# Analysis of Lumbar Joint Movement and Dynamics of Weightlifters

## TL;DR

This study examines how different weightlifting techniques affect lumbar spine movement and stress, finding that straight leg hard pulls increase injury risk.

## Contribution

The study introduces a novel comparison of lumbar joint dynamics across different hard pull techniques using kinematic and finite element analysis.

## Key findings

- Straight leg hard pull causes greater lumbar flexion (90°) and higher peak torque (893 N·m) compared to traditional and hexagonal barbell hard pulls.
- Straight leg hard pull results in higher peak stress at L5 vertebral body (997 MPa) and L4–5 intervertebral disc (45.6 MPa) than other techniques.
- L5 vertebral body experiences significantly higher stress than other lumbar vertebrae during weightlifting.

## Abstract

To analyze the effects of different hard pull actions on lumbar joint movement and dynamics in weightlifting and evaluate their contribution to the risk of lumbar spine injury.

The study recruited eight national second level and above weightlifters as volunteers, and conducted detailed kinematic and dynamic analysis of different hard pull actions through exercise experiments and finite element analysis (FEA).

The lumbar flexion angles of traditional hard pull and hexagonal barbell hard pull were 58° and 55°, respectively, while the lumbar flexion angle of straight leg hard pull was 90°. The first peak torque of straight leg hard pull was 893 N∙m, significantly higher than the traditional hard pull of 749 N∙m and the hexagonal barbell hard pull of 640 N∙m. In terms of stress distribution, the peak stress of straight leg hard pull at the L5 vertebral body was 997 MPa, and the peak stress of L5 trabecular bone was 3.3 MPa, both higher than traditional hard pull and hexagonal barbell hard pull. The peak stress of the lumbar intervertebral disc was also highest in straight leg tension, with the peak stress of the L4–5 lumbar intervertebral disc being 45.6 MPa.

Straight leg hard pull causes greater damage to the lumbar spine due to its larger lumbar flexion angle and higher peak stress. The damage to the L5 vertebral body during weightlifting is much higher than that of other lumbar vertebrae. Therefore, it is recommended to reduce straight leg hard pull during weightlifting training and strengthen protective measures for the L5 vertebral body to reduce lumbar spine injury.