Cardiovascular responses during submaximal electrical stimulation-induced leg cycling in individuals with paraplegia

This study investigated the cardiovascular responses during electrical stimulation-induced leg cycling (ES-LCE) in people with paraplegia (PARA) compared with voluntary leg cycling (VOL) at similar levels of oxygen uptake in able-bodied (AB) individuals. Six PARA with sensory and motor complete spinal cord lesions (TS-T9) and six AB participated in this study. Oxygen uptake (VO2), stroke volume (SV), heart rate (HR) and cardiac output (Q) were measured at rest and during submaximal, steady-state leg cycling. At the highest power output achieved (9.2 +/- 2.4 W for PARA versus 42.8 +/- 1.0 W for AB), VO2 was augmented above resting levels to 0.75 +/- 0.11 min(-1) in PARA and to 0.74 +/- 0.071 min(-1) in AB. HR and SV were also increased during ES-LCE in PARA (92.1 +/- 8-6 beats min(-1) and 93.9 +/- 11.3 ml bea(-1), respectively) and during VOL in AB (83.9 +/- 9.2 beats min(-1) and 89.7 +/- 9.0 ml beat(-1), respectively). At an equivalent submaximal VO2, HR and SV were not different between the two groups, however, Q was higher in PARA (6.6 +/- 0.7 versus 4.1 +/- 0.9 1 min l(-1) deltaVO2). These data suggest that ES-LCE at relatively low power outputs elicits increases in several cardiovascular variables in PARA. Furthermore, it is possible that ES-LCE leads to a 'hyperkinetic circulation' (a greater Q for a given VO2).