Muscle fatigue in some neurological disorders

Abstract

Fatigue of tibialis anterior (TA) was induced by repetitive electrical stimulation. Using this test, patients with upper motor neuron muscle weakness owing to multiple sclerosis (MS) and injuries to the spinal cord showed greater fatigability of their TA muscles, suggesting that the muscle fiber population changed toward that typical of fatigable motor units. During repetitive stimulation, in addition to the decrement in tension there was an increase in half-relaxation time of tetanic contractions at 40 Hz in both subjects and patients. The increase in half relaxation during repeated activity was greater in patients with MS and spinal cord injury than in healthy subjects, suggesting that the long-term inactivity affected the efficiency of the Ca2+ uptake mechanism of their muscle fibers. Thus long-term inactivity of patients with upper motoneuron dysfunction leads to increased fatigability of their muscles and exaggerates the slowing of muscle relaxation after prolonged exercise.

Evidence of an abnormal intramuscular component of fatigue in multiple sclerosis

“…24,29,33 Because both CMAP and maximum force in part reflect muscle size, it is possible that the preexercise reductions of CMAP amplitude, MVC, and stimulated force observed in the patients may have been the result of differences in muscle size. Differences in muscle size between groups may have been due to disuse atrophy in MS or difference in sex distribution between the two groups.…”

“…34,35 Previous studies have shown that peripheral sources of fatigue are also important in spastic muscles. 24,29 Lenman et al suggested secondary changes in spastic muscles are similar to those of immobilization and disuse. 24 In another study of a small number of patients with various types of spastic paraparesis, greater changes in energy metabolites accompanied the excessive muscle fatigue observed in patients compared to controls, which suggested that intramuscular factors may contribute to fatigue in spastic paraparesis.…”

“…24,29 Lenman et al suggested secondary changes in spastic muscles are similar to those of immobilization and disuse. 24 In another study of a small number of patients with various types of spastic paraparesis, greater changes in energy metabolites accompanied the excessive muscle fatigue observed in patients compared to controls, which suggested that intramuscular factors may contribute to fatigue in spastic paraparesis. 29 Recently, in patients with MS, we have observed both reduced muscular oxidative capacity, 19 Therefore, the main objective of this study was to investigate muscle fatigue in MS patients, and to determine the extent to which muscle fatigue was related to clinical status and perceived fatigue.…”

Core muscle characteristics during walking of patients with multiple sclerosis

“…The greater volume may be due to an increased proportion of type 2 fibers on this side, which are known to have greater cross-sectional area. While it is suggested that muscle characteristics of patients with MS shift to a higher proportion of type 2 fibers [24,[30][31], impaired neural drive to the muscles may prevent increased strength. However, it is likely that the shift in fiber type characteristics on one side of the body is not sufficient to cause imbalanced muscle volume.…”

Physical Rehabilitation in Multiple Sclerosis: General Principles and High-Tech Approaches

“…Утомляемость может проявляться отсутствием физической и психической энергии, неконтролируемой апатией, иногда утомляе-мостью отдельных мышечных групп при повторяющихся движениях [12].…”