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How’s your Skeleton Doing?

By Christopher R. Shuhart, M.D., CCD, MHA

In early May I ran a search query on “fractures” at VeloNews.com. 201 hits were returned. I’ve been riding for thirty years and over time I had accumulated a sense of fatalism about cyclists and broken bones: eventually, every rider will either suffer a fracture or know someone who has done so while riding.

My work in bone health and osteoporosis over the last ten years has tempered my cynicism, and I think it’s time for road cyclists to understand that there’s something about our skeletons that puts us at increased risk for fractures — our bones are weaker than we think. Simply put, longer, more intense hours in the saddle, over time, are associated with weaker bones, all other things being equal. We cyclists will break bones more easily than someone just as fit whose frame is exposed to the increased stresses of weight bearing, resistance or irregular loads. Fractures are less about the crashes than we like to think.

Let’s examine some of the available evidence to support the hypothesis that cyclists have “frailer” bones. First, it’s important to understand that there is no evidence which says that cycling causes weaker bones, only some mounting evidence associating cycling with a less robust skeleton. That said, recent studies show that young, competitive male cyclists have a bone density disadvantage compared to age and size-matched recreational exercisers, independent of calcium intake or testosterone levels. Runners have repeatedly bested cyclists for bone density— even when size, fitness level and age are all factored out — competitive mountain bikers win against roadies even when similar adjustments are made. Additionally, there appears to be a “dose-response” relationship between hours, intensity of training, and bone density, where more is not necessarily better for skeletal health.

Not only do cyclists end up at a disadvantage compared to other similar athletes, we actually lose significant bone mass over the course of a competitive season. One postulated cause: calcium loss in sweat. Giving riders calcium during steady-state exercise appears to blunt the rise in blood markers of detrimental bone metabolism. Unfortunately, season-long calcium supplementation does not appear to affect losses in bone density.

Photo by Wheels in Focus

Have you broken a bone while riding?

There are many possible confounding factors at work in these and other studies. They are hampered by small sample sizes, short monitoring periods, and limited ability to quantify and classify cycling exercise. And if you’re a girl, there’s next to no science regarding bone loss with cycling exercise — ironic considering women have twice as many lifetime osteoporotic fractures as men.

In bone health, fracture risk — not bone density — is the Holy Grail. There is no evidence that cycling-associated bone changes increase fracture risk. To prove an association would require hundreds or even a thousand participants to be followed carefully over time. Stay tuned.

Why then do cyclists have an apparent increased risk? Likely, it’s the nature of riding: weight supported in the saddle, exercising largely in a steady-state mode. If there’s one thing that’s known about bone mass, it’s that irregular, repetitive and unpredictable loading causes living bones to respond by getting stronger. This helps explain improved skeletal strength for the mountain rider, the triathlete, and the runner or cross-trainer. You might also guess then that swimmers

are at risk — and you’d be correct.

It’s also possible that more competitive and elite cyclists are genetically pre-determined to have a smaller, lighter skeleton, which makes them faster uphill, but more likely to break bones.

My unscientific (read here: not based on good evidence) recommendation is to integrate cross-training into your year-round regimen. This is particularly important for those of us beyond age 35. You’ll never, ever have more bone mass after that age. Better natural bone mass means a lower chance of fractures.

Those with other risks — smoking history, excessive alcohol consumption, family history of osteoporosis, use of cortisone medications, loss of menstruation and more — may even want to consider a baseline bone density test. All riders need to optimize their calcium intake and vitamin D status as a foundation for excellent skeletal health. Consult the National Osteoporosis Foundation (www.nof.org) for more information. Ride smart, ride safe, and consider doing everything you can to prevent your first or next fracture out on the road.

Christopher Shuhart, M.D., MHA, CCD, is a certified clinical densitometrist who specializes in bone health and osteoporotic disorders. He has been practicing in primary care since 1991 and spent 18 years with Swedish Physicians Magnolia clinic in Seattle. A recreational rider, tandem enthusiast, he raced while attending medial school. He can be reached at 206-215-5950.