New research published in Scientific Reports has shown for the first time that human intervertebral discs may strengthen in response to certain forms of exercise. Whilst degeneration has been associated with certain activities in the past, exercise has never before been shown linked to improvements in the intervertebral disc—something previously thought impossible by many.
“Some authors have argued that intervertebral disc metabolism in humans is too slow to respond anabolically to exercise within the human lifespan,” the researchers explain. “Here we show that chronic running exercise in men and women is associated with better intervertebral disc composition…and with hypertrophy.”
“We expect that tissues will adapt to loads placed upon them,” Lead author Daniel Belavy (Burwood, Australia) and colleagues wrote. In the case of the intervertebral disc, much more evidence has been gathered as to which kinds of exercise involve potentially damaging loading types than beneficial ones. A sport such as golfing—which involves flexion of the spine with torsion—is generally considered to have a damaging loading effect on the intervertebral disc. “Whilst this information can inform what activities people should avoid to preserve intervertebral disc integrity, it does not inform us on exercise or habitual physical activity to ‘strengthen’ the intervertebral disc,” the authors commented.
Data which have been previously obtained on the intervertebral disc turnover rate—using animal, intervertebral disc cell and tissue models—have suggested that there may be “a ‘likely anabolic window’” for beneficial disc loading. Rodent models linking treadmill running with beneficial intervertebral disc effects, coupled with the availability of human intra-discal pressure data concerning various activities, Belavy and team hypothesised that “people who perform regular upright running activity will show better intervertebral disc tissue quality.”
Quality of the disc was measured by “higher T2-times in [the] intervertebral disc,” in those who regularly run, compared with the discs of healthy but physically inactive people. “Furthermore,” the authors wrote, “to better understand what types of physical activity are likely beneficial for [the] intervertebral disc, we explored the relationship between habitual physical activity…and intervertebral disc quality.”
Recruiting men and women aged between 25 and 35 years old (n=79), the team included only those who had either participated in no sport (24), run between 20 and 30km per week (joggers, 30) or run more than 50km per week (long-distance runners, 25) as standard over the past five-years. As well as measuring T2-times—which “indicate better intervertebral disc hydration and glycosaminoglycan content”—participants’ intervertebral disc characteristics and lumbar muscle morphology were recorded, as well as characteristics such as sex, body mass and height. Extra accelerometry data acquired over eight days were recorded during all walking hours for 10 individuals.
In keeping with anabolic intervertebral disc results in animal studies, the researchers found that those who engaged in jogging and long-distance running “showed better hydration and glycosaminoglycan,” indicated by significantly higher lumbar T2-times compared to the inactive group. This effect was most strongly recorded in the disc nucleus. The long-distance runners also showed greater intervertebral disc height compared to the vertebral body, an effect present from L3/L4 to L5/S1. Greater differences in intervertebral disc characteristics were observed between the long-distance running group and the inactive participants than between the joggers and the inactive group, but these were not significant. These results, however, were not related to total activity levels. Lumbar muscle size was consistent between the three groups.
Accelerometry data revealed that accelerations between 0.44g and 0.59g mean amplitude deviation were linked most strongly to intervertebral disc T2-time. Ambulation at 2m/s fell within this window, the authors observed, while walking at ≤1.5m/s and running at ≥2.5m/s fell outside. According to the team, this “is in line with the notion that high-impact loading is considered to be detrimental to the intervertebral disc and vertebral endplate” and suggests “a ceiling effect of [the benefits of] exercise for both volume of upright axial spine loading and intensity.”
Interestingly, running causes repetitive loading of the spine, which is usually associated with disc degeneration at the lower lumbar levels. Not only did runners in this study show healthier intervertebral disc characteristics than inactive participants, but this effect was most marked at the lower lumbar levels. “Repetitive axial loading of the spine under body weight during running” may in fact “be beneficial for the lower lumbar intervertebral discs,” the authors surmised.
Noting that the sturdy is limited in its cross-sectional design, the team consider their research to be a “first step”, concluding that “[these] findings will be a starting point for to better define exercise protocols and physical activity profiles for intervertebral disc anabolism in humans.”