Daenen, Liesbeth, Varkey, Emma, Kellmann, Michael et al. · The Clinical journal of pain · 2015 · DOI
This review examines how exercise affects people with chronic pain, including ME/CFS. While exercise helps many chronic pain conditions, some patients—especially those with ME/CFS, fibromyalgia, and chronic whiplash—experience worsening symptoms or 'crashes' after exercising. The authors emphasize that exercise programs need to be carefully tailored to each person, with proper recovery time built in, rather than using a one-size-fits-all approach.
This study directly addresses a central challenge in ME/CFS management: why standard exercise prescriptions can worsen symptoms in some patients. By highlighting the concept of dysfunctional endogenous analgesia (impaired pain relief mechanisms) during exercise and emphasizing the critical role of recovery, it provides scientific rationale for post-exertional malaise and supports the need for individualized, conservative exercise approaches in ME/CFS rather than aggressive rehabilitation programs.
This narrative review does not establish causal mechanisms for post-exertional malaise in ME/CFS or prove that all patients experience exercise-induced flares equally. It does not provide quantitative data on the prevalence of dysfunctional analgesia in ME/CFS or definitive guidelines for safe exercise dosing. The review cannot determine whether recovery strategies alone can normalize exercise tolerance in ME/CFS patients.
About the PEM badge: “PEM required” means post-exertional malaise was an explicit required diagnostic criterion for participant inclusion in this study — not that PEM was studied, observed, or discussed. Studies using criteria that do not require PEM (e.g. Fukuda, Oxford) are tagged “PEM not required”. How the atlas works →
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