Effects of experimental muscle pain on mechanical properties of single motor units in human masseter

摘要: Abstract Objective : Muscle pain is known to influence muscle activity but the details of its effects on mechanical properties single motor units (SMU) have not been described. We recently reported a decreased firing rate SMU in human masseter during painful contractions with constant force output. Force output can be modulated by discharge relation contractile SMU. Therefore, objective present study was measure clarify mechanism which underlies decrease jaw-muscle pain. Methods A spike-triggered averaging (STA) technique used determine low-threshold recorded fine wire electrodes voluntary isometric contraction. The twitch amplitude, contraction time, and half-relaxation time were determined from averaged records before experimental induced injection 0.2 ml (100 μg/ml) capsaicin 8 healthy subjects. Injections isotonic saline served as non-painful control 11 Results amplitude significantly increased capsaicin-evoked ( P Conclusions Potentiation could possible compensatory maintain when decreases. This finding therefore provides new information adaptation function