Preferred foot strategy for sprint initiation in children

Abstract

Research question: Sprinters set their preferred feet on starting blocks. Are there any strategies for children,who have not acquired mature sprint skill in accelerated run, to choose their preferred foot at sprint initiation? Introduction: Laterality and/or limb preference is determined by preferential use of unilateral limb in voluntary movements [1]. Although no significant difference was found in kinematics between preferred and non-preferred foot during gait initiation in adults [2], children seem to choose their motoric behavior dependent on their limbpreference. If so, attaining highhorizontal velocity of whole-body center of mass from 0m/s (i.e., sprint initiation) could be affected by limb preference. The purpose of this studywas to detect the preferred foot strategy on sprint initiation in children. Materials andmethods: Thirty-three children participated (20 boys and 13 girls, age 12.8±1.0 yrs). Lower limb preference was assessed in previous studies [3] (right =21, left = 7). Four trials of 5-m sprint were performed. Sprint timewasmeasuredwith a phototube sensor. Forces and resultant impulses from each foot were calculatedwith force platforms. At start position, participantswere instructed to put one foot on the front platform and the other foot on the rear platform. No other instructions were given during the 1st and 2nd trials. The tester observed their preferential foot placing on the platform and the initial swinging leg. Then, for the 3rd and 4th trials, participants were instructed to replace their front and rear feet on starting position contrary to the 1st and 2nd trials, and the initial swing leg was observed. Front-rear (FR) strategy was defined as participants always using their front or rear legs as the initial swing leg, while right-left (RL) strategy was defined as participants using their preferred limb as the initial swing leg. Results: In the 1st and 2nd trials, 13 out of 33 participants put their right foot on the front and 20 participants set left on the front. Swing initiation from front leg was seen in 20 participants, while the rear leg initiation in 9. There was no significant correlation between limb preference, preferential foot placing, and initiating the swing. For the 3rd and 4th trials, 20 participants changed their initial swinging leg to the opposite side, suggesting FR strategy; while, 2 participants started with the same foot, suggesting RL strategy. The others had no constant strategy of initial swing leg. Sprint times of 3rd and 4th trials were significantly slower than the 1st and 2nd trials (p<0.01). No significant differences in the maximumground reaction force and impulsewere found between trials (0.173=p=0.991). Discussion: The sprint initiation in children is determined by the front-rear strategy rather than the preferred foot strategy.