Now, before jumping to the conclusion that cycling causes osteopenia, I want to say it’s important when looking at results like this to consider alternative perspectives. Perhaps having low bone density means having lower bodyweight, and the reason pros have lower bone density isn’t because they are really good cyclists, but rather they are really good cyclists in part because of their lower bone density. Less weight is an advantage in cycling. Not as much advantage as in running, but runners have higher bone density for other reasons. It’s the impact and weight bearing aspects of exercise that increase bone density and mineralization, so the nature of running makes athletes have stronger bones. With that in mind, however, I don’t think it’s a big enough justification to assume that cycling isn’t potentially detrimental to bone health. At the very least it won’t help your bones.
So let’s examine the results. Cyclists have consistently lower bone density and content in the lumbar (lower) spine compared to pretty much everyone else, whether other athletes or non-athletes. Also, pelvic, hip, and femoral (the big bone in your leg) values are consistently reduced, and these are major areas of concern for breaks, especially in aging people. Relative to other sports, high impact falls are a major concern for cyclists as well. And the older the athlete, the bigger the difference, so the effect may worsen with time.
Now let’s not get too carried away with these results. Inactivity is associated with poor bone health as well, so if you love cycling or are a professional, this isn’t a doomsday prophecy. Cycling seems to be of little detriment to those who do it recreationally. If you are at risk for osteoporosis, or if you’re a professional, you may want to include both weight bearing exercise (e.g. weight lifting) and impact exercise (e.g. running) into your routine to help balance the impact on your bone health. As long as you pay attention to your bone health while cycling there’s no reason to not do what you love.