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 (T5–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 l min–1 in PARA and to 0·74 ± 0·07 l 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 beat–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 l min l–1ΔVO2). 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).