The quantification of motor fatigability in the upper limb in persons with multiple sclerosis

Abstract

Motor fatigability is a frequently occurring symptom in persons with multiple sclerosis (MS). This motor fatigability can be measured both subjectively and objectively. Subjective measurements are often used, but largely interpreted emotionally. Objective measurements are very variable and not specifically defined. A commonly used method to measure motor fatigability is to calculate a fatigue index with a sustained contraction of 30 seconds. The main purpose of this study is to examine possible differences in motor fatigability of the upper limb in persons with MS. Another purpose is to investigate if there is a generalizability of motor fatigability in the different muscle groups of the upper limb. In addition this study also examines if there is an association between motor fatigability and the expanded disability status scale (EDSS), maximal strength and perceived difficulty to perform activities of daily life (ADL). Persons with MS and healthy controls performed three maximal voluntary contractions and a sustained contraction of 30 seconds of the shoulder abductors, elbow flexors, handgrip and finger abductor in order to determine the maximal strength and static fatigue indexes. Motor fatigability is not higher for persons with MS than healthy controls, except for the elbow flexors. Additionally motor fatigability could not be associated with EDSS score, maximal strength and perceived difficulty to perform ADL. As well there was no generalizability of fatigability in the muscles of the upper limb.