Better Anaerobic Fatigue Measures Could Help Improve Quality of Life with MS

By Annette M. Boyle

Multiple sclerosis patients often report fatigue, but it isn’t always clear how that condition affects their functionality. New research is seeking to establish clearer definitions and measures of fatigue in an effort to help improve quality of life for MS patients.

WASHINGTON—Of all the symptoms of multiple sclerosis, fatigue consistently rates as the most debilitating and most common. How the neurodegenerative disease causes fatigue and how it can best be measured and ameliorated remains unclear, but two VA researchers suggest that clearly separating the perception of fatigue from fatigability can move research forward.

The researchers, Bryant Seamon, DPT, a clinical research associate in the Muscle Morphology, Mechanics and Performance Laboratory (MMMPL) and Michael Harris-Love, DSc, MPT, director of the MMMPL at the Washington, DC, VAMC outlined the limitations of current fatigue assessments in multiple sclerosis (MS) in a recent article in Frontiers in Neurology.1

“We have all experienced fatigue (often expressed as a feeling of tiredness or exhaustion), it is becoming more apparent that there is not always a direct link between how ‘fatigued we feel’ and how long we can perform a given task. This is supported by studies that show how fatigue questionnaires do not consistently correlate with activity performance,” Harris-Love explained.

Raina Groover, left, participated in a trial on physical telerehabilitation for veterans with MS several years ago. Here, she goes over some exercises with VA physical therapist Susan Conroy during a clinic visit. VA photo by Mitch Mirkin

They noted that exercise interventions often show significant changes in functional capacity and independence measures, but patients report only slight changes in fatigue scores on questionnaires. Conversely, self-reported fatigue has a stronger correlation to depression than to current clinical measures for fatigue symptoms in MS, isometric measures of muscle fatigue or functional assessments such as gait speed or the six-minute walk test.

To increase the utility of fatigue measures, Seamon and Harris-Love advocated dividing fatigue into two trait components that can be evaluated separately: the perception of fatigue and the ability to perform a task. “’Perception of fatigue’ defines subjective sensations related to an individual’s symptom complaint and is the result of homeostatic and psychological factors. ‘Fatigability’ relates to task performance and is defined by a change in performance relative to an objective criterion,” they wrote.

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