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

Abstract

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