Fatigue Is Associated with Exercise Endurance and Quality of Life, but Not Self-Reported Physical Activity in Individuals with MS

Background: The fatigue experienced by individuals with MS can have an impact on many aspects of their lives, including activities of daily living and quality of life.

Objectives: The objective of this study was to determine the association between self-reported fatigue levels, health-related quality of life and the ability to sustain a moderate level of exercise (endurance).

Methods: MS patients (40 women, 13 men, n=53) with a mean age of 51.6±10.8 years (range=25-72 yrs), average EDSS of 3.3±1.9 (range=1.0-6.5) and 14.2±9.4 years since diagnosis (range=1-35 yrs) participated in this study. Patients were included if they could continuously pedal a cycle ergometer for a minimum of 10 minutes at a light to moderate intensity. Testing occurred on 2 separate days, separated by 1 week to allow for recovery. On Day 1, subjects completed the Modified Fatigue Impact Scale (MFIS) and a peak graded exercise test to voluntary exhaustion on a cycle ergometer. On Day 2 subjects completed the SF-36, Physical Activity and Disability Survey (PADS) and an endurance exercise test at 60% of the peak workload assessed on Day 1. Data were analyzed for associations among the measured variables (Pearson-Product Correlations) using SAS.

Results: Significant correlations were shown between MFIS total score and SF-36 total score (r=-.582, p<.0001), as well as the subscales of the SF-36: general health (r=-.540, p<.0001), energy/fatigue (r=-.707, p<.0001), physical functioning (r=-.360, p=.0074), physical health-role limitations (r=-.631, p<.0001), social functioning (r=-.637, p<.0001), emotional wellbeing (r=-.363, p=.0069), emotional problems-role limitations (r=-.409, p=.0021), and pain (r=-.566, p<.0001). In addition, MFIS was also significantly correlated with exercise endurance time (r=-.557, p=.0017). However, MFIS was not significantly correlated with self-reported physical activity (PADS) (r=-.187, p=.1764).

Conclusions: Muscle fatigue and its perception have an impact on many aspects of quality of life, including physical health, social functioning, pain and overall wellbeing. Importantly, self-reported fatigue was associated with objective measures of exercise endurance. These data suggest that MS patients’ perception of fatigue is an important part of their capacity to exercise. However, it is unclear why their self-reported fatigue was not associated with self-reported physical activity. It is likely that they tend to overestimate their amount of physical activity since they appear to accurately report their fatigue.

This study was partially funded by NIDRR grant H133G120081.