In an animal model of intervertebral disc degeneration, both multifidus muscle fibers and fiber bundles were stiffer 12 weeks after injury,30 although in a model of spinal stiffness induced by ectopic calcification in ENT1‐deficient mice, reduced single fiber stiffness was observed, with no change in fiber bundle mechanics.31 This evidence concerns the gene SLC29A1 and Intervertebral disk degeneration.