Timing of Gun Fire Influences Sprinters' Multiple Joint Reaction Times of Whole Body in Block Start.

Mitsuo Otsuka,Toshiyuki Kurihara,Tadao Isaka

doi:10.3389/fpsyg.2017.00810

Abstract

Experienced sprinters are specifically adapted to pre-planning an advanced motor program. Herein, sprinters are able to immediately accelerate their center of mass forward with a whole-body coordinated motion, following a steady state crouched position. We examined the effect of variable timing of reaction signals on multiple joint reaction times (RT) and whole-body RT for specialist sprinters. Twenty well-experienced male sprinters performed five start-dashes from a block start under five variable foreperiod (FP) length conditions (1.465, 1.622, 1.780, 1.938, and 2.096 s), with trials randomly timed between a warning and an imperative tone. Participants’ sprinting motion and ground reaction forces of their four limbs during the block start were measured simultaneously. Whole-body RT was significantly shorter when FP length was longer; the values of whole-body RT were 117 ± 5 ms, 129 ± 5 ms, 125 ± 4 ms, 133 ± 6 ms, and 156 ± 8 ms in the 2.096, 1.938, 1.780, 1.622, and 1.465-s FP-length conditions, respectively. A repeated-measures analysis of variance found a significant joint-by-FP length interaction in joint-moment RT. These findings suggest that FP length affects coordinated motion in four limbs and whole-body RT. This information will be able to lead to new methods for start signals in sprint running events and advance our understanding of the association between FP length and dynamic coordinated motion.

Highlights

Experienced sprinters are adapted to accelerating their center of mass immediately forward after being in a steady set crouched position (Otsuka et al, 2014)
The reaction times (RT) is relatively longer after a shorter foreperiod (FP), which is the duration between warning and imperative signals and ranges from 0.5 to 3.0 s
A similar time-moment curve was observed in the rear-arm shoulder; joint RT was delayed compared to the front-arm shoulder

Summary

Introduction

Experienced sprinters are adapted to accelerating their center of mass immediately forward after being in a steady set crouched position (Otsuka et al, 2014) This block start motion sequence consists of eight steps: first, crouching down for the ‘on your marks’ position with legs flexed markedly on two starting blocks and with hands on the ground, second, being steady in the ‘on your marks’ position, third, hearing a warning signal, the ‘set’ command, fourth, extending legs for the crouched ‘set’ position, fifth, being in the ‘set’ position in which the forward arms crutch position is important for subsequent acceleration (Slawinski et al, 2010), sixth, hearing an imperative signal, i.e., gunfire, seventh, taking off the hands and extending legs while taking off the rear foot and the front foot from block starts, respectively, and eighth, connecting to the subsequent acceleration phase in which sprinters run with a forward-leaned posture (e.g., Kugler and Janshen, 2010; Morin et al, 2011, 2012). This is due to the fact that involving a delay in RT to an imperative signal by stimuli that are too closely spaced (psychological refractory period, e.g., Telford, 1931) and by unplanning the subsequent motor program

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