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This paper introduces an 8-channel transcutaneous neuromuscular stimulator, called ExoStim, which was designed and developed to provide stimulation to the lowerlimb muscles of spinal cord injured individuals. The intended purposes of the ExoStim were to act as a skin-surface precursor to an implantable neuromuscular stimulator for the specific tasks of increasing paralyzed leg strength and endurance, enabling the performance of basic lower-limb functional tasks, and familiarizing patients with functional electrical stimulation training. The initial design specifications included portability (~500 g), battery-powered output, constant current control (0-300 mA), 8 channels of biphasic stimulation (charge-balanced, constant current), and microprocessor control of all stimulation parameters. Various tests, including output power characteristics, environmental, mechanical, and battery life, were performed on three prototype units to validate our design specifications. Having successfully passed all tests, the ExoStim is now ready to be deployed to clinical trial sites for further evaluation with spinal cord injured subjects.

This study investigated control of heart rate (HR) and mean arterial pressure (MAP) at rest and during electrical stimulation (ES) leg cycling exercise (LCE) in paraplegics (Para). Seven men with complete spinal lesions (T(5)-T(11)) and six able-bodied (AB) men participated in this study. Beat-to-beat changes in HR and MAP were recorded during carotid sinus perturbation. Carotid baroreflex function curves were derived at rest and during ES-LCE for Para and during voluntary cycling (Vol) for AB. From rest to ES-LCE, oxygen uptake (VO(2)) increased (by 0.43 l/min) and HR rose (by 11 beats/min), yet MAP remained unchanged. In AB, Vol increased VO(2) (by 0.53 l/min), HR (by 22 beats/min), and MAP (by 8 mmHg). ES-LCE did not alter the carotid sinus pressure (CSP)-MAP relationship, but it displaced the CSP-HR relationship upward relative to rest. No rightward shift was observed during ES-LCE. Vol by AB produced an upward and rightward displacement of the CSP-MAP and CSP-HR relationships relative to rest. These findings suggested that the carotid sinus baroreflex was not reset during ES-LCE in Para.

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