In many ways your bones are like a tree - strong, yet supple. Your bones can withstand a tremendous amount of force, and yet they are flexible enough to not be brittle. The balance of mineral content and density is a precise one. Too great a variation in either direction can mean your bones aren’t strong enough to resist external forces or flexible enough to withstand an impact.
Your bones are also like your muscles, in that they respond to training. It’s well known that resistance exercise combined with a suitable diet will improve bone density in healthy adults. The problem is, as we age our bones can get weaker. Even worse, sometimes our bodies don’t respond to stimuli in the same way.
To shed some light on this issue, the researchers in this study looked at the bone health of various senior populations, ages 65 and older. Specifically, they looked at all of the following factors: age, sex, bodyweight, calcium and vitamin D consumption, and leg strength. Many of the participants were also elite senior athletes. The rest of the subjects were not athletes, but otherwise healthy.
Some of the results were expected. Sex, age, weight, and nutrition all had a major effect on bone density. Knee flexion strength (but not knee extension, oddly), also had an effect, but only on the hip bones. The other major result comes as a surprise, at least on the surface: being an elite athlete didn’t appear to yield significantly stronger bones.
To my mind, there are three factors we need to consider when we analyze these results:
- Bodyweight: Bodyweight was one of the biggest factors on bone density, in part because load and impact are are each affected by bodyweight. The athletes who participated in the study were lighter than the non-athletes. Since the athletes' bones were just as strong as the non-athletes, it’s possible the athletics made up the difference.
- Type of Sport: Less than half of the athletes were runners. The researchers noted that running increases whole-body bone density, but the number of cyclists and swimmers present in the study may have reduced this effect.
- Activity Level of Non-Athletes: Finally, the non-athletes were all healthy in this study, and so they were not necessarily inactive. Perhaps they did not represent a real sampling of the senior population.
So there you have it. Athletics don’t necessarily keep your bones healthier. Nevertheless, pound-for-pound, athletics seem to be effective and may also decrease bodyweight while still maintaining healthy bones.