Lower Extremity Joint Stiffness And Energy Generation In Gait Transitions

Abstract

Walk-to-run (WRT) or run-to-walk transitions (RWT) occur when walking at a constantly accelerated speed or running at a constantly decelerated speed. Lower extremity joint level kinetic patterns are related to gait transition mechanisms. Little is known about lower extremity joint stiffness, or mechanical work generation in the WRT and RWT processes. PURPOSE: To identify ankle, knee and hip joint stiffness and mechanical work generation patterns in WRT and RWT processes. METHODS: Ten middle age healthy subjects (50.7 ± 6.0 years, 173.4 ± 11.4 cm, 69.7 ± 14.9 kg) participated in treadmill WRT (1.8 m/s - 2.4 m/s) and RWT (2.4 m/s - 1.8 m/s) tests, with acceleration and deceleration set to 0.1 m/s2 and - 0.1 m/s2, respectively. Five steps were selected for data analysis: transition step (S0); two steps before transition (S-2, S-1); two steps after transition (S1, S2). Joint stiffness (Kjoint) was calculated as change in sagittal plane joint moment (∆Mjoint) divided by sagittal plane joint angular displacement (∆θjoint) in the braking phase of ground contact (Kjoint = ∆Mjoint/∆θjoint). Stance phase joint positive mechanical work (Wjoint+ ) was calculated as the sum of all positive net joint power integrated over time. RESULTS: In WRT, Kankle at S2 was higher than S-2 (p = 0.0004), S-1 (p = 0.0007) and S0 (p = 0.0001); Khip at S1 was higher than S-2 (p = 0.0002) and S-1 (p = 0.0001). In RWT, Kankle at S2 was lower than S-2 (p = 0.0009) and S-1 (p = 0.0006); Khip at S-1 was higher than S1 (p = 0.001) and S2 (p = 0.0003). In WRT stance phase, Wankle+ and Wknee+ were 34% and 60% higher, respectively at S0 compared with S-1; while for Whip+ there was a significant decrease (p = 0.0006) at S0 compared with S-1. In RWT stance phase, Wankle+ and Wknee+ at S0 were 28% and 42% lower than S-1, respectively; while Whip+ at S0 was 78% higher than S-1. CONCLUSIONS: Both WRT and RWT affected Kankle and Khip in the transition step and subsequent steps. Stance phase joint energy generation tended to transfer from proximal to distal during WRT, and vice versa during the RWT process. (Supported by Betty Foster McCue Scholarship.)