Hand position affects elbow joint load during push-up exercise

Electromagnetic motion sensors and a piezoelectric force plate were used to record simultaneously upper-extremity motion and forces in nine health male subjects during push-ups in six different hand positions. The intersegmental loading pattern on the elbow joint during a push-up exercise was investigated. The importance of hand position on these loads was examined. Peak forces exerted on the elbow joint along the forearm axis averaged 45% of the body weight for the 'normal' hand position and were significantly decreased if hands were positioned either 'apart' or 'superior' from 'normal'. The peak torque in the 'normal' position tended to produce elbow flexion and was 2305.9 N cm, or 56% of the maximal isometric extensor torque, which was significantly different from hands 'apart' and hand 'together' at 29 and 71% of the maximal isometric torque, respectively. The maximum torque about the forearm axis tended to produce forearm pronation with a mean value of 315.4 N cm (35% of the maximal isometric supinator torque). The maximum valgus torque at the elbow opposed by the medial ligamentous structure was 1241 N cm and was significantly increased if the hand was positioned superiorly. The valgus torque increased by 42% for the one-handed push-up under simulated fall condition. The results of this analysis give an insight into the biomechanics of a normal elbow and to its load-carrying capacity. The data may be extrapolated to the design of rehabilitation programs and possibly to the mechanisms of forearm injury during a fall.