Physical activity levels in ME/chronic fatigue syndrome before and after a 2-day cardiopulmonary exercise test protocol, 2026, Receno

[Dolphin]

https://www.tandfonline.com/doi/full/10.1080/21641846.2026.2620357

Research Article

Physical activity levels in myalgic encephalomyelitis/chronic fatigue syndrome before and after a 2-day cardiopulmonary exercise test protocol​

Candace N. Receno
,
Sebastian Harenberg
,
Jared Stevens
,
Staci R. Stevens
&
Betsy Keller
Received 17 Mar 2025, Accepted 19 Jan 2026, Published online: 27 Jan 2026

ABSTRACT​

Objective:​

This study characterized physical activity levels in people with Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (MECFS) before and after a 2-day cardiopulmonary exercise test (CPET) protocol. Activity levels of people with MECFS were compared to sedentary controls and separated into day and night activity to elucidate circadian differences.

Methods:​

People with MECFS (n = 58) and sedentary controls (CTRL; n = 41) completed a 2-day CPET. For six days prior to testing and 10 days following testing, participants wore an ActiGraph GT3X-BT accelerometer on the dominant wrist to track daily activity. Physical activity intensity was separated into sedentary, light, and moderate/vigorous zones based on accelerometry cut-off points. Linear mixed effects models were used to compare differences in activity levels between groups.

Results:​

People with MECFS spent significantly more time in sedentary activity and less time in light and moderate/vigorous activity compared to the control group. These differences persisted when further separated into daytime and nighttime hours.

Conclusion:​

Those with MECFS spend a larger portion of their day in sedentary activities compared to sedentary controls. MECFS also spend comparatively less time in light-vigorous activities throughout the day, suggesting that people with MECFS are overall generally much less physically active than sedentary otherwise healthy individuals.
KEYWORDS:

• Accelerometry
• circadian
• daytime physical activity
• MECFS
• ME/CFS

 

[Utsikt]

A shame it’s paywalled..

Those with MECFS spend a larger portion of their day in sedentary activities compared to sedentary controls. MECFS also spend comparatively less time in light-vigorous activities throughout the day, suggesting that people with MECFS are overall generally much less physically active than sedentary otherwise healthy individuals.

If the data is robust, this would mean that all of the «sedentary controls» would have to be reconsidered, and some of the observed differences might still be caused by the lower activity levels.

We need more tracking like this long term.

 

[Nightsong]

The main finding of the present study affirms, again, that people with MECFS spend proportionately greater time in sedentary versus light-to-vigorous physical activity behaviors compared to sedentary controls. Other studies of objectively measured physical activity in MECFS ranged in duration from 4 to 14 days and were consistent with the results of the 24-hour continuous activity monitoring over 16-days in the present study [10,11,14,15].

Also not evident in slope values, further examination of the first three days following CPETs revealed the highest levels of sedentary level activity in MECFS concurrent with the lowest levels of light and moderate/vigorous activity both before and after the CPETs. For light and moderate/vigorous activity levels, MECFS did not attain their pre-CPET levels until Day 8 following CPETs. Notably, controls maintained higher levels of moderate-vigorous activities compared to MECFS over the 10 days following CPETs.

The differences in moderate/vigorous physical activity slopes between groups appears to be driven largely by differences in daytime activity. The initial decline in MECFS during the three days following CPETs is concerning, however, the gradual decline in moderate-vigorous physical activity after CPETs in sedentary controls is also troubling. Even 10 days following CPETs, moderate-vigorous physical activity level in controls appear below pre-CPET levels.

Data from subjective symptom surveys submitted prior to ‘pre-resting’ for the 2-day CPET suggest that normal, daily activity levels of MECFS may exceed tolerable thresholds, provoking PEM symptoms. If so, the ‘pre-rest’ 6-day period of pre-CPET data collection may underestimate the chronic level of daily physical activity of many with MECFS necessary to simply ‘live life’.

 

[forestglip]

however, the gradual decline in moderate-vigorous physical activity after CPETs in sedentary controls is also troubling

Maybe sedentary people are sedentary for a reason. Maybe more people than we thought have very mild ME/CFS or something like it.

 

[Dolphin]

The differences in moderate/vigorous physical activity slopes between groups appears to be driven largely by differences in daytime activity. The initial decline in MECFS during the three days following CPETs is concerning, however, the gradual decline in moderate-vigorous physical activity after CPETs in sedentary controls is also troubling. Even 10 days following CPETs, moderate-vigorous physical activity level in controls appear below pre-CPET levels.

It’s good they are willing to say this explicitly. I was worried they might downplay the effects of the 2-day CPET as they make money from them.

 

[Utsikt]

Even 10 days following CPETs, moderate-vigorous physical activity level in controls appear below pre-CPET levels.

Especially concerning when you factor in that the pre-CPET activity levels during pre-resting might have been lower than their normal activity levels:

Data from subjective symptom surveys submitted prior to ‘pre-resting’ for the 2-day CPET suggest that normal, daily activity levels of MECFS may exceed tolerable thresholds, provoking PEM symptoms. If so, the ‘pre-rest’ 6-day period of pre-CPET data collection may underestimate the chronic level of daily physical activity of many with MECFS necessary to simply ‘live life’.

 

[jnmaciuch]

Maybe sedentary people are sedentary for a reason. Maybe more people than we thought have very mild ME/CFS or something like it.

Yeah that's something that came up recently talking to some people doing exercise physiology--studies selecting for sedentary controls just tend to recruit people with a whole range of underlying health conditions (or skewing towards less diagnosed health conditions, if certain diagnoses were excluded from recruitment). It's recommended for control groups to match the range of activity levels in the general population and try to control for activity levels in the statistical analysis if sample size allows.

If we can't get a sedentary control group that matches the activity level of ME/CFS I think we're still comparing apples to oranges anyways and just increasing the chances that some of the oranges are actually grapefruits (or apples, even). wait...I think I've lost the metaphor

 

[Turtle]

Yeah that's something that came up recently talking to some people doing exercise physiology--studies selecting for sedentary controls just tend to recruit people with a whole range of underlying health conditions (or skewing towards less diagnosed health conditions, if certain diagnoses were excluded from recruitment). It's recommended for control groups to match the range of activity levels in the general population and try to control for activity levels in the statistical analysis if sample size allows.

If we can't get a sedentary control group that matches the activity level of ME/CFS I think we're still comparing apples to oranges anyways and just increasing the chances that some of the oranges are actually grapefruits (or apples, even). wait...I think I've lost the metaphor

Why are those sedentary people called Healthy Controls?

 

[jnmaciuch]

Why are those sedentary people called Healthy Controls?

I think people just default to that in contrast to their disease group. I doubt most studies who use the term are comprehensively checking someone’s entire medical history, making sure no underlying conditions were missed, and assessing specific reasons for low activity level

 

[MrMagoo]

Is the problem that everyone isn’t exercising enough? Not just us, but ordinary people too! (Is this sarcasm? I might be being facetious IDK)
How do you find someone as sedentary as us who isn’t ill?

 

[Felis Catus]

Yeah that's something that came up recently talking to some people doing exercise physiology--studies selecting for sedentary controls just tend to recruit people with a whole range of underlying health conditions (or skewing towards less diagnosed health conditions, if certain diagnoses were excluded from recruitment).

I didn't know that was the case. Admittedly, I haven't thought much about it. I understand it's hard to get it perfectly right but do you perhaps know what gets through that shouldn't, if they just required no suspected or diagnosed chronic conditions, no long recoveries in recent history?

If we can't get a sedentary control group that matches the activity level of ME/CFS I think we're still comparing apples to oranges anyways and just increasing the chances that some of the oranges are actually grapefruits (or apples, even). wait...I think I've lost the metaphor

It's late here and my brain fog is strong, so I might not be following... How could we get a healthy sedentary control group with the same level of activity as seen in ME/CFS when ME/CFS comes with reduction in activity by default?

I had a period of about 15 years of sedentary lifestyle. I had no reason to believe something was wrong with my health. I just... prefered my sedentary activities. But even that included walking to the supermarket, café, bakery, bus stop, up/down the stairs, moving spontaneously around the flat or workplace, household chores,... on top of the cognitive activities. I'm not sure pwME could match that.

 

[jnmaciuch]

I didn't know that was the case. Admittedly, I haven't thought much about it. I understand it's hard to get it perfectly right but do you perhaps know what gets through that shouldn't, if they just required no suspected or diagnosed chronic conditions, no long recoveries in recent history?

I suspect it varies from study to study. If you’re looking for a disease-specific biomarker then it might not be the worst thing to include people with other diagnoses in your controls. But specifically for exercise tests you would need to ensure that your hypothesis can still be tested with a less-than-healthy group. I’m not sure how diligent various groups are being

It's late here and my brain fog is strong, so I might not be following... How could we get a healthy sedentary control group with the same level of activity as seen in ME/CFS when ME/CFS comes with reduction in activity by default?

You’re following! I’m basically saying it’s very difficult to find an equivalently low-activity group of healthy controls anyways, so trying to seek out sedentary controls might not actually control for confounders as intended and might end up introducing new problems. Depends on the specific question being investigated, though.

 

[ScoutB]

If it's true we're more sedentary than sedentary controls I wonder if that lends any support to the theory that we are less deconditioned than one would expect for our activity level. Has there ever been a study collecting activity data and considering it along with, say, dexa scans in pwME? Though of course you'd want similarly sedentary controls there to compare with too...

 

[Sean]

Maybe sedentary people are sedentary for a reason. Maybe more people than we thought have very mild ME/CFS or something like it.

I am increasingly of the view that humans are rarely if ever sedentary (on a prolonged basis) for no good reason, and the real reasons for being sedentary rarely if ever include psycho-drama morality-play nonsense. That characterisation is just the superficial narrative mythologies we spin to cover our ignorance, and justify abandoning those people.

Quite the contrary, humans want to be active most of the time. It is our default and preferred state. Nobody likes having to sit back and watch their life pass by without being able to participate in it.

 

[Hutan]

Results:​

People with MECFS spent significantly more time in sedentary activity and less time in light and moderate/vigorous activity compared to the control group. These differences persisted when further separated into daytime and nighttime hours.

Conclusion:​

Those with MECFS spend a larger portion of their day in sedentary activities compared to sedentary controls. MECFS also spend comparatively less time in light-vigorous activities throughout the day, suggesting that people with MECFS are overall generally much less physically active than sedentary otherwise healthy individuals.

I'm a bit bemused by the definitive way the results are presented here. I mean, they looked at 58 people with ME/CFS and they didn't tell us about the severity of the participants in the abstract. That hardly qualifies them to make a statement about all people with ME/CFS.

If they had chosen 58 people who are essentially bed bound, the conclusion that they spend a larger portion of their day in sedentary activities than sedentary controls would be stating the obvious. But, I can think of some people diagnosed with ME/CFS who are more active than some sedentary people. The conclusion doesn't really offer anything useful.

 

[SNT Gatchaman]

they didn't tell us about the severity of the participants in the abstract

Data collected were part of a larger study [31], in which people with MECFS met Canadian Consensus Criteria [34] affirmed by expert physicians. Inactive control participants endorsed no/low physical activity when directly asked about exercise habits, and were deemed otherwise healthy by a physician. Low physical activity was defined as having a predominantly sedentary occupation and/or engaging in only 3–4 h per day of walking or standing, with no regular participation in organized leisure-time physical activities (e.g. fitness walking or exercise classes).

[31] is Cardiopulmonary and metabolic responses during a 2-day CPET in myalgic encephalomyelitis/chronic fatigue syndrome: translating reduced oxygen consumption to impairment status to treatment considerations (2024) which is open access.

ME/CFS participants were primarily of mild to moderate illness severity, indicated by the Bell Activity Scale

Bell Activity scale for the group was 35.5 (12.0), a little higher in males.
Hours in bed/day 9.8 (1.6)

 

[SNT Gatchaman]

Don't love this part of the discussion —

Ultimately, compared to well-matched sedentary controls, those with MECFS still demonstrated significantly more sedentary time and less time in light-vigorous activities. Since physical activity participation is highly related to mortality and risk of disease in healthy individuals [20,21], the concern regarding the risk of developing other chronic diseases, such as cardiovascular disease, decreased pulmonary function, or sarcopenia, in MECFS is clear. Those with MECFS become ‘activity avoiders’ in an effort to mitigate pain, fatigue, and other related symptoms [7], creating a vicious cycle that further predisposes to illness-related deconditioning.

[7] is Physical activity in chronic fatigue syndrome: Assessment and its role in fatigue (1997) which includes the following on deconditioning —

Analogous to mechanisms described in chronic pain patients (Keefe & Gil, 1986; Philips, 1983; Weisenberg, 1987), Wessely and colleagues hypothesized about the role of avoidance of physical activity in the perpetuation of fatigue in CFS (Wessely et al., 1991). According to these authors the patient experiences genuine symptoms and learns that physical activity aggravates these symptoms, in particular fatigue and myalgia, and attributes them to ongoing physical illness. The patient tries to prevent symptoms by avoiding physical activity. Prolonged inactivity leads to physical deconditioning such that symptoms emerge at progressively lower levels of physical activity. Hence, a vicious circle of avoidance and symptoms has been established. However, there are no empirical data to support this hypothesis in CFS.

This paper continues —

It is clear that efforts to increase physical activity levels in MECFS should be highly nuanced and physiologically-based to avoid symptom exacerbation. Thus, increases in PA should only occur after pacing strategies allowing for individuals to achieve a stable baseline with little/no provocation of PEM symptoms has been successfully implemented, utilizing plenty of time to recover between exercises, little/no time spent in heart rate intensities above ventilatory threshold, and exercise sessions occurring several days apart to account for latent PEM symptoms [22].

Which is all very pacing-up and BACME-like.

 

[alktipping]

Don't love this part of the discussion —



[7] is Physical activity in chronic fatigue syndrome: Assessment and its role in fatigue (1997) which includes the following on deconditioning —



This paper continues —



Which is all very pacing-up and BACME-like.

The myth of a stable baseline in M E /C F S should be discontinued .Life itself gets in the way of achieving any long term stability .

 

[Dolphin]

I remember people complaining when Keller got people to do exercises during an Invest in ME conference when patients would generally already be pushed themselves just attending.

 

[Trish]

It saddens me that with so few people researching ME/CFS we get people who have been researching it for years and appeared to be doing worthwhile work show so little understanding of the reality of PEM, the impossibility of maintaining a stable baseline, and the long term consequences of trying to exercise, even carefully as they advise.

Maybe they only get to see mild to moderate cases, as severe and very severe ME/CFS generally preclude even attending a clinic, let alone putting yourself through a 2 day CPET.