Author(s): YAMAZAKI, Y., MATSUI, S., NORO, H., HATA, K., ISHIKAWA, M., LEE, R.Y., YANAGIYA, T., Institution: JUNTENDO UNIVERSITY, Country: JAPAN, Abstract-ID: 1459

INTRODUCTION:
The towing sprint is one of the assisted sprinting training methods. It can increase sprinting speed due to improved step frequency and step length1),2). Consequently, the kinematics and kinetics of assisted sprinting differ from normal sprinting, including shorter contact time2), smaller knee angle change during stance phase3), and larger impulse4).
Therefore, assisted sprinting improves sprint velocity by altering the kinematics of lower leg and resultant force. However, most of the previous research has compared assisted sprinting with normal sprinting, leaving the acute effects of assisted sprinting on subsequent sprint performance unexplored. Hence, this study aimed to determine the acute effect of assisted sprinting on kinematics and kinetics of subsequent sprinting.
METHODS:
Nineteen male sprinters (age: 20.0 ± 1.7 years, height: 1.74 ± 0.06 m, weight: 66.0 ± 4.8 kg, world athletics score: 883.6 ± 96.2 score) performed maximal sprinting. Each sprinting sequence involved three trials: two unassisted 60-m sprinting before and after a single assisted sprinting using a motorized towing device with a 10% body weight load in isotonic mode. The sprinting motion from 50 to 60-m was recorded using two video cameras (240 fps). Sprinting speed, spatiotemporal and kinematic variables were calculated from the captured video in the sagittal plane. Plantar loading in the forefoot, midfoot, rearfoot and their total loading during sprinting were recorded using wireless, mobile insole sensor. Peak plantar loading and impulse during stance phase were calculated.
RESULTS:
No significant differences were found in sprinting speed and spatiotemporal variables between Pre and Post. However, the mean values of hip flexion and extension angular velocities during the flight phase were significantly higher in the Post compared to the Pre (hip flexion: Pre 370.92 ± 38.20 deg/s, Post 405.41 ± 42.27 deg/s, hip extension: Pre 363.96 ± 35.88 deg/s, Post 389.60 ± 31.14 deg/s). Both peak total plantar loading and impulse were higher in the Post compared to the Pre, particularly in the rearfoot, although no significant differences were observed in plantar loading.
CONCLUSION:
Sprinting speed was not significantly increased following the assisted sprinting, although the acute effect of increasing the thigh swinging velocity was observed.

【References】
1) Mero & Komi, Eur J Appl Physiol, 1986.
2) Clark et al., J Strength Cond Res, 2021.
3) Sugiura & Aoki, Advances in exercise and sports physiology, 2008.
4) Mero et al., Int J Sports Med, 1987.