Abstract
AbstractBackground: Myalgic Encephalomyelitis/Chronic Fatigue Syndrome (ME/CFS) is a debilitating illness characterised by severe fatigue which causes a significant reduction in levels of activity. Post exertional malaise (PEM), unrefreshing sleep, cognitive impairment, and/ or orthostatic intolerance are all key symptoms of the illness. PEM is described as a unique attribute of ME/CFS which results in significant worsening of symptoms following a physiological, cognitive, or emotional stressor. Due to this, those with ME/CFS are required to manage their activity levels to control PEM symptoms. Nevertheless, there is some evidence that graded exercise interventions could improve symptoms in ME/CFS although this is contested with some arguing that graded exercise programmes cause a worsening of symptoms. The aim of this thesis is to explore the relationship between ME/CFS and physical activity.
Methods and Findings: The first objective was to assess if people with ME/CFS had a reduced peak oxygen uptake (VO2peak) compared to apparently healthy controls as this may increase their risk of all-cause mortality. A meta-analysis of 32 cross-sectional studies demonstrated that pooled mean VO2peak was 5.2 (95%CI 3.8 to 6.6) ml.kg−1min−1 lower in people ME/CFS vs. healthy controls. This study provided evidence that ME/CFS patients have a substantially reduced VO2peak compared to controls which could increase their risk of all-cause mortality. However, there was insufficient data to ascertain the impact of peak exercise testing on ME/CFS symptoms in the days following testing.
A meta-analysis was conducted on studies which conducted repeat maximal exercise tests separated by 24h. The difference in work rate (WR) at anaerobic threshold (AT) (n=4) was -20.64 (95%CI -40.95 to -0.33)W in favour of controls, demonstrating that people with ME/CFS had a reduced power output at AT in the second of the two tests compared to apparently healthy controls. The effect size for this difference was large (d = -0.95) providing evidence that WR at AT effectively discriminates between ME/CFS and controls. These findings provide evidence of an objective and measurable response to repeat high intensity exercise which provides some evidence of a possible physiological element of the illness and may provide a potential objective marker in future studies.
In light of this evidence it was important to assess the effectiveness of exercise interventions in managing symptoms of fatigue in ME/CFS. Meta-analysis of studies assessing the effectiveness of graded exercise demonstrated that the pooled percentage difference for the overall effect (n=10) was -13.4% (95%CI -24.2 to -2.6) in favour of intervention. This indicates that exercise results in a clinically relevant reduction in fatigue. However, when studies using the Oxford Criteria case definition were removed from the analysis (n=5) the percentage difference reduced to -9% (95%CI -21.8 to -3.7). The findings indicate a degree of uncertainty around the effectiveness of exercise programmes in ME/CFS which would support evidence from survey data that graded exercise programmes may only be effective for a limited number of people with ME/CFS.
To explore this in more detail, in-depth interviews were conducted with six people with ME/CFS using an interpretive phenomenological analysis. Participants described feeling as though they are losing themselves and feel a lack of legitimacy about the hidden nature of the illness. Those with ME/CFS described ‘battling’ their illness which is not commonly cited in other chronic health conditions. Those with ME/CFS described wanting to be more active although this is contrasted with the unpredictability of the illness. People with ME/CFS described a desire for others to empathise and demonstrate understanding of their illness. Nevertheless, there was some evidence that when people with ME/CFS were able to engage in activities which had personal meaning this resulted in improvement in mood. Evidence indicated the potential for an activity management strategy in ME/CFS.
A new form a graduated physical activity was considered for people with ME/CFS. The proposed intervention is designed to be flexible in intensity and duration depending on the symptom profile of the individual and allow individuals to choose from a number of possible activities.
| Date of Award | 19 Feb 2021 |
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| Original language | English |
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| Supervisor | Alan Batterham (Supervisor), Gregory Atkinson (Supervisor) & Samantha Harrison (Supervisor) |