Characteristics of the Shrug Motion and Trapezius Muscle Activity During the Power Clean

Nagao, H and Ishii, Y. Characteristics of the shrug motion and trapezius muscle activity during the power clean. J Strength Cond Res 35(12): 3288-3295, 2021-Although the shrug motion and trapezius muscle activity are commonly considered as important in Olympic weightlifting exercises, there are no data on the shrug motion in Olympic weightlifting. Providing objective data on shrug motion and upper trapezius muscle (TZ) activity during power clean (PC) will help coaches properly evaluate technique and select accessory exercises. The purpose of this study was to clarify the role of the shrug motion and TZ activity during PC. Twenty trained men performed the PC at 50, 70, and 90% of 1 repetition maximum (1RM). Kinematics motion data and TZ surface electromyography were recorded. The range of motion of the shrug angle (sROM) and scapular adduction angle (aROM) were calculated during each phase of the PC. The TZ activity of each phase was evaluated by the root-mean-square of TZ activity (TZ%RMS), normalized by the maximal voluntary contraction. In the first pull and transition phases, TZ%RMS was significantly larger (p < 0.05; η2 = 0.10, 0.11) at 90% 1RM than at 50% 1RM. In the second pull phase, the sROM and aROM were significantly larger (p < 0.01; η2 = 0.19, 0.19) at 50% 1RM than at 90% 1RM, and the TZ%RMS was significantly larger (p < 0.01; η2 = 0.30) at 50% 1RM than at 70% 1RM and 90% 1RM, and at 70% 1RM than at 90% 1RM. Trapezius muscle activity appears to work to maintain scapular position, especially in the first pull and transition phases. In the second pull phase, the TZ was aggressively contracted to elevate the scapula and pull the barbell, but the sROM decreased as the load increased.