backs. The explained variance between the external load and neuromuscular fatigue latent constructs at the individual player level was 4.4% and 32.2% in the forwards and the backs models, respectively. This discrepancy may be explained by differences in match-play external loads and/or the specificity of the tests to measure indicators of fatigue. These may differ due to, for example, the activities undertaken in the different positional groups.

The purpose of the study was to develop new knowledge about the everyday realities when implementing periodised training programmes in professional soccer Academies. Specifically, this project enhances understanding in relation to 1) those stakeholders involved in periodised training programmes in professional soccer Academies, 2) factors that facilitate and constrain the design, implementation, and monitoring of periodised programmes, 3) the extent to which practitioners perceive that education programmes adequately prepared them for this aspect of their work. Academy managers, coaches and sport science support staff were approached to complete an online survey, with 30 individuals (33.6 ± 9.5 years old) agreeing to do so. Findings highlight that practitioners "have" to adapt their practices accordingly in response to contextually constraining factors. Here, the importance of developing richer insights into the social aspects of work in applied settings, greater recognition of facilitating and constraining factors, and an improved awareness and development of the educational interventions that can prepare practitioners in applied practice is emphasised.

The purpose of this study was to assess whether dynamic torque ratios (DCR) from isokinetic strength assessments of eccentric knee flexors (eccKF) and concentric knee extensors (conKE) display differences when stratified into specific angle-specific DCR (DCR AST ) groups. Fifty-two professional female soccer players (age 21.30 ± 4.44 years; height 166.56 ± 5.17 cm; mass 61.55 ± 5.73 kg) from the English Women's Super League completed strength assessments of both lower limbs on an isokinetic dynamometer at 60°∙s -1. Angle-specific torque (AST) were used to calculate DCR AST to create sub-groups using clustering algorithms. The results identified for the dominant side that the Medium DCR AST group elicited significantly higher conKE AST when compared to Low and High DCR AST groups at increased knee extension ( P ≤ 0.05). For the non-dominant side, the High DCR AST group had significantly higher and lower eccKF and conKE AST compared to the Low DCR AST group at increased knee extension ( P ≤ 0.05). This study highlights that the inclusion of AST data may subsequently help practitioners to prescribe exercise that promotes strength increases at targeted joint angles. In turn, these approaches can be used to help reduce injury risk, identify rehabilitation responses and help inform return to play.

The purpose of the study was to (1) assess the training load experienced during pre-season and in-season meso-cycles within youth academy soccer players and (2) investigate the extent to which the intended periodized approach was implemented, considering those factors that affected its realization. An explanatory sequential mixed-method design comprising two phases was adopted. Phase 1 encompassed the quantitative analysis of training load data, using 10 Hz GPS, and consisted of 17 youth academy soccer players (age 17 ± 1 yrs; stature 179 ± 9 cm; body mass 72 ± 9 kg), from a professional English soccer academy. Phase 2 involved the collection of qualitative data in relation to the data collected in phase 1 of the study. Three semi-structured interviews were conducted with the lead strength and conditioning coach at the same academy, to gain his reflections on the data, its alignments with desired outcomes, and factors that impacted on the enactment of the periodized training programme. The results provide original information on the training load experienced within a youth soccer academy and novel insights into the complex realities of enacting periodized training programmes in practice.

This study investigated if basic need satisfaction and frustration mediated the associations between autonomy-supportive and controlling coaching behaviours and participants' development of eight different life skills in youth sport. British sports participants ( N = 309, M age = 14.71) completed measures assessing the study variables. Correlational analyses showed that autonomy-supportive coaching behaviours were positively associated with the satisfaction of participants' three basic needs (autonomy, competence, and relatedness) and their development of all eight life skills, whereas controlling coaching behaviours were only positively related to the frustration of participants' three basic needs. Mediational analyses revealed that satisfaction of all three basic needs combined (total need satisfaction) mediated the associations between autonomy-supportive coaching behaviours and participants' development of the eight life skills. Relatedness satisfaction mediated the associations between autonomy-supportive coaching behaviours and participants' development of all eight life skills except for goal setting; autonomy satisfaction mediated the associations between autonomy-supportive coaching behaviours and participants' time management skills; and competence satisfaction mediated the associations between autonomy-supportive coaching behaviours and participants' goal setting and emotional skills. Based on such findings, coaches should look to display autonomy-supportive behaviours that help to satisfy participants' three basic psychological needs and promote their life skills development in sport.

This study investigated the relationships between the coach, parent, and peer motivational climate and participants' life skills development in youth sport. In total, 308 participants ( M age  = 14.67, SD  = 2.20) completed a survey assessing the motivational climate (mastery and ego) and their life skills development in sport (teamwork, goal setting, social skills, emotional skills, problem solving and decision making, leadership, time management, and interpersonal communication). Multiple regression analyses found that a peer-created mastery-climate had the strongest positive associations with all eight life skills and total life skills. Coach and parent mastery-oriented climates were also positively related to five of the life skills and total life skills. A parent-created ego-climate had the strongest negative association with all life skills except for goal setting; whereas, a coach-created ego-climate was negatively related to three life skills and total life skills. Contrary to expectations, a peer-created ego-climate was positively associated with three life skills and total life skills. In practice, these novel results suggest that peers have the greatest positive influence on participants' life skills development in sport and all three social agents should be encouraged to create a mastery-climate to help promote participants' life skills development.

We examined associations between youth 24-hour activity behaviour compositions and mental health. Data were collected from 359 participants (aged 9-13 years). Activity behaviours (sleep, sedentary time (ST), light physical activity (LPA) and moderate-to-vigorous physical activity (MVPA)) were assessed using wrist-worn accelerometers. Questionnaires and a computerized cognitive test battery assessed mental health outcomes. Linear mixed models examined associations between activity behaviour compositions and mental health. Post-hoc analyses modelled the influence of reallocating fixed durations of time between activity behaviours on mental health. ST was associated with worse internalizing problems (all participants; p < 0.05) and poorer prosocial behaviour (primary school participants only; p < 0.05), relative to the other activity behaviours. LPA was associated with worse cognitive test scores among primary school participants; p < 0.05). For all participants, reallocating time to ST from sleep and MVPA was associated with higher internalizing problems. Among primary school participants, reallocating time to ST from any other behaviour was associated with poorer prosocial behaviour, and reallocating time to LPA from any other behaviour was associated with lower executive function. Children's mental health may be promoted by schools integrating opportunities for MVPA throughout the day. Our results provide further evidence for the influence of daily activity behaviours on youth mental health.

Ankle injuries are highly prevalent in ballet, with strength highlighted as a primary risk factor. To profile ankle strength, fourteen female ballet dancers (age: 19.29 ± 1.59 years) completed an isokinetic testing protocol comprising concentric eversion (CON EV ) and inversion (CON INV ), and, eccentric inversion (ECC INV ) trials at four angular velocities (30° · s -1 , 60° · s -1 , 90° · s -1 , 120° · s -1 ) for both the dominant and non-dominant limb. In addition to Peak Torque (PT) and the corresponding Dynamic Control Ratios (DCRs), angle-specific derivatives of strength (AST) and Functional Range (FR) were calculated. There was no evidence of any significant bilateral strength asymmetry (p = 0.90) across all metrics, and no significant interactions with limb and contraction mode or velocity. A significant main effect for contraction mode (p = 0.001) highlighted greater ECC INV strength - which was maintained with increasing isokinetic velocity - in contrast to reductions in CON EV and CON INV strength. Specifically, dancers are ECC INV dominant at angular velocities greater than 60° · s -1 , which is likely to be characteristic of most functional tasks. The lack of bilateral asymmetry may be attributed to dance training interventions that facilitate bilateral development, but ipsilateral mode and velocity-specific asymmetries have implications for injury risk and the training needs of female ballet dancers.

With potential implications for recovery and conditioning practices, the aim of this study was to assess the cumulative and residual response of angle specific eccentric knee flexor (eccKF) strength indices following soccer-specific activity. Thirteen semi-professional soccer players were therefore required to complete a 90-minute soccer-specific treadmill running. with eccKF isokinetic strength assessments completed pre-trial, immediately post-trial, and 48 hours post-trial. The strength assessments comprised the completion of 5 repetitions at angular velocities of 60 and 300 deg·s -1 . Isokinetic data was analysed for measures of peak torque (PT), angle of peak torque (APT), functional range (FR), and angle specific torque (AST). Significant post-trial impairments were observed for measures of slow velocity PT 60 (6.6%) and AST 300 (12.5%). Further significant differences were observed 48 hours post-trial for PT 300 (10.7%) and PT 60 (12.8%) PT, APT 60 (~15°), and AST 300 (>13.6%). These data have implications for post exercise recovery monitoring and the prescription of recovery modalities and conditioning practices in the 2 days following match-play. The AST and APT responses highlight the importance of analysis of the entire strength-angle curve and at a range of angular velocities.

This study aimed to assess the effect of playing surface (Natural [NT] and Artificial [AT] Turf) on the fatigue response to a soccer-specific exercise protocol (SSEP). Eighteen male soccer players completed the SSEP on NT and AT with pre-, post-, and 48 h post-assessments of eccentric knee flexor (eccKF) and concentric knee extensor peak torque (PT), peak countermovement (CMJ) and squat jump (SJ) height, and Nordic hamstring break angle. No significant main effects for surface or any surface and time interactions were observed for any of the outcome measures, except for eccKF PT recorded at 3.14 rad · s -1 , which was significantly lower 48 h post-trial in the AT condition (AT = 146.3 ± 20.4 Nm; NT = 158.8 ± 24.7 Nm). Main effects for time were observed between pre- and post-trial measures for eccKF PT at all angular velocities, Nordic break angle, CMJ and SJ height. Nordic break angle, and both CMJ and SJ height were significantly impaired 48 h post-trial when compared to pre-trial. The findings of the current study suggest surface dependent changes in eccKF PT which may have implications for recovery and subsequent performance after competition on AT.

The aim of this study was to assess the influence of a half-time (HT) re-warm up (RWU) strategy on measures of performance and the physical and perceptual response to soccer-specific activity. Ten male soccer players completed a control (CON) and RWU trial, in which participants completed 60 min (4 x 15-min periods with a 15-min HT interspersing the third and fourth periods) of a soccer-specific exercise protocol. The CON trial comprised a passive 15-min HT, whilst the RWU trial comprised a passive 12-min period, followed by a 3-min RWU. The RWU elicited an improvement in 20 m sprint times ( d = 0.6; CON: 3.42 ± 0.20 s; RWU: 3.32 ± 0.12 s), and both squat ( d = 0.6; CON: 26.96 ± 5.00 cm; RWU: 30.17 ± 5.13 cm) and countermovement jump height ( d = 0.7; CON: 28.15 ± 4.72 cm; RWU: 31.53 ± 5.43 cm) following the RWU and during the initial stages of the second half. No significant changes were identified for 5 m or 10 m sprint performance, perceived muscle soreness, or PlayerLoad TM . Ratings of perceived exertion were however higher (~2 a.u) following the RWU. These data support the use of a HT RWU intervention to elicit acute changes in performance.

This study aimed to investigate deprivation and sex differences in selected health-relatedfitness measures in 9-12-year-old children. Data were captured on 3,407 children (49.3% boys; aged 10.5 ± 0.6 years). Cardiorespiratory fitness(20 m multistage shuttle run test; 20 m MSRT), muscular strength (handgrip strength) and body mass index (BMI) were measured. Welsh Index of Multiple Deprivation (WIMD) scores were used to make quintile groups. A two-way Analysis of Variance examined differences in BMI z-score by sex and WIMD quintiles. Two-wayAnalysis of Covariances investigated the effect of sex and WIMD quintiles on grip strength and shuttles achieved in 20 m MSRT, adjusting for BMI z-score and maturation, repectively. Independent of sex, children in the middle quintile had a significantly higher mean BMI z-score ( p = 0.029) than their least deprived counterparts. There was a significant increase in grip strength ( p = 0.005) and20 m MSRT (boys p < 0.001; girls p = 0.028) between most and least deprived quintiles. Significant differences in 20 m MSRT score were more apparent with decreases in deprivation in boys.Overall, inequalities exist in health-related fitness by sex and deprivation. These results can be used to inform focused services to improve current and future health.

Average acceleration (AvAcc) and intensity gradient (IG) have been proposed as standardised metrics describing physical activity (PA) volume and intensity, respectively. We examined hypothesised between-group PA differences in AvAcc and IG, and their associations with health and well-being indicators in children. ActiGraph GT9X wrist accelerometers were worn for 24-h·d -1 over 7days by 145 children aged 9-10. Raw accelerations were averaged per 5-s epoch to represent AvAcc over 24-h. IG represented the relationship between log values for intensity and time. Moderate-to-vigorous PA (MVPA) was estimated using youth cutpoints. BMI z-scores, waist-to-height ratio (WHtR), peak oxygen uptake (VO 2 peak), Metabolic Syndrome risk (MetS score), and well-being were assessed cross-sectionally, and 8-weeks later. Hypothesised between-group differences were consistently observed for IG only (p < .001). AvAcc was strongly correlated with MVPA ( r = 0.96), while moderate correlations were observed between IG and MVPA ( r = 0.50) and AvAcc ( r = 0.54). IG was significantly associated with health indicators, independent of AvAcc ( p < .001). AvAcc was associated with well-being, independent of IG ( p < .05). IG was significantly associated with WHtR ( p < .01) and MetS score ( p < .05) at 8-weeks follow-up. IG is sensitive as a gauge of PA intensity that is independent of total PA volume, and which relates to important health indicators in children.

This study aimed to validate the Sedentary Sphere posture classification method from wrist-worn accelerometers in children. Twenty-seven 9-10-year-old children wore ActiGraph GT9X (AG) and GENEActiv (GA) accelerometers on both wrists, and activPAL on the thigh while completing prescribed activities: five sedentary activities, standing with a phone, walking (criterion for all 7: observation) and 10-min free-living play (criterion: activPAL). In an independent sample, 21 children wore AG and GA accelerometers on the non-dominant wrist and activPAL for two days of free-living. Per cent accuracy, pairwise 95% equivalence tests (±10% equivalence zone) and intra-class correlation coefficients (ICC) analyses were completed. Accuracy was similar, for prescribed activities irrespective of brand (non-dominant wrist: 77-78%; dominant wrist: 79%). Posture estimates were equivalent between wrists within brand (±6%, ICC > 0.81, lower 95% CI ≥ 0.75), between brands worn on the same wrist (±5%, ICC ≥ 0.84, lower 95% CI ≥ 0.80) and between brands worn on opposing wrists (±6%, ICC ≥ 0.78, lower 95% CI ≥ 0.72). Agreement with activPAL during free-living was 77%, but sedentary time was underestimated by 7% (GA) and 10% (AG). The Sedentary Sphere can be used to classify posture from wrist-worn AG and GA accelerometers for group-level estimates in children, but future work is needed to improve the algorithm for better individual-level results.

This study used accelerometer and self-report measures of overall sedentary time (ST) and screen time behaviours to examine their respective associations with adiposity among UK youth. Participants (Year groups 5, 8, and 10;  n =292, 148 girls) wore the SenseWear Armband Mini accelerometer for eight days and completed the Youth Activity Profile, an online report tool designed to estimate physical activity and ST.Stature, body mass and waist circumference were measured to classify adiposity outcomes (overweight/obese and central obesity). One-way between groups ANOVA and adjusted linear, logistic and multinomial logistic regression analyses were conducted. There was a significant main effect of age on total ST across the whole week ( F (2, 289)=41.64,  p ≤0.001). ST increased monotonically across Year 5 (581.09±107.81 min·d-¹), 8 (671.96±112.59 min·d-¹) and 10 (725.80±115.20 min·d-¹), and all pairwise comparisons were significant at  p ≤0.001. A steep age-related gradient to mobile phone use was present ( p ≤0.001). ST was positively associated with adiposity outcomes independent of moderate-to-vigorous intensity physical activity (MVPA;  p ≤0.001). Engaging in >3 hours of video gaming daily was positively associated with central obesity (OR=2.12,  p ≤0.05) but not after adjustment for MVPA. Results further demonstrate the importance of reducing overall ST to maintain healthy weight status among UK youth.

This study investigated the effects of two separate doses of sodium bicarbonate (NaHCO 3 ) on 4 km time trial (TT) cycling performance and post-exercise acid base balance recovery in hypoxia. Fourteen club-level cyclists completed four cycling TT's, followed by a 40 min passive recovery in normobaric hypoxic conditions (FiO 2  = 14.5%) following one of either: two doses of NaHCO 3 (0.2 g.kg -1 BM; SBC2, or 0.3 g.kg -1 BM; SBC3), a taste-matched placebo (0.07 g.kg -1 BM sodium chloride; PLA), or a control trial in a double-blind, randomized, repeated-measures and crossover design study. Compared to PLA, TT performance was improved following SBC2 (p = 0.04, g = 0.16, very likely beneficial), but was improved to a greater extent following SBC3 (p = 0.01, g = 0.24, very likely beneficial). Furthermore, a likely benefit of ingesting SBC3 over SBC2 was observed (p = 0.13, g =  0.10), although there was a large inter-individual variation. Both SBC treatments achieved full recovery within 40 min, which was not observed in either PLA or CON following the TT. In conclusion, NaHCO 3 improves 4 km TT performance and acid base balance recovery in acute moderate hypoxic conditions, however the optimal dose warrants an individual approach.

The aim of the current study was to investigate positional specific physical performance and external load responses to short term fixture congestion in English professional soccer. A total of 515 match observations were categorised as G1: the first game in a week with >4 days following a previous game, G2: the second game in a week played <4 days since G1, and G3: the third game in a week played with <4 days between each of the previous games. Global positioning system and accelerometer-based metrics were partitioned into fifteen-minute epochs. These data were then analysed using a linear mixed model to assess both the within and between game positional differences. Total, low-intensity (<4.0 m·s -1 ), medium-intensity (MID; 4.0-5.5 m·s -1 ), and sprint distance (>7.0 m·s -1 ) were significantly different across games. No between game positional differences were identified; however, within match position specific differences were observed for measures of MID and HID. No significant differences were evident for accelerometer derived metrics between games or across positions. The current data suggests that the use of fifteen minute within game epochs enables the detection of alterations in physical output during congested schedules. The observed within game positional differences has implications for player specific conditioning and squad rotation strategies.

Wrist-based accelerometers are now common in assessing physical activity (PA) and sedentary behaviour (SB) in population-based studies, but there is a scarcity of raw acceleration cutpoints in older adults. The study aimed to determine and evaluate wrist-based GENEActiv (GA) and hip-based ActiGraph GT3X+ (AG) raw acceleration cutpoints for SB and moderate-to-vigorous PA (MVPA) in older adults ≥60 years of age. A laboratory-based calibration analyses of 34 healthy older adults involved receiver operator characteristic (ROC) curves to determine raw acceleration cutpoints for SB and MVPA. ROC analysis revealed an area under the curve (AUC) of 0.88 for GA SB and MVPA, and 0.90 for AG SB and 0.94 for AG MVPA. Sensitivity optimised SB and specificity optimised MVPA GA cutpoints of 57 mg and 104 mg, and AG cutpoints of 15 mg and 69 mg were also generated, respectively. Cross-validation analysis revealed moderate agreement for GA and AG SB cutpoints, and fair to substantial agreement for GA and AG MVPA cutpoints, respectively. The resultant cutpoints can classify older adults as engaging in SB or not engaging in MVPA but the sensitivity optimised SB cutpoints should be interpreted with a degree of caution due to their modest cross-validation results.

This study investigated the relationships between parental behaviours and players' life skills development and enjoyment within youth soccer. In total, 317 players (Mage = 12.83, SD = 1.70, age range = 10-16 years) completed a survey assessing parental behaviours (praise and understanding, directive behaviour, and pressure), perceived life skills development (teamwork, goal setting, time management, emotional skills, interpersonal communication, social skills, leadership, and problem solving and decision making), and enjoyment of soccer. Multiple regression analyses found that praise and understanding was the key contributor to the outcome variables, making the largest unique contribution to teamwork, goal setting, leadership, and total life skills. Directive behaviour made the largest unique contribution to emotional skills, and problem solving and decision making; whereas pressure made the largest unique contribution to participants' time management and social skills. In practice, the results suggest that parents should display praise and understanding behaviours, which were the main contributor to players' development of life skills within soccer.

This randomised controlled trial investigated changes in eccentric hamstring strength, 10m sprint speed, and change-of-direction (COD) performance immediately post Nordic hamstring curl (NHC) intervention and following a 3-week detraining period. Fourteen male team sports athletes were randomised to a do-as-usual control group (CG; n = 7) or to a NHC intervention group (NHC; n = 7). Isokinetic dynamometry at 180°/s evaluated eccentric hamstring strength immediately post-intervention as the primary outcome measure. Secondary outcomes included 10 m sprint time and COD. Each outcome was measured, pre, immediately post-intervention and following a 3-week detraining period. Immediately post-intervention significant group differences were observed in the NHC group for eccentric hamstring strength (31.81 Nm -1 vs. 6.44 Nm -1 , P = 0.001), COD (-0.12 s vs. 0.20 s; P = 0.003) and sprint (- 0.06 s vs. 0.05 s; P = 0.024) performance. Performance improvements were maintained following a detraining period for COD (-0.11 s vs. 0.20 s; P = 0.014) and sprint (-0.05 s vs. 0.03 s, P = 0.031) but not eccentric hamstring strength (15.67 Nm -1 vs. 6.44 Nm -1 , P = 0.145) These findings have important implications for training programmes designed to reduce hamstring injury incidence, whilst enhancing physical qualities critical to sport.

This investigation assessed the effect of dietary nitrate (NO 3 - ) supplementation, in the form of beetroot juice (BR), on repeat-sprint performance in normoxia and normobaric hypoxia. 12 male team-sport athletes (age 22.3 ± 2.6 y, VO 2peak 53.1 ± 8.7 mL.kg -1 .min -1 ) completed three exercise trials involving a 10 min submaximal warm-up and 4 sets of cycling repeat-sprint efforts (RSE; 9 × 4 s) at sea level (CON), or at 3000 m simulated altitude following acute supplementation (140 mL) with BR (HYP BR ; 13 mmol NO 3 - ) or NO 3 - depleted BR placebo (HYP PLA ). Peak (PPO) and mean (MPO) power output, plus work decrement were recorded during the RSE task, while oxygen consumption (VO 2 ) was measured during the warm-up. There were no significant differences observed between HYP BR and HYP PLA for PPO or MPO; however, work decrement was reduced in the first RSE set in HYP BR compared with HYP PLA . There was a moderate effect for VO 2 to be lower following BR at the end of the 10 min warm-up (ES = 0.50 ± 0.51). Dietary NO 3 - may not improve repeat-sprint performance in hypoxia but may reduce VO 2 during submaximal exercise. Therefore, BR supplementation may be more effective for performance improvement during predominantly aerobic exercise.

The ability to compare published group-level estimates of objectively measured moderate-to-vigorous physical activity (MVPA) across studies continues to increase in difficulty. The objective of this study was to develop conversion equations and demonstrate their utility to compare estimates of MVPA derived from the wrist and hip. Three studies of youth (N = 232, 9-12yrs, 50% boys) concurrently wore a hip-worn ActiGraph and a wrist-worn GENEActiv for 7-days. ActiGraph hip count data were reduced using four established cutpoints. Wrist accelerations were reduced using the Hildebrand MVPA 200 mg threshold. Conversion equations were developed on a randomly selected subsample of 132 youth. Equations were cross-validated and absolute error, absolute percent error, and modified Bland-Altman plots were evaluated for conversion accuracy. Across equations R 2 adj was 0.51-0.56 with individual-level absolute error in minutes ranging from 7 (wrist-to-hip Puyau) to 14.5 minutes (wrist-to-hip Freedson 3MET) and absolute percent differences ranging from 13.9%-24.5%. Group-level cross-validation to convert hip-to-wrist MVPA resulted in average absolute percent errors ranging from 3.1%-4.9%. Conversion of wrist-to-hip MVPA resulted in average absolute percent errors ranging from 3.0%-10.0%. We recommend the use of these equations to compare published estimates of MVPA between the wear-site cut-point combinations presented.

The aim of this study was to investigate the effects of sodium bicarbonate (NaHCO 3 ) on 4 km cycling time trial (TT) performance when individualised to a predetermined time to peak blood bicarbonate (HCO 3 - ). Eleven male trained cyclists volunteered for this study (height 1.82 ± 0.80 m, body mass (BM) 86.4 ± 12.9 kg, age 32 ± 9 years, peak power output (PPO) 382 ± 22 W). Two trials were initially conducted to identify time to peak HCO 3 - following both 0.2 g . kg -1 BM (SBC2) and 0.3 g . kg -1 BM (SBC3) NaHCO 3 . Thereafter, on three separate occasions using a randomised, double-blind, crossover design, participants completed a 4 km TT following ingestion of either SBC2, SBC3, or a taste-matched placebo (PLA) containing 0.07 g . kg -1 BM sodium chloride (NaCl) at the predetermined individual time to peak HCO 3 - . Both SBC2 (-8.3 ± 3.5 s; p < 0.001, d = 0.64) and SBC3 (-8.6 ± 5.4 s; p = 0.003, d = 0.66) reduced the time to complete the 4 km TT, with no difference between SBC conditions (mean difference = 0.2 ± 0.2 s; p = 0.87, d = 0.02). These findings suggest trained cyclists may benefit from individualising NaHCO 3 ingestion to time to peak HCO 3 - to enhance 4 km TT performance.

This study compared children's physical activity (PA) levels, the prevalence of children meeting current guidelines of ≥60 minutes of daily moderate to vigorous PA (MVPA), and PA-health associations using individually calibrated (IC) and empirical accelerometer cutpoints. Data from 75 (n = 32 boys) 10-12 year old children were included in this study. Clustered cardiometabolic (CM) risk, directly measured cardiorespiratory fitness (CRF), anthropometric and 7 day accelerometer data were included within analysis. PA data were classified using Froude anchored IC, Evenson et al. (Evenson, K. R., Catellier, D. J., Gill, K., Ondrak, K. S., & McMurray, R. G. (2008). Calibration of two objective measures of physical activity for children. Journal of Sports Sciences, 26(14), 1557-1565. doi:10.1080/02640410802334196) (Ev) and Mackintosh et al. (Mackintosh, K. A., Fairclough, S. J., Stratton, G., & Ridgers, N. D. (2012). A calibration protocol for population-specific accelerometer cutpoints in children. PLoS One, 7(5), e36919. doi:10.1371/journal.pone.0036919) (Mack) cutpoints. The proportion of the cohort meeting ≥60mins MVPA/day ranged from 37%-56% depending on the cutpoints used. Reported PA differed significantly across the cutpoint sets. IC LPA and MPA were predictors of CRF (LPA: standardised β = 0.32, p = 0.002, MPA: standardised β = 0.27 p = 0.013). IC MPA also predicted BMI Z-score (standardised β = -0.35, p = 0.004). Ev VPA was a predictor of BMI Z-score (standardised β = -0.33, p = 0.012). Cutpoint choice has a substantial impact on reported PA levels though no significant associations with CM risk were observed. Froude IC cutpoints represent a promising approach towards classifying children's PA data.

The main aim of this study was to psychometrically test the Physical Education Predisposition Scale (PEPS) with a cohort of Australian students, to assess secondary school students' perceived PE ability and PE worth. Secondary aims were to explore how the two variables were related and to investigate age and gender differences. Altogether, 266 Year 7, 8, 9 and 10 students (aged 12-16 years), from four schools within the South Eastern region of Melbourne, completed the PEPS at both time points. Principal components analysis revealed the presence of a simple two-factor structure explaining 66.9% of the variance. Factor 1 (labelled perceived PE worth) reflected enjoyment and attitude (α = .91), and factor 2 (labelled perceived PE ability) represented perceptions of competence and self-efficacy (α = .92). Significant positive correlations were observed between the two factors (r = .50-.82, P < .001). Boys scored significantly higher than girls on perceived PE ability (P = .01), and year 7 students scored significantly higher compared to Year 9 students (P = .002). Our results support the potential of the PEPS as a concise measurement tool for use in the PE setting, for both teachers and researchers.

This study assessed children's physical activity (PA) levels derived from wrist-worn GENEActiv and hip-worn ActiGraph GT3X+ accelerometers and examined the comparability of PA levels between the two devices throughout the segmented week. One hundred and twenty-nine 9-10-year-old children (79 girls) wore a GENEActiv (GAwrist) and ActiGraph GT3X+ (AGhip) accelerometer on the left wrist and right hip, respectively, for 7 days. Mean minutes of light PA (LPA) and moderate-to-vigorous PA (MVPA) per weekday (whole-day, before-school, school and after-school) and weekend day (whole-day, morning and afternoon-evening) segments were calculated, and expressed as percentage of segment time. Repeated measures analysis of variance examined differences in LPA and MVPA between GAwrist and AGhip for each time segment. Bland-Altman plots assessed between-device agreement for LPA and MVPA for whole weekday and whole weekend day segments. Correlations between GAwrist and AGhip were weak for LPA (r = 0.18-0.28), but strong for MVPA (r = 0.80-0.86). LPA and MVPA levels during all weekday and weekend day segments were significantly higher for GAwrist than AGhip (p < 0.001). The largest inter-device percent difference of 26% was observed in LPA during the school day segment. Our data suggest that correction factors are needed to improve raw PA level comparability between GAwrist and AGhip.

A systematic observation method has been one of the most popularly employed methods in coaching research. Kahan's review of this method conducted between 1975 and 1997 highlighted the key trends in this research, and offered methodological guidance for researchers wishing to use this method in their research. The purpose of this review was to provide an update of the use of a systematic observation method in coaching research and assess the extent to which the calls made by Kahan have been addressed. While in some respect this field of study has progressed (i.e., the introduction of qualitative methods), researchers adopting this method have failed to attend to many of the issues Kahan raised. For this method to continue to make a positive contribution towards the coaching research literature, researchers need to more critically reflect on how and why they are employing this method. At present, some of the decisions made by researchers who have conducted work in this area are not justified with a rationale. It is our intention that this review will serve as guidance for researchers and practitioners, and editors and reviewers of journals when attempting to assess the quality of this type of work.

This study aims to assess fundamental movement skill (FMS) proficiency, physical self-confidence levels, and the relationship between these variables and gender differences among adolescents. Three hundred and ninety five adolescents aged 13.78 years (SD = ±1.2) from 20 schools were involved in this study. The Test of Gross Motor Development-2nd Edition (TGMD), TGMD-2 and Victorian Skills Manual were used to assess 15 FMS. Participants' physical self-confidence was also assessed using a valid skill-specific scale. A significant correlation was observed between FMS proficiency and physical self-confidence for females only (r = 0.305, P < 0.001). Males rated themselves as having significantly higher physical self-confidence levels than females (P = 0.001). Males scored significantly higher than females in FMS proficiency (P < 0.05), and the lowest physical self-confidence group were significantly less proficient at FMS than the medium (P < 0.001) and high physical self-confidence groups (P < 0.05). This information not only highlights those in need of assistance to develop their FMS but will also facilitate in the development of an intervention which aims to improve physical self-confidence and FMS proficiency.

This paper examines the video-based pedagogical practices of Terry (pseudonym), a head coach of a professional junior academy squad. Data were collected through 6 in-depth, semi-structured interviews and 10 field observations of Terry's video-based coaching in situ. Three embracing categories were generated from the data. These demonstrated that Terry's video-based coaching was far from apolitical. Rather, Terry strategically used performance analysis technologies to help fulfil various objectives and outcomes that he understood to be expected of him within the club environment. Kelchtermans' micropolitical perspective, Callero's work addressing role and Groom et al.'s grounded theory were primarily utilised to make sense of Terry's perceptions and actions. The findings point to the value of developing contextually grounded understandings of coaches' uses of video-based performance analysis technology. Doing so could better prepare coaches for this aspect of their coaching practice.

The effects of sodium phosphate and caffeine supplementation were assessed on repeated-sprint ability. Using a randomised, double-blind, Latin-square design, 12 female, team-sport players participated in four trials: (1) sodium phosphate and caffeine, (2) sodium phosphate and placebo (for caffeine), (3) caffeine and placebo (for sodium phosphate) and (4) placebo (for sodium phosphate and caffeine), with ~21 days separating each trial. After each trial, participants performed a simulated team-game circuit (4 × 15 min quarters) with 6 × 20-m repeated-sprints performed once before (Set 1), at half-time (Set 2), and after end (Set 3). Total sprint times were faster after sodium phosphate and caffeine supplementation compared with placebo (Set 1: P = 0.003; Set 2: d = -0.51; Set 3: P < 0.001; overall: P = 0.020), caffeine (Set 3: P = 0.004; overall: P = 0.033) and sodium phosphate (Set 3: d = -0.67). Furthermore, total sprint times were faster after sodium phosphate supplementation compared with placebo (Set 1: d = -0.52; Set 3: d = -0.58). Best sprint results were faster after sodium phosphate and caffeine supplementation compared with placebo (Set 3: P = 0.007, d = -0.90) and caffeine (Set 3: P = 0.024, d = -0.73). Best sprint times were also faster after sodium phosphate supplementation compared with placebo (d = -0.54 to -0.61 for all sets). Sodium phosphate and combined sodium phosphate and caffeine loading improved repeated-sprint ability.

The aim of the study was to investigate the behaviours, cognitive processes and practice activities of 12 English youth professional soccer coaches across 6 different age groups. Systematic observation data were collected using a modified version of the Coach Analysis and Intervention System which provided a detailed analysis of coaching behaviours performed during practice. Interpretive interviews were then triangulated with the behavioural data to identify the cognitive processes underlying the behaviours performed. The behavioural results showed that the coaches of the younger age groups used more instruction and the coaches of the older age groups used more divergent questioning and significantly more total feedback and punitive behaviours. The coaches of the younger age groups used more training form activities than the coaches of the older age groups who used more playing form activities. However, the interviews revealed that instead of the age of athletes' directly affecting the cognitive process of coaches it was in fact the coaches underlying beliefs about coaching, their previous experiences and perceived pressures from the context that determined the behaviours performed.

The use of portable urine osmometers is widespread, but no studies have assessed the validity of this measurement technique. Furthermore, it is unclear what effect freezing has on osmolality. One-hundred participants of mean (±SD) age 25.1 ± 7.6 years, height 1.77 ± 0.1 m and weight 77.1 ± 10.8 kg provided single urine samples that were analysed using freeze point depression (FPD) and refractometry (RI). Samples were then frozen at -80°C (n = 81) and thawed prior to re-analysis. Differences between methods and freezing were determined using Wilcoxon's signed rank test. Relationships between measurements were assessed using intraclass correlation coefficients (ICC) and typical error of estimate (TE). Osmolality was lower (P = 0.001) using RI (634.2 ± 339.8 mOsm · kgH2O(-1)) compared with FPD (656.7 ± 334.1 mOsm · kgH2O(-1)) but the TE was trivial (0.17). Freezing significantly reduced mean osmolality using FPD (656.7 ± 341.1 to 606.5 ± 333.4 mOsm · kgH2O(-1); P < 0.001), but samples were still highly related following freezing (ICC, r = 0.979, P < 0.001, CI = 0.993-0.997; TE = 0.15; and r=0.995, P < 0.001, CI = 0.967-0.986; TE = 0.07 for RI and FPD respectively). Despite mean differences between methods and as a result of freezing, such differences are physiologically trivial. Therefore, the use of RI appears to be a valid measurement tool to determine urine osmolality.