The influence of delivery method and impact location on soccer heading kinetics in adolescent and adult females

OBJECTIVES: Novel metrics characterizing power and energy transfer could provide comprehensive descriptions of heading biomechanics. This study characterizes these metrics across ball delivery methods and impact locations and uses descriptive measures to compare metric distributions. We hypothesize that headers from long kicks have higher magnitudes and that power and energy metrics exhibit greater distributional spread than peak kinematics. DESIGN: Prospective cohort design over one season of play. METHODS: 19 athletes (College: n = 13; U15: n = 6) were instrumented with custom mouthpiece sensors. Peak resultant kinematics and 12 metrics describing impact power and energy transfer were calculated. Headers were characterized by ball delivery and impact location. Mixed-effects models assessed the relationship between these factors while adjusting for level of play and session type. Skewness and kurtosis were used to compare metric distributions. RESULTS: 529 headers were analyzed. All outcome measures were significantly associated with ball delivery method. Balls delivered via long kicks (n = 206) displayed greater magnitudes. Headers using the forehead (n = 224) tended to present lower power ratios, a metric quantifying the proportion of rotational head motion relative to translational head motion. Power and energy metrics displayed greater skewness and kurtosis than peak head kinematics. CONCLUSIONS: Power and energy metrics demonstrated greater distributional spread and may provide a complementary characterization of head loading alongside peak kinematics for more comprehensive analyses. These metrics are also easy to interpret, providing additional tools for exposure monitoring and future studies examining impact characteristics and clinical outcomes for injury risk and cumulative head impact exposure.