Cardiac output in paraplegic subjects at high exercise intensities

The purpose of this investigation was to compare cardiac output (Qc) in paraplegic subjects (P) with wheelchair-confined control subjects (C) at high intensities of arm exercise. At low and moderate exercise intensity Qc was the same at a given oxygen uptake (VO2) in P and C. A group of 11 athletic male P with complete spinal-cord lesions between T6 and T12 and a group of 5 well-matched athletic male C performed maximal arm-cranking exercise and submaximal exercise at 50%, 70% and 80% of each individual's maximal power output (Wmax). Maximal VO2 (VO2max) was significantly lower, VO2max per kilogram body mass was equal and maximal heart rate (fc) was significantly higher in P compared to C. At VO2 of 1.3, 1.5 and 1.7 l.min-1, and for P 65%-90% of the VO2max, Qc was not significantly different between the groups, although, Qc in P was achieved with a significantly lower stroke volume (SV) and a significantly higher fc. Although the SV was lower in P, it followed the same pattern as SV in C during incremental exercise, i.e. an increase in SV until about 45% Wmax and thereafter a stable SV. The similar Qc at a given VO2 in both groups indicated that, even at high exercise intensities, circulation in P can be considered isokinetic with a complete compensation by fc for a lower SV.