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Benjamin M. Jackson, Ted Polglaze, Brian Dawson, Trish King and Peter Peeling

In team sports, rapid changes in speed and direction are common, however changes in direction have been found to reduce the accuracy of GPS-derived distance measures, 13 and accelerations >4 m·s −2 have been found to reduce the reliability of GPS-derived speed measures. 14 Consequently, important

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David S. Haydon, Ross A. Pinder, Paul N. Grimshaw and William S.P. Robertson

classifications, 1 as well as performance outcomes. 2 Despite an increase in popularity and research in wheelchair rugby (WCR), there is currently a limited understanding of how the level of activity limitation affects key kinematic variables and their impact on chair acceleration and sprint performance

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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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Claire J. Brady, Andrew J. Harrison, Eamonn P. Flanagan, G. Gregory Haff and Thomas M. Comyns

Successful performance in sprint events requires rapid acceleration and a high maximum velocity. The starting-block phase and the subsequent acceleration phase are 2 important phases of sprint events, shown to directly generate results in a 60- and 100-m sprints. 1 During the acceleration phase

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Martin Buchheit, Hani Al Haddad, Ben M. Simpson, Dino Palazzi, Pitre C. Bourdon, Valter Di Salvo and Alberto Mendez-Villanueva

The aims of the current study were to examine the magnitude of between-GPS-models differences in commonly reported running-based measures in football, examine between-units variability, and assess the effect of software updates on these measures. Fifty identical-brand GPS units (15 SPI-proX and 35 SPIproX2, 15 Hz, GPSports, Canberra, Australia) were attached to a custom-made plastic sled towed by a player performing simulated match running activities. GPS data collected during training sessions over 4 wk from 4 professional football players (N = 53 files) were also analyzed before and after 2 manufacturersupplied software updates. There were substantial differences between the different models (eg, standardized difference for the number of acceleration >4 m/s2 = 2.1; 90% confidence limits [1.4, 2.7], with 100% chance of a true difference). Between-units variations ranged from 1% (maximal speed) to 56% (number of deceleration >4 m/s2). Some GPS units measured 2–6 times more acceleration/deceleration occurrences than others. Software updates did not substantially affect the distance covered at different speeds or peak speed reached, but 1 of the updates led to large and small decreases in the occurrence of accelerations (–1.24; –1.32, –1.15) and decelerations (–0.45; –0.48, –0.41), respectively. Practitioners are advised to apply care when comparing data collected with different models or units or when updating their software. The metrics of accelerations and decelerations show the most variability in GPS monitoring and must be interpreted cautiously.

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Jace A. Delaney, Grant M. Duthie, Heidi R. Thornton, Tannath J. Scott, David Gay and Ben J. Dascombe

Rugby league involves frequent periods of high-intensity running including acceleration and deceleration efforts, often occurring at low speeds.

Purpose:

To quantify the energetic cost of running and acceleration efforts during rugby league competition to aid in prescription and monitoring of training.

Methods:

Global positioning system (GPS) data were collected from 37 professional rugby league players across 2 seasons. Peak values for relative distance, average acceleration/deceleration, and metabolic power (Pmet) were calculated for 10 different moving-average durations (1–10 min) for each position. A mixed-effects model was used to assess the effect of position for each duration, and individual comparisons were made using a magnitude-based-inference network.

Results:

There were almost certainly large differences in relative distance and Pmet between the 10-min window and all moving averages <5 min in duration (ES = 1.21–1.88). Fullbacks, halves, and hookers covered greater relative distances than outside backs, edge forwards, and middle forwards for moving averages lasting 2–10 min. Acceleration/deceleration demands were greatest in hookers and halves compared with fullbacks, middle forwards, and outside backs. Pmet was greatest in hookers, halves, and fullbacks compared with middle forwards and outside backs.

Conclusions:

Competition running intensities varied by both position and moving-average duration. Hookers exhibited the greatest Pmet of all positions, due to high involvement in both attack and defense. Fullbacks also reached high Pmet, possibly due to a greater absolute volume of running. This study provides coaches with match data that can be used for the prescription and monitoring of specific training drills.

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Kyle M.A. Thompson, Alanna K. Whinton, Shane Ferth, Lawrence L. Spriet and Jamie F. Burr

the current study. Practical Applications The findings of this study suggest 3 sets of 5-minute occlusions performed prior to sprinting do not provide an adequate stimulus to improve acceleration ability. This suggests that track and field coaches aiming to improve short-distance sprint performance in

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Jeffrey M. Janot, Kelly A. Auner, Talisa M. Emberts, Robert M. Kaatz, Kaelyn M. Matteson, Emily A. Muller and Mitchell Cook

Purpose:

Previous research has stated that dryland sled pulling trains first-step quickness in hockey players. Further research has demonstrated that off-ice horizontal training (sled pull, parachute, etc) relates well to on-ice acceleration and speed. However, there is limited literature pertaining to on-ice resistance training that aims to enhance speed and acceleration in hockey players. The purpose of the current study was to determine if on-ice BungeeSkate training would improve on-ice speed and acceleration in youth hockey players.

Methods:

Twenty-three Peewee and Bantam hockey players (age 11–14) were recruited, with 20 participants completing the study. Pretesting and posttesting consisted of an on-ice 44.8-m speed test, a 6.1-m acceleration test, and a 15.2-m full-speed test. The training protocol consisted of 8 sessions of 5 BungeeSkate training exercises per session, 2 times per week for a 4-wk period.

Results:

The results of this study showed that speed and top speed were significantly increased (P < .05) by 4.2% and 4.3%, respectively. Acceleration was also slightly improved but not significantly.

Conclusions:

A 4-wk BungeeSkate training intervention can improve acceleration and speed in youth hockey players. This training method could be a valid adjunct to existing strategies to improve skill development in hockey and is shown to improve speed and acceleration in relatively short training sessions. This may be most advantageous for hockey coaches and players who are looking to maximize training benefits with limited ice time.

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Tom G.A. Stevens, Cornelis J. de Ruiter, Cas van Niel, Roxanne van de Rhee, Peter J. Beek and Geert J.P. Savelsbergh

Purpose:

A local position measurement (LPM) system can accurately track the distance covered and the average speed of whole-body movements. However, for the quantification of a soccer player’s workload, accelerations rather than positions or speeds are essential. The main purpose of the current study was therefore to determine the accuracy of LPM in measuring average and peak accelerations for a broad range of (maximal) soccerspecific movements.

Methods:

Twelve male amateur soccer players performed 8 movements (categorized in straight runs and runs involving a sudden change in direction of 90° or 180°) at 3 intensities (jog, submaximal, maximal). Position-related parameters recorded with LPM were compared with Vicon motion-analysis data sampled at 100 Hz. The differences between LPM and Vicon data were expressed as percentage of the Vicon data.

Results:

LPM provided reasonably accurate measurements for distance, average speed, and peak speed (differences within 2% across all movements and intensities). For average acceleration and deceleration, absolute bias and 95% limits of agreement were 0.01 ± 0.36 m/s2 and 0.02 ± 0.38 m/s2, respectively. On average, peak acceleration was overestimated (0.48 ± 1.27 m/s2) by LPM, while peak deceleration was underestimated (0.32 ± 1.17 m/s2).

Conclusion:

LPM accuracy appears acceptable for most measurements of average acceleration and deceleration, but for peak acceleration and deceleration accuracy is limited. However, when these error margins are kept in mind, the system may be used in practice for quantifying average accelerations and parameters such as summed accelerations or time spent in acceleration zones.

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Ryu Nagahara, Alberto Botter, Enrico Rejc, Masaaki Koido, Takeshi Shimizu, Pierre Samozino and Jean-Benoit Morin

Purpose:

To test the concurrent validity of data from 2 different global positioning system (GPS) units for obtaining mechanical properties during sprint acceleration using a field method recently validated by Samozino et al.

Methods:

Thirty-two athletes performed maximal straight-line sprints, and their running speed was simultaneously measured by GPS units (sampling rate: 20 or 5 Hz) and either a radar or laser device (devices taken as references). Lower-limb mechanical properties of sprint acceleration (theoretical maximal force, theoretical maximal speed, maximal power) were derived from a modeling of the speed–time curves using an exponential function in both measurements. Comparisons of mechanical properties from 20- and 5-Hz GPS units with those from reference devices were performed for 80 and 62 trials, respectively.

Results:

The percentage bias showed a wide range of overestimation or underestimation for both systems (-7.9% to 9.7% and -5.1% to 2.9% for 20- and 5-Hz GPS), while the ranges of its 90% confidence limits for 20-Hz GPS were markedly smaller than those for 5-Hz GPS. These results were supported by the correlation analyses.

Conclusions:

Overall, the concurrent validity for all variables derived from 20-Hz GPS measurements was better than that obtained from the 5-Hz GPS units. However, in the current state of GPS devices’ accuracy for speed–time measurements over a maximal sprint acceleration, it is recommended that radar, laser devices, and timing gates remain the reference methods for implementing the computations of Samozino et al.