Velocity‐Dependent and Movement‐Specific Ergogenic Effects of a Custom‐Made Mouthguard on Isokinetic Shoulder Strength in University Rugby Players

BACKGROUND/AIM: Mouthguards are essential for preventing orofacial trauma in contact sports, such as rugby. However, comfort issues often hinder athlete compliance. Demonstrating an ergogenic effect could encourage greater use. This study aimed to examine the impacts of wearing a custom-made mouthguard on isokinetic shoulder strength, focusing on its velocity-dependent effects and its influence on inter-limb asymmetry. MATERIALS AND METHODS: Twenty-nine male university rugby players performed maximal concentric isokinetic shoulder movements in a diagonal pattern (adduction and abduction) using a dynamometer. A randomized, crossover design compared performance with a custom-made mouthguard and without a mouthguard for both dominant and non-dominant limbs at angular velocities of 60°/s, 120°/s, and 180°/s. Key metrics included peak torque and rate of force development. RESULTS: Mouthguard use showed a significant main effect, with significantly higher peak torque and rate of force development compared to without a mouthguard (p < 0.05). A significant interaction between mouthguard condition and angular velocity was observed for rate of force development, suggesting that the ergogenic effect was most pronounced at the lowest velocity (60°/s). Improvements were significantly greater during adduction than during abduction. However, mouthguard use did not alter the existing non-dominant/dominant strength ratio. CONCLUSIONS: Wearing a custom-made mouthguard acted as a velocity-dependent ergogenic aid, which enhanced both maximal and explosive shoulder strength, particularly during low-velocity, high-force movements. Although it improved overall strength, it did not correct existing strength asymmetries. These findings highlighted the potential value of mouthguards for enhancing fundamental force generation capacity under controlled conditions, which might improve athlete compliance and safety.