An interventional study of Swimming and Cycling in ME/CFS, Long COVID and Post- COVID-19 Syndrome, sponsored by Simon Fraser University. Suspended at 1 site in Canada. Open to participants aged 18 Years to 80 Years, including healthy volunteers. Per ClinicalTrials.gov, last updated 2026-03-30.
Sponsored by Simon Fraser University · Not applicable, Interventional, and Supportive care
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]
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.
Inclusion Criteria For ME/CFS participants:
Exclusion Criteria for all participants:
Inclusion Criteria for healthy controls:
Individuals with ME/CFS and related conditions
Behavioral: Swimming · Behavioral: Cycling
Healthy age and sex matched controls
Behavioral: Swimming · Behavioral: Cycling
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.
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.
Symptoms
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.
Time frame: From enrollment until minimally three days post final exercise session (11~15 days total)
Heart Rate Variability
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.
Time frame: From enrollment until minimially three days after one or both exercise sessions (11~15 days total)
Time to recovery
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.
Time frame: From enrollment to the post-exercise recovery periods from days ~9-11 and ~13-15.
Exercise Load
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.
Time frame: Exercise days ~8 and ~12.
Severity of ME/CFS
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).
Time frame: Baseline
Plan to share: No
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Simon Fraser University