Lower limb joint work modulation during split-belt treadmill walking

Split-belt treadmills (SBT) have become a valuable tool for studying motor learning and rehabilitating gait impairments. How SBT alters the mechanical demands of the lower extremity joints remains unclear. Clarifying these demands may inform whether SBT training is appropriate for different clinical populations. In this study, we compared lower-limb joint mechanical work and ground reaction forces (GRFs) between tied-belt walking and SBT walking. We collected kinetic and kinematic data from twenty young adults walking on an instrumented dual-belt treadmill. The protocol included 3 min of Baseline walking (both belts at 1 m/s), 6 min of Adaptation (left belt increased to 2 m/s), and 3 min of Post Adaptation (after the left belt returned to 1 m/s). We calculated sagittal plane joint mechanical work of the ankle, knee and hip over the stance phase. We used linear mixed models to determine the effect of adaptation period on joint work and GRFs. From Baseline to Late Adaptation, positive mechanical work increased at the fast-side ankle (p = 0.025) and the slow-side hip (p < 0.001). Additionally, negative joint mechanical work increased bilaterally at the knees (p < 0.001). We also observed increased propulsive forces on the fast-side (p < 0.001) and increased first peak vertical GRF on the slow-side (p < 0.001). Recognizing these joint-specific demands can help guide the clinical application of split-belt treadmill training.