Modulation of ankle EMG in spinally contused rats through application of neuromuscular electrical stimulation timed to robotic treadmill training

Abstract

While neuromuscular electrical stimulation (NMES) has enabled patients of neuromotor dysfunction to effectively regain some functions, analysis of neuromuscular changes underlying these functional improvements is lacking. We have developed an NMES system for a rodent model of SCI with the long term goal of creating a therapy which restores control over stepping back to the spinal circuitry. NMES was applied to the tibialis anterior (TA) and timed to the afferent feedback generated during robotic treadmill training (RTT). The effect of NMES+RTT on modifications in EMG was compared with that of RTT alone. A longitudinal study with a crossover design was conducted in which group 1 (n=7) received 2 weeks of RTT only followed by 2 weeks of NMES+RTT; group 2 (n=7) received 2 weeks of NMES+RTT followed by RTT only. On average, both types of training helped to modulate TA EMG activity over a gait cycle, resulting in EMG profiles across steps with peaks occurring just before or at the beginning of the swing phase, when ankle flexion is most needed. However, NMES+RTT resulted in concentration of EMG activation during the initial swing phase more than RTT only. In conjunction with these improvements in EMG activation presented here, a more complete analyses comparing changes after NMES+RTT vs. RTT is expected to further support the notion that NMES timed appropriately to hindlimb stepping could help to reinforce the motor learning that is induced by afferent activity generated by treadmill training.