Metabolic responses to arm ergometry and functional neuromuscular stimulation

Area of Science:

• Exercise Physiology
• Rehabilitation Medicine
• Neuromuscular Function

Background:

• Paraplegia results in significant muscle atrophy and reduced functional capacity.
• Assessing the physiological responses to exercise in individuals with spinal cord injuries is crucial for rehabilitation.

Purpose of the Study:

• To evaluate the cardiopulmonary and cardiovascular responses to functional neuromuscular stimulation (FNS) in complete paraplegic males.
• To compare the metabolic and ventilatory responses during FNS, arm ergometry (AE), and combined FNS + AE.

Main Methods:

• Four male subjects with complete paraplegia underwent FNS of the lower extremities using transcutaneous intramuscular electrodes.
• Cardiopulmonary (CP) and cardiovascular (CV) parameters, including VO2, VCO2, VE, and lactic acid (LA), were measured during maximal seated AE, FNS, and FNS + AE.

Main Results:

• Mean MET levels were 4.8 for FNS, 7.2 for AE, and 10.3 for FNS + AE.
• Lactic acid levels increased with combined FNS + AE (115 mg%), indicating a transition from anaerobic to aerobic metabolism.
• Ventilatory and VO2 responses during FNS + AE approached those of sedentary normals, suggesting muscle mass as the primary limitation.

Conclusions:

• The aerobic and anaerobic capacities of paraplegic subjects are primarily limited by available muscle mass.
• FNS combined with arm ergometry offers a viable method to significantly increase exercise intensity in paraplegic individuals.
• Cardiovascular and cardiopulmonary systems appear capable of supporting higher metabolic demands than typically achieved in paraplegic exercise.