Quadriceps oxygenation during steady state FES-rowing in persons with spinal cord injury

Functional electrical stimulation (FES) rowing is an effective and well-tolerated type of cardiovascular exercise for persons with spinal cord injury (SCI). However optimal health and fitness benefits can only be achieved if the exercise time is sufficient. Due to the consequences of paralysis and the nature of surface FES, muscular fatigue is a common problem in electrically stimulated muscles, which restricts exercise time. One of the possible underlying reasons for this fatigue is inadequate muscle perfusion and oxygenation. Muscle oxygenation was monitored in the rectus femoris by near-infrared spectroscopy in five SCI volunteers during 10 min of steady state FES-rowing. The results show that muscle deoxygenation reached a steady state in the FES-rowers and in two rowers oxygenated haemaglobin and total haemaglobin even increased. Furthermore, long-term follow data in one subject showed that the ability to reach a steady state in perfusion during FES-rowing was correlated with fatigue resistence. The results suggest that muscle perfusion is a limiting but trainable factor for persons with SCI involved in FES-exercise.