Hemodynamic Responses to Peak Arm-Crank Exercise in Thoracic Level Paraplegics 483

Abstract

It has long been debated in the literature as to whether upper body exercise is limited centrally or peripherally. It has been suggested that aerobic capacity in the spinal cord injured (SCI) may be limited by the relatively greater intramuscular pressure generated during upper body exercise. Brechue et al. (1995) concluded that “skeletal muscle VO2max is limited by O2 delivery secondary to a restriction of blood flow.” The purpose of this study was to measure the hemodynamic responses of paraplegics during a graded exercise test (GXT) to peak oxygen consumption and examine the relation of these responses to aerobic capacity(VO2peak). The subjects for this study were 10 thoracic level paraplegics. The GXT was performed on an arm-crank ergometer using an intermittent protocol. The following variables were measured: peak heart rate, peak systolic blood pressure (SBP), peak mean aterial pressure (MAP), and peak rate pressure product (RPP). Heart rate was measured by telemetry. Exercise blood pressures were measured by reducing the power output by one half and instructing the subject to continue cranking with one arm. Blood pressure was then measured on the free arm. These variables were then correlated with VO2peak with a significance level set at p*< 0.05:Table Results show a significant correlation between VO2peak and peak SBP. These findings are consistent with the hypothesis that aerobic capacity in the paraplegic population may be limited by the delivery of oxygen secondary to the ability to perfuse the exercising muscles.