Dhondt, Evy, Danneels, Lieven, Rijckaert, Johan et al. · European journal of pain (London, England) · 2021 · DOI
This study tested whether being physically or mentally tired changes how the body's spinal cord responds to pain signals. Researchers measured a reflex that happens in the spinal cord when stimulated with electrical pulses to a nerve in the leg, both before and after participants either rested, did tiring leg exercises, or completed a difficult mental task. They found that low-to-moderate levels of fatigue—whether physical or mental—did not change this spinal reflex, suggesting the body's pain-dampening systems stay stable even when tired.
ME/CFS patients experience profound, often disabling fatigue and frequently report pain symptoms, yet the relationship between fatigue and pain processing at the spinal level remains poorly understood. This mechanistic study contributes foundational knowledge about whether fatigue dampens pain-inhibitory pathways, which has implications for understanding why some pain-focused treatments may remain effective even when patients are severely fatigued.
This study does not demonstrate how severe or prolonged fatigue—as seen in ME/CFS—affects pain processing; it only examined low-to-moderate experimental fatigue in healthy people. It does not prove that pain and fatigue are completely independent in ME/CFS patients, nor does it establish causation between any variables. The findings in healthy controls may not translate to patients with chronic fatigue syndrome, where neurophysiological processes may be fundamentally altered.
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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