The aim of this study was to identify the features of isokinetic shoulder and trunk muscle strength of volleyball attackers with shoulder problems and to compare them with those of baseball pitchers.18 competitive high school volleyball attackers and 16 competitive high school baseball pitchers were studied.6 of the attackers and 7 of the pitchers were suffering from shoulder pain but the other players had no history of shoulder pain. The tests were conducted using a Biodex system 3 multi-joint dynamometer. The shoulders were tested for their flexion and extension muscle strength on the scapula plane and trunk muscle strength were tested for their flexion, extension and torso-rotational strengths. The results were compared between the normal group (N-G)and the shoulder injured group (S-G) and also between the attackers and the pitchers. We observed weakness of shoulder flexion strength in S-G of both athletes and the flexion to extension muscle strength ratio was significantly lower in S-G of the attackers. We also noticed the decline of trunk torso rotation to shoulder extension muscle strength ratio in the same group. In comparisons between the attackers and pitchers of N-G, trunk flexion to extension muscle strength ratio of attackers was significantly higher. The reason of the above results, we assumed that the force created from lower extremities was used for jumping in volleyball, while in baseball, it is used for pitching. We also considered that force required for spiking is created from the trunk in volleyball. Characteristics of shoulder muscle strength as dynamic stabilizer are similar in both volleyball and baseball. Appropriate proximal kinetic chain rehabilitation for the leg, hip and trunk should be selected in accordance with the characteristics of sports activities to prevent shoulder injuries. Especially for volleyball attackers, trunk muscle training is a prerequisite to prevent shoulder injuries.
