Effects of Barbell Bouncing on Joint Kinematics in Deadlifts: 2194 Board #346 June 2, 2: 00 PM - 3: 30 PM.

Different lifting strategies are utilized to complete higher repetition sets of deadlift. Some coaches emphasize pausing on the floor between repetitions while others allow the athlete to bounce the bar off the floor. To date, little is known about biomechanical differences between these techniques. PURPOSE: To determine the effect of bouncing the barbell between repetitions on joint angles compared to pausing between repetitions while deadlifting. METHODS: Healthy, physically active men (n=11) aged 18-30yrs with a minimum of one-year deadlifting experience completed two sessions. During the first session, participant’s one repetition maximum (1RM) for the conventional deadlift were determined. The second session consisted of 4 sets of 5 repetitions using 75% of their 1RM for each technique (bounce and pause) performed in a randomized order. Ground reaction force and kinematic data of the feet, shanks, thighs, pelvis and trunk were collected. Additionally, marker sets placed on the bar determined bounce height and bar height when positive acceleration was restored (PAR) following the bounce. Center of Pressure (CP) to ankle joint distance and ankle, knee, hip and trunk angular positions were determined at PAR. RESULTS: The bar reached an average bounce height of .057m and was not significantly related to barbell load (r= .365, P= .27). The CP was significantly anterior during the bounce condition compared to pause condition (P=.031, 95% CI: .002 to .037m). A technique by joint analysis of variance failed to reveal significant differences in joint angles between the techniques (P=.19). CONCLUSION: Although joint angles did not differ between techniques, significant change in CP location indicates a more anterior body position. Cumulative effects may result in participants using the musculature in the lower back instead of the musculature in the pelvis. Further research should be conducted to test this hypothesis by considering joint kinetics and heavier load intensities.