Load‐Carrying Lumbar Spine Kinematics in Active‐Duty Marines

Abstract

The purpose of this study was to measure kinematic changes in the lumbar spines of Marines carrying loads. We hypothesized that loads would increase lumbar lordosis and disc compression. Sagittal T2 MR images of the lumbar spine were acquired on a 0.6T vertical MRI scanner in 39 active‐duty Marines. Each Marine was scanned without load (BL) and after 45 min of standing with 50lbs of load (WL). Custom software was used to measure whole spine angles, intervertebral angles, and regional disc heights. Paired t‐tests were used to identify significant differences between tasks (α = 0.05). The overall position of the spine was significantly more horizontal at WL (71.6±6.8°) compared to BL (84.2±4.6°). Lumbar lordosis was reduced during WL (46.0±9.0°) compared with BL (58.2±9.1°). Sagittal intervertebral angles were significantly increased in L1L2 (BL=3.8±2.2°, WL=5.2±2.2°) and reduced in L4L5 (BL=10.2±2.7°, WL=6.9±4.5°) and L5S1 (BL=9.7±3.0°, WL=4.3±2.7°). Significant disc compression was evident anteriorly at L4L5 (BL=13.1±1.8mm, WL=12.5±2.4mm) and L5S1 (BL=12.4±2.9mm, WL=11.0±2.8mm) and reduced in the posterior region at L4L5 (BL=8.6±1.1mm, WL=9.1±1.4mm). Load carrying induced lumbar spine flexion, anterior disc compression and posterior disc distraction. These findings suggest a spine posture aimed to realign the center of mass of the soldier and load carrying system, but it may also increase lumbar spine susceptibility to shear‐load induced injuries.Grant Funding Source: US ARMY RDECOM N6311610MP00182