Is Swimming a More Tolerable Form of Movement for Individuals With Myalgic Encephalomyelitis/ Chronic Fatigue Syndrome? (ME/CFS)

March 24, 2026 updated by: Alexandra Coates, Simon Fraser University

Investigating the Effect of Swimming on Autonomic and Symptomatic Responses in Individuals With Myalgic Encephalomyelitis/Chronic Fatigue Syndrome

Individuals with ME/CFS experience profound exercise intolerance and post-exertional malaise. This remote (app-based) pilot study explores whether light, fully self-paced, swimming may be a tolerable form of movement for people with ME/CFS and related conditions, due to the distinct physiological effects of water immersion. The horizontal posture and hydrostatic pressure of water supports venous return and reduces orthostatic stress, while cool water exposure may influence autonomic and inflammatory responses. We are recruiting adults with mild-to-moderate ME/CFS and related conditions for this study examining short-term symptom and autonomic responses to gentle swimming. Participants will choose their own intensity and duration and may stop at any time. A light cycling session is available as an optional comparator for those who feel comfortable doing so. [Note: this is not an exercise training or rehabilitation study, and participation is only intended for individuals who can tolerate some gentle activity and can be in public spaces without triggering post-exertional malaise. You should be comfortable with swimming, but flotation or other assistive devices are welcome]

Study Overview

Status

Suspended

Conditions

Intervention / Treatment

Detailed Description

Myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) is a debilitating multisystem disorder characterized by extreme fatigue, sleep dysfunction, pain, and post-exertional malaise and/or post-exertional fatigue, and is accompanied by orthostatic intolerance, and neuroendocrine and immune manifestations. The defining feature of ME/CFS is the delayed onset (~12-48 h) exacerbation of symptoms following physical, cognitive, orthostatic, and even emotional exertion, termed post-exertional malaise (PEM). As such, despite the known benefits of exercise for improving function in most disease states including other multisystem inflammatory disorders like sepsis, exercising with ME/CFS is generally contraindicated to avoid a worsening of the condition.

It has been demonstrated that neurovascular dysregulation underlies much of the exercise intolerance in ME/CFS. When neurovascular function is normalized with pharmacologic cholinergic stimulation in ME/CFS patients performing upright cycling exercise, cardiac output, right atrial pressures, and maximal oxygen consumption are improved, possibly preventing post-exertional malaise. Water immersion can also be used to normalize cardiac output and right atrial pressures, as the prone/supine postures and hydrostatic pressure of the water act to passively encourage venous return. Furthermore, the human dive reflex (when the face is submerged in cool water) increases parasympathetic activation to the heart, slowing down heart rate. There is also evidence of anti-inflammatory effects of swimming in patients with cardiovascular, neurological, and rheumatological diseases, which could also improve inflammation in ME/CFS patients. The purpose of this study is to determine whether light-to-moderate swimming may be a more tolerable form of movement for individuals with ME/CFS.

Study Type

Interventional

Enrollment (Estimated)

50

Phase

  • Not Applicable

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • Canada
    • British Columbia
      • Burnaby, British Columbia, Canada, V5A 1S6
        • Simon Fraser University

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

Yes

Description

Inclusion Criteria For ME/CFS participants:

  • Be between the ages of 18-80
  • Meet the criteria of (ME/CFS). The diagnostic criteria for ME/CFS according to the primary Canadian Consensus Criteria are: 1. Fatigue (significant physical and mental fatigue that is new onset, unexplained, persistent or recurrent, and substantially reduces activity level), 2. Post-exertional malaise and/or post-exertional fatigue (general feeling of discomfort, weakness and/or fatigue, and potentially worsening associated symptoms, following physical or mental exertion; slow recovery which is usually longer than 24 hours), 3. Sleep dysfunction (unrefreshing sleep or disturbances in sleep quantity or rhythm), and 4. Pain (significant degree of muscle and/or joint pain, and/or significant headaches of new type, pattern or severity). This may include individuals with (but not limited to) Post-Viral Fatigue Syndrome, Long-Covid 19, Overtraining Syndrome (OTS), and/or co-occurring Postural Orthostatic Tachycardia Syndrome (POTS), Fibromyalgia, and/or Mast Cell Activation Syndrome (MCAS).
  • Experience some degree of post exertional malaise and have some degree of exercise intolerance upon physical exertion.
  • Must have been previously physically active and be able to swim
  • Must be considered moderate-to-mild CFS (not severe or very severe) with a FUNCAP27 score between 3.0-5.8.
  • Must be able to do some light physical activity and go to public places without causing post-exertional malaise.

Exclusion Criteria for all participants:

  • Individuals with cardiovascular, pulmonary, metabolic, renal, endocrine, autoimmune, neurological, inflammatory condition, infectious disease, or mental illness that makes exercise participation a risk will be excluded from the study.
  • Individuals who are pregnant will be excluded from the study.
  • Individuals with musculoskeletal injuries that prevent exercise participation will be excluded from the study

Inclusion Criteria for healthy controls:

  • Be between the ages of 18-80
  • Must be physically active and be able to swim.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

  • Primary Purpose: Supportive Care
  • Allocation: Non-Randomized
  • Interventional Model: Crossover Assignment
  • Masking: None (Open Label)

Arms and Interventions

Participant Group / Arm
Intervention / Treatment
Experimental: ME/CFS group
Individuals with ME/CFS and related conditions
Behavioral: Swimming
Following a week of baseline HRV and symptoms tracking, all participants will be asked to perform a light swimming session. This session should be at a self-selected intensity and duration, however it should always be performed at an intensity that is under a rating of perceived exertion of 5/10 (easy to moderate at most). Recommended duration is ~15-30 min. Participants may use flotation or assistive devices as they wish. Cool water is recommended.
Behavioral: Cycling
After a minimum of three days of recovery following swimming, and once the visible application indicates a stable recovery score of at least 4/5 (and the participant feels okay), they may optionally complete a cycling session on a stationary bike. This biking session will also be at a self-selected duration and intensity (effort <5/10), which does not need to match the first session. If participants feel that they are unable to complete the biking exercise session, they can still participate in the study and only complete the swimming. If they believe that it would exacerbate symptoms and cause harm, they should not do the biking.
Active Comparator: Control Group
Healthy age and sex matched controls
Behavioral: Swimming
Following a week of baseline HRV and symptoms tracking, all participants will be asked to perform a light swimming session. This session should be at a self-selected intensity and duration, however it should always be performed at an intensity that is under a rating of perceived exertion of 5/10 (easy to moderate at most). Recommended duration is ~15-30 min. Participants may use flotation or assistive devices as they wish. Cool water is recommended.
Behavioral: Cycling
After a minimum of three days of recovery following swimming, and once the visible application indicates a stable recovery score of at least 4/5 (and the participant feels okay), they may optionally complete a cycling session on a stationary bike. This biking session will also be at a self-selected duration and intensity (effort <5/10), which does not need to match the first session. If participants feel that they are unable to complete the biking exercise session, they can still participate in the study and only complete the swimming. If they believe that it would exacerbate symptoms and cause harm, they should not do the biking.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Symptoms
Time Frame: From enrollment until minimally three days post final exercise session (11~15 days total)
Daily symptoms will be recorded in the Visible app each evening as part of the evening check-in. All available symptoms listed on the app will be evaluated (44 items, rated 0-3, with 0=none, and 3= severe). The total score will be the sum of all 44 items.
From enrollment until minimally three days post final exercise session (11~15 days total)
Heart Rate Variability
Time Frame: From enrollment until minimially three days after one or both exercise sessions (11~15 days total)
HRV will be collected each morning upon waking, and in the seated-upright position, through the Visible application. This is assessed with lnRMSSD plotted on a 0-100 scale. Analyses will focus on changes in HRV from baseline to 24, 48, and 72 hours post-swim session compared to post-bike session.
From enrollment until minimially three days after one or both exercise sessions (11~15 days total)

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Time to recovery
Time Frame: From enrollment to the post-exercise recovery periods from days ~9-11 and ~13-15.
The time to recovery from each exercise session will be assessed. This will be defined as the number of days it takes for the readiness scores to reach at least a 4 out of 5 on the Visible App.
From enrollment to the post-exercise recovery periods from days ~9-11 and ~13-15.
Exercise Load
Time Frame: Exercise days ~8 and ~12.
The intensity and duration of the exercise sessions will be determined as the duration of the exercise in minutes multiplied by the rating of perceived exertion for the session (sRPE) on a Borg 0-10 scale.
Exercise days ~8 and ~12.
Severity of ME/CFS
Time Frame: Baseline
The functional capacity 27 scale will be used to assess the functional severity of each participant's condition. The scale has 27 statements, that are ranked from on a likert scale of 0-6, with 0 being "unable to perform that activity", and 6 being "unproblematic - does not affect other activities." The average score from all 27 statements is used as the overall score. Only participants with a score ≥3.0 and <5.8 will be included in the study (representing mild-to-moderate ME/CFS).
Baseline

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Simon Fraser University

Investigators

  • Principal Investigator: Alexandra Coates, PhD, Biomedical Physiology and Kinesiology, Simon Fraser University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Helpful Links

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

February 20, 2026

Primary Completion (Estimated)

January 1, 2027

Study Completion (Estimated)

June 1, 2027

Study Registration Dates

First Submitted

February 25, 2026

First Submitted That Met QC Criteria

March 5, 2026

First Posted (Actual)

March 6, 2026

Study Record Updates

Last Update Posted (Actual)

March 30, 2026

Last Update Submitted That Met QC Criteria

March 24, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 30003523
  • n2cx3 (Registry Identifier: OSF Registries)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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