A biomechanical anlysis of the bench press

Open Access
Author:
Duffey, Michael J
Graduate Program:
Kinesiology
Degree:
Doctor of Philosophy
Document Type:
Dissertation
Date of Defense:
August 21, 2008
Committee Members:
  • John Henry Challis, Committee Chair
  • Andris Freivalds, Committee Member
  • William E Buckley, Committee Member
  • Jinger Gottschall, Committee Member
Keywords:
  • EMG
  • grip width
  • weight lifting
  • benc press
  • force
  • biomechanics
Abstract:
The goal of this research project was to increase the body of knowledge concerning the biomechanics of the bench press as performed by novice lifters. The purpose of the first study was to determine how the kinematics of a bench press change during a set to failure. To examine these changes, subjects performed a maximal single lift (1-RM) and then as many repetitions as possible at 75% of the 1-RM load. Statistical analysis revealed differences between maximal and submaximal lifts, and that the kinematics of a submaximal lift change as a subject approaches failure in a set. The time to lift the bar increased from the first to the last repetition, causing a decrease in both mean and peak upward velocity. Peak upward velocity occurred much earlier in the lift phase in these later repetitions. Subjects also kept 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 the set. 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. Statistical analysis revealed the average lateral force applied along the bar to be 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 were not different when compared as a percentage of the load lifted. The purpose of the third study was to determine how EMG activity, lift kinematics, and vertical and lateral forces applied to the bar are affected when performing the bench press at five different grip widths. Statistical analysis revealed that vertical and lateral forces decreased as grip width increased. Peak and mean EMG levels were not systematically affected by grip width. This research project has shown that performing the bench press with a wider grip is more efficient than a narrow grip. The submaximal and training lifts of novice lifters are substantially different from their maximal lifts and these novice lifters displayed different kinematic, kinetic, and muscle activation patterns than those reported for experienced recreational and competitive lifters.