(18) FORCE-LOAD AND VELOCITY-LOAD CURVES FOR CLEAN PULL SHRUGS OFF BOXES – LESS VARIABILITY THAN EXPECTED

Purpose: Recent research has examined how velocity-based training (VBT) might be used for the sport of weightlifting (WL) and the use of WL derivative lifts for other sports (Kissick et al. 2025, Suchomel et al. 2025). The purpose of the present study was to determine how removal of the eccentric phase by lifting from boxes affects both the concentric forces and velocities for different relative loads during the clean pull shrug exercise. Methods: Ten well-trained competitive weightlifters (n=5 females, n=5 males) performed multiple clean pull shrugs from the mid-thigh position and the bar starting from a static position while setting on lifting boxes with 2” increments. Single repetitions were performed at 70%, 80%, 90%, 100%, 110% and 120% of clean 1 RM loads. System (body + bar) vertical ground reaction forces (GRF) were assessed with a 1-dimensional force plate (RoughDeck, Rice Lake, WI) and vertical bar velocities were assessed with a linear velocity transducer (Transducer Techniques, Temeculah, CA) positioned immediately above the bar. Resulting electrical signals were acquired and analyzed with a data acquisition system sampling at 1000 Hz (BioPac MP150, Golota, CA). Peak and mean values for bar velocity and system GRF at each load were used to determine the velocity-load and force-load curves as determined with linear regression. Additionally, a 1-way ANOVA with Tukey post hoc analysis determined if any dependent variables significantly differed between relative loads (p< .05). Results: Values for each dependent variable are shown in the figure below (X±SD; *p< .05 vs. 70% 1RM). Regression equations and R² values for each variable are shown in the inset boxes. It should be noted that the relative loads (% 1 RM) were expressed as decimals, resulting in very low slope values for all variables. Coefficients of variability (%CV) for all variables and all loads ranged between 20.3%-28.9%. Conclusions: Due to the high velocities for all loads of this exercise, only peak velocity at 70% and 120% 1 RM were sig. different, influenced in part by the large CV% for velocity at each load, but also by the small differences in velocity across the load spectrum. No sig. differences were observed across loads for peak or mean force. Despite external masses increasing 71% from 70% 1 RM to 120% 1 RM, forces only increased 10.8% and 23.4% for peak and mean forces, respectively. Apparently, the large increases in bar mass were countered by critical decreases in bar acceleration that resulted in very small changes in vertical forces. Practical Applications: VBT does not appear to be a valuable tool for this type of exercise. Bar velocity does not effectively differentiate training loads for this weightlifting derivative, and the forces produced by the externals loads used were surprisingly similar. This illustrates how many different loads of weightlifting derivatives may generate the desired velocities and forces. Acknowledgements: This project was supported by DC Blocks and by the Clara Wu and Joseph Tsai Foundation.