Hand grip fatigability in persons with multiple sclerosis according to hand dominance and disease progression.

BACKGROUND Hand grip strength in both the dominant and non-dominant hands is often used to assess upper limb impairment. Excessive hand grip fatigability is another important measure, as fatigability may also influence activities of daily living. OBJECTIVE To investigate to what extent hand grip fatigability in multiple sclerosis is dependent on hand dominance, muscle strength and disease progression. METHODS Thirty persons with multiple sclerosis and 16 healthy controls performed 15 repeated maximal hand grip contractions and a 30 s sustained contraction in order to determine dynamic and static fatigue indices. Fatigability was compared between the dominant and non-dominant hands and between the more and less affected hands in a subgroup of persons with multiple sclerosis with asymmetrical hand grip strength impairment. Furthermore, fatigability was compared between controls and subgroups of persons with multiple sclerosis with different disease progression. RESULTS There was no difference in fatigability between dominant and non-dominant hands in healthy controls or in persons with multiple sclerosis. Similarly, there was no difference between the more and less affected hands in the subgroup of persons with multiple sclerosis with asymmetrical hand grip impairment. The dynamic fatigue index did not discriminate persons with multiple sclerosis from controls. While the static fatigue index was not different between healthy controls and persons with multiple sclerosis with low to moderate (< 6) Expanded Disability Status Scale (EDSS), it was significantly higher in persons with multiple sclerosis with high (≥ 6) EDSS scores. The static fatigue index was related to the EDSS score, but not to maximal grip strength. CONCLUSION Fatigability of hand grip strength in persons with multiple sclerosis is not influenced by hand dominance or muscle strength, but there is a correlation with disease progression. Differences in fatigability between healthy controls and, in particular, persons with multiple sclerosis with high EDSS, were found during sustained, but not during dynamic, contractions.