Fig. 1

An example of the LabView output. A The displacement curve, the y-axis represent vertical displacement for each trajectory point along the lumbar lordosis (x-axis). Each load trajectory is presented as a unique color (each trial with a different load). B The cumulative displacement (mm) for each segment across loads. C The force (N) versus displacement curve (mm) for each segment. In this example, we would omit the light-yellow 40 N line (mass 4) as the displacement recorded was less than that recorded with 30 N (mass 3), suggesting muscle guarding. This is also illustrated by the skewness of the plot in (C) (red circle). After data cleaning, the stiffest segment was L5 with a global stiffness score of 5.5, and the least stiff segment was L2 with a global stiffness score of 4.2 (B)