Load moment, muscle strength and level of muscular activity during internal rotation training of the shoulder

Existing studies of shoulder joint loading, muscle strength and muscular activity do not, from the point of view of clinical application, adequately cover these factors, knowledge of which is important for the design of optimal exercises for training shoulder impairments. In the present study, exercises using a weight-and-pulley device have been analysed in order to map the resistance moments of force in relation to the muscular strength capacity of shoulder internal rotators , and to map the activation of these muscles in response to the resistance from the device. The relationships established in the study provide a basis for optimising various types of shoulder training exercises. For example, an angle of 40 degrees between frontal plane and shoulder-pulley line has been found to give the best adaptation of resistance to strength. The study also demonstrates the possibility of using a pulley apparatus for shoulder inward rotator muscle training.