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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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Ted Polglaze and Matthias W. Hoppe

, and shown to be applicable for both acceleration and deceleration. 6 An alternative P met model exists, derived from the mechanical determinants of energy expenditure (EE) during running 7 ; however, this commentary will focus on the original and more prominent version. 4 Both models derive P met

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Julio Tous-Fajardo, Oliver Gonzalo-Skok, José Luis Arjol-Serrano and Per Tesch

Purpose:

To examine the effects of a novel isoinertial eccentric-overload and vibration training (EVT) paradigm on change-ofdirection (COD) speed and multiple performance tests applicable to soccer.

Methods:

Twenty-four young male players were assigned to an EVT (n = 12) or conventional combined (CONV, n = 12) group, once weekly for 11 wk. EVT consisted of 2 sets of 6–10 repetitions in 5 specific and 3 complementary exercises. CONV used comparable volume (2 sets of 6–10 reps in 3 sequences of 3 exercises) of conventional combined weight, plyometric, and linear speed exercises. Pre- and postintervention tests included 25-m sprint with 4 × 45° COD every 5th m (V-cut test), 10- and 30-m sprints, repeat-sprint ability, countermovement jump, and hopping (RJ5).

Results:

Group comparison showed very likely to likely better performance for EVT in the COD (effect size [ES] = 1.42), 30-m (ES = 0.98), 10-m (ES = 1.17), and average power (ES = 0.69) and jump height (ES = 0.69) during RJ5. There was a large (r = –.55) relationship between the increase in average hopping power and the reduced V-cut time.

Conclusions:

As EVT, not CONV, improved not only COD ability but also linear speed and reactive jumping, this “proof-of-principle” study suggests that this novel exercise paradigm performed once weekly could serve as a viable adjunct to improve performance tasks specific to soccer.

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Heidi R. Thornton, André R. Nelson, Jace A. Delaney, Fabio R. Serpiello and Grant M. Duthie

decelerations are categorized into thresholds, and the distance covered within these thresholds established, there was an inverse relationship between the magnitude of the change in speed and the accuracy the units for measures of acceleration and deceleration. Global positioning system technology is rapidly

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Esther Morencos, Blanca Romero-Moraleda, Carlo Castagna and David Casamichana

by the manufacturer 8 and are similar to those used by time motion investigations in hockey. 10 The numbers of accelerations and decelerations were analyzed using recently defined thresholds (low, 1–1.9 m·s −2 ; moderate, 2–2.9 m·s −2 ; high, >3 m·s −2 ). 19 Sprint number, sprint distance, and

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John F. Fitzpatrick, Kirsty M. Hicks and Philip R. Hayes

instantaneous velocity during acceleration, deceleration, and constant velocity movements during linear, multidirectional, and soccer-specific activities. 25 , 26 The external load measures used for analysis were total distance and acceleration and deceleration distance >2 m·s −2 . Arbitrary high-speed running

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Jordan L. Fox, Robert Stanton, Charli Sargent, Cody J. O’Grady and Aaron T. Scanlan

players to more accelerations and decelerations. Likewise, players may execute more jumps to reduce opposition scoring efficiency (eg, contest shots) and regain possession (eg, gather rebounds) when in a losing position during games. Similar external workload volume (PL) was recorded during wins and

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D.S. Blaise Williams III, Jonathan H. Cole and Douglas W. Powell

Running during sports and for physical activity often requires changes in velocity through acceleration and deceleration. While it is clear that lower extremity biomechanics vary during these accelerations and decelerations, the work requirements of the individual joints are not well understood. The purpose of this investigation was to measure the sagittal plane mechanical work of the individual lower extremity joints during acceleration, deceleration, and steady-state running. Ten runners were compared during acceleration, deceleration, and steady-state running using three-dimensional kinematics and kinetics measures. Total positive and negative joint work, and relative joint contributions to total work were compared between conditions. Total positive work progressively increased from deceleration to acceleration. This was due to greater ankle joint work during acceleration. While there was no significant change in total negative work during deceleration, there was a greater relative contribution of the knee to total negative work with a subsequent lower relative ankle negative work. Each lower extremity joint exhibits distinct functional roles in acceleration compared with deceleration during level running. Deceleration is dominated by greater contributions of the knee to negative work while acceleration is associated with a greater ankle contribution to positive work.

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Patricia S. Pohl and Carolee J. Winstein

The purpose of ihis study was to compare the effects of a single practice session on performance strategies used by young and older adults to decrease movement time (MT) while maintaining accuracy of an aiming task. Five young and 5 older adult males practiced until each accumulated 500 target hits in each of two complexity conditions as defined by Fitts’s law. Participants decreased MT with practice; however, older adults had longer MTs than the young, particularly in the high-complexity condition. With practice in the low-complexity condition, participants decreased absolute acceleration and deceleration times but maintained the relative amount of MT devoted to temporal phases. In contrast, with practice in the high-complexity condition, participants decreased absolute deceleration and dwell time and changed the temporal structure. Results suggest that older adults can decrease MT with practice and that the performance strategies adopted to speed performance are more a function of task complexity than age.

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Olav Krigolson, Jon Bell, Courtney M. Kent, Matthew Heath and Clay B. Holroyd

We used the event-related potential (ERP) methodology to examine differences in neural processing between visually and memory-guided reaches. Consistent with previous findings (e.g., Westwood, Heath, & Roy, 2003), memory-guided reaches undershot veridical target location to a greater extent than their visually guided counterparts. Analysis of the ERP data revealed that memory-guided reaches were associated with reduced potentials over medial-frontal cortex at target presentation and following movement onset. Further, we found that the amplitudes of the potentials over medial-frontal cortex for visually and memory-guided reaches were significantly correlated with the peak accelerations and decelerations of the reaching movements. Our results suggest that memory-guided reaches are mediated by a motor plan that is generated while a target is visible, and then stored in memory until needed—a result counter to recent behavioral theories asserting that memory-guided reaches are planned just before movement onset via a stored, sensory-based target representation.