Comparison in peak torque rotations between dominant and non-dominant arms in powerlifters

Abstract

The shoulder joint is naturally instable because of anatomic structure, and depends of passive and active elements, ligaments and muscle, respectively, for proper stability. The bench press, upper body exercise, is one of three exercises of Powerlifting (PL), based on maximum strength. The strength balance between dominant (D) and non-dominant (ND) upper limbs is fundamental to develop a good lift and joint safety. Therefore, not only major muscles are important as pectoral major, but also stability muscles as rotator cuff for shoulder external rotation. To compare, in recreational powerlifters, relative peak torque between dominant and non-dominant arms, in external and internal rotation at 60°/s and 180°/s concentric action velocity for external (ER) and internal rotation (IR) in shoulder joint. Participants, nine powerlifters (height: 1.73±0.06cm; weight: 84.1±13.0kg; bench press 1 repetition maximum: 116.4±19.1kg; PL minimal experience: 2 years). The muscle group strength for ER and IR were assessed bilateral by Biodex System 4Pro isokinetic dynamometer. The participants were in a seated position, 45° shoulder abduction, 60°/s and 180°/s concentric mode was adopted for lever velocity for ER and IR in shoulder joint. Dominant and non-dominant sides peak torque normalized to body weight (PT/BW; Nm.kg-1) were compared with paired student's t-test. Significant difference (p=0.02) was found at the PT/BW for the ER movements between the dominant (47.8±5.8 Nm.kg-1) and non-dominant (44.3±6.1Nm.kg-1) sides at the velocity of 60°/s, but there was no significant difference between sides in IR (p=0.15; D=71.7±16.3Nm.kg-1, ND=66.1±12Nm.kg-1); and at 180°/s for ER (p=0.24; D=48±5.3 Nm.kg-1, ND=45.7.1±8.6 Nm.kg-1) and IR (p=0.24; D=68.7±15.5Nm.kg-1, ND=64.6±8.6 Nm.kg-1). For recreational powerlifters, there is only difference between dominant and non-dominant arms in ER movement at 60°/s, which suggests a necessity of unilateral exercises for a better balance between sides