Modulation of leg muscle activity and gait kinematics by walking speed and bodyweight unloading.

During rehabilitation, many patient groups are being trained using bodyweight-supported treadmill training. However, little is known about modulation of time and distance parameters, joint movements and leg muscle EMG patterns by very low walking speeds or partial bodyweight unloading. We collected data from 20 healthy young volunteers who walked on a treadmill at walking speeds varying between 0.5 and 5.0 km h(-1) (0.14-1.39 ms(-1)) and with 0%, 25%, 50% and 75% bodyweight unloading. We found that cadence and stride length were largely influenced by walking speed, while bodyweight unloading influenced these measures only at 75%. However, the relative duration of the gait phases changed largely only at walking speeds less than 2.5 km h(-1), but was influenced by all different bodyweight unloading conditions. Joint trajectories of knee and ankle joint, as well as leg muscle EMG activity patterns changed largely at walking speeds slower than 2.5 km h(-1) and with 75% bodyweight unloading. We concluded that the parameters we investigated changed minimally at walking speeds faster than 2.5 km h(-1) and bodyweight unloading conditions less than 50%. Therefore, standards for EMG activity and joint angle trajectories should only be compared when the training is done with velocities higher than 2.5 km h(-1) and less than 50% body weight unloading.