Bones

The news that Lance Armstrong broke his shin running the New York marathon should give cyclists pause. The link between osteoporosis and cycling is well known. And when an athlete at Lance's level breaks a leg bone through repetitive stress, the lesson's severity likely doesn't quite apply to those of us more toward the median of cycling accomplishment. But there are things to be remembered and learned from this precipitating event.

Lance was hyper-trained, and his bones are more porous likely for two main reasons: he had an incredibly low body mass index (there is a correlation between low BMI and osteoporosis, but see my post on BMI for some reflections on the problems with that measure), and a lack of weight-bearing exercise. He then turned to running, and trained at a fairly high level to participate in an endurance run. It was akin to spending years as a professional deep sea diver and then scaling Everest a year after quitting the sea. The body was bound to complain.

There's a fair amount of lore about what causes osteoporosis in your average person. The most common misconception is that drinking soda is a cause, with the theory being that the phosphoric acid in most colas leeches calcium from the bones and weakens them. However, research has shown that this is probably exactly wrong -- high intake of phosphoric acid may actually strengthen bones. This is actually a classic "correlation, not causation" case of confusion. Phosphoric acid is in colas, and people who drink colas have been found to have weaker bones. However, this is because they are drinking sodas instead of milk, and displacing so much calcium from your diet will lead to weaker bones. Correlation, not causation.

But the link between a lack of weight-bearing exercise and osteoporosis is clear. The jarring and shaking of pounding the pavement stimulates osteoclasts, the precursors of bone, leading to more bone formation. Go long enough with suppressed osteoclast stimulation, the natural processing of calcium and reabsorption of bone outstrips its replacement, and you get Swiss cheese at the microscopic level. Soon enough, the holes combine and, snap, you can have what is termed a "fragility fracture."

Walk, jump, dance, run, climb stairs, and do plyometrics. Jar those bones, shake those osteoclasts, and activate those bones. Then, give them what they need to grow and rebuild: eat the cheese and yogurt, drink that skim milk. Or the next break you have may not be a lucky break.