Time-varying behaviour, test-retest reliability and concurrent validity of lateral trunk lean and toe-out angles during prolonged treadmill walking

Lateral trunk lean over the stance limb and toeing-out are potential adaptive gait mechanisms that reduce knee joint loading. The purpose of the present study was to evaluate the time-varying behaviour, the test-retest reliability and the concurrent validity of lateral trunk lean angle and toe-out angle during prolonged walking in healthy adults. Twenty healthy volunteers (51 ± 8 years, 12 females) completed two test sessions at least 24 h apart but within the same week. For each participant, at each session, three-dimensional gait kinematics were assessed intermittently during 60 min of treadmill walking. Additionally, over-ground three-dimensional gait analysis was performed immediately before and after the treadmill walking. Maximum lateral trunk lean angle and maximum toe-out angle did not change over time (p > 0.05), were consistent from day to day (test-retest reliability: ICC = 0.61-0.72 and 0.90-0.95, respectively) and were consistent with over-ground measures (concurrent validity: ICC = 0.88 and 0.92, respectively). These findings suggest that lateral trunk lean angle and toe-out angle are consistent during prolonged walking and that these measures are reliable and valid for use in studying adaptive gait mechanisms.