Self-Reported Fatigue and Energy Cost During Walking Are Not Related in Patients With Multiple Sclerosis

Kempen JCE, de Groot V, Knol DL, Lankhorst GJ, Beckerman H. Self-reported fatigue and energy cost during walking are not related in patients with multiple sclerosis. Arch Phys Med Rehabil 2012;93:889-95. Objectives: To determine whether there is a relationship between self-reported fatigue and the energy cost of walking (ECw), and how self-reported fatigue and ECw relate to physical functioning in patients with multiple sclerosis (MS). Design: Cross-sectional cohort study, using structural equation modeling. Setting: Home environment and at a university medical center. Participants: Patients (N=75) were obtained from a longitudinal study on outcome measurement and functional prognosis in early MS. Patients were included if they were able to walk for 6 minutes without being assisted by a person. The age range was between 28.0 and 69.7 years and the median Expanded Disability Status Scale was 2.5 (range, 1.0-6.5). Interventions: Not applicable. Main Outcome Measures: Self-reported fatigue was measured with the Fatigue Severity Scale, the vitality subscale of the Medical Outcomes Study 36-Item Short-Form Health Survey (SF-36), and a visual analog scale. Physical functioning was determined with the physical functioning subscale of the SF-36, fast walking speed, and comfortable walking speed. The ECw (J.kg(-1).m(-1)) was measured with the energy cost of the walking test. Results: The relationship between ECw and latent variable fatigue had a beta=-.188 (P=.236), that between ECw and physical functioning (SF-36 physical functioning) had a beta=-.344 (P=.001), and that between fatigue and physical functioning had a beta=-.448 (P=.000). Conclusions: Fatigue and ECw are not related in patients with MS with mild to moderate walking problems. ECw and fatigue are independent determinants of physical functioning.