The effects of mouth guard usage on neuromuscular activation and muscle performance

To assess the effects of a commercially-available mouth guard on neuromuscular activation and muscle performance, 8 participants completed a balanced and randomized study with (S-MG) and without (Con) a sport mouth guard. Each participant performed two tests with both elbow flexors and knee extensors muscles: a 1-min contraction at 100% of maximum voluntary contraction (MVC) and an 80% MVC until exhaustion. During 100% MVC, force decay (F%) and the root mean square (RMS) of the electromyogram (EMG) were calculated. During 80% MVC, the time the force target (t-target) and the coefficient of variation (CV) of the force signal were determined. MVC was significantly higher in S-MG than in Con in both muscle groups (P<0.05). F% was significantly lower in S-MG than in Con in the knee-extensors (61.1±1.7% and 68.9±1.3% in S-MG and Con, respectively; P<0.05) but not in the elbow flexors. At 80% MVC, higher t-target values were observed in S-MG compared to Con for the knee-extensors (18.1±2.5 s and 12.9±2.7 s in S-MG and Con, respectively; P<0.05), but not for the elbow flexors. CV was significantly lower in S-MG compared to Con in both muscle groups. These findings indicate that despite neuromuscular activation was not altered, S-MG usage increased maximum force production, endurance time and force stability, especially in the lower limb muscles.