Exercise Therapy Debates
The exercise therapy debate in ME/CFS is closely linked to the psychogenic model and the PACE trial, but warrants separate discussion because of its direct clinical consequences.
1 Arguments For Graded Exercise Therapy
Proponents of GET argued that ME/CFS symptoms were perpetuated by a cycle of deconditioning and fear avoidance: patients reduced activity due to fatigue, became deconditioned, experienced worsening symptoms, and further reduced activity. GET aimed to break this cycle through progressive, therapist-guided increases in physical activity. The theoretical basis rested on the observation that deconditioning produces symptoms overlapping with ME/CFS (fatigue, orthostatic intolerance, reduced exercise capacity) and the assumption that these symptoms were functionally equivalent. The PACE trial and earlier studies using broad diagnostic criteria appeared to support this approach.
A methodological caveat weakens the evidence base commonly cited in support of graded exercise for post-viral conditions. The meta-analyses and rehabilitation trials that report positive exercise effects (e.g., the Cochrane review of exercise therapy (Larun et al. 2024), the REGAIN trial for post-COVID-19 condition, and related telerehabilitation studies) include substantial proportions of participants with other comorbidities that would independently benefit from exercise—up to ~30% in some trials (asthma, diabetes, chronic heart disease) (Appelman et al. 2025). None systematically induced, monitored, or avoided post-exertional malaise. The presence of these comorbidity-confounded participants means the positive effect sizes may partly reflect improvements in those comorbid conditions rather than in the fatiguing illness itself, a limitation that reduces the strength of the inference that graded exercise benefits the core pathophysiology.
2 Evidence of Harm
The evidence against GET in ME/CFS is now extensive:
- Patient surveys: 51% of ME/CFS patients report GET worsened their condition across surveys in four countries (Kindlon 2011)
- Physiological evidence: Two-day CPET demonstrates that exertion produces measurable metabolic failure, not psychological fear—though group-average VO₂ decline is contested (positive studies (Keller et al. 2024) (Lim et al. 2020) vs null replication (Mancini et al. 2026)); elevated RPE and chronotropic incompetence are consistent findings
- Guideline withdrawals: NICE (2021) withdrew GET, CDC (2022) removed exercise recommendations, and multiple national guidelines now explicitly warn against GET (National Institute for Health and Care Excellence 2021)
- Long COVID confirmation: A Nature Reviews Cardiology commentary reported that 75% of 477 Long COVID patients experienced worsening symptoms and function after following exercise recommendations, with 85% showing PEM combined with cardiovascular autonomic dysfunction Rhijn-Brouwer et al. (2024)
- Deconditioning refutation: The NIH study documented that exercise impairment exceeds what deconditioning predicts, and equal maximum grip strength argues against deconditioning as the primary mechanism (Walitt et al. 2024)
3 Current Recommendations
The current consensus among ME/CFS specialists is:
- Pacing, not GET: Activity management within the energy envelope (Section Pacing and Energy Management) is the recommended approach
- Individualized activity: Any movement or exercise must be guided by individual CPET-derived thresholds, not population-based formulas (Section Exercise and Movement)
- Never push through PEM: The defining clinical principle is that PEM is a pathological signal, not a psychological barrier to be overcome
- Safe movement is possible: Within the energy envelope, gentle movement (stretching, isometric exercises, recumbent activities) can prevent deconditioning complications without triggering PEM