The symptom of fatigue is a frequent complaint in multiple sclerosis (
MS) patients. Signs of fatigability have been documented in these pati
ents as well. However, correlation with signs of objective fatigue had
not been clarified in MS. The aim of this study was to ascertain the
existence of muscular fatigue in multiple sclerosis patients, and to f
ind out if there is a correlation between the subjective symptom of fa
tigue and muscular fatigue. Fifty MS patients and 50 age and sex match
ed volunteers were studied using isometric and isotonic tests using th
e dominant hand. Strength was studied in the baseline condition and al
so after recovery of either an isotonic (experiment A) or isometric ef
fort (experiment B), Maximum strength, strength in relationship to wei
ght, slope of fatigability in 11 consecutive contractions, and strengt
h and duration of a maximum effort were calculated. Fatigue as a sympt
om was measured using the Fatigue Severity Scale (FSS) and the Fatigue
Descriptive Scale (FDS). Non-parametric techniques were used for the
statistical analysis. Patients with MS had less isometric and isotonic
strength, but the recovery was the same as recovery in the control gr
oup. There was a negative linear correlation between the symptom of fa
tigue and the baseline strength. In conclusion, this study supports th
e existence of signs of muscular fatigue in MS patients. However, the
recovery after exercise is normal. The correlation between the baselin
e scores in strength and the symptom of fatigue suggest that the same
cause (probably pyramidal deficits) may be involved in both of them. E
ur J Neurol 5:579-585 (C) 1998 Lippincott Williams & Wilkins.