This study examined the effects of jaw clenching, and a self-adapted, jaw repositioning mouthpiece on force production during maximum countermovement vertical jump and maximum isometric mid-thigh clean pull assessments in an attempt to determine any ergogenic effects attributable to clenching, jaw repositioning mouthpiece use, or the combination of both. Thirty-six male subjects performed vertical jump and isometric clean pull assessments from a force platform under various mouthpiece and clench conditions. A 3x2 (mouthpiece x clench) repeated measures ANOVA was conducted to analyze each of the following force production variables for both assessments: peak force, normalized peak force, and rate of force development. Additionally, jump height was analyzed for the vertical jump. Results revealed improvements in peak force (F1,35 = 15.84, p < 0.001, [eta]p2= 0.31), normalized peak force (F1,35 = 16.28, p < 0.001, [eta]p2= 0.32), and rate of force development (F1,35 = 12.89, p = 0.001, [eta]p2= 0.27) during the isometric clean pull assessment when participants maximally clenched their jaw, regardless of mouthpiece condition. There were no statistically significant differences in jump height, peak force, normalized peak force, or rate of force development during the vertical jump for any treatment condition. This study supports previous research demonstrating that the implementation of remote voluntary contractions such as jaw clenching can lead to concurrent activation potentiation and a resulting ergogenic effect during activities involving and requiring high force production.
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