Running Gait Kinetics Associated With Hamstring And Quadriceps Strength Profiles

PURPOSE: The relationships between hamstring and quadriceps strength on running biomechanics remains unknown. The purpose of this study is to evaluate the potential relationships between hamstring and quadriceps strength and running gait kinetics in healthy adult athletes. METHODS: We conducted a cross sectional study of 554 healthy uninjured athletes (Female: 355, mean age: 35 ± 12 yrs; Male: 199, mean age 41 ± 13 yrs) who underwent structured clinical and gait assessments at a hospital-affiliated sports medicine clinic between the years of 2013-2021. Measures of interest included total isometric hamstring and quadriceps strength (newtons) using handheld dynamometer protocol (mean maximal force based on 2 trials on each side), and running biomechanics at self-selected moderate speed on forceplate treadmill: cadence (steps/minute), height-normalized step length (cm), body-weight adjusted maximum ground reaction force (%BW), and stance phase as percent of total gait cycle (%stance). Linear regression was used to assess the relationships between mass-normalized hamstring and quadriceps strength and running biomechanics, with age and sex as covariates. RESULTS: Mass-normalized quad strength and hamstring strength were both directly associated with higher cadence (t: 2.98-3.36; p: <.001) and inversely associated with stance phase % (t: -5.01 - 4.31; p < .001). Hamstring strength was also directly associated with height-normalized step lengths (t = 3.06, p < .002) and inversely associated with mass-normalized max GRF amplitudes (%BW) (t:-1.92, p = .05). There was no association between quad strength and step length or max GRF amplitude. CONCLUSIONS: Greater hamstring strength was associated with reduced BW-adjusted max GRF, which may have meaningful implications in energy absorption and reduced stress on the lower extremity. Greater total quadriceps and hamstring strength were each independently associated with higher cadence and reduced percentage of the gait cycle in stance phase, both of which have been associated with lower injury risk and more efficient running economy.