Spine and Holistic Health · Module 2 · Spinal biomechanics

Spinal Biomechanics Lab

Run a lifting and posture simulator with live torque and disc compression, practise torque and moment arm problems in newtons and newton metres, sort motions by plane, axis and region, and reason through workplace and safety scenarios. Values are rounded teaching estimates. Nothing here is graded.

Part 1: Lifting Simulator

Teaching modelA simplified two dimensional model of the low back (the L5 S1 level) for a 75 kg adult. It estimates torque, back muscle force and disc compression from the load, its distance and the trunk angle. Real spines share load among many muscles and tissues, so treat every number as a rough estimate.

Simulator readouts
MeasureValue

How the model works: weight = mass × 9.81 N per kg. Torque about the low back = load weight × load distance + upper body weight (about 58 percent of body weight) × 0.25 m × sin(trunk angle). Back muscle force = torque ÷ 0.05 m, the erector spinae moment arm. Compression ≈ muscle force + (load + upper body weight) × cos(trunk angle) + extra from bracing; shear ≈ (load + upper body weight) × sin(trunk angle). The load displacement curve is a lab style curve for one lumbar segment: the dot shows how far into its range the segment is bent, which depends on trunk angle and whether the back is rounded. Guideline lines (3,400 N compression) come from workplace lifting guidance and are design limits, not injury thresholds.