The effects of heading motion and sex on lower extremity biomechanics in soccer players.

ABSTRACT

BACKGROUND: Soccer is one of the most popular sports worldwide, which subsequently increases the number of injuries experienced by players. Furthermore, a large percentage of all anterior cruciate ligament injuries occur while playing soccer. In order to more clearly understand injury mechanisms, it is important to make the testing environment as real-life as possible. Inclusion of an external focus and secondary task, such as heading a soccer ball, may increase joint loading during landing. The purpose of this study was to investigate the effect of a forward heading motion on lower extremity kinetics and kinematics between sexes during a stop-jump task and a jump-heading task. METHODS: Ten male and ten female soccer players performed stop-jumps with no soccer ball present and jump-headings with a soccer ball present. Three-dimensional kinematics and kinetics were collected and analyzed during the landing. 2 × 2 mixed design analysis of variances (ANOVA) were performed to examine sex × jump task interactions and determine the main effects of sex and jump task. RESULTS: Results indicated jump-heading yields greater peak vertical ground reaction forces, an 8% increase in peak knee extension moments, a reduced initial knee flexion angle by approximately 5°, and an increased initial hip flexion angle by approximately 7°. Additionally, females exhibited 5.6° greater peak knee abduction angles compared to men, regardless of task. CONCLUSIONS: Inclusion of an overhead target may have distracted the athletes from focusing on frontal plane knee control when landing, and could potentially lead to increased ACL stress.