E.M. Teeple, K.D. Charlton, N.M. McPherson, C.J. Wright

Whitworth University, Spokane, WA

The utilization of remote voluntary contractions (RVC) in the upper extremities to elicit concurrent activation potentiation (CAP) in the lower extremities has been well studied. However, little research has been focused on the effect of CAP on upper extremity force production. PURPOSE: The purpose of this study was to examine the impact of voluntary jaw-clenching on force production and neuromuscular recruitment during an isometric biceps brachii contraction. METHODS: 26 undergraduate students (male = 10, female = 16, age = 20.65 ± 1.22 years, height = 170.46 ±7.94 cm, weight = 76.6 ±17.78 kg), with no history of upper-arm injury were recruited. During a single session, participants performed 3 maximum voluntary isometric contractions while biting on a mouth guard. They also completed 3 maximum voluntary isometric contractions with a relaxed jaw. The condition order was counterbalanced. During each contraction, force production was recorded via a dynamometer (kg of force) and muscle activation was recorded from the biceps brachii via electromyography (EMG). The average EMG amplitude was normalized for each participant across all max voluntary isometric contractions. A dependent groups t-test (alpha level p ≤ 0.05) was used to measure the differences between mouth guard and no mouth guard conditions. RESULTS: There was significantly greater force production for the mouth guard condition compared to the no mouth guard condition (mouth guard: 22.33 ± 6.70 kg; no mouth guard: 21.63 ± 6.60 kg; t = 3.001, df = 24, p = 0.006). There was no significant difference between the mouth guard conditions for neuromuscular recruitment (mouth guard: 3630.72 ± 1486.51 mV; no mouth guard: 3493.32 ± 1373.29 mV; t=0.889, df=25, p=0.383). CONCLUSION: Inducing CAP with a mouth guard during an isometric biceps brachii contraction significantly increased force production, however, it had no effect on neuromuscular recruitment in the biceps brachii. This mouth guard technique may be useful to improve performance in both athletes and non-athletes during activities that require the biceps brachii to work anaerobically for short periods of time. Future researchers should more thoroughly explore the effects of CAP on the upper extremities, including more precise EMG analysis techniques.

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