Child And Adolescent Hamstrings:Quadriceps Strength Ratio Effects On Running Biomechanics

Abstract

PURPOSE: There is limited research on strength and gait biomechanics implications in young runners. The purpose of this study was to assess the relationship of hamstrings-to-quadriceps strength (H:Q) ratio with mass-adjusted peak ground reaction force (GRF), and percentage of gait spent in stance phase (stance%) in children and adolescents. METHODS: Healthy runners age 9-21 years who received anthropomorphic measures, isometric muscle strength testing using hand-held dynamometry, and a running gait analysis on force plate treadmill were included. Linear regressions were used to assess the relationship between H:Q ratio with GRF and stance% by age and sex. Independent t-tests were used to compare strength measures by H:Q ratio symmetry (more symmetric: ≥0.6; less symmetric: <0.6). RESULTS: Data from 796 athletes was analyzed; most were 14-17 years old (48.2%) and females (71%). Those with less symmetric H:Q ratio had significantly weaker hamstrings (Mean Difference: 5.90 Nm [0.33], p = 0.04), however there were equivocal quadriceps measures regardless of H:Q symmetry (p = 0.16). H:Q ratio was inversely associated with mass-adjusted GRF, and directly associated with stance%. Interaction effects were seen between age, sex, and H:Q ratio (Table). CONCLUSIONS: In this young runner population, variance in the H:Q ratio was primarily attributable to relative hamstring weakness. H:Q ratio was inversely associated with mass-adjusted GRF and directly associated with stance%, both running biomechanics features which have been associated with injury risk. Unique gait pattern differences between sexes and developmental levels were identified.