Motor fatigability after low-intensity hand grip exercises in persons with multiple sclerosis

• During low-intensity hand grip exercises, PwMS do not have more motor fatigability, compared to healthy controls. Recovery after low-intensity exercises is comparable to healthy controls.
• PwMS report more perceived fatigability in their non-dominant hand after low-intensity exercise, but not in the dominant hand.
• There is no relation between the strength decline during maximal contractions and after low-intensity contractions, therefore, assessment of fatigability should be task-specific and intensity specific.

IntroductionDuring maximal, sustained contractions, persons with multiple sclerosis (PwMS) show higher motor fatigability in comparison with healthy persons. It is not known if motor fatigability is also different between PwMS and healthy persons during low-intensity exercises. Thus, the aim of this study was to determine the difference in hand grip fatigability between healthy persons and PwMS for both hands during low-intensity hand grip exercises.Methods19 PwMS and 19 healthy controls performed 18 min of hand grip exercises at a maximum of 25% of the maximal voluntary strength, with an electronic hand dynamometer. Perceived fatigability, maximal hand grip strength and muscle activity (electromyography) of the wrist flexors and extensors were recorded in between these exercises for the dominant and non-dominant hand.Results and discussionThere was a significant decrease in maximal hand grip strength after exercising in both groups and for both hands, mainly situated in the first 6 min. In contrast to what was hypothesized, PwMS did not show more decline in strength than healthy controls, neither in the dominant nor the non-dominant hand. There was no group difference in the increase of the perceived fatigability in the dominant hand. However, for the non-dominant hand, the perceived fatigability after exercising increased more in PwMS than in healthy controls. Additionally, there was no relation between fatigue indices, as assessed with short maximal contractions and the strength decline after low-intensity repetitive exercises.