Study finds skeletal shrinkage among cyclists

Bone density problem could be caused by sweating

by Tom Henry   July 6, 2009  

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Last week it was sperm count. This week it’s bones. Maybe it’s the sight of all those super-fit, Lycra-clad man-machines hitting the Tour De France circuit, but suddenly a rash of health-related stories around cycling has broken out.

Notwithstanding the risks to health from heavy metal objects whizzing past at 50 mph-plus, now there’s the chance that if you really hammer it and sweat hard, you could develop osteoporosis before too long.

So a study undertaken by a cycling scientist from the University of Oklahoma suggests. Aaron Smathers had suffered various broken bones in crashes and scans revealed his bones were less dense than average for his age.

He looked into it further and interviewed other riders. The bone density of 32 males, most in their late 20s and early 30s, was compared to that of age-matched controls, men who were active but not competitive athletes. Bone scans showed that almost all of the cyclists had significantly less bone density in the spine than the control group.

Some of the racers, young men in their 20s, had osteopenia in their spines, a medical condition only one step below full-blown osteoporosis. “To find guys in their twenties with osteopenia was surprising and pretty disturbing,” said Smathers.

Now, on the face of it that’s quite scary, especially when injuries to bones are relatively commonplace, especially in competitive cycling. And it seems to back up the findings of another study, published last year, that looked at a group of racers over a season and found that at the end of the season they had lost a significant portion of bone density in their hips (though not in their spines). The better news is that after a three-month follow-up examination they showed a small amount of bone recovery.

No-one is quite sure as yet why competitive cyclists should suffer in this way. Cycling causes little impact to skeletons. Bones react to external stresses by strengthening bone. But the Smathers study seems to indicate that energy imbalance and sweating might be factors. A rider can lose hundreds of milligrams of calcium an hour through sweat. Although the riders in both Smathers’ and the Colorado study were ingesting more than the recommended daily allowance of calcium for their age, they may still have had a deficit of the mineral, which is essential to bone-building. Some researchers say that calcium must be taken during exercise to be most effective.

But let’s not forget that for any cyclist other than those in serious competitive training, the above is hardly an issue. Aaron Smathers said: “The studies to date have looked primarily at racers. That’s a very specialized demographic. These guys train for hours at a very high intensity. They sweat a lot. They never go for runs. They don’t usually do much weight-lifting.

“For competitive riders, I’d recommend spending some time weight-training,” he added, “and if you do race or train hard and often on a bike, consider a bone scan. It’s good to know your status.”