Cardiac output during exercise in paraplegic subjects

Summary

The purpose of this study was to measure the cardiac output using the CO₂ rebreathing method during submaximal and maximal arm cranking exercise in six male paraplegic subjects with a high level of spinal cord injury (HP). They were compared with eight able bodied subjects (AB) who were not trained in arm exercise. Maximal O₂ consumption ($\dot V$O_2max) was lower in HP (1.1 1·min⁻¹, SD 0.1; 17.5 ml·min⁻·kg, SD 4) than in AB (2.5 1·min⁻¹, SD 0.6; 36.7 ml·min⁻¹·kg, SD 10.7). Maximal cardiac output was similar in the groups (HP, 141·min⁻¹ SD 2.6; AB, 16.81·min⁻¹ SD 4). The same result was obtained for maximal heart rate (f _c,max (HP, 175 beats·min⁻¹, SD 18; AB, 187 beats·min⁻, SD 16) and the maximal stroke volume (HP, 82 ml, SD 13; AB, 91 ml, SD 27). The slopes of the relationshipf _c/$\dot V$O₂ were higher in HP than AB (P<0.025) but when expressed as a %$\dot V$O_2max there were no differences. The results suggests a major alteration of oxygen transport capacity to active muscle mass in paraplegics due to changes in vasomotor regulation below the level of the lesion.