Physical activity in mild multiple sclerosis: contribution of perceived fatigue, energy cost, and speed of walking

Fatigue is a frequent symptom in multiple sclerosis (MS) that can interfere with a patient's daily functioning. The cause of MS fatigue, its clinical characteristics, and its relationship to other symptoms remain poorly understood. Structured interviews were conducted with 32 patients with MS and 33 normal healthy adults. Fatigue proved to be both more frequent and more severe among the patients with MS. Multiple sclerosis fatigue was unrelated to either depression or global impairment. Multiple sclerosis fatigue appears to be a distinct clinical entity, often disabling, that can be distinguished from normal fatigue, affective disturbance, and neurologic impairment.

This study provided validity evidence for the Godin-Shephard Leisure-Time Physical Activity Questionnaire (GSLTPAQ) to classify respondents into active and insufficiently active categories. Members of a fitness center [45 women and 55 men; mean (SD) age=45.5 (10.6) yr.] completed the questionnaire. Using only moderate and strenuous scores, those with a leisure score index≥24 were classified as active; those with a score≤23 were classified as insufficiently active. VO2max, percentage of body fat, and electronic records of fitness center attendance were the validation variables. In a visit to the fitness center, participants completed the GSLTPAQ and a certified exercise specialist performed a physical fitness evaluation. A multivariate analysis of covariance (MANCOVA) indicated the group of respondents classified as active had higher VO2max and lower percentage of body fat than the group of respondents classified as insufficiently active. An analysis of covariance (ANCOVA) indicated the group of respondents classified as active had higher electronic records of fitness center attendance than the group of respondents classified as insufficiently active. Therefore, these pieces of validity evidence support the use of the questionnaire's classification system among healthy adults.

Although fatigue is recognized as a symptom of MS, there have been insufficient methods for evaluating this symptom. We administered the Fatigue Impact Scale to 85 MS patients and 20 hypertensive patients. Neurologic impairment, mental health, and general health status were also assessed. MS patients reported significantly higher fatigue impact than hypertensive patients. Most MS patients reported fatigue as either their worst (14%), or one of their worst (55%) symptoms. Disease classification and neurologic impairment had little bearing on Fatigue Impact Scale scores in the MS sample. The best predictive models for mental health and general health status in the MS sample both included the Fatigue Impact Scale as a significant factor. This study demonstrates that: 1) fatigue is a very prevalent and severe problem in MS, 2) fatigue impact cannot be predicted by clinical measures of neurologic impairment, 3) fatigue has a significant effect on the mental health and general health status of MS patients.