Author(s): SUGAJIMA, Y., KANEKO, K., ISHIDA, N., OMORI, T., KATO, T., YAMAMOTO, H., Institution: ASAHI UNIVERSITY, Country: JAPAN, Abstract-ID: 438

INTRODUCTION:
Para-powerlifting, a highly competitive sport, challenges athletes to lift maximum bench press weights within strict time limits. Successful lifts demand not only strength but also precise and stable movements. Our prior study1) hinted at a potential connection between asymmetry in para-powerlifters bench press movements and variations in upper limb strength. This study aims to scrutinize whether the utilization of a mouthguard (MG) can effectively alleviate the observed left-right asymmetry in bench press movements.
METHODS:
Ten male university rugby players, familiar with MG usage (height: 173.3±5.3 cm, weight: 90.1±10.9 kg, age: 21.4±0.5 years), willingly participated. Bench press repetitions at 25%, 50%, and 70% of individual one-repetition maximum (1RM) were performed, with each weight category involving five consecutive lift repetitions to assess stability. Trials were conducted under two conditions: with and without MG, using a custom-made 3 mm thick mouthguard. High-speed recordings of bench press movements (250 frames per second) were made using ten infrared cameras (Vicon). Reflective markers were strategically placed on the shafts ends, upper body locations, and both arms. Center of pressure (COP) during bench press was measured with a pressure plate (Kistler). Various measurements, including body composition, muscle thickness, shoulder and elbow joint angles, were taken and used to quantify COP displacement (COPy) at the bench press movements bottom and top positions. Repeated measures two-way ANOVA statistically evaluated the impact of MG on lift weight differences and left-right asymmetry.
RESULTS:
No statistically significant differences were observed in muscle mass between dominant and non-dominant arms. Similarly, muscle thickness and joint ranges exhibited no substantial variations between sides. In bench press movements, no significant disparities were found in shaft, elbow, and shoulder heights between lift weights and MG presence or absence at both bottom and top positions. The non-dominant/dominant ratios of shaft height also demonstrated no significant variations across different lift weights and MG conditions. Elbow joint angles and COPy showed no significant differences.
CONCLUSION:
This investigation found no significant left-right asymmetry in shaft height during bench press movements bottom and top positions, irrespective of lift weights and MG usage. However, noticeable differences in speed between left and right sides during continuous bench press repetitions contributed to variations in shaft height. Future research should focus on movements with substantial speed differences, exploring nuanced left-right speed or acceleration differences throughout the lifting process.