Neuro-mechanics of muscle coordination during recumbent pedaling in post-acute stroke patients.

Motor impairment after stroke has been hypothesized to be related, among others, to impairments in the modular control of movement. In this study we analyzed muscle coordination and pedal forces during a recumbent pedaling exercise from a sample of post-acute stroke patients (n=5) and a population of age-matched healthy individuals (n=4). Healthy subjects and the less impaired patients showed a shared modular organization of pedaling based on 4 similar muscle synergies. The most impaired patient, characterized by a Motricity Index of 52/100, showed a reduced complexity (only 2 muscle synergies for the affected side). Differences between healthy subjects and post-stroke patients in the execution of the task were identified in terms of unbalance in mechanical work production, which well corresponded to the level of impairment. This pedaling unbalance could be traced back to different activation strategies of the 4 identified modules. Investigation on a more representative sample will provide a full characterization of the neuro-mechanics of pedaling after stroke, helping our understandings of the disruption of motor coordination at central level after stroke and of the most effective solutions for functional recovery.