Effect of Trunk Position on Trapezius Muscle Activity and Ratio during Performing Modified Seated Cable Row Exercise

Background Changes in trunk angle as part of modifying the seated cable row exercise (MSCRE) are associated with trapezius muscle activity and ratio. Purpose This study aimed to determine the changes in muscle activity and ratio for the upper trapezius (UT), middle trapezius (MT), and lower trapezius (LT) muscles during the MSCRE in healthy participants without shoulder pain. Study design Cross-sectional study Methods We included participants who were 23 healthy individuals aged 23–39 years. The participants performed a pulling motion three times during the MSCRE at each of the following trunk angles: upright posture 0˚, forward lean 30˚, and backward lean 20˚. Surface electromyography was performed for the UT, MT, and LT muscles during the 5-s isometric contraction, with the participant in a preset position, while the muscle activity was normalized with the maximal voluntary isometric contraction using the manual muscle test. Results The UT and LT muscle activities showed significant differences in angle ( p <0.05); the highest muscle activity was observed for the UT at backward lean 20˚ and LT at forward lean 30˚. The UT/MT and UT/LT ratios showed significant differences in angle ( p <0.05), with the highest values observed at backward lean 20˚ for both the ratios. Conclusions These results suggest that the forward lean 30˚ trunk angle was most suitable for the MSCRE in the selective strengthening of the LT muscle, indicating that the trunk should be tilted forward during exercise for normal and balanced recovery of trapezius muscle activities in shoulder rehabilitation.