A biomechanical analysis of the bench press.

Weight training is a popular activity offering many physical and psychological benefits and the bench press is one of the most popular weight training exercises among both competitive and recreational lifters. The purpose of this study was to increase the body of knowledge concerning the biomechanics of the bench press as performed by novice lifters. Muscular activity and the kinematics of the lifter, as well as the kinematics and kinetics of the bar, were assessed during different variations of the exercise. While most training regimens incorporate multiple repetition sets, there is little data describing how the kinematics of a lift change during a set to failure. The purpose of the first study was to examine these changes in novice lifters. Subjects were recruited and asked to perform a maximal single lift (1-RM) and then as many repetitions as possible at 75% of the 1-RM load; three-dimensional kinematic data were recorded and analyzed for all lifts. Statistical analysis revealed differences between the maximal and submaximal lifts, and also that the kinematics of a submaximal lift change as a subject approaches failure in a set. Within the set, the time to lift the bar more than doubled from the first to the last repetition, causing a decrease in both mean and peak upward velocity. Furthermore, the peak upward velocity occurred much earlier in the lift phase in these later repetitions. The path the bar followed also changed, with subjects keeping the bar more directly over the shoulder during the lift. In general, most of the kinematic variables analyzed became more similar to those of the maximal lift as the subjects progressed through a set, but there was considerable variation between subjects as to which repetition was most like the maximal lift. The purpose of the second study was to determine the vertical and lateral forces applied along the bar during a maximal and a submaximal effort bench press lift. Novice lifters were asked to perform a maximal and submaximal (80% of maximal lift) bench press. These lifts were performed using a bar instrumented to record forces applied to it in the vertical direction as well as along the long axis of the bar (lateral force). Statistical analysis revealed the average lateral force was between 22 and 29% of the applied vertical force. The profile of the lateral force tended to be similar to the profile of the vertical force in both lifts. The absolute vertical and lateral forces were greater for the maximal lift than for the submaximal lift, but these forces were not different when compared as a percentage of the load lifted. Thus, it is clear that a substantial portion of the force generated by the lifter is applied along the long axis of the bar. The purpose of the third study was to determine how electromyographic (EMG) activity, lift kinematics, and vertical and lateral forces applied to the bar were affected when performing the bench press at different grip widths. Again, novice lifters were recruited and asked to perform a maximal bench press at self-selected grip width, and then five submaximal (75% of maximal lift) lifts at predetermined grip widths. EMG data were recorded for the pectoralis, the triceps, the biceps, and the anterior deltoid. Statistical analysis revealed that peak vertical and lateral forces decreased as grip width increased, with the magnitude of the lateral forces remaining about one quarter of the vertical forces. Higher peak forces and EMG recordings were observed in the descent rather than the lift phase; neither peak nor mean EMG levels were systematically affected by grip width. Given that the same load was lifted with smaller vertical and lateral...