Analysis of isometric shoulder strength of rifle shooters and the development of a sport strength profile

Abstract

Background Previous research on sports that primarily involve the shoulder are limited to those that use overhead arm actions which include high velocity, large dynamic movements. In contrast rifle shooting is static involving isometric muscle action. Objective The objective was to determine the physiological and biomechanical requirements that influence a rifle shooter, including muscle strengths and weaknesses, to also determine whether asymmetry was an influencing factor, to assist in developing a new sport strength profile to cover motionless, repetitive, isometric sports. Method Both shoulders of 9 healthy competing, air rifle shooters (4 male, 5 female) were tested isometrically, using a KINCOM 125E Plus Isokinetic Dynamometer during flexion, extension, abduction, adduction, internal and external rotation. Internal and external rotation were tested at 60◦ and the other joint actions were tested at 90◦, being deemed appropriate to the natural stance adopted during shooting. Result No statistical evidence was found to support the hypothesis that the dominant arm is stronger overall during the shoulder actions performed. Significant statistical difference was only established between non-dominant and dominant arms during external rotation during average and peak force measurements, where the dominant arm was found to be the strongest. However, there was a pattern of greater strength in the dominant shoulder during the primary joint actions used in shooting (External rotation, Extension & Abduction). Conclusion Further studies are required on a larger sample population to include more detailed testing of all movements at the shoulder joint. A sports strength profile was determined which can be used for rehabilitation and training.