Effects of arm cranking exercise on muscle oxygenation between active and inactive muscles in people with spinal cord injury.

We investigated the effects of the incremental arm-cranking exercise (ACE) on tissue oxygen saturation (StO) between active and inactive muscles, and the relationship between peak oxygen uptake (VO) and changes in the StO in inactive muscles. Observational study. Community-based supervised intervention. 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. The ACE was performed at a rate increasing by 10 watts min until exhaustion. VO, heart rate (HR), and StO. While VO 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 were observed among the groups (P > 0.05). In inactive muscles (vastus lateralis), the StO 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 in the AB were significantly greater than in the incomplete SCI. 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 regardless of their group.