Repeat Exercise Testing Identifies Abnormalities, Subgroups

18 CFS patients (1994 criteria) and 12 matched sedentary controls were recruited into Professor Julia Newton’s center at Newcastle University (U.K.). Participants were tested for cardiopulmonary fitness and magnetic resonance spectroscopy to assess muscle bioenergetic function in response to three bouts of exercise. Similar to other studies, CFS patients as a group had reduced cardio-respiratory reserve and lower anaerobic threshold compared to sedentary controls. The response to maximal voluntary contraction (MVC) separated the CFS subjects into two distinct groups. ”The group of CFS patients who achieved normal levels of phosphocreatinine (PCr) depletion (>33%) had comparable MCV values to the normal controls, but exhibited markedly greater muscle acidosis. The second group had low PCr depletion and no excess acidosis, but this appeared to be entirely as a consequence of having markedly lower MVC values than either the normal PCr depletion CFS patients or the normal controls.” Eight CFS patients fell into the first group and 10 were in the second group. Both groups reported maximal perceived effort during the exercise challenge and both groups reported similar rates of pain upon exercise. In the first group, exercise induced profound and sustained acidosis. “We believe that the local and systemic sequalae of this sustained acid exposure contribute significantly to the expression of fatigue in CFS.” However, based on objective measures, the second group exhibited a reduced drive to exercise, possibly due to perceived negative consequences of exercise. (The study was not designed to determine reasons for differences between the two groups.) The authors stated, ”Our findings suggest that MR-directed stratification strategies would represent a potentially important tool in future studies of exercise and exercise therapy in CFS.” (European Journal of Clinical Investigation, June 10, 2011)

Tags: , June 10, 2011