Estimating 3-D L5/S1 moments during manual lifting using a video coding system: validity and interrater reliability

Area of Science:

• Biomechanics
• Occupational Health
• Ergonomics

Background:

• L5/S1 joint loading is crucial for quantifying low-back stress during lifting.
• Traditional measurement methods are confined to laboratory settings, limiting field applicability.

Purpose of the Study:

• To validate a novel video coding system for estimating 3D L5/S1 joint moments.
• To assess the interrater reliability of this video-based estimation method.

Main Methods:

• Compared video-estimated L5/S1 joint moments against motion tracking system data for simulated lifting tasks.
• Evaluated interrater reliability using 10 raters applying the video coding system.

Main Results:

• The video system showed good validity for peak moment (r=.91) and cumulative moment (r=.88) in the sagittal plane.
• Interrater reliability (intraclass correlation) ranged from .51 to .89 across different planes.

Conclusions:

• The proposed video coding system provides a valid and reliable estimation of L5/S1 joint loading from side-view video clips.
• This system serves as a viable alternative for back load estimation when motion tracking is not feasible.