Neuromuscular function after muscle fatigue in Charcot-Marie-Tooth type 1A patients

Introduction. The effect of recovery time on neuromuscular function following a fatiguing task was compared between patients with Charcot-Marie-Tooth 1A (CMT1A) and healthy individuals in both upper and lower limbs. Methods. Torque of elbow flexors and knee extensors and surface electromyogram (sEMG) of biceps-brachii and vastus-lateralis were recorded from 8 CMT1A-patients and 8 matched healthy individuals during maximal voluntary contraction (MVC) before (PREfatigue-MVC), 10s after (10s-POSTfatigue-MVC) and 10min after (10min-POSTfatigue-MVC) a fatiguing task at 80% MVC until exhaustion. Results. Only in the lower limb, torque and root-mean-square of sEMG (RMS) during PREfatigue-MVC were lower (P<0.05) in patients (91.93±45.95Nm; 0.11±0.07mV) than controls (161.06±75.5Nm; 0.24±0.16mV). In the 10-min-POSTfatigue-MVC, muscle-fiber conduction velocity (MFCV) and RMS, expressed as a percentage of PREfatigue-MVC, were lower (P<0.05) in patients (MFCV:90.3±6.91%;RMS:84.50±9.89%) than controls (MFCV:100.87±5.1%; RMS:92.71±11.84%). Conclusions. CMT1A patients are not only weaker than healthy individuals in the knee extensors, but they also have impaired neuromuscular recovery following fatigue.