Measuring recovery from exercise in ME/CFS


US researchers used a  2-day exercise study (CPET) to discover how long it took people with ME/CFS to recover from exercise. The 80 participants with ME/CFS took an average of almost 2 weeks to recover from a 2-day CPET, whereas healthy people only needed an average of two days.

Almost 10% of those with ME/CFS took more than 3 weeks to recover, with one person feeling he had not recovered after a full year. Recovery time back to the pre-exercise level was not affected by the severity of symptoms prior to taking part in the study.


“it is likely that persons with ME constantly live in the long tail of the recovery response. While activities of daily living are not as stressful as the 2-day CPET, recovery from less intense activities of daily living is likely to follow a similar decay curve.

Such a response to physical activity would be consistent with the ubiquitous complaint from persons with ME that they have constant and persistent PEM. Most persons with ME would constantly experience exertion falling on an incompletely recovered decay curve, and thus their symptoms would increase to a high steady-state level.”

“Our data suggests that around 7–8% will have a prolonged recovery of 1–2 months, with a very small percentage of ME subjects feeling that they never recover.”

The researchers had not found this response to exercise outside ME/CFS, until people with long COVID began to report PEM from 2020.


Recovery from Exercise in Persons with Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome (ME/CFS), by Geoffrey E Moore, Betsy A Keller, Jared Stevens, Xiangling Mao, Staci R Stevens, John K Chia, Susan M Levine, Carl J Franconi  and Maureen R Hanson in Medicina 2023, 59(3), 571; [] 15 March 2023
(This article belongs to the Special Issue Advances in ME/CFS Research and Clinical Care)


Research abstract:

Background and Objectives:

Post-exertional malaise (PEM) is the hallmark of myalgic encephalomyelitis/ chronic fatigue syndrome (ME/CFS), but there has been little effort to quantitate the duration of PEM symptoms following a known exertional stressor. Using a Symptom Severity Scale (SSS) that includes nine common symptoms of ME/CFS, we sought to characterize the duration and severity of PEM symptoms following two cardiopulmonary exercise tests separated by 24 h (2-day CPET).

Materials and Methods: Eighty persons with ME/CFS and 64 controls (CTL) underwent a 2-day CPET. ME/CFS subjects met the Canadian Clinical Criteria for diagnosis of ME/CFS; controls were healthy but not participating in regular physical activity. All subjects who met maximal effort criteria on both CPETs were included. SSS scores were obtained at baseline, immediately prior to both CPETs, the day after the second CPET, and every two days after the CPET-1 for 10 days.

Results: There was a highly significant difference in judged recovery time (ME/CFS = 12.7 ± 1.2 d; CTL = 2.1 ± 0.2 d, mean ± s.e.m., Chi2 = 90.1, p < 0.0001). The range of ME/CFS patient recovery was 1–64 days, while the range in CTL was 1–10 days; one subject with ME/CFS had not recovered after one year and was not included in the analysis. Less than 10% of subjects with ME/CFS took more than three weeks to recover. There was no difference in recovery time based on the level of pre-test symptoms prior to CPET-1 (F = 1.12, p = 0.33).

Mean SSS scores at baseline were significantly higher than at pre-CPET-1 (5.70 ± 0.16 vs. 4.02 ± 0.18, p < 0.0001). Pharmacokinetic models showed an extremely prolonged decay of the PEM response (Chi2 > 22, p < 0.0001) to the 2-day CPET.


ME/CFS subjects took an average of about two weeks to recover from a 2-day CPET, whereas sedentary controls needed only two days. These data quantitate the prolonged recovery time in ME/CFS and improve the ability to obtain well-informed consent prior to doing exercise testing in persons with ME/CFS. Quantitative monitoring of PEM symptoms may provide a method to help manage PEM.

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