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 run, 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 osteopenia in the spine or hip, the researchers report in their study, published in the journal Metabolism.
Osteopenia 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 estrogen levels after menopause can leave women particularly vulnerable to the condition. However, two million US men have osteoporosis, and nearly 12 million more have osteopenia.
Focus of study on men
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 a week for two years or longer.
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.
Low impact exercise best
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 said.
"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.
– (Amy Norton, Reuters Health, November 2007)