Abstract

Since the quality of the spike is a major determinant for the outcome of the game, a lot of practice time is allocated to this technique. Howeve,r the frequent execution of these specific movement patterns during the numerous practice sessions can cause a disequilibrium in the force production of the different shoulder muscles. Since this disequilibrium could cause chronic muscle damage, it is important do determine if the force ratios of the hitting arm are different from those observed in the non-hitting arm. To investigate this, the strength of the intenral (IR) and external (ER) rotators of both shoulders of 11 female volleyball players were mueasured. A comparision of the IR/ER ratios showed that the hitting arm attained significant higher strength values than the non-hitting arm. The PTBW-values indicated that this was not only due to the stronger internal rotation strength of the hitting arm, but also because of a weaker external rotation strength compared to the non-hitting arm. This finding was not only apparent at the level of maximal strength (speed 60 degrees/sec) butr also at the level of strength endurance (test speed 180 degrees/sec). Although these adapted IR/ER ratios increase hitting power, the increased instability of the shoulder could result in higher injury rates. Verf.-Referat