Figure 1
From: Quantifying intervertebral disc mechanics: a new definition of the neutral zone
A typical load-deflection curve from experimental data of a flexion-extension experiment on a goat lumbar spine segment. The range of motion (ROM) is the total range of deformation upon maximal loading (+/- 2 Nm in this example). The neutral zone is the area with the least internal resistance against bending, thus the steepest slope of the load-displacement curve. NZ indicates the neutral zone as defined by Wilke et al[7]. In this concept, the neutral zone stiffness is the inverse tangent to the curve at the intersection points with the y-axis (straight lines).