Lumbar spinal column laxity contributes to instability, increasing the risk of low back injury and pain. Until the laxity increase due to the cyclic loads of daily living can be quantified, the associated injury risk cannot be predicted clinically. This work cyclically loaded 5‐vertebra lumbar motion segments (7 skeletally‐mature cervine specimens, 5 osteoporotic human cadaver specimens) for 20 000 cycles of low‐load low‐angle (15°) flexion. The normalized neutral zone lengths and slopes of the load‐displacement hysteresis loops showed a similar increase in spinal column laxity across species. The intervertebral kinematics also changes with cyclic loading. Differences in the location and magnitude of surface strain on the vertebral bodies (0.34% ± 0.11% in the cervine specimens, and 3.13% ± 1.69% in the human cadaver specimens) are consistent with expected fracture modes in these populations. Together, these results provide biomechanical evidence of spinal column damage during high‐cycle low‐load low‐angle loading.

The erector spinae muscle is categorized as the intermediate layer of the intrinsic back muscles. Textbooks often describe the iliocostalis thoracis as originating superior to the iliocostalis lumborum. Six cadavers were dissected to reveal the iliocostalis thoracis origin and insertion points which show that the iliocostalis thoracis has fascicular attachments to the common erector spinae tendon. After reviewing nine common anatomy textbooks, 66.7% did not describe the iliocostalis thoracis as having fascicular extension into the common erector spinae tendon in both the text and illustrations. Interestingly, 22.2% of these textbooks had text that explained the attachments differently than the illustrations showed. While all cadaver specimens are inherently different, this finding shows that textbooks should reflect the fact that the iliocostalis thoracis originates from the common erector spinae tendon. This outcome could influence the healthcare a patient receives for antalgic compensatory posture associated with low back pain.