Perceived fatigue and muscle fatigability in persons with multiple sclerosis

Patients with multiple sclerosis (MS) often report increased levels of perceived fatigue, which negatively influence their life. The current thesis studied fatigue in MS patients from different angles. The increased perceived fatigue in MS patients is multifactorial, and a combination of factors is necessary to explain the perceived fatigue. One of these factors is the fatigability of the muscle. The muscle fatigability is caused by both central and peripheral mechanisms. In MS patients the contribution of central factors is larger than in controls, and it seems to be stronger for SPMS patients than RRMS patients. This knowledge may influence future treatments. Muscle fatigability does not only affect physical output, but also a concurrent cognitive task. During a dual task. the greater the muscle fatigability, the stronger the effect on cognitive performance, especially in MS patients. Also, a more complex bimanual task versus a simple bimanual task reduces performance of MS patients more than that of controls. Furthermore, we found that dual tasks are executed differently by young and middle-aged participants. Middle-aged participants prepare less, which results in slower but more accurate responses.