Abstract
Objective: We investigated the effects of the incremental arm-cranking exercise (ACE) on tissue oxygen saturation (StO(2)) between active and inactive muscles, and the relationship between peak oxygen uptake (VO(2peak)) and changes in the StO(2) in inactive muscles.Design: Observational study.Setting: Community-based supervised intervention.Participants: The participants were individuals with motor and sensory complete spinal cord injury (complete SCI; n = 8) and motor complete but sensory incomplete SCI (incomplete SCI; n = 8), and able-bodied (AB) individuals (n = 8) matched for age, height, and body mass index.Intervention: The ACE was performed at a rate increasing by 10 watts min(-1) until exhaustion.Outcome Measures: VO(2peak), heart rate (HR), and StO(2).Results: While VO(2peak) was similar among the groups, peak HR was significantly higher in both SCI groups than in the AB (P < 0.05). In active muscles (biceps brachii), no differences in the StO(2) were observed among the groups (P > 0.05). In inactive muscles (vastus lateralis), the StO(2) in the AB and the incomplete SCI began to decrease at approximately 40% of the peak work rate; however, they remained unchanged in the complete SCI. The reductions in StO(2) in the AB were significantly greater than in the incomplete SCI.Conclusions: These results suggest that sympathetic vasoconstriction occurred in the incomplete SCI and AB, although it did not occur in the complete SCI, probably due to a reduction in sympathetic nerve activity. Sympathetic vasoconstriction in inactive muscles may not contribute to an individual's VO(2peak) regardless of their group.