Thoracic-Worn Accelerometers Detect Fatigue-Related Changes in Vertical Stiffness During Sprinting.

ABSTRACT: Horsley, BJ, Tofari, PJ, Halson, SL, Kemp, JG, Johnston, RD, and Cormack, SJ. Thoracic-worn accelerometers detect fatigue-related changes in vertical stiffness during sprinting. J Strength Cond Res 38(2): 283-289, 2024-Thoracic-mounted accelerometers are valid and reliable for analyzing gait characteristics and may provide the opportunity to assess running-related neuromuscular fatigue (NMF) during training and competition without the need for additional tests, such as a countermovement jump (CMJ). However, their sensitivity for detecting fatigue-related changes in gait across different speeds is unclear. We, therefore, assessed the changes in accelerometer-derived gait characteristics, including vertical stiffness (K vert ), following a repeated sprint protocol (RSP). Sixteen recreationally active subjects performed single and repeated CMJs on a force plate and 40 m run throughs overground at 3-4, 5-6, and 7-8 m·s -1 pre-post a 12 × 40 m RSP. Gait characteristics (contact time, step frequency, step length, K vert , etc.) were derived from an accelerometer contained within a global navigation satellite system unit on the thoracic spine using a validated algorithm. Changes in running gait and CMJ performance were assessed using a linear mixed-effects model (95% confidence interval [95% CI]; effect size [ES]). Significance was set at p < 0.05. A significant reduction in K vert occurred at 7-8 m·s -1 following the RSP (-8.51 kN·m -1 [-13.9, -3.11]; p = 0.007; ES [95% CI] = -0.39 [-0.62, -0.15]) which coincided with a decreased jump height (-0.03 m [-0.04, -0.01]; p = 0.002; ES [95% CI] = -0.87 [-1.41, -0.30]). However, all other gait characteristics were not significantly different irrespective of speed. Thoracic-worn accelerometers can detect changes in K vert at 7-8 m·s -1 which may be useful for monitoring NMF during sprinting. However, a RSP does not result in altered gait mechanics in subsequent running at lower speeds.

Validity and Reliability of Thoracic-Mounted Inertial Measurement Units to Derive Gait Characteristics During Running.

ABSTRACT: Horsley, BJ, Tofari, PJ, Halson, SL, Kemp, JG, Chalkley, D, Cole, MH, Johnston, RD, and Cormack, SJ. Validity and reliability of thoracic-mounted inertial measurement units to derive gait characteristics during running. J Strength Cond Res 38(2): 274-282, 2024-Inertial measurement units (IMUs) attached to the tibia or lumbar spine can be used to analyze running gait but, with team-sports, are often contained in global navigation satellite system (GNSS) units worn on the thoracic spine. We assessed the validity and reliability of thoracic-mounted IMUs to derive gait characteristics, including peak vertical ground reaction force (vGRF peak ) and vertical stiffness (K vert ). Sixteen recreationally active subjects performed 40 m run throughs at 3-4, 5-6, and 7-8 m·s -1 . Inertial measurement units were attached to the tibia, lumbar, and thoracic spine, whereas 2 GNSS units were also worn on the thoracic spine. Initial contact (IC) from a validated algorithm was evaluated with F1 score and agreement (mean difference ± SD ) of gait data with the tibia and lumbar spine using nonparametric limits of agreement (LoA). Test-retest error {coefficient of variation, CV (95% confidence interval [CI])} established reliability. Thoracic IMUs detected a nearly perfect proportion (F1 ≥ 0.95) of IC events compared with tibia and lumbar sites. Step length had the strongest agreement (0 ± 0.04 m) at 3-4 m·s -1 , whereas contact time improved from 3 to 4 (-0.028 ± 0.018 second) to 7-8 m·s -1 (-0.004 ± 0.013 second). All values for K vert fell within the LoA at 7-8 m·s -1 . Test-retest error was ≤12.8% for all gait characteristics obtained from GNSS units, where K vert was most reliable at 3-4 m·s -1 (6.8% [5.2, 9.6]) and vGRF peak at 7-8 m·s -1 (3.7% [2.5, 5.2]). The thoracic-spine site is suitable to derive gait characteristics, including K vert , from IMUs within GNSS units, eliminating the need for additional sensors to analyze running gait.

Validity and Reliability of Methods to Determine Barbell Displacement in Heavy Back Squats: Implications for Velocity-Based Training.

Appleby, BB, Banyard, H, Cormack, SJ, and Newton, RU. Validity and reliability of methods to determine barbell displacement in heavy back squats: Implications for velocity-based training. J Strength Cond Res 34(11): 3118-3123, 2020-The purpose of this study was to investigate the validity and reliability of methods for determining barbell displacement during heavy back squats. Twelve well-trained rugby union players (mean ± SD 1 repetition maximum [1RM] 90° squat = 196.3 ± 29.2 kg) completed 2 sets of 2 repetitions at 70, 80, and 90% of 1RM squats. Barbell displacement was derived from 3 methods across 4 load categories (120-129, 140-149, 160-169, and 180-189 kg) including: a (a) linear position transducer (LPT) attached 65 cm left of barbell center, (b) 3D motion analysis tracking of markers attached to either end of a barbell, and (c) cervical marker (C7) (criterion measurement). Validity was calculated using the typical error of the estimate as a coefficient of variation (CV%) ±90% confidence interval (CI), mean bias as a percentage, and the Pearson product moment correlation (r). Intraday reliability was calculated using the intraclass correlation coefficient and the typical error expressed as a percentage of CV% ±90% (CI). Mean displacement for C7, LPT, and the barbell ends was 520, 529, and 550-564 mm, respectively. Validity of the LPT compared with the criterion was acceptable (CV% = 2.1-3.0; bias = 0.9-1.5%; r = 0.96-0.98), whereas that of the barbell ends was less (CV% = 2.7-7.5; bias = 4.9-11.2%; r = 0.71-0.97). The CV% reliability of the C7 marker across the load categories was 6.6%, the LPT 6.6%, and the barbell ends between 5.9 and 7.2%. Despite reliable measures, overestimation of displacement occurs as the tracking location moves to the barbell ends in weighted back squats. The LPT demonstrated high validity to the criterion and high trial-to-trial reliability.

Unilateral and Bilateral Lower-Body Resistance Training Does not Transfer Equally to Sprint and Change of Direction Performance.

Appleby, BB, Cormack, SJ, and Newton, RU. Unilateral and bilateral lower-body resistance training does not transfer equally to sprint and change of direction performance. J Strength Cond Res 34(1): 54-64, 2020-Given maximal strength can be developed using bilateral or unilateral resistance training, the purpose of this study was to determine the magnitude of transfer of unilateral or bilateral resistance training to sprint and change of direction (COD) performance. Thirty-three trained participants (average training age = 5.4 ± 2.9 years and 1 repetition maximum [1RM] 90° squat = 177.6 ± 26.7 kg) completed either a bilateral group (BIL, n = 13), unilateral (UNI, n = 10), or comparison (COM, n = 10) 18-week randomized controlled training design. Training involved 2 lower-body, volume-load-matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (squat) or unilateral (step-up) resistance exercise. Strength was assessed through 1RM squat and step-up, in addition to 20-m sprint and a customized 50° COD test. The effect size statistic ± 90% confidence limit (ES ± CL) was calculated to examine the magnitude of difference within and between groups at each time point. BIL and UNI groups improved their trained and nontrained strength exercise with an unclear difference in adaptation of squat strength (ES = -0.34 + 0.55). Both groups improved 20-m sprint (ES: BIL = -0.38 ± 0.49 and UNI = -0.31 ± 0.31); however, the difference between the groups was unclear (ES = 0.07 ± 0.58). Although both groups had meaningful improvements in COD performance, bilateral resistance training had a greater transfer to COD performance than unilateral resistance training (between-groups ES = 0.59 ± 0.64). Both bilateral and unilateral training improved maximal lower-body strength and sprint acceleration. However, the BIL group demonstrated superior improvements in COD performance. This finding potentially highlights the importance of targeting the underlying physiological stimulus that drives adaptation and not exercise selection based on movement specificity of the target performance.

Reliability of Squat Kinetics in Well-Trained Rugby Players: Implications for Monitoring Training.

Appleby, BB, Cormack, SJ, and Newton, RU. Reliability of squat kinetics in well-trained rugby players: implications for monitoring training. J Strength Cond Res 33(10): 2635-2640, 2019-The aim of this study was to determine the within-session reliability in kinetic variables of the squat in well-trained athletes during a typical resistance training protocol. Fifteen subjects completed 2 testing sessions. Session 1 was establishment of 1 repetition maximum (1RM) squat, and session 2 involved 2 sets of 2 maximal effort repetitions of the squat at 70, 80, and 90% of 1RM with 3D motion analysis and ground reaction force (GRF) measurement using 2 in-ground triaxial force plates. Reliability was calculated using typical error ± 90% confidence limits, expressed as the coefficient of variation and intraclass correlation coefficient. The smallest worthwhile change (SWC%), calculated as 0.2 × between-subject SD, was used to determine the smallest important change in performance. Peak GRF and average GRF were found to have acceptable measures of reliability with the combined left and right leg average GRF capable of detecting the SWC. Independent limb contributions were reliable (left and right, or dominant and nondominant). Reliable kinetics can be obtained in back squat performance typical of a resistance training session in well-trained athletes. This suggests that coaches integrating force plate technology within training sessions may effectively capture between 1 and 6 training sets among several athletes, facilitating analysis and intervention on larger data sets.

Specificity and Transfer of Lower-Body Strength: Influence of Bilateral or Unilateral Lower-Body Resistance Training.

Appleby, BB, Cormack, SJ, and Newton, RU. Specificity and transfer of lower-body strength: Influence of bilateral or unilateral lower-body resistance training. J Strength Cond Res 33(2): 318-326, 2019-To examine the development of lower-body strength using either bilateral or unilateral resistance training. Developmental rugby players (n = 33; mean training age = 5.4 ± 2.9 years; 1 repetition maximum [1RM] 90° squat = 178 ± 27 kg) completed an 18-week randomized controlled training design (bilateral group [BIL], n = 13; unilateral group [UNI], n = 10; comparison, n = 10). The 8-week training phase involved 2 lower-body, volume-load matched resistance sessions per week (6-8 sets × 4-8 reps at 45-88% 1RM), differing only in the prescription of a bilateral (back squat) or unilateral (step-up) resistance exercise. Maximum strength was assessed by a randomized order of 1RM back squat and step-up testing and analyzed for within- and between-group differences using effect sizes (ES ± 90% confidence limits [CL]). Both training groups showed practically important improvements in their trained exercise (ES ± 90% CL: BIL = 0.67 ± 0.48; UNI = 0.74 ± 0.38) with transfer to their nontrained resistance exercise (BIL step-up = 0.27 ± 0.39: UNI squat = 0.42 ± 0.39). The difference between groups in adaptation of squat strength was unclear (BIL ES = -0.34 ± 0.55), while the UNI group showed an advantage in step-up training (ES = 0.41 ± 0.36). The results demonstrate that practically important increases in lower-body strength can be achieved using bilateral or unilateral resistance training and development of that strength may be expressed in the movement not trained, supporting the transfer of strength training between exercises of similar joint movements and muscles. Coaches may choose to incorporate unilateral strength training where the prescription of bilateral training may be inhibited.

Kinetics and Kinematics of the Squat and Step-up in Well-Trained Rugby Players.

Appleby, BB, Newton, RU, and Cormack, SJ. Kinetics and kinematics of the squat and step-up in well-trained rugby players. J Strength Cond Res 33(7S): S36-S44, 2019-The purpose of this study was to compare and contrast the kinetics and kinematics of squat and step-up performance in well-trained athletes. Triaxial ground reaction force (GRF) and 3D kinematic data were collected in 4 maximal effort repetitions each at 70, 80, and 90% of 1 repetition maximum (1RM) of squat and step-up. The difference in concentric phase kinetics and kinematics between the squat and step-up was compared using effect sizes (ES ± 90% confidence limits [CLs]) classified as: less than 0.2 as trivial; 0.2-0.6 as small; 0.6-1.2 as moderate; and 1.2-2.0 as large. Where the 90% CL crossed negative and positive 0.2 values, the effect was considered "unclear.n Ground reaction force was higher for the step-up than squat at all relative intensities per leg (peak GRF ES: 2.56 ± 0.19 to 2.70 ± 0.37; average GRF ES: 1.45 ± 0.27 to 1.48 ± 0.29). Per leg, the difference in concentric impulse favored the step-up compared with squat at 70% 1RM (ES = 0.71 ± 0.40) and 80% 1RM (ES = 0.30 ± 0.41) but was unclear at 90% 1RM (ES = -0.25 ± 0.47). The squat peak velocity was greater compared with step-up at all intensities (ES = -1.74 ± 0.48 to -1.33 ± 0.48). Despite a lower external load and a single base of support, per leg, the step-up produced comparable GRF because the squat suggesting overload provided by the step-up is sufficient for maximal strength development. Future research may investigate the efficacy of the step-up in a training intervention for the development of lower-body strength.

Self-Paced Team-Sport Match Simulation Results in Reductions in Voluntary Activation and Modifications to Biological, Perceptual, and Performance Measures at Halftime and for up to 96 Hours Postmatch.

Tofari, PJ, Kemp, JG, and Cormack, SJ. Self-paced team-sport match-simulation results in reductions in voluntary activation and modifications to biological, perceptual, and performance measures at halftime and for up to 96 hours postmatch. J Strength Cond Res 32(12): 3561-3572, 2018-Assessing responses to soccer match play is limited by match variability or unrealistic simulations. To address this, the biological, perceptual, and performance responses were assessed using a self-paced, simulated soccer match protocol using a nonmotorized treadmill. Twelve male team-sport athletes performed the 90-minute simulation. Match activity, quadriceps twitch interpolation (voluntary activation [%VA] and potentiated twitch [POT]), biochemical markers, strength and power performance, rating of perceived exertion (RPE), and self-report wellness were collected prematch, halftime, postmatch, and 2, 24, 48, 72, and 96-hour postmatch. Change compared with prematch was calculated using effect size ±90% confidence limit, and relationships were assessed using regression analysis. Subjects covered 12,445.8 ± 768.7 m at 87.1 ± 3.2% maximal heart rate (mean ± SD). Reductions in %VA and POT was present at halftime (-0.38 ± 0.46 and -0.79 ± 0.30, respectively) and persisted postmatch. Squat jump height decreased at halftime (-0.42 ± 0.31) and was decreased until Post96. Perceptual fatigue, soreness (-0.92 ± 0.88 and -1.49 ± 0.76, respectively), and creatine kinase (CK) (1.11 ± 0.43) peaked at Post24. Pretest strength (N·kg) correlated with changes in CK (r = -0.58 to -0.81), peak oxygen consumption (V[Combining Dot Above]O2peak) correlated with reduced perceived wellness at Post24 (r = 0.44-0.58) and RPE post (r = -0.71 ± 0.28). High-speed running correlated with soreness (r = 0.42) and very high-speed running with reduced POT (r = 0.61). Previously, unreported half-time reductions in %VA and POT plateaued by postmatch, suggesting a role in regulating second-half performance. Perceptual and neuromuscular responses seem related to running intensity. Greater lower-body strength and V[Combining Dot Above]O2peak were associated with less CK (i.e., muscle damage) and perceptual responses postmatch, respectively, suggesting a training focus should be placed on these capacities.

Injury epidemiology of tennis players at the 2011-2016 Australian Open Grand Slam.

AIM: To examine the epidemiology and in-event treatment frequency of injury at the 2011-2016 Australian Open tournaments. METHODS: Injury incidence was defined as a medical consultation by a tournament physician and in-event treatment frequency as the mean total number of follow-up medical/physiotherapy consultations (2013-2016 tournaments only). Data were collated by sex, injury region and type and reported as frequencies per 10 000 game exposures. Incidence rate s± 95% CI and rate ratios were used to test effects for injury, sex and year. RESULTS: Female players experienced more injuries than male players (201.7 vs 148.6). The shoulder (5.1±1.1 injuries per year), foot (3.2±1.1), wrist (3.1±1.5) and knee (3.1±1.1) were the most commonly injured regions among females. Knee (3.5±1.6), ankle (2.3±1.3) and thigh (2.3±1.5) were the most prevalent male injuries. Upper arm injuries and in-event treatment frequency increased by ≥2.4 times in both sexes over the 5-year period. Muscle injuries were most frequent. There was a greater than twofold increase in men and women with stress fractures over the 5-year period. The torso region, including the neck, thoracic spine, trunk and abdominal, lumbar spine, hip and groin, pelvis/buttock, attracted high in-event treatment frequencies in both sexes. CONCLUSION: Investigation of injury at the Australian Open suggests that females are more commonly injured than males. Upper and lower extremity injuries affected females while lower limb injuries were more prominent in males. There was an increasing rate of in-event treatments of upper limb and torso injuries as well as stress fractures during the observation period.

Discovering frequently recurring movement sequences in team-sport athlete spatiotemporal data.

Athlete external load is typically analysed from predetermined movement thresholds. The combination of movement sequences and differences in these movements between playing positions is also currently unknown. This study developed a method to discover the frequently recurring movement sequences across playing position during matches. The external load of 12 international female netball athletes was collected by a local positioning system during four national-level matches. Velocity, acceleration and angular velocity were calculated from positional (X, Y) data, clustered via one-dimensional k-means and assigned a unique alphabetic label. Combinations of velocity, acceleration and angular velocity movement were compared using the Levenshtein distance and similarities computed by the longest common substring problem. The contribution of each movement sequence, according to playing position and relative to the wider data set, was then calculated via the Minkowski distance. A total of 10 frequently recurring combinations of movement were discovered, regardless of playing position. Only the wing attack, goal attack and goal defence playing positions are closely related. We developed a technique to discover the movement sequences, according to playing position, performed by elite netballers. This methodology can be extended to discover the frequently recurring movements within other team sports and across levels of competition.

Effects of consecutive days of match play on technical performance in tennis.

Elite tennis is characterised by repeated bouts of up to 5-set match play, yet little is known about the technical requirements of shots played. This study therefore investigated technical performance changes over consecutive days of prolonged, simulated tennis match play. A total of 7 well-trained men tennis players performed 4 consecutive days of competitive 4-h match play. Matches were notated to determine between-day changes in groundstroke and serve performance, as well as point and match durations. Changes ≥75% likely to exceed the smallest important effect size (0.2) were considered meaningful and represented as effect size ± 90% confidence interval. Effective playing time reduced on days 3 and 4, alongside likely increases in "stretch" groundstrokes over the 4 days (mean effect size ± 90% confidence interval; 0.57 ± 0.38) and "stretch" backhand returns on days 2 and 3 (0.39 ± 0.54 and 0.67 ± 0.55). Relative unforced errors increased on day 4 (vs. day 2; 0.36 ± 0.22) and second-serve winning percentage reduced after day 1 (-0.47 ± 0.50). Further, a likely increase in emotional outbursts characterised day 3 (vs. day 2; 0.73 ± 0.57). Consecutive-day match play impairs hitting accuracy, stroke positioning and emotional responses; an understanding of which prepares players for elite-standard tennis tournament play.

Comparison of ergometer- and track-based testing in junior track-sprint cyclists. Implications for talent identification and development.

Talent identification (TID) and talent development (TDE) programmes in track sprint cycling use ergometer- and track-based tests to select junior athletes and assess their development. The purpose of this study was to assess which tests are best at monitoring TID and TDE. Ten male participants (16.2 ± 1.1 year; 178.5 ± 6.0 cm and 73.6 ± 7.6 kg) were selected into the national TID squad based on initial testing. These tests consisted of two 6-s maximal sprints on a custom-built ergometer and 4 maximal track-based tests (2 rolling and 2 standing starts) using 2 gear ratios. Magnitude-based inferences and correlation coefficients assessed changes following a 3-month TDE programme. Training elicited meaningful improvements (80-100% likely) in all ergometer parameters. The standing and rolling small gear, track-based effort times were likely and very likely (3.2 ± 2.4% and 3.3 ± 1.9%, respectively) improved by training. Stronger correlations between ergometer- and track-based measures were very likely following training. Ergometer-based testing provides a more sensitive tool than track-based testing to monitor changes in neuromuscular function during the early stages of TDE. However, track-based testing can indicate skill-based improvements in performance when interpreted with ergometer testing. In combination, these tests provide information on overall talent development.

Self-Reported Wellness Profiles of Professional Australian Football Players During the Competition Phase of the Season.

Gallo, TF, Cormack, SJ, Gabbett, TJ, and Lorenzen, CH. Self-reported wellness profiles of professional Australian football players during the competition phase of the season. J Strength Cond Res 31(2): 495-502, 2017-With the prevalence of customized self-report measures in high-performance sport, and the incomplete understanding of athletes' perceived wellness in response to matches and training load, the objective of this study was to explore weekly wellness profiles within the context of the competitive season of professional Australian football. Internal match load, measured through the session-rating of perceived exertion method, match-to-match microcycle, stage of the season, and training load were included in multivariate linear models to determine their effect on weekly wellness profile (n = 1,835). There was a lower weekly training load on a 6-day microcycle compared with a 7-day and 8-day microcycle. Match load had no significant impact on weekly wellness profile, while there was an interaction between microcycle and days postmatch. There was a likely moderately lower wellness Z-score 1 day postmatch for an 8-day microcycle (mean; 95% confidence interval: -1.79; -2.02 to -1.56) compared with a 6-day (-1.19; -1.30 to -1.08) and 7-day (-1.22; -1.34 to -1.09) cycle (d; 95% confidence interval: -0.82; -1.3 to -0.36, -0.78; -1.3 to -0.28, respectively). The second half of the season saw a possibly small reduction in overall wellness Z-score than the first half of the season (0.22; 0.12-0.32). Finally, training load had no effect on wellness Z-score when controlled for days postmatch, microcycle, and stage of the season. These results provide information on the status of players in response to matches and fixed conditions. Knowing when wellness Z-score returns to baseline relative to the length of the microcycle may lead practitioners to prescribe the heaviest load of the week accordingly. Furthermore, wellness "red flags" should be made relative to the microcycles and stage of the season to determine an athlete's status relative to their typical weekly profile.

Pre-training perceived wellness impacts training output in Australian football players.

The impact of perceived wellness on a range of external load parameters, rating of perceived exertion (RPE) and external load:RPE ratios, was explored during skill-based training in Australian footballers. Fifteen training sessions involving 36 participants were analysed. Each morning before any physical training, players completed a customised perceived wellness questionnaire (sleep quality, fatigue, stress, mood and muscle soreness). Microtechnology devices provided external load (average speed, high-speed running distance, player load and player load slow). Players provided RPE using the modified Borg category-ratio 10 RPE scale. Mixed-effect linear models revealed significant effects of wellness Z-score on player load and player load slow. Effects are reported with 95% confidence limits. A wellness Z-score of -1 corresponded to a -4.9 ± 3.1 and -8.6 ± 3.9% reduction in player load and player load slow, respectively, compared to those without reduced wellness. Small significant effects were also seen in the average speed:RPE and player load slow:RPE models. A wellness Z-score of -1 corresponded to a 0.43 ± 0.38 m·min(-1) and -0.02 ± 0.01 au·min(-1) change in the average speed:RPE and player load slow:RPE ratios, respectively. Magnitude-based analysis revealed that the practical size of the effect of a pre-training perceived wellness Z-score of -1 would have on player load slow was likely negative. The results of this study suggests that monitoring pre-training perceived wellness may provide coaches with information about the intensity of output that can be expected from individual players during a training session.

Activity profile of high-level Australian lacrosse players.

Despite lacrosse being one of the fastest growing team sports in the world, there is a paucity of information detailing the activity profile of high-level players. Microtechnology systems (global positioning systems and accelerometers) provide the opportunity to obtain detailed information on the activity profile in lacrosse. Therefore, this study aimed to analyze the activity profile of lacrosse match-play using microtechnology. Activity profile variables assessed relative to minutes of playing time included relative distance (meter per minute), distance spent standing (0-0.1 m·min), walking (0.2-1.7 m·min), jogging (1.8-3.2 m·min), running (3.3-5.6 m·min), sprinting (≥5.7 m·min), number of high, moderate, low accelerations and decelerations, and player load (PL per minute), calculated as the square root of the sum of the squared instantaneous rate of change in acceleration in 3 vectors (medio-lateral, anterior-posterior, and vertical). Activity was recorded from 14 lacrosse players over 4 matches during a national tournament. Players were separated into positions of attack, midfield, or defense. Differences (effect size [ES] ± 90% confidence interval) between positions and periods of play were considered likely positive when there was ≥75% likelihood of the difference exceeding an ES threshold of 0.2. Midfielders had likely covered higher (mean ± SD) meters per minute (100 ± 11) compared with attackers (87 ± 14; ES = 0.89 ± 1.04) and defenders (79 ± 14; ES = 1.54 ± 0.94) and more moderate and high accelerations and decelerations. Almost all variables across positions were reduced in quarter 4 compared with quarter 1. Coaches should accommodate for positional differences when preparing lacrosse players for competition.

Validity and Reliability of Methods to Assess Movement Deficiencies Following Concussion: A COSMIN Systematic Review.

BACKGROUND: There is an increased risk of subsequent concussion and musculoskeletal injury upon return to play following a sports-related concussion. Whilst there are numerous assessments available for clinicians for diagnosis and during return to play following concussion, many may lack the ability to detect these subclinical changes in function. Currently, there is no consensus or collated sources on the reliability, validity and feasibility of these assessments, which makes it difficult for clinicians and practitioners to select the most appropriate assessment for their needs. OBJECTIVES: This systematic review aims to (1) consolidate the reliability and validity of motor function assessments across the time course of concussion management and (2) summarise their feasibility for clinicians and other end-users. METHODS: A systematic search of five databases was conducted. Eligible studies were: (1) original research; (2) full-text English language; (3) peer-reviewed with level III evidence or higher; (4) assessed the validity of lower-limb motor assessments used to diagnose or determine readiness for athletes or military personnel who had sustained a concussion or; (5) assessed the test-retest reliability of lower-limb motor assessments used for concussion management amongst healthy athletes. Acceptable lower-limb motor assessments were dichotomised into instrumented and non-instrumented and then classified into static (stable around a fixed point), dynamic (movement around a fixed point), gait, and other categories. Each study was assessed using the COSMIN checklist to establish methodological and measurement quality. RESULTS: A total of 1270 records were identified, with 637 duplicates removed. Titles and abstracts of 633 records were analysed, with 158 being retained for full-text review. A total of 67 records were included in this review; 37 records assessed reliability, and 35 records assessed the validity of lower-limb motor assessments. There were 42 different assessments included in the review, with 43% being non-instrumented, subjective assessments. Consistent evidence supported the use of instrumented assessments over non-instrumented, with gait-based assessments demonstrating sufficient reliability and validity compared to static or dynamic assessments. CONCLUSION: These findings suggest that instrumented, gait-based assessments should be prioritised over static or dynamic balance assessments. The use of laboratory equipment (i.e. 3D motion capture, pressure sensitive walkways) on average exhibited sufficient reliability and validity, yet demonstrate poor feasibility. Further high-quality studies evaluating the reliability and validity of more readily available devices (i.e. inertial measurement units) are needed to fill the gap in current concussion management protocols. Practitioners can use this resource to understand the accuracy and precision of the assessments they have at their disposal to make informed decisions regarding the management of concussion. TRAIL REGISTRATION: This systematic review was registered on PROSPERO (reg no. CRD42021256298).

International field hockey players perform more high-speed running than national-level counterparts.

This study compared the activity profile of national and international male field hockey athletes. Sixteen players (mean (±SD) age, stature, and body mass: 22 ± 4 y, 178 ± 8 cm, and 78 ± 9 kg, respectively) competing in the national-level Australian Hockey League (AHL) and 16 players [mean (±SD) age, stature, and body mass: 27 ± 4 y, 179 ± 5 cm, and 77 ± 5 kg, respectively] competing in the international Champions Trophy (CT) tournament participated in this study. Global positioning systems assessed total distance (TD), meters per minute (m·min(-1)), and high-speed running distance (HSR; >4.17 m·s(-1)). Differences in multistage fitness test performance, movement between competition, positions, and halves were assessed using effect size and percent difference ±90% confidence intervals. The CT players had a 10.1% greater multistage fitness test, 13.9% and 42.0% more TD and HSR, respectively, than AHL. During CT, strikers performed 10.1 ± 7.4% less HSR than midfielders and 26.6 ± 8.2% more HSR than defenders. The AHL defenders covered less TD and HSR distance compared with strikers and midfielders (8.1 ± 3.6% and 8.4 ± 2.6%; 36.1 ± 11.1% and 51.5 ± 12.1%, respectively). The AHL strikers, midfielders, and defenders (19.9 ± 8.8%, 32.1 ± 7.9%, and 30.3 ± 10.7%, respectively), all performed less HSR distance than their CT counterparts. Finally, TD decreased from the first to second halves across all positions (6.1-7.5%) in both competitions. International competition increases the running profile of hockey players, with greater HSR at the elite level and positional differences including decreased running during the second half in both competitions.

Business Class Travel Preserves Sleep Quality and Quantity and Minimizes Jet Lag During the ICC Women's T20 World Cup.

PURPOSE: To determine the impact of the quality and quantity of sleep during an international flight on subsequent objective sleep characteristics, training and match-day load, self-reported well-being, and perceptions of jet lag of elite female cricketers during an International Cricket Council Women's T20 World Cup. METHODS: In-flight and tournament objective sleep characteristics of 11 elite female cricketers were assessed using activity monitors. Seated in business class, players traveled west from Melbourne, Australia, to Chennai, India. The outbound flight departed Melbourne at 3:30 AM with a stopover in Dubai for 2 hours. The arrival time in Chennai was 8:10 PM local time (1:40 AM in Melbourne). The total travel time was 19 hours 35 minutes. Perceptual ratings of jet lag, well-being, and training and competition load were collected. To determine the impact of in-flight sleep on tournament measures, a median split was used to create subsamples based on (1) in-flight sleep quantity and (2) in-flight sleep quality (2 groups: higher vs lower). Spearman correlation coefficients were calculated to assess the bivariate associations between sleep measures, self-reported well-being, perceptual measures of jet lag, and internal training and match-day load. RESULTS: Mean duration and efficiency of in-flight sleep bouts were 4.72 hours and 87.45%, respectively. Aggregated in-flight sleep duration was 14.64 + 3.56 hours. Players with higher in-flight sleep efficiency reported higher ratings for fatigue (ie, lower perceived fatigue) during the tournament period. Tournament sleep duration was longer, and bed and wake times were earlier compared with habitual. Compared with other nights during the tournament, sleep duration was shorter following matches. CONCLUSIONS: Maximizing in-flight sleep quality and quantity appears to have implications for recovery and sleep exhibited during competition. Sleep duration was longer than habitual except for the night of a match, which suggests that T20 matches may disrupt sleep duration.

Does Site Matter? Impact of Inertial Measurement Unit Placement on the Validity and Reliability of Stride Variables During Running: A Systematic Review and Meta-analysis.

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