Experimental and simulative characterization of the neuromuscular response to passive cycling with dynamically...

Passive cycling has been proposed as a potential therapy in neurologically impaired patients. We recently developed a robotic system for cycling rehabilitation, the Haptic Cycling Trainer (HaCT), which can provide targeted dynamic assistance and resistance during a cycle, while allowing for dynamic changes in crank arm length. This system can be used, among other possibilities, for passive cycling and potentially improve upon the current administration of this therapy. Here we used the HaCT system to characterize the neuromuscular response to passive cycling with dynamically changing crank arm lengths. We compared the experimental results with those obtained with a controller-based predictive simulation of passive cycling, replicating the experimental conditions. Through the comparison of the experimental and simulation results, we found that passive cycling elicits the stretch reflex activity of the hamstrings and that this activity is modulated by changing the length of the crank arm.Clinical Relevance-This work shed light on the unvoluntary muscular activations related to spinal reflex modulation that can be achieved through passive cycling exercises.