Exercise and chronic fatigue syndrome: maximize function, minimize post-exertional malaise.

Sir, As board members of the International Association for Chronic Fatigue Syndrome ⁄Myalgic Encephalomyelitis, we agree with Van Cauwenbergh et al.’s view [1] that exercise treatment should be carefully tailored to each individual with chronic fatigue syndrome (CFS) and have recently published a Primer directed at physicians [2]. Although a time-contingent approach may work for a percentage of patients, we recommend that any exercise be prescribed to maximize function while minimizing post-exertional malaise. A significant number of patients who exercise according to a set schedule despite increasing symptoms may suffer temporary setbacks and sometimes prolonged disability. Primer recommendations are based on our authors’ decades of experience treating thousands of patients with CFS as well as studies showing subjects with CFS have abnormal cardiometabolic [3] and immune responses [4] to repeated aerobic exercise, which may account for some of the symptoms of post-exertional malaise. Furthermore, the randomized controlled trials cited in the Van Cauwenbergh study do not address the numerous surveys from different countries in which 28–82% of patients have reported that exercise therapy may have led to a decline in their health. Kindlon [5] recently explored possible reasons for this discrepancy, including the heterogeneity of patients with CFS and the way that harms and treatment compliance have been monitored and reported in trials. We appreciate the significant contributions of randomized controlled trials to the medical knowledge base but that should be tempered with clinical experience and other types of evidence. Sincerely,