Allen, CR, Dabbs, NC, Zachary, CS, and Garner, JC. The acute effect of a commercial bite-aligning mouthpiece on strength and power in recreationally trained men. J Strength Cond Res 28(2): 499–503, 2014—Because of the relative newness of mouthpieces, there are few investigations into using performance mouthpieces during sport and physical activity to substantiate claims of performance enhancement. The purpose of this study was to investigate the acute effect of a commercially available, noninjury preventive, performance mouthpiece on practical acute performance measures of power and strength. A within-subjects design was used to evaluate 21 (N = 21) recreationally trained college aged males on the performance of a maximum countermovement vertical jump (CMVJ) from a force platform and 1 repetition maximum (1RM) bench press exercise for the following conditions: with mouthpiece (MP) and without mouthpiece (noMP). Rate of force development (RFD) and peak vertical force (PF) were derived from force platform data. Statistical analysis revealed no significant differences between conditions for CMVJ height (p = 0.13), RFD at 200 ms (p = 0.09), PF (p = 0.08), and 1RM bench press (p = 0.45). These data indicate that the use of this particular jaw aligning mouthpiece specifically in an attempt to produce an ergogenic effect on performance is unwarranted.