Blood flow and muscle fatigue in SCI individuals during electrical stimulation.

Our purpose was to measure blood flow and muscle fatigue in chronic, complete, spinal cord-injured (SCI) and able-bodied (AB) individuals during electrical stimulation. Electrical stimulation of the quadriceps muscles was used to elicit similar activated muscle mass. Blood flow was measured in the femoral artery by Doppler ultrasound. Muscle fatigue was significantly greater (three- to eightfold, P < or = 0.001) in the SCI vs. the AB individuals. The magnitude of blood flow was not significantly different between groups. A prolonged half-time to peak blood flow at the beginning of exercise (fivefold, P = 0.001) and recovery of blood flow at the end of exercise (threefold, P = 0.009) was found in the SCI vs. the AB group. In conclusion, the magnitude of the muscle blood flow to electrical stimulation was not associated with increased muscle fatigue in SCI individuals. However, the prolonged time to peak blood flow may be an explanation for increased fatigue in SCI individuals.