Muscle activity during the incline shoulder press in relation to the exercise intensity

Background: The incline machine shoulder press (IMSP) is an alternative resistance exercise to the bench press associated with throwing performance. The muscle activity during IMSP has not yet been described in females and at different exercises intensities. Objectives: The aim of this present study was to investigate changes in the activity of prime movers during the IMSP in relation to the exercise intensity in female athletes. Methods: Eight female athletes experienced in resistance training were screened for peak electromyography amplitude normalized for maximum voluntary isometric contraction during the IMSP with increasing loads of 40%, 60%, 80% and 100% of 1 repetition maximum (1RM). The selected muscles were the anterior deltoid (AD), pectoralis major (PM), triceps brachii long head (TBlong) and triceps brachii lateral head (TBlat). Results: The results of Friedman ANOVA showed increased muscle activity along with exercise intensity in all prime movers (p < .001). The Kruskal-Wallis ANOVA showed inter-muscle differences at exercise intensity of 40% 1RM (p = .004, ηp2 = .52), 60% 1RM (p = .005, ηp2 = .55), 80% 1RM (p = .035, ηp2 = .46) and 100% 1RM (p = .002, ηp2 = .52), where TBlat showed lower activity than other muscle groups at each exercise intensity. The TBlong showed lower activity than the PM and AD at 40% 1RM, and the PM activity was lower than that of AD and TBlong at 100% 1RM. Conclusions: The IMSP is an exercise which activated AD and TBlong more than PM and TBlat during maximal lifting effort. Therefore, the IMSP should be understood as the exercise which might substantially overload the AD and TBlong during maximal lifts. Coaches should use the IMSP if they desire to activate TBlong more than TBlat during upper limb pressing.