A Biomechanical Analysis of the Effects of Bouncing the Barbell in the Conventional Deadlift.

Krajewski, K, LeFavi, R, and Riemann, B. A biomechanical analysis of the effects of bouncing the barbell in the conventional deadlift. J Strength Cond Res 33(7S): S70-S77, 2019-The purpose of this study is to analyze biomechanical differences between the bounce and pause styles of deadlifting. Twenty physically active males performed deadlifts at their 75% one-repetition maximum testing using both pause and bounce techniques in a within-subjects randomized study design. The average peak height the barbell attained from the 3 bounce style repetitions was used to compute a compatible phase for analysis of the pause style repetitions. Net joint moment impulse (NJMI), work, average vertical ground reaction force (vGRF), vGRF impulse, and phase time were computed for 2 phases, liftoff to peak barbell height and the entire ascent. Additionally, the ankle, knee, hip, and trunk angles at the location of peak barbell bounce height were computed. During the liftoff to peak barbell height phase, although each of the joints demonstrated significantly less NJMI and work during the bounce style, the hip joint was impacted the most. The average vGRF was greater for the bounce; however, the vGRF impulse was greater for the pause. The NJMI results for the ascent phase were similar to the liftoff to peak barbell height phase, whereas work was significantly less for the bounce condition compared with the pause condition across all 3 joints. Strength and conditioning specialists using the deadlift should be aware that the bounce technique does not allow the athlete to develop maximal force production in the early portion of the lift. Further analyses should focus on joint angles and potential vulnerability to injury when the barbell momentum generated from the bounce is lost.