Non-linear Lower Extremity Joint Torque Changes Observed during Preparation for Walk-to-run Gait Transition

Abstract

PURPOSE: To investigate lower extremity torque components changes in preparation for gait transition with increased walking speed. METHODS: 11 male and 3 female college students (age: 22.6 ± 1.9 years, body mass: 75.4 ± 12.8 kg, height: 1.73 ± 0.08 m) were recruited for this study. Participants walked on a force plates embedded treadmill (AMTI, MA, USA) with continuously changed walking speed approaching walk-to-run transition. Ground reaction forces and kinematic data (VICON, Oxford, UK) were obtained at sampling rate of 1000 Hz and 200 Hz, respectively. The results of inverse dynamics were further decomposed into net joint torque (NET), gravitational torque (GTT), motion-dependent torque (MDT), contact torque (EXT), and generalized muscle torque (MST) for the last five strides before gait transition. Owe-way MANOVA employed to exam the difference among the five strides. Post hoc polynomial trend analyses were also employed to examine the trend with the five strides whenever suitable. RESULTS: Significant difference of all three lower extremity joints was detected during stance phase. Positive / negative values represent extension / flexion torque. EXT and MST of ankle (0.15 ± 0.02 vs. 0.15 ± 0.03 vs. 0.16 ± 0.02 vs. 0.15 ± 0.02 vs. 0.01 ± 0.01 nm/kg; -0.18 ± 0.02 vs. -0.18 ± 0.03 vs. -0.19 ± 0.03 vs. -0.18 ± 0.02 vs. -0.04 ± 0.01 nm/kg); knee (-0.60 ± 0.11 vs. -0.64 ± 0.11 vs. -0.74 ± 0.12 vs. -0.70 ± 0.11 vs. -1.34 ± 0.12 nm/kg; 0.51± 0.09 vs. 0.55 ± 0.09 vs. 0.63 ± 0.09 vs. 0.59 ± 0.10 vs. 1.25 ± 0.09 nm/kg) displayed significantly decrease / increase at last stride before gait transition during early stance phase (p < .05), as were the knee (-0.27 ± 0.03 vs. -0.31 ± 0.04 vs. -0.28 ±0.04 vs. -0.28 ± 0.04 vs. -0.13 ± 0.02 nm/kg; 0.36 ± 0.03 vs. 0.41 ± 0.03 vs. 0.39 ± 0.04 vs. 0.38 ± 0.04 vs. 0.23 ± 0.02 nm/kg) and hip (0.74 ± 0.08 vs. 0.78 ±0.07 vs. 0.73 ± 0.08 vs. 0.75 ±0.09 vs. 0.21 ± 0.04 nm/kg; -1.11± 0.07 vs. -1.15 ± 0.07 vs. -1.13 ± 0.06 vs. -1.15 ± 0.07 vs. -0.74 ± 0.03 nm/kg) responses at end of stance phase (p < .05). These variables also displayed significantly quadratic trend as speed increase (p < .05). CONCLUSIONS: Nonlinear changes in active / passive torques magnitudes observed during gait transition through continuously increased walking velocity. Gait transition was initiated during strides before gait transition.