Bicycling may do a man's heart good, but it won't do much for his bones, the results of a new study suggest.
Researchers found that compared with men who regularly ran, men whose primary physical activity was bicycling were much more likely to have low bone density in the hips or spine.
In general, cyclists had lower bone mass throughout the body and 63 percent had osteopaenia in the spine or hip, the researchers report in their study, published in the journal Metabolism. Osteopaenia refers to abnormally low bone mass that could progress to the brittle-bone disease osteoporosis.
Osteoporosis is often thought of as a woman's health issue because waning oestrogen levels after menopause leave women particularly vulnerable to the condition.
Lead investigator, Dr Pamela S. Hinton, said she decided to study men because "they have been largely ignored when it comes to osteoporosis."
Hinton and her colleagues at the University of Missouri, Columbia, recruited 43 men between the ages of 20 and 59 who were serious runners or cyclists. All had been training at least six hours per week for two years or longer.
Generally lower bone mass
Along with their generally lower bone mass the researchers found, men in the cycling group were seven times more likely to have osteopenia of the spine than runners were.
Running, jumping and other weight-bearing activities put the bones under stress. This forces the bones to respond by becoming stronger. In contrast, low-impact exercise, like biking or swimming, works the heart and trims the waistline, but puts little strain on the bones.
"There are many health benefits of any type of aerobic exercise, including biking and swimming," Hinton told Reuters Health.
"However," she added, "it is important that individuals who spend significant amounts of time engaging in non-weight-bearing forms of exercise do something extra to strengthen their bones."
For people who can't jog or jump rope - due to an injury or arthritis, for example - strength training with weights offers an alternative, according to Hinton. She also noted that "power lifting" is considered more effective for building bone than is standard strength training.
Source: Metabolism, November 2007. – (Reuters Health)