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Michelle A. Sandrey, Yu-Jen Chang and Jean L. McCrory

time (prefatigue and postfatigue). The dependent variables were the linear envelope measurements of the medial gastrocnemius (MG), SOL, and tibialis anterior and tibial peak accelerations (resultant acceleration takeoff and landing). Participants A total of 30 active college-aged students with and

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Hatice Mujde Ayık and Michael J. Griffin

Characteristics of the Mediolateral Acceleration Used in the Study Waveform r.m.s. acceleration, m·s −2 Peak acceleration, m·s −2 r.m.s. velocity, m·s −1 Peak velocity, m·s −1 CF Waveform r.m.s. acceleration, m·s −2 Peak acceleration, m·s −2 r.m.s. velocity, m·s −1 Peak velocity, m·s −1 CF f  = 1 Hz; Part A f

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Oren Tirosh, Guy Orland, Alon Eliakim, Dan Nemet and Nili Steinberg

frequency 34 domains was calculated as follows: (a) Peak acceleration attenuation coefficient—(1 – “peak positive acceleration measured at the lower spine”/“peak positive acceleration of the tibia measured at foot contact”) × 100, where peak acceleration attenuation coefficient representing the attenuation

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James W. Roberts

based on endpoint variability is robust ( Elliott et al., 2004 ; Worringham, 1991 ), it remains to be seen whether the same assumption of a normal trend in the response distribution unfolds at earlier kinematic landmarks (peak acceleration [PA], peak velocity [PV], and peak deceleration [PD]). Indeed

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

on the wheel). 4 , 17 Performance Variables Five-meter-sprint time was recorded using a laser timing system (Kinematic Measurement System, Fitness Technology, Australia). Peak acceleration for each stroke was recorded using a triaxial accelerometer (x8m-3mini, Gulf Data Concepts, USA) secured to the

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Hermann Zbinden-Foncea, Isabel Rada, Jesus Gomez, Marco Kokaly, Trent Stellingwerff, Louise Deldicque and Luis Peñailillo

measure Description Flight time s Time spent in the air from jump takeoff to landing Peak force during eccentric phase N Greatest force achieved during the eccentric phase Peak force during concentric phase N Greatest force achieved during the concentric phase Peak acceleration m/s 2 Greatest acceleration

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Alison Schinkel-Ivy, Timothy A. Burkhart and David M. Andrews

To date, there has not been a direct examination of the effect that tissue composition (lean mass/muscle, fat mass, bone mineral content) differences between males and females has on how the tibia responds to impacts similar to those seen during running. To evaluate this, controlled heel impacts were imparted to 36 participants (6 M and 6 F in each of low, medium and high percent body fat [BF] groups) using a human pendulum. A skin-mounted accelerometer medial to the tibial tuberosity was used to determine the tibial response parameters (peak acceleration, acceleration slope and time to peak acceleration). There were no consistent effects of BF or specific tissue masses on the un-normalized tibial response parameters. However, females experienced 25% greater peak acceleration than males. When normalized to lean mass, wobbling mass, and bone mineral content, females experienced 50%, 62% and 70% greater peak acceleration, respectively, per gram of tissue than males. Higher magnitudes of lean mass and bone mass significantly contributed to decreased acceleration responses in general.

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Melissa M.B. Morrow, Wendy J. Hurd, Emma Fortune, Vipul Lugade and Kenton R. Kaufman

This study aimed to define accelerations measured at the waist and lower extremities over a range of gait velocities to provide reference data for choosing the appropriate accelerometer for field-based human activity monitoring studies. Accelerations were measured with a custom activity monitor (± 16g) at the waist, thighs, and ankles in 11 participants over a range of gait velocities from slow walking to running speeds. The cumulative frequencies and peak accelerations were determined. Cumulative acceleration amplitudes for the waist, thighs, and ankles during gait velocities up to 4.8 m/s were within the standard commercial g-range (± 6g) in 99.8%, 99.0%, and 96.5% of the data, respectively. Conversely, peak acceleration amplitudes exceeding the limits of many commercially available activity monitors were observed at the waist, thighs, and ankles, with the highest peaks at the ankles, as expected. At the thighs, and more so at the ankles, nearly 50% of the peak accelerations would not be detected when the gait velocity exceeds a walking velocity. Activity monitor choice is application specific, and investigators should be aware that when measuring high-intensity gait velocity activities with commercial units that impose a ceiling at ± 6g, peak accelerations may not be measured.

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Adriana M. Holmes and David M. Andrews

The purpose of this research was to examine the effects of voluntarily manipulating muscle activation and localized muscle fatigue on tibial response parameters, including peak tibial acceleration, time to peak tibial acceleration, and the acceleration slope, measured at the knee during unshod heel impacts. A human pendulum delivered consistent impacts to 15 female and 15 male subjects. The tibialis anterior and lateral gastrocnemius were examined using electromyography, thus allowing voluntary contraction to various activation states (baseline, 15%, 30%, 45%, and 60% of the maximum activation state) and assessing localized muscle fatigue. A skin-mounted uniaxial accelerometer, preloaded medial to the tibial tuberosity, allowed tibial response parameter determination. There were significant decreases in peak acceleration during tibialis anterior fatigue, compared to baseline and all other activation states. In females, increased time to peak acceleration and decreased acceleration slope occurred during fatigue compared to 30% and 45%, and compared to 15% through 60% of the maximum activation state, respectively. Slight peak acceleration and acceleration slope increases, and decreased time to peak acceleration as activation state increased during tibialis anterior testing, were noted. When examining the lateral gastrocnemius, the time to peak acceleration was significantly higher across gender in the middle activation states than at the baseline and fatigue states. The acceleration slope decreased at all activation states above baseline in females, and decreased at 60% of the maximum activation state in males compared to the baseline and fatigue states. Findings agree with localized muscle fatigue literature, suggesting that with fatigue there is decreased impact transmission, which may protect the leg. The relative effects of leg stiffness and ankle angle on tibial response need to be verified.

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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.