We aimed to investigate the influence of impeding horizontal force around the COM during gait on common neural drives to ankle muscles using the EMG-EMG coherence analyses.
Twenty healthy young adults with right-leg dominance performed three gait conditions for each 5 min; normal gait without additional horizontal force and gait with aiding and impeding horizontal forces around the waist at the second sacral spine level. The aiding and impeding horizontal forces were applied in the sagittal plane via a horizontal rope connected to a waist belt and suspended a 5% body weight container. Reflective markers were applied on the heels on both sides, head of the fifth metatarsal head, lateral malleolus, lateral knee joint space, and greater trochanter on the right side, and the first metatarsal head on the left side of the participants. Motion analyses in the sagittal plane were performed to evaluate the trailing limb angle (TLA) as an indicator of forward propulsion, which was calculated as the angle between the line connecting the greater trochanter and the fifth metatarsal head and vertical axis to the floor at terminal stance on the right side. The average EMG-EMG coherence of the proximal and distal parts of the tibialis anterior muscle (TA-TA) and medialis and lateralis gastrocnemius muscles (MG-LG) in the 7.5 to 15 Hz (alpha) and 15 to 35 Hz (beta) frequency bands were calculated during the three gait conditions using each 200 gait cycles.
TLA significantly increased in the impeding force condition than the normal gait and aiding force condition. MG-LG coherence in the alpha band significantly increased in the impeding force condition than the normal gait and aiding force condition, whereas MG-LG coherence in the beta band significantly increased in the impeding force condition only compared to the aiding force condition.
Impeding horizontal force around the COM during gait could increase forward propulsion due to the common neural drives primarily from the subcortical origin such as the spinal origin, with some cortical involvement, to triceps surae muscles.
Gait training with impeding horizontal force increases the forward propulsion and common neural drive from the subcortical origin, which may be an effective physiotherapy practice for improving gait function in patients with central nervous system disorders.
Coherence
Propulsion force
