Inter-limb step asymmetry in closed and open skill sprint accelerations in soccer players

Abstract

Purpose: Inter-limb differences may have detrimental effects on sports performance. There is a need to understand the comparison of asymmetries between open and closed skill tasks. The study investigated inter-limb step asymmetry responses to closed and open skill acceleration sprint running tasks. Material and Methods: 3D motion analysis kinematic data of step characteristics were collected from 20 male soccer players (mean±SD: 21±1.9 years, 78.7±7.7 kg, 1.78±0.06 m) for bilaterally located lower-limb markers during the initial 20 m of closed and open skill acceleration sprint running trials. Step velocity, step length, step frequency, flight time, contact time and flight distance were calculated. In the closed skill condition, players were aware of the final sprint distance prior to initiation. In the open skill conditions, players were informed of the final sprint distance (20 or 40 m) immediately after initiating the run. Results: Players displayed significant (0.10 to 10.3 %, p<0.05) asymmetries in their step characteristics during closed skill acceleration sprint performances. Positive correlations (r=0.51 to 0.77, p<0.05) were evidenced between the asymmetry scores in the closed skill and in the open skill 20 m and 40 m conditions. Asymmetry scores were not found to be associated with sprint performance (r=-0.13 to 0.30, p>0.05), suggesting that asymmetry may be functional or dysfunctional. Conclusions: Skilled soccer players are able to regulate step characteristic asymmetries across closed and open skill tasks. Symmetry should not be assumed when assessing open and closed skill acceleration sprint performance in soccer players. Practitioners should be aware of these asymmetries when implementing programmes.