Relationship between thoracic kyphosis and serve speed and shoulder muscle strength in adolescent volleyball players

The aim of this study was to investigate the relationship between thoracic kyphosis, serve speed and shoulder muscle strength in adolescent volleyball players. Forty (20 female, 20 male) adolescent volleyball players between the ages of 14 and 18 were included in this study (Age: 16,3±0,76 years; BMI: 20,3±1,69 kg/m2). Shoulder joint internal and external rotation range of motion measurements were performed with a manual goniometer, the thoracic kyphosis was measured with a Spinal Mouse, serve speed was measured with a radar gun, shoulder internal and external rotator concentric muscle strength were measured with IsoMed 2000® isokinetic dynamometer at 60°/sec and 300°/sec angular velocities, and explosive strength measurements were performed with the seated single arm shot put test. The Pearson correlation test was used to analyze the relationship between variables. As a result of the statistical analysis, a negative and moderate correlation (r=-0,452) was found between thoracic kyphosis and serve speed (p<0,05). Similarly, a negative and moderate correlation (r=-0,463) was found between thoracic kyphosis and shoulder external rotator muscle strength at 60°/sec angular velocity (p<0,01). No correlation was found between thoracic kyphosis and shoulder internal rotator muscle strength at 60°/sec angular velocity (r=-0,272) and shoulder external and internal rotator muscle strength at 300°/sec angular velocity (respectively, r=-0,061, r=-0,250) (p>0,05). The results of this study show that the increase in thoracic kyphosis may negatively affect serve speed and shoulder external rotator muscle strength in adolescent volleyball players. Thus, we believe that regular posture assessment in adolescent volleyball players is important in terms of creating an individual training and exercise programs. Thoracic posture exercises, to be given according to the findings obtained as a result of the evaluation, may also be beneficial in terms of providing performance improvement and preventing injuries in athletes.