Exacerbation of Fatigue following Interval and Continuous Exercise in Patients with Chronic Fatigue Syndrome

Abstract

A post-exertional exacerbation of fatigue is a characteristic feature of chronic fatigue syndrome (CFS). This phenomenon typically arises after a relatively small amount of physical or cognitive activity, after which the exacerbation may last for days. Graded exercise therapy (GET) is beneficial for the management of CFS, using cautious, symptom-limited increases in gentle aerobic exercise. However, it has modest effectiveness and the dose of exercise required to elicit an improvement in function, yet not trigger worsened symptoms, is unclear. High intensity interval training offers a novel avenue to potentially increase the prescribed dose of exercise, and thereby achieve greater increases in function.

PURPOSE: to determine if the exacerbation of symptoms in patients with CFS following a bout of exercise differs between high-intensity interval training (HIIT) or continuous (CONT) aerobic exercise of the same duration and mechanical work.

METHODS: Participants with specialist diagnosed CFS performed two 20 minute bouts of cycling, separated by at least 2 weeks. The bouts were either a continuous moderate intensity (70% age predicted heart rate max (APHRM)) or high intensity interval exercise, with the order counterbalanced. Self-report questionnaires capturing fatigue (0-10), sleep and related symptoms, algometry, actigraphy and heart rate variability were collected across 2 days before and 3 days following the exercise. Comparisons between exercise bouts were made using paired sample t-test.

RESULTS: Preliminary analysis of the first 5 moderately affected (unable to work) participants (30.2±10.3yrs, 63.7±9.7kg, 4 female) work (HIIT 76,064J vs. CONT 78,378J, p=0.12) and overall exertion (RPE HITT 14.1±1.1 vs. CONT 14.5±0.9, p=0.61) was similar between the exercise bouts, while mean heart rate (HITT 78±6% vs. CONT 74±5% APHRM, p<0.05) and RPE in the legs (HITT 15.4±1.6 vs. CONT 13.8±1.2, p<0.05) were higher for the interval compared to continuous exercise. Mean fatigue scores increased in the 72 hours following exercise, though to a slightly lesser extent for the interval exercise (HITT: pre 3.9±1.4, post 4.3±1.1, p =0.08 vs. CONT: pre 3.8±1.2, post 4.7±0.8, p<0.05).

CONCLUSION: A bout of high intensity interval training did not exacerbate fatigue any more than continuous exercise of comparable volume