The use of the supine training position to enhance aerobic training was evaluated in a 10-week upper-body exercise study. Fourteen subjects with quadriplegia (QD) were matched on initial peak power output (PO) values and then randomly assigned to either a supine (SUP, n = 7) or sitting (SIT, n = 7) training group. Peak VO2 and PO were measured pretraining and posttraining in both the supine and sitting positions. There were significant (p < .01) increases in peak VO2 (720 to 780 mL.min-1) and PO (29.3 to 33.3W) with training. Although the SIT group exhibited a small training effect size (0.1), while the SUP group exhibited a moderate effect size (0.6), the interaction between time and training group failed to reach significance (p = .07) because of a large injury level-related variation in VO2. The training effect achieved by the SUP group generalized to the sitting position, as their peak VO2 increased 80mL.min-1 in the sitting position. Endurance improved (p < .0001) in all subjects, with time to exhaustion increasing from 52min to 135min over the 10 weeks of training. The sum of 4 skinfolds decreased (p < .05) from 67.5 to 61.0mm. The lack of change in stroke volume at rest and at 50% of peak PO suggests that an inotropic adaptation of the heart, commonly observed in subjects without SCI, did not occur in this population. However, a 4.7bpm increase (p < .01) in resting heart rate (HR) and a near significant increase (p = .07) in peak HR from pretraining to posttraining suggests a training-induced chronotropic adaptation of the heart. Although improvements in aerobic capacity can be achieved by training in either supine or sitting positions, the training effect size was larger in the supine position. Improvements in SV were not observed in either training position; this may be because of low absolute workloads were used. Central cardiovascular adaptation may occur in subjects with QD but changes are reflected as chronotropic and not inotropic adaptations.