Shoulder kinematics and symmetry at different load intensities during bench press exercise

This study aimed to analyze between-shoulder kinematics symmetry at different load intensities considering full range of movement (ROM), mean and maximum velocities (V-MEAN, V-MAX), and accelerations (A(MEAN), A(MAX)) of shoulders during phases 2 (characterized by positive acceleration and negative velocity, eccentric) and 3 (characterized by positive acceleration and velocity, concentric) of bench press exercise (BP); as well as to compare unilateral kinematics variables between the different load intensity intervals. Twenty-seven participants were evaluated during phases 2 and 3 of BP at different load intervals: interval 1 (55-75% 1-repetition maximum: 1RM), interval 2 (75-85% 1RM) and interval 3 (85-100% 1RM). Kinematics variables were determined using the Xsens MVN Link System. Results showed that full ROM was higher in left than right shoulder at all intensities (p = 0.008-0.035). V-MEAN, V-MAX, A(MEAN), and A(MAX) were different in both shoulders for interval 3 during phase 2 and were lower as load intensity increased in both shoulders (p = 0.001-0.029). During phase 3, only V-MAX on interval 2 was different between shoulders. Moreover, V-MEAN, V-MAX, A(MEAN), and A(MAX) were greater during interval 1 compared with the others in both shoulders (p = 0.001-0.029). Therefore, there exists a kinematics asymmetry between both shoulders during phases 2 and 3 of bench press, although the acceleration was similar during both phases at all load intensities. Moreover, kinematic parameters differ between loads of 55-75% RM compared to 75-100% RM loads.