Body weight unloading is essential for enhancing stability and balance during gait rehabilitation. Techniques such as mechanical overhead unloading and underwater immersion modulate sensory feedback and motor commands, yet the neuromotor mechanisms underlying biomechanical changes in gait and muscle activity remain unclear. This series of studies investigates neurophysiological adaptations to body weight support (BWS) during gait and balance using non-invasive electroencephalography (EEG) and electromyography (EMG) to identify neural adaptation biomarkers. We hypothesized that BWS would reduce lower limb muscle loads and cortical engagement during walking.

Our investigation focuses on four specific aims:​ 1. Determine the influence of bodyweight unloading on human electrical brain and muscle dynamics during standing balance in an underwater environment:​ Reduced body weight in an underwater environment decreased ankle plantar flexor muscle activity and increased alpha band EEG spectral power from the right premotor cortex. Underwater balance perturbations increased muscle activations surrounding the ankle and knee joints, and increased theta and decreased alpha and beta band EEG spectral power from the premotor cortex, prefrontal, and parietal cortices. 2. Compare lower limb biomechanics during body weight supported treadmill locomotion using mechanical overhead unloading and underwater buoyancy:​ We achieved high gait event detection accuracy during on-land body weight supported treadmill walking. Underwater gait event detection required specific training data due to biomechanical differences, but we successfully classified gait events using single-axis inertial measurement unit data and machine learning. 3. Identify human myoelectric and electrocortical activation dynamics during body weight supported treadmill locomotion using mechanical overhead unloading and underwater buoyancy:​ Underwater walking reduced frontoparietal alpha and beta band EEG spectral power, while increasing EMG activity from the rectus femoris, biceps femoris, tibialis anterior, and lateral gastrocnemius muscles, compared to on-land walking with and without mechanical unloading. 4. Identify neural correlates of human electrocortical and myoelectric adaptations during body weight supported treadmill locomotion:​ Phase-dependent cortico-muscular synergies revealed neural and muscular adaptations during body weight supported walking. Compared to walking without BWS or with 50% BWS, during the stance phase, 30% BWS reduced physical and neural demands, as indicated by reduced EMG activation and increased alpha band EEG spectral power.

Our findings improve our understanding of neuromotor control during body weight supported treadmill walking that can enhance targeted rehabilitation strategies and advance neurotechnologies for gait rehabilitation.