An electromyographic analysis of shoulder muscle activation during push-up variations on stable and labile surfaces

Background: Numerous exercises are used to strengthen muscles around the shoulder joint including the push-up and the push-up plus. An important consideration is the addition of surface instability in the form of swiss ball for rehabilitation and strength. The justification for the use of the swiss ball is based on its potential for increasing muscular demand required to maintain postural stability and for improving joint proprioception. Evidence for this is lacking in literature. Purpose of the Study: To compare the myoelectric amplitude of shoulder muscles during push-ups on labile and stable surface. Study Design: Same subject experimental study. Materials and Methods: Thirty healthy male subjects in the age group 20-30 years with a mean height of 173.65 cm ( SD 2.56) and a mean weight of 69.9 kg (SD 0.2) were taken. Surface electromyogram was recorded from triceps, pectoralis major, serratus anterior and upper trapezius while performing push-up and push-up plus exercises, both on labile and stable surface. Results: Significant increase in muscle activity was observed in pectoralis major and triceps muscle (only during eccentric phase of elbow pushups), while serratus anterior and upper trapezius showed no change in activation level on swiss ball. Conclusion: The addition of a swiss ball is capable of influencing shoulder muscle activity during push-up variations, although the effect is task and muscle dependent.