Physiological recruitment of large populations of motor units using electrical stimulation of afferent pathways

Neuromuscular electrical stimulation (NMES) is commonly used in rehabilitation settings and technologies, but the evoked muscle activation patterns are different from voluntary contractions in several undesirable ways. In this study, we propose a novel scheme for NMES that relies on low-amplitude stimulation of afferent pathways using high stimulation frequencies. Experimental and simulated results indicated that temporal summation of the consecutive synaptic inputs to motor neurons from the stimulated afferent fibers evoked contractions involving many motor neurons, each generating action potentials at relatively low discharge rates. These results indicate that this type of stimulation may be used for functional purposes to overcome the large degree of fatigability normally associated to NMES applied to motor fibers.