Relationship between neuromuscular and perceived fatigue and locomotor performance in patients with multiple sclerosis

BACKGROUND: Fatigue is a common problem in patients with multiple sclerosis; however, the impact of neuromuscular and perceived fatigue on locomotor performance is currently unknown in these patients. AIM: The aim of this study was: 1) to determine the relationship between perceived and neuromuscular fatigue and locomotor performance in patients with multiple sclerosis; 2) to determine if neuromuscular and perceived fatigue depend on the severity of the pathology defined by the Expanded disability status scale score (EDSS). DESIGN: Observational study. SETTING: Outpatients from a hospital rehabilitation department. POPULATION: Thirty patients with multiple sclerosis underwent clinical (spasticity, strength, perceived fatigue and locomotor performance) and isokinetic evaluations (peak torque of knee flexor and extensor muscles and neuromuscular fatigue of knee extensor muscles). METHODS: The main outcome measures were perceived and neuromuscular fatigue and locomotor performance. Secondary outcomes were strength of the weakest limb and peak isometric torque of knee flexor and extensor muscles, spasticity, EDSS. RESULTS: There were no significant correlations between perceived or neuromuscular fatigue and locomotor performance. Locomotor performance was correlated with EDSS, spasticity, strength of the weakest limb and peak isometric torque of knee flexor and extensor muscles. Eighty‑three percent of the variance of the 6MWT could be explained by EDSS score, strength of the weakest limb (MRCsum), torque produced during the last five contractions of the fatigue protocol and peak isometric torque of knee flexor muscles. Patients with moderate disability (EDSS Score 4-6) had greater levels of neuromuscular fatigue than patients with mild disability (<4). CONCLUSIONS: Although fatigue is a disabling symptom of multiple sclerosis, and neuromuscular fatigue was found to be higher in more disabled patients, locomotor performance was correlated with strength and spasticity but not with fatigue. CLINICAL REHABILITATION IMPACT: Nevertheless, fatigue was related to 6MWT performance since torque produced during the last five contractions of the fatigue protocol was one of the factors which explained performance.