Does the Intervertebral Disc Adapt to Load?

Abstract

Abstract: Many in the scientific community have been debating the extent to which the spine can adapt. While it is widely accepted that vertebral bones can adapt and become stronger/denser with appropriately dosed loading, there are still many unanswered questions regarding intervertebral discs (IVDs). Recently, some are claiming that IVDs can adapt to stress under load and become stronger and more resilient over time based on the findings from a recent study “Imaging of exercise-induced spinal remodeling in elite rowers” by Frenken et al 2022 in the Journal of Science and Medicine in Sport. The Frenken paper investigates the Glycosaminoglycan (GAG) content of the IVD amongst elite rowers over the course of a training period. They found a temporary increase in this protein and believed that it indicates lumbar disc “remodeling effects” in response to training. This study does show that repetitive loading of the spine does support nutrient transport across the vertebral endplates and an increase in GAG. However, with research showing that a reduction in GAG content is associated with IVD degeneration (a negative adaptation), many have been led to believe the opposite to be accurate; an increase in GAG content means the disc is positively adapting. However, this assumption may be incorrect as it is based on an association, not causation. The proof of nutrient availability isn’t the same as mechanism utility. If in fact, the disc was truly adapting we would likely NOT see an overwhelming amount of research showing an extremely high prevalence of disc degeneration in rowers. The Frenken paper and many more do support the notion that the GAG content alters in response to certain stimuli; however, we can NOT conclude that a temporary increase in GAG content supports the hypothesis that the IVD adapts positively to load.