Physiologic effects of electrical stimulation leg cycle exercise training in spinal cord injured persons

The purpose of this study was to assess the physiologic training effects of functional electrical stimulation leg cycle ergometer (FES-LCE) exercise in persons with spinal cord injury (SCI) who were previously untrained in this activity. Ten persons with quadriplegia (C5 to C7) and eight with paraplegia (T4 to T11) performed FES-LCE training on an ERGYS I ergometer 10 to 30 minutes per day, 2 or 3 days per week for 12 to 16 weeks (36 total sessions). Training session power output (PO) ranged from 0.0W (no external resistance) to 30.6W. Each subject completed discontinuous graded FES-LCE and arm crank ergometer (ACE) tests before and after training for determinations of peak lower and upper extremity metabolic, pulmonary, and hemodynamic responses. Compared with pretraining, this SCI group exhibited significantly (p ≤ .05) higher posttraining peak PO (+45%), oxygen uptake ([O₂], + 23%), pulmonary ventilation (+27%), heart rate (+11%), cardiac output ([Qt], + 13%) and significantly lower total peripheral resistance ([TPR], - 14%) during FES-LCE posttests. There were no significant changes in peak stroke volume (+6%), mean arterial pressure ([MAP], - 5%), or arteriovenous oxygen difference ([a-vO₂diff],+10%) during posttraining FES-LCE tests. In addition, no significant differences were noted for the peak level of any monitored variable during ACE posttests after FES-LCE training. The rise in total vascular conductance, implied by the significant decrease in posttraining TPR during FES-LCE tests, denotes that a peripheral circulatory adaptation developed in the persons with SCI during FES-LCE exercise training. An increase in total vascular conductance was accompanied by an elevation in peak Q̇t that supported the heightened peak O₂ and maintained peak MAP; this enabled a moderate widening of the a-vO₂diff to partially support the enhanced peak aerobic power. The lack of augmentation of posttraining peak V̇O₂ or Q̇t with untrained upper extremity muscle groups may be due to (1) the specificity of the lower limb training, (2) local fatigue of the upper extremity musculature, or (3) peripheral rather than central circulatory training adaptations in persons with SCI during the short-term FES-LCE training program implemented in this study.