INFLUENCE OF LOAD AND STRETCH SHORTENING CYCLE ON THE KINEMATICS, KINETICS AND MUSCLE ACTIVATION THAT OCCURS DURING EXPLOSIVE UPPER-BODY MOVEMENTS

Although explosive power in lower-body movements has been extensively studied, there is a paucity of research examining such movements in th e upper body. This study aimed to investigate the influence of load an d the stretch shortening cycle (SSC) on the kinematics, kinetics! and muscle activation that occurs during maximal effort throws. A total of 17 male subjects performed SSC and concentric only (GO) bench throws using loads of 15%, 30%, 45%, 60%, 75%, 90% and 100% of their previous ly determined one repetition maximum bench press. The displacement, ve locity, acceleration force and power output as well as the electromyog ram (EMG) from pectoralis major, anterior deltoid, and triceps brachii were recorded for each throw. The results were compared using multiva riate analysis of variance with repeated measures. A criterion alpha l evel of P less than or equal to 0.05 was used. Similar force velocity power relationships were determined for this multijoint upper-body mov ement as has been found for isolated muscles, single joint movements, and vertical jumping. The highest power output was produced at the 30% [563 (104) W] and 45% [560 (86) W] loads during the SSC throws. Force output increased as a function of load; however, even the lighter loa ds resulted in considerable force due to the high accelerations produc ed. Average velocity, average and peak force, and average and peak pow er output were significantly higher for the SSC throws compared to the CO throws. However, peak velocity and height thrown were not potentia ted by performing the pre-stretch because the duration and range of mo vement allowed the ability of the muscle to generate force at high sho rtening velocities to dominate the resulting throw. As such, explosive movements involving longer concentric actions than experienced during brief SSC movements may be limited by the ability of the muscle to pr oduce force during fast contraction velocities.