EXERCISE PERFORMANCE AND FATIGUABILITY IN PATIENTS WITH CHRONIC FATIGUE SYNDROME

To examine the role of delay in recovery of peripheral muscle function following exercise in the fatigue experienced by patients with the ch ronic fatigue syndrome (CFS) and to examine the influence of effort pe rception in limiting exercise performance in these patients, a study w as carried out on a group of twelve patients with chronic fatigue synd rome and 12 sex and age-matched sedentary control subjects. Symptom li mited incremental cycle exercise tests including measurements of perce ived exertion were performed followed by examination of the contractil e properties of the quadriceps muscle group for up to 48 hours. Muscle function was assessed by percutaneous electrical stimulation and maxi mum voluntary contractions. Muscle function at rest and during recover y was normal in CFS patients as assessed by maximum isometric voluntar y contraction, 20:50 Hz tetanic force ratio and maximum relaxation rat e. Exercise duration and the relationship between heart rate and work rate during exercise were similar in both groups. CFS patients had hig her perceived exertion scores in relation to heart rate during exercis e representing a reduced effort sensation threshold of 3.2 units on an unmodified Borg scale in CFS patients. Patients with chronic fatigue syndrome show normal muscle physiology before and after exercise. Rais ed perceived exertion scores during exercise suggest that central fact ors are limiting exercise capacity in these patients.