Altered effort and deconditioning are not valid explanations of myalgic encephalomyelitis/chronic fatigue syndrome

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a complex, systemic disease with significant pathophysiological uncertainties and variable presentations 1 . Here, we challenge Walitt et al.’s 2 conclusion that post-infectious (PI) ME/CFS is a disorder defined by altered effort preference, leading to activity avoidance and subsequent deconditioning. We believe this interpretation risks reinforcing skepticism about the serious biological nature of ME/CFS and its hallmark of post-exertional malaise (PEM), as well as its potential misclassification as a mental health condition.