Influence of Repetitions-to-Failure Deadlift on Lumbo-Pelvic Coordination, With and Without Body Armor

Abstract

Ramirez, VJ, Bazrgari, B, Spencer, A, Gao, F, and Samaan, MA. Influence of repetitions-to-failure deadlift on lumbo-pelvic coordination, with and without body armor. J Strength Cond Res 38(10): 1732-1738, 2024-Repetition-to-failure (RTF) deadlift is a training modality for building lifting capacity that is often implemented by service members to maintain a minimum level of physical fitness. Despite its physiological benefits, little is known about the effects of RTF on the biomechanics of lumbar spine. Additionally, the effects of heavy deadlift training with body armor are unknown. The aim of this study was to investigate the effects of RTF deadlift on lumbo-pelvic coordination and posture, with and without body armor. Twenty-three healthy subjects, recreational powerlifters, were recruited for this study. Kinematics of the trunk and pelvis were measured using a 3D motion capture system while subjects conducted RTF deadlifts with a 68-kg low-handle hexagonal bar with and without a simulated body armor (22.68 kg). Lumbo-pelvic coordination was characterized using a vector coding approach and coupling angle variability (CAV) using circular statistics, over 3 equally divided segments of the lifting phase. More specifically, the coupling angle values were used to determine the coordination pattern between the thorax and pelvis. Trunk and pelvis ranges of motion and the amount of in-phase lumbo-pelvic coordination pattern increased with RTF deadlift. Additionally, CAV of the first and the third segments of deadlift cycle increased with RTF deadlift. Increase in variability of lumbo-pelvic coordination and peak trunk flexion (i.e., indication of increased mechanical demand of lifting on the spine), as a result of RTF deadlifting, can have deleterious soft tissue responses and contribute to an increase in risk of lower back injury.

Figure 1.

Starting (top row) and ending (bottom row) positions of a deadlift cycle with (right column) and without (left column) simulated body armor (vest).

Figure 2.

Trunk and pelvis angular motion for sample lowering and lifting cycles extracted from the initial and final stage of RTF deadlift of a subject. Lifting phase (right side of the curve) was used for coordination pattern identification and coupling angle variability measures. Each lifting phase (defined as lifting cycle in the text) was divided into 3 segments of equal trunk angular motion (denoted by circle markers) for these calculations. Positive/negative trunk angle denotes trunk flexion/extension; positive pelvic tilt denotes pelvic flexion. Circular markers are added for descriptive purpose and do not accurately represent the end point of first, second, and third segments of lifting cycle. RTF = repetitions-to-failure.