While maintaining a steady exercise regimen is one of the best things people can do for their general good health, recent studies suggest an alarming correlation between bicycling and the onset of osteopenia (lower-than-normal bone density) or osteoporosis (very low bone mineral density), even among those who are young and fit.
Cycling is a low-impact sport that puts little mechanical load on the bones and joints and is a wonderful cardiovascular exercise that people can enjoy into their later years.
When it comes to the risk of thinning bones, however, it’s the weight-bearing nature of exercise that signals bones to create more mass. Without such stress, bones do not get stronger, and become more prone to injury.
A recent study that appeared in Medicine & Science in Sports & Exercise found that competitive male road cyclists showed significantly lower bone mineral density in their spines than a control group of men who were moderately physically active.
Although the cyclists had a greater calcium intake, they were still more likely to have osteopenia and osteoporosis than those in the control group. A similar study in Bone illustrated that male road cyclists had lower bone mineral density than male mountain bikers after adjusting for body weight and age.
The distinction could be found in that mountain biking, with its variable terrain, provides more impact for bone growth than road cycling or racing. Swimmers may also be at risk, because that sport requires similarly little mechanical loading, leaving the lower spine particularly vulnerable.
Another challenge facing cyclists and swimmers in relation to bone density is calorific intake. Cycling and swimming are notorious for burning up calories (witness, Michael Phelps’s notorious 12,000 calorie diet), however, hard-core cyclists may not be eating enough to offset what they burn when they exercise, depriving their bodies of bone-strengthening nutrients such as calcium and vitamin D.
These caloric shortfalls could also trigger physiological problems such as lower levels of estrogen in women and testosterone in men, both hormones that have protective effects on bones and slow the rate of bone breakdown.
“Unfortunately, many people consider osteoporosis a disease that primarily concerns women and the elderly,” says Dr. Warren P. Levy, “Of course, exercise is good for people, but in order to maintain healthy bones, avid cyclists and swimmers should be mindful of incorporating cross-training weight-bearing exercise into their routines.
People do not achieve peak bone mass until their late twenties, so if cyclists or swimmers are in their early or mid twenties, and they’re not doing any exercise that’s going to load their spine and help them achieve peak bone mass, they may be putting themselves at risk for a fracture.”