Fatigue and the energetic costs of walking

Epub ahead of printKempen et al.  Self-Reported Fatigue and Energy Cost During Walking Are Not Related in Patients With Multiple Sclerosis.Arch Phys Med Rehabil. 2012 Mar 20. 

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).

PARTICIPANTS: MSers (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).

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 β=-.188 (P=.236), that between ECw and physical functioning (SF-36 physical functioning) had a β=-.344 (P=.001), and that between fatigue and physical functioning had a β=-.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.


"MS-related fatigue, a percept, is not related to the energy cost of walking. A percept is a term we use as for the perception by the cortex of something in our external or internal environment. Fatigue is an important symptom and is usually a feedback mechanism to tell our bodies to take a rest. In MS this system goes awry; in MS there is a disconnect between what the brain perceives as fatigue and the energy requirements of performing a task such as walking. This confirms that fatigue is a complex symptom and will need to be tackled at multiple levels if we want to make a difference to MSers."

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