Influence of baseball practice on strength ratios in shoulder rotator muscles: A new position for isokinetic assessment

Objective: To determine the strength ratios in the shoulder rotator muscles of teenage baseball players, using a new test position.

Methods: Ten asymptomatic baseball players of the French cadet team(15.87 ± 0.80 yr) underwent dynamic isokinetic strength assessment of the shoulder rotators at two angular velocities: 90 and 180°.s ^{-1} . The peak torque of the internal rotators(IR) and external rotators (ER) was recorded. One conventional ratio and two dynamic ratios were determined at each angular velocity. The mean group values were statistically analyzed.

Results: Mean ER peak torque was significantly higher in the dominant than in the non-dominant arm at both velocities (p < 0.05). The dynamic ratio (ER conc/IR ecc) was significantly higher in the dominant than in the non-dominant arm (p < 0.01). In the same position, baseball players had higher conventional and dynamic ratios (IR conc/ER ecc) than those reported in the literature for sedentary subjects.

Conclusion: Intensive baseball practice affects the shoulder rotator muscles. The IR values indicated greater strength than in sedentary subjects. The difference in ER between the dominant and non-dominant arms underlines the effect of pitching technique and suggests the need for further investigations.