Skip to content

Start Here
Atlas
Evidence
Research
Ask
Updates
About
Support

Evidence Atlas

ME/CFS Atlas — A public knowledge atlas for ME/CFS

Start Here
Atlas
Evidence
Research
Ask
FAQ
Glossary
Updates
Methodology
Press
Retractions
Contribute
About
Support
Contact

Weekly research digest — no spam

ME/CFS Atlas is an evidence reference platform, not a medical provider. Content is for informational purposes only and does not constitute medical advice. Always consult a qualified healthcare professional.

Generator v1·Scanner v1.4·Lint gate: enforce·See methodology

© 2026 ME/CFS Atlas

ME/CFS Evidence Browser — Classified Studies on Myalgic Encephalomyelitis

Evidence browser

Search and filter 6,205 studies by evidence level, diagnostic criteria, PEM status, and research domain. Each entry links to the original source.

Studies sorted by evidence level, then year. Browse by topic instead →

Evidence level (E0–E3) reflects study type and replication, not methodological quality. A weak systematic review still sits at E0. How evidence levels work →

Sort

746 studies

E0 — Consensus654E1 — Replicated321E2 — Moderate2,807E3 — Preliminary2,423

ME/CFS4,040Long COVID224Post-infectious190Overlapping1,064

Required for diagnosis417Not specified / unclear2,251Not required3,537

Post-Exertional Malaise1,082Cognitive Dysfunction1,749Pain1,628Unrefreshing Sleep805Orthostatic Intolerance484

Cytokines821Gene Expression573Metabolomics477Neuroimaging472Autoantibodies460

Infection-Triggered1,182Long COVID Overlap604Pediatric496Severe232

Strong Phenotyping445Sex-Stratified330Severe ME Included119

Systematic Review272Meta-Analysis61RCT301

Peer-reviewed6,148Preprint3Unclear54

421–440 of 746 studies

E2 ModerateCohortPEM not requiredCross-Sectional

Perceived exertion in fatiguing illness: civilians with chronic fatigue syndrome.

Cook, Dane B, Nagelkirk, Paul R, Peckerman, Arnold et al.·Medicine and science in sports and exercise·2003

This study looked at how hard exercise feels to people with ME/CFS compared to healthy people. Researchers had both groups exercise on a treadmill and rate their effort. While people with ME/CFS said exercise felt harder at moderate intensities, when researchers compared effort levels to each person's maximum oxygen capacity, there was no real difference—suggesting the difference in how hard it felt might be explained by their lower fitness level rather than a problem with how their body perceives effort.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredObservational

Enterovirus related metabolic myopathy: a postviral fatigue syndrome.

Lane, R J M, Soteriou, B A, Zhang, H et al.·Journal of neurology, neurosurgery, and psychiatry·2003

Researchers tested muscle samples from ME/CFS patients to see if they contained enterovirus (a type of virus). They found that about 21% of ME/CFS patients had enterovirus in their muscles, while none of the healthy control subjects did. Patients with enterovirus in their muscles were more likely to show abnormal lactate (a byproduct of muscle work) buildup during exercise, suggesting their muscles weren't using energy efficiently.

Energy MetabolismPost-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Blood volume and its relation to peak O(2) consumption and physical activity in patients with chronic fatigue.

Farquhar, William B, Hunt, Brian E, Taylor, J Andrew et al.·American journal of physiology. Heart and circulatory physiology·2002

This study looked at whether people with ME/CFS have lower blood volume (the amount of fluid circulating in their bodies) and whether this might explain their exercise problems. Researchers compared 17 ME/CFS patients with 17 healthy controls, measuring blood volume and fitness capacity. They found that ME/CFS patients had significantly reduced exercise capacity and a trend toward lower blood volume, and these two measurements were strongly related to each other.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredLongitudinal

Prognosis of chronic fatigue in a community-based sample.

Taylor, Renee R, Jason, Leonard A, Curie, Carrie J·Psychosomatic medicine·2002

Researchers followed up with people from a large community study to see which factors predict whether chronic fatigue gets better or worse over time. They found that how severe fatigue was at the start, and especially whether exercise made symptoms worse for 24 hours or more (a symptom called postexertional malaise), were the strongest predictors of whether someone would still have chronic fatigue years later.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Is physical deconditioning a perpetuating factor in chronic fatigue syndrome? A controlled study on maximal exercise performance and relations with fatigue, impairment and physical activity.

Bazelmans, E, Bleijenberg, G, Van Der Meer, J W et al.·Psychological medicine·2001

This study tested whether ME/CFS patients are in poor physical condition compared to healthy people, and whether being out of shape might be making their illness worse. Researchers had 20 ME/CFS patients and 20 healthy controls perform exercise tests while measuring heart rate, oxygen use, and other body functions. The study found no significant difference in physical fitness between the two groups, suggesting that poor fitness is not the main reason ME/CFS patients struggle with exercise.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Cardiovascular responses of women with chronic fatigue syndrome to stressful cognitive testing before and after strenuous exercise.

LaManca, J J, Peckerman, A, Sisto, S A et al.·Psychosomatic medicine·2001

This study compared how the hearts and blood pressure of women with ME/CFS respond to stressful mental tasks compared to healthy women. Researchers found that women with ME/CFS had a weaker cardiovascular response to cognitive stress than healthy controls, and this pattern held true even after exercise. The study also found that women with more severe ME/CFS symptoms had the lowest cardiovascular responses to stress.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

The effect of exercise on gait and balance in patients with chronic fatigue syndrome.

Paul, L M, Wood, L, Maclaren, W·Gait & posture·2001

This study looked at whether people with ME/CFS have problems with walking and balance, and whether light exercise makes these problems worse. Researchers compared 11 ME/CFS patients with 11 healthy people and found that while ME/CFS patients did show different walking patterns, their balance was similar to healthy controls, and the exercise test did not worsen either group's balance or gait.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCase-Control

Cognitive compromise following exercise in monozygotic twins discordant for chronic fatigue syndrome: fact or artifact?

Claypoole, K, Mahurin, R, Fischer, M E et al.·Applied neuropsychology·2001

This study asked whether exercise makes thinking and memory problems worse in people with ME/CFS. Researchers tested 21 pairs of identical twins where one twin had ME/CFS and one did not, asking them to exercise until exhausted and then testing their memory, attention, and thinking speed. The twins with ME/CFS did not show worse cognitive decline after exercise compared to their healthy twin, suggesting that exercise itself does not damage thinking ability.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Physiological responses to incremental exercise in patients with chronic fatigue syndrome.

Inbar, O, Dlin, R, Rotstein, A et al.·Medicine and science in sports and exercise·2001

Researchers compared how the bodies of 15 people with ME/CFS responded to a gradually increasing exercise test on a treadmill, compared to 15 healthy people. People with ME/CFS showed lower heart rates and weaker cardiovascular responses during exercise, even when they appeared to be pushing themselves as hard as they could. This suggests their bodies may have trouble with either heart function or muscle oxygen use during physical exertion.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredObservational

Identifying physical activity patterns in chronic fatigue syndrome using actigraphic assessment.

van der Werf, S P, Prins, J B, Vercoulen, J H et al.·Journal of psychosomatic research·2000

Researchers used a motion-tracking device to measure physical activity patterns in 277 ME/CFS patients over 12 days and compared them to 47 healthy people. Patients with ME/CFS showed less intense bursts of activity, shorter activity periods, and longer rest times afterward. About one-fourth of patients were identified as 'pervasively passive'—meaning they had very low activity levels throughout the entire study period.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Normal carnitine levels in patients with chronic fatigue syndrome.

Soetekouw, P M, Wevers, R A, Vreken, P et al.·The Netherlands journal of medicine·2000

This study tested whether a chemical called carnitine, which helps muscles produce energy, was missing in people with ME/CFS. Researchers measured carnitine levels in 25 women with ME/CFS and compared them to 25 healthy women. They found that carnitine levels were actually normal in the ME/CFS patients, which contradicted earlier studies that suggested carnitine deficiency might cause the condition.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Exercise capacity in chronic fatigue syndrome.

De Becker, P, Roeykens, J, Reynders, M et al.·Archives of internal medicine·2000

This study measured how much exercise women with ME/CFS could tolerate compared to healthy women without the condition. Patients with ME/CFS were able to exercise at only about half the capacity of healthy controls—they couldn't reach high heart rates and couldn't sustain heavy workloads. The findings show that ME/CFS significantly limits physical ability in ways that can be objectively measured.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Muscle fibre characteristics and lactate responses to exercise in chronic fatigue syndrome.

Lane, R J, Barrett, M C, Woodrow, D et al.·Journal of neurology, neurosurgery, and psychiatry·1998

Researchers examined muscle samples from 105 ME/CFS patients to understand why they have abnormal responses to exercise, particularly high lactate levels. They found that patients with high lactate responses had fewer type 1 muscle fibres (which are energy-efficient), but this wasn't because they were inactive—it appeared to be a specific muscle problem related to ME/CFS itself.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCase-Control

[Risk factors for ischemic heart disease in patients with chronic fatigue syndrome].

Vilikus, Z, Marecková, H, Janatková, I et al.·Sbornik lekarsky·1998

This study compared heart disease risk factors between people with ME/CFS and healthy controls. Researchers found that despite ME/CFS patients exercising less overall, they had no higher risk for heart disease than the control group. This suggests that reduced exercise activity in ME/CFS does not appear to increase cardiovascular risk in the way it might in other conditions.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearCross-Sectional

Effects of exercise on cognitive and motor function in chronic fatigue syndrome and depression.

Blackwood, S K, MacHale, S M, Power, M J et al.·Journal of neurology, neurosurgery, and psychiatry·1998

This study compared how people with ME/CFS, people with depression, and healthy people performed on thinking and strength tests before and after exercise on a treadmill. People with ME/CFS reported feeling much more tired and struggling harder during the exercise than the other groups. After exercising, people with ME/CFS had bigger drops in their ability to focus and pay attention compared to healthy people, suggesting that exercise affects their thinking ability in a specific way.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Influence of exhaustive treadmill exercise on cognitive functioning in chronic fatigue syndrome.

LaManca, J J, Sisto, S A, DeLuca, J et al.·The American journal of medicine·1998

This study looked at how exercise affects thinking and mental processing in people with ME/CFS compared to healthy people. Both groups did exhausting exercise on a treadmill, then took thinking tests right after and 24 hours later. People with ME/CFS performed worse on these thinking tests after exercise, particularly on tasks involving speed and attention, and their thinking stayed impaired the next day.

Post-Exertional Malaise

E2 ModerateCohortPEM unclearObservational

Physical activity before and after exercise in women with chronic fatigue syndrome.

Sisto, S A, Tapp, W N, LaManca, J J et al.·QJM : monthly journal of the Association of Physicians·1998

This study tracked the physical activity of 20 women with ME/CFS and 20 healthy volunteers for two weeks using a movement monitor worn at the waist. After all participants did a strenuous treadmill exercise test, researchers measured how their activity changed. Women with ME/CFS showed a noticeable drop in activity levels after the exercise, with the biggest decrease happening around days 12-14, and they took more rest breaks during the day.

Post-Exertional Malaise

E2 ModerateBehavioralPEM not requiredCross-Sectional

Physical fatigability and exercise capacity in chronic fatigue syndrome: association with disability, somatization and psychopathology.

Fischler, B, Dendale, P, Michiels, V et al.·Journal of psychosomatic research·1997

This study looked at how people with ME/CFS respond to exercise by measuring whether they can reach their target heart rate during activity. Researchers found that many patients don't reach expected heart rates and that this relates to how disabled they feel in daily life. Interestingly, anxiety and depression didn't explain why people avoided strenuous exercise, suggesting that avoidance behavior in ME/CFS may have different causes than in other conditions.

Post-Exertional Malaise

E2 ModerateCohortPEM not requiredCross-Sectional

Metabolic and cardiovascular effects of a progressive exercise test in patients with chronic fatigue syndrome.

Sisto, S A, LaManca, J, Cordero, D L et al.·The American journal of medicine·1996

Researchers tested how well women with ME/CFS could exercise compared to healthy controls by having them walk on a treadmill until exhaustion. Women with ME/CFS had lower aerobic fitness levels than healthy controls, but their hearts and lungs appeared to work normally. Importantly, the maximal exercise test did not cause a major flare-up of fatigue or other ME/CFS symptoms.

Post-Exertional Malaise

E2 ModerateCohortPEM requiredCross-Sectional

Decreased vagal power during treadmill walking in patients with chronic fatigue syndrome.

Cordero, D L, Sisto, S A, Tapp, W N et al.·Clinical autonomic research : official journal of the Clinical Autonomic Research Society·1996

This study compared how the nervous system controls heart rate in people with ME/CFS versus healthy volunteers during and after treadmill walking. Researchers found that people with ME/CFS had weaker parasympathetic (rest-and-recover) nervous system activity during walking, and this activity dropped even further after exercise stopped. This abnormality might help explain why ME/CFS patients feel worse after physical activity.

Post-Exertional Malaise

← Previous Next 20 studies →

Or browse by topic

PEM Immune Neuro Metabolic Biomarkers Severe ME Long COVID Cognitive

Curated Collections

Thematic groupings by clinical question or research area.

Neuroinflammation Evidence

PET imaging and other studies providing evidence for brain inflammation in ME/CFS.

Metabolism & Mitochondria

Metabolomics and mitochondrial function studies revealing energy metabolism disruption.

Biomarkers

Studies identifying potential biological markers for ME/CFS diagnosis and stratification.

PEM-Specific Research

Studies specifically examining post-exertional malaise, the hallmark symptom of ME/CFS.