Assessing Between-limb Differences In Prospectively Injured And Uninjured Runners Using Dynamical Measures Of Gait

Abstract

Between limb differences in the dynamic interactions of leg joints and segments may reflect rotational stresses and soft tissue strain experienced during gait, leading to greater insight of running related injury mechanisms than discrete measures. PURPOSE: Determine between limb differences in coordinative variability (CAV) in prospectively injured and uninjured runners. METHODS: Over ground running (4.0 m/s ± 5%) was recorded with motion capture at enrollment. An injury was any running related pain that caused modified training for ≥1 day. Coupling angles between sagittal knee, transverse shank and frontal ankle angles were calculated via vector coding. Mean CAV was calculated for each couple within each third of stance (initial, mid, late). Asymmetry was quantified as the percent difference in CAV between legs. Wilcoxon Signed Rank Tests were used to compare CAV between legs within each group and between-group differences in CAV asymmetry were assessed with Mann-Whitney U Tests. RESULTS: Injured (n=16) runners had significantly greater shank-ankle and knee-shank CAV in the injured leg in initial and late stance but lower shank-ankle CAV in mid stance (P<0.05; Fig. 1). Uninjured (n=15) runners had significantly greater shank-ankle CAV in the right leg in initial and mid stance but in the left leg in late stance, and greater knee-shank CAV in the right leg in mid-stance (P<0.05). CAV asymmetry was similar between groups. CONCLUSION: We recommend comparing injured legs of injured runners to the matched leg of uninjured runners, rather than randomly selecting legs from the uninjured group. Greater knee-shank CAV in initial and late stance may influence prospective injury risk.Fig 1: Group mean CAV across stance for the injured and uninjured legs in the injured runners (top row) and between right and left legs in the uninjured runners (bottom row). Vertical dashed lines demarcate initial, mid and late stance. *p<0.05 indicates significant differences in CAV between legs.