VARIABILITY OF PHYSIOLOGICAL AND PERCEPTIVE RESPONSES TO EXERCISE IN THE CHRONIC FATIGUE SYNDROME

Abstract

2060 The chronic fatigue syndrome (CFS) is a condition known to have a cyclic aetiology, yet the exact nature or cause of either the fatigue or its fluctuation is uncertain. Eight subjects diagnosed with CFS completed an incremental treadmill walking test to volitional exhaustion on four separate occasions, each one week apart. Submaximal and maximal oxygen uptake (VO2), heart rate (HR), blood lactate (BLa) and rating of perceived exertion (RPE) were recorded on each occasion. The mean intra-subject coefficient of variation (CV) of VO2peak was 11.8 ± 5.6% (range 8.0 - 25.2%) indicating a high degree of variability in the point of volitional exhaustion from week to week. Although the CV for ventilatory threshold (VT) was slight (2.1 ± 0.6%), RPE at VT was highly variable (26.2 ± 6.7%). All results for each individual were expressed as a change from baseline (week 1) for all subsequent data analysis. Significant (p<0.05) correlations were observed between the change in VO2peak and the change in HRpeak (r=0.94) and BLapeak (r=0.75) suggesting that the variation in volitional exhaustion was not the result of changes in cardiac insufficiency or lactate accumulation. However, a significant correlation was also observed between the change in VO2peak and the change in RPE at VT (r=−0.85) suggesting that altered perceptions of exertion may be responsible for the variation in volitional exhaustion. These data suggest that the fatigue associated with CFS may be due, at least in part, to a central rather than a peripheral aetiology.