Introduction: Muscles that attached to the scapula control its position and changing in the function of these muscles is an important factor to biomechanics abnormality of shoulder. Movement of scapula and scapulohumeral rhythm have major role in the movement of the shoulder and arm. Kyphosis is the most common abnormality of spinal that effect on the movement of the shoulder. On the other hand repetitive nature of volleyball movements may lead to significant problems related to the spinal column. This research seeks to study the relationship between kyphosis and scapulohumeral rhythm in professional volleyball players.
Methodology: The study population included 40 professional female volleyball players (age: 25.40±3.68 years, height: 1.64±0.07 m, weight: 63.4 ±9.52 kg, body mass index: 23.51 ± 3.76 kg per square meter) who exercise three times a week and have four years of professional experience were selected. We used flexible ruler to measure kyphosis and LSST method for scapulohumeral rhythm.
Results: Pearson correlation test results showed a significant relationship between Kyphosis and the distance between the two scapula (p=0.01, r=0.389), between Kyphosis and scapulohumeral rhythm right at an angle of zero degrees (p=0.001, r=0.561), angle of 90 degrees (p=0.01, r= 0.394) and also the distance left scapula blade at an angle of zero degrees (p=0.001, r=0.531) and angle of 45 degree (p=0.02, r=0.350), but there was no significant relationship between the other variables.
Discusstion: Scapula go to upward rotation and stop earlier In abdouction movment of arm at vollyball players with kyphosis. These factors, together with relatively shoulder protraction would limit the range of motion of scapulothoracic and shoulder joint and also disrupt the scapulohumeral rhythm. Because of the muscle weakness in upper of back, couples forces that rotate the scapula, do not act in a timely manner and change coordination at shoulder. In this study, weakness in muscle holders of scapula and spine caused disrupt scapulohumeral rhythm of volleyball players that were suffering from kyphosis.