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Victoria Penpraze, John J. Reilly, Christina M. MacLean, Colette Montgomery, Louise A. Kelly, James Y. Paton, Thomas Aitchison and Stan Grant

There is limited evidence on how much and on which days accelerometry monitoring should be performed to obtain a representative measurement of physical activity (PA) in young children. We measured 76 children (40 M and 36 F, mean age 5.6 years ([SD ± 0.4]) on 7 days using Actigraph accelerometers. Mean daily PA was expressed in counts per min (cpm). Reliability increased as the number of days and hours of monitoring increased, but only to 10 hr per day. At 7 days of monitoring for 10 hr per day, reliability was 80% (95% CI [70%, 86%]). The number of days was more important to reliability than the number of hours. The inclusion or exclusion of weekend days made relatively little difference. A monitoring period of 7 days for 10 hr per day produced the highest reliability. Surprisingly short monitoring periods may provide adequate reliability in young children.

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Ari Nummela, James Stray-Gundersen and Heikki Rusko

The purpose of this investigation was to examine the influence of running velocity, stride characteristics, training background, gender, and caliber of a runner on the changes in ground contact time during a 400-m run. Thirteen male and 4 female sprinters ran a 400-m time trial on the track, and 8 male sprinters and 6 male endurance athletes ran a simulated 400-m trial at constant velocity on the treadmill. A special shoe insert was placed in the track spike to determine contact time, and a video camera was used to determine split times for each 40 m. Two threshold points were identified during the 400-m run, with the first occurring when the running velocity began to decrease. The threshold points were affected by the individual running strategy and reflected fatigue-induced changes in the running velocity; they also were independent of gender, training background, and caliber of an athlete.

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César Meylan, Joshua Trewin and Kelly McKean

The aims of the current study were to examine the external validity of inertial-based parameters (inertial movement analysis [IMA]) to detect multiplanar explosive actions during maximal sprinting and change of direction (COD) and to further determine its reliability, set appropriate magnitude bands for match analysis, and assess its variability during international women’s soccer matches. Twenty U20 female soccer players, wearing global positioning system (GPS) units with a built-in accelerometer, completed 3 trials of a 40-m sprint and a 20-m sprint with a change of direction to the right or left at 10 m. Furthermore, 13 women’s national-team players (157 files; 4–27 matches/player) were analyzed to ascertain match-to-match variability. Video synchronization indicated that the IMA signal was instantaneous with explosive movement (acceleration, deceleration, COD). Peak GPS velocity during the 40-m sprint showed similar reliability (coefficient of variation [CV] = 2.1%) to timing gates but increased before and after COD (CV = 4.5–13%). IMA variability was greater at the start of sprints (CV = 16–21%) than before and after COD (CV = 13–16%). IMA threshold for match analysis was set at 2.5 m · s–1 · s–1 by subtracting 1 SD from the mean IMA during sprint trials. IMA match variability (CV = 14%) differed from high-speed GPS metrics (35–60%). Practitioners are advised that timing lights should remain the gold standard for monitoring sprint and acceleration capabilities of athletes. However, IMA could be a reliable method to monitor explosive actions between matches and assess changes due to various factors such as congested schedule, tactics, heat, or altitude.

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Warren Young, Stuart Cormack and Michael Crichton

Purpose:

The main purpose of this study was to determine the relationships between countermovement jump (CMJ) variables and acceleration and maximum speed performance.

Methods:

Twenty-three elite Australian football players were tested on a CMJ, which yielded several kinematic and kinetic variables describing leg muscle function. A 40 m sprint was also conducted to assess acceleration (10 m time) and an estimate of maximum speed (fying 20 m time). Players from one Australian Football League (AFL) club were tested and Pearson correlations for CMJ variables and sprint performance were calculated.

Results:

Jump height, peak velocity, peak force, and peak power had less than 50% common variance, and therefore represented independent expressions of CMJ performance. Generally, the correlations between CMJ variables and sprinting performance were stronger for maximum speed (small to large effect sizes) than for acceleration (trivial to moderate sizes). The variable that produced the strongest correlation with acceleration was jump height (r = -0.430, P = .041) and with maximum speed was peak power/weight (r = -0.649, P = .001).

Conclusions:

The results indicate that if an integrated system comprising a position transducer and a force platform is available for CMJ assessment, jump height and peak power/weight are useful variables to describe leg muscle explosive function for athletes who perform sprints.

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Denise Jennings, Stuart Cormack, Aaron J. Coutts, Luke Boyd and Robert J. Aughey

Purpose:

To assess the validity and reliability of distance data measured by global positioning system (GPS) units sampling at 1 and 5 Hz during movement patterns common to team sports.

Methods:

Twenty elite Australian Football players each wearing two GPS devices (MinimaxX, Catapult, Australia) completed straight line movements (10, 20, 40 m) at various speeds (walk, jog, stride, sprint), changes of direction (COD) courses of two different frequencies (gradual and tight), and a team sport running simulation circuit. Position and speed data were collected by the GPS devices at 1 and 5 Hz. Distance validity was assessed using the standard error of the estimate (±90% confidence intervals [CI]). Reliability was estimated using typical error (TE) ± 90% CI (expressed as coefficient of variation [CV]).

Results:

Measurement accuracy decreased as speed of locomotion increased in both straight line and the COD courses. Difference between criterion and GPS measured distance ranged from 9.0% to 32.4%. A higher sampling rate improved validity regardless of distance and locomotion in the straight line, COD and simulated running circuit trials. The reliability improved as distance traveled increased but decreased as speed increased. Total distance over the simulated running circuit exhibited the lowest variation (CV 3.6%) while sprinting over 10 m demonstrated the highest (CV 77.2% at 1 Hz).

Conclusion:

Current GPS systems maybe limited for assessment of short, high speed straight line running and efforts involving change of direction. An increased sample rate improves validity and reliability of GPS devices.

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Justin Durandt, Jason C. Tee, Sebastian K. Prim and Michael I. Lambert

Purpose:

The 5-m repeat-sprint test (5-m RST) measures resistance to fatigue after repeated bouts of short-duration, high-intensity activity. This study determined the components of fitness associated with performance in 5-m RSTs.

Methods:

Speed (10-m and 40-m sprints), strength (bench press), agility, strength endurance (pull-ups and push-ups), and aerobic power (20-m shuttle-run test) were measured in male provincial- or national-level rugby (n = 110), hockey (n = 59), and soccer (n = 55) players.

Results:

Subjects with either high (HI) or low (LO) resistance to fatigue in the 5-m RST differed in body mass (76.9 ± 11.6 kg vs 102.1 ± 18.9 kg, HI vs LO, respectively, P < .001), agility (14.55 ± 0.41 seconds vs 15.56 ± 0.30 seconds, P < .001), bench press (86 ± 20 kg vs 114 ± 33 kg, P = .03), pull-ups (13 ± 4 vs 8 ± 5, P = .02), push-ups (56 ± 12 vs 39 ± 13, P = .002), and 20-m shuttle-run test (20-m SRT; 133 ± 11 vs 87 ± 12 shuttles, P < .001). Body mass, strength, and aerobic power were the best predictors of 5-m RST performance: 5-m RST = –1.274(mass) + 0.756(1RM bench press) + 2.053(number of 20-m SRT shuttles) + 549.409 (R 2 = .66).

Conclusions:

Performance in the 5-m RST is predicted best by a combination of factors including body mass, strength, and aerobic ability, rather than by any single component of fitness.

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Thomas A. Haugen, Espen Tønnessen and Stephen Seiler

Purpose:

To compare sprint and countermovement-jump (CMJ) performance among competitive soccer players as a function of performance level, field position, and age. In addition, the authors wanted to quantify the evolution of these physical characteristics among professional players over a 15-y period.

Methods:

939 athletes (22.1 ± 4.3 y), including national-team players, tested 40-m sprint with electronic timing and CMJ on a force platform at the Norwegian Olympic Training Center between 1995 and 2010.

Results:

National-team and 1st-division players were faster (P < .05) than 2nd-division (1.0–1.4%), 3rd- to 5th-division (3.0–3.8%), junior national-team (1.7–2.2%), and junior players (2.8–3.7%). Forwards were faster than defenders (1.4%), midfielders (2.5%), and goalkeepers (3.2%) over 0–20 m (P < .001). Midfielders jumped ~2.0 cm lower than the other playing positions (P < .05). Sprinting velocity peaked in the age range 20–28 y and declined significantly thereafter (P < .05). Players from 2006–2010 had 1–2% faster 0–20 m and peak velocity than players from the 1995–1999 and 2000–2005 epochs, whereas no differences in CMJ performance were observed.

Conclusions:

This study provides effect-magnitude estimates for the influence of performance level, position, and age on sprint and CMJ performance in soccer. While CMJ performance has remained stable over the time, there has been a small but positive development in sprinting velocity among professional players.

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Alex Ross, Nicholas D. Gill and John B. Cronin

Anthropometrical and physical characteristics have been used to distinguish players of different competition levels and position groups; however, there is no literature on rugby sevens.

Purpose:

To compare the anthropometrical and physical characteristics of international and provincial rugby sevens players and between forwards and backs.

Methods:

To assess whether differences exist, 65 rugby sevens players including 22 international players and 43 provincial-level players were assessed for height, mass, body composition, speed, repeated-sprint ability, lower-body power, upper-body strength, and maximal aerobic endurance during in-season preparation for tournaments.

Results:

Clear differences (2.8−32%; small to very large effect sizes) were observed in all anthropometrical and physical measures between international and provincial players, with the largest differences observed in repeated-sprint ability (5.7%; very large effect size), 40-m-sprint time (4.4%; large effect size), 50-kg squat-jump peak power (32%; large effect size), and multistage fitness-test performance (19%; large effect size). Fewer and smaller differences (0.7−14%; trivial to large effect sizes) were found when comparing forwards and backs, with body height being the most discriminant characteristic (3.5%; large effect size).

Conclusions:

Lower-level rugby sevens players should seek to improve their overall physical profile, particularly their repeated-sprint ability, to reach higher levels in rugby sevens. Furthermore, positional status may have little importance when preparing for rugby sevens.

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Gregory S. Anderson

The purpose of this study was to determine the validity of using the 1600-m distance run (DR) and the maximal multistage 20-m shuttle run (SR) as predictors of aerobic capacity in active boys 10 to 12 years of age. The influence of weight and maximal sprint running speed on test performance scores were also investigated. Both the DR and SR were found to have concurrent validity in the group studied, correlated to a directly measured VO2max (ml kg−1·min−1) determined through a progressive bicycle ergometer test. However, predicted VO2max values using SR results differed significantly from measured values. Weight was not found to be significantly correlated with either of the predictive methods, whereas maximal sprint running speed, as measured through a 40-m dash, was found to correlate significantly with the results of both the DR and SR. These results suggest that the combined influence of running efficiency and anaerobic energy production significantly influence the performance of both predictive methods.

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Mark Russell, Aden King, Richard. M. Bracken, Christian. J. Cook, Thibault Giroud and Liam. P. Kilduff

Purpose:

To assess the effects of different modes of morning (AM) exercise on afternoon (PM) performance and salivary hormone responses in professional rugby union players.

Methods:

On 4 occasions (randomized, crossover design), 15 professional rugby players provided AM (~8 AM) and PM (~2 PM) saliva samples before PM assessments of countermovement-jump height, reaction time, and repeated-sprint ability. Control (passive rest), weights (bench press: 5 × 10 repetitions, 75% 1-repetition maximum, 90-s intraset recovery), cycling (6 × 6-s maximal sprint cycling, 7.5% body mass load, 54-s intraset recovery), and running (6 × 40-m maximal sprints, 20-s intraset recovery) interventions preceded (~5 h) PM testing.

Results:

PM sprint performance improved (P < .05) after weights (>0.15 ± 0.19 s, >2.04% ± 2.46%) and running (>0.15 ± 0.17 s, >2.12% ± 2.22%) but not cycling (P > .05). PM jump height increased after cycling (0.012 ± 0.009 m, 2.31% ± 1.76%, P < .001) and running (0.020 ± 0.009 m, 3.90% ± 1.79%, P < .001) but not weights (P = .936). Reaction time remained unchanged between trials (P = .379). Relative to control (131 ± 21 pg/mL), PM testosterone was greater in weights (21 ± 23 pg/mL, 17% ± 18%, P = .002) and running (28 ± 26 pg/mL, 22% ± 20%, P = .001) but not cycling (P = .072). Salivary cortisol was unaffected by AM exercise (P = .540).

Conclusions:

All modes of AM exercise improved at least 1 marker of PM performance, but running appeared the most beneficial to professional rugby union players. A rationale therefore exists for preceding PM competition with AM exercise.