Intramuscular Coherence of the Lower Flexor Muscles During Robotic Ankle-assisted Gait

Background: A close-fitting assisted walking device (RE-Gait) designed to assist ankle movements might be a novel approach for acquiring the forefoot rocker function in the gait cycle. The purpose of the present study was to investigate the effects of using RE-Gait by evaluating the intramuscular coherence (IMC) of the two parts of the tibialis anterior muscles (TA) in the initial, mid, and terminal swing phase, which could indicate whether the common synaptic drive of motor neurons was populated.Methods: Seventeen healthy volunteers walked on a treadmill at a comfortable speed before, during, and immediately after 15-minute RE-Gait intervention (pre / RG / post). RE-Gait supported plantar flexion at toe lift-off in the terminal stance phase and dorsiflexion in the initial swing phase. Electromyograms of the right lower leg and gait parameters were analyzed for each session.Results: After RE-Gait intervention, the step length was significantly increased. IMC of the two parts of the TA muscles in the beta frequency band in the initial swing phase was significantly enhanced during RE-Gait intervention compared with pre session. In addition, IMCs in the beta and low-gamma frequency bands were significantly correlated with the enhancement ratio of the step length.Conclusions: These results suggest that robotic ankle planter flexion and dorsiflexion assistance in the pre- and initial swing phase would be effective for learning adaptively modified walking by activating corticospinal tracts. RE-Gait will be a useful tool for re-learning of gait with smooth switching with appropriate forefoot rocker function.

Increased intramuscular coherence is associated with temporal gait symmetry during split-belt locomotor adaptation

When walking on a split-belt treadmill where one belt moves faster than the other, the nervous system consistently attempts to maintain symmetry between legs, quantified as deviation from double support time or step length symmetry. It is known that the cerebellum plays a critical role in locomotor adaptation. Less is known about the role of corticospinal drive in maintaining this type of proprioceptive-driven locomotor adaptation. The objective of this study was to examine the functional role of oscillatory drive in relation to changes in spatiotemporal gait parameters during split-belt walking adaptation. Eighteen healthy participants adapted and deadapted on a split-belt treadmill; 13 out of 18 participants repeated the paradigm two more times to examine the effects of reexposure. Coherence analysis was used to quantify the coupling between electromyography (EMG) from the proximal (TAprox) and distal tibialis anterior (TAdist) muscle during the swing phase of walking. EMG-EMG coherence was examined within the alpha (8–15 Hz), beta (15–30 Hz), and gamma (30–45 Hz) frequencies. Our results showed that 1) beta- and gamma-band coherence (markers of corticospinal drive) increased during early split-belt walking compared with baseline walking in the slow leg, 2) beta-band coherence decreased from early to late split-belt adaptation in the fast leg, 3) alpha-, beta-, and gamma-band coherence decreased from first to third split-belt exposure in the fast leg, and 4) there was a relationship between higher beta coherence in the slow leg TA and smaller double support asymmetry. Our results suggest that corticospinal drive may play a functional role in the temporal control of split-belt walking adaptation. NEW & NOTEWORTHY This is the first study to examine the functional role of intramuscular coherence in relation to changes in spatiotemporal gait parameters during split-belt walking adaptation. We found that the corticospinal drive measured by intramuscular coherence in tibialis anterior changes with adaptation and that the corticospinal drive is related to temporal but not spatial parameters. This study may give insight as to the specific role of the motor cortex during gait.