The reported p-values show the statistical significance of the difference between the trends for opposite directions of loading (two-sample Kolmogorov-Smirnov).

The distribution of strains (Figs 5, 6 and 7) in the cranio-caudal direction of the L4 vertebra and the L4-L5 intervertebral disc (computed as median strains over circumferential lines), and the distribution of strains in the circumferential direction of the L4 vertebra and the L4-L5 intervertebral disc (computed as median strains over cranio-caudal lines) were examined for the different loading scenarios.