The purpose of this study was to assess selected central cardiovascular functions of spinal cord injured, quadriplegic subjects at varying levels of oxygen uptake (VO sub 2). Subjects included 11 untrained, male college students with C5, C6, or C7 complete quadriplegia and 11 able-bodied reference subjects. Exercise was performed on a Monark cycle ergometer modified for arm-cranking in the sitting position. Open-circuit spirometry was used to measure oxygen uptake. Impedance cardiography and ECG were utilized to measure stroke volume, heart rate, and ejection fraction. Results indicated that in quadriplegics, increases in VO sub 2 appear to be controlled primarily by 0 sub 2 extraction by peripheral tissues with very limited 0 sub 2 delivery capability. These findings support the hypothesis that the functional syndrome of quadriplegia produces a set of predictable "hypokinetic" circulatory responses to dynamic arm exercise. Tables and figures illustrate the data. (Author/JD)