Illumination | Spring 2008

"For a while, it was thought that women didn't suffer from heart disease, and it took a while to change that belief," Hinton says. "And it seems like we're still in the process of changing the misconception about bone loss in men."

Connie Weaver, distinguished professor of foods and nutrition at Purdue University, couldn't agree more. "There haven't been many clinical studies on males, especially with any twist like this, when they're younger and active," says Weaver. "Her study won't allow you to determine the mechanism, but it was big enough to determine the phenomenon, so that's a lot of human interest."

The study is also important because it confirms that weight bearing exercise is beneficial to bone, and extends these findings to a new population, Weaver says. "Here you have healthy, mid-age males, and they've been less studied, so this adds to our understanding."

To be eligible for Hinton's investigation, athletes had to have been consistently active for at least six hours per week in either running or cycling, but not both, for the past two years. Potential participants with current or previous medical conditions were excluded, as were those who had implanted metal devices or who used medication impacting bone density. Applicants who smoked cigarettes were also left out, because research shows smoking reduces bone mineral density and increases fracture risk. Those who made the cut were, well, a cut above.

"Some of the cyclists may train upwards of 15 to 20 hours per week; it's not just someone riding down the trail," Hinton says.

Hinton and her team began work on the investigation by collecting data in four parts. They first weighed and measured the men to determine their body mass index. Then they collected blood samples to determine serum markers of bone turnover in the blood, indications of how much bone resorption and bone formation were taking place. They also measured levels of hormones important to bone, such as testosterone and estrogen. Next, Hinton and her team used "dual X-ray absorptiometry," or a DXA scan, to measure bone mineral content in various key areas: the lumbar section of the spine, hips, arms, legs and full bodies of participants.

The researchers asked the runners and cyclists to record their daily activities and nutritional intake. Finally, Hinton asked each participant to fill out a medical history so that researchers could control for the effects of past activity.

Hinton hypothesized that cyclists would have lower bone density than runners. Cycling has cardiovascular benefits and puts only a small amount of stress on the bones, but the fact that cyclists aren't physically hitting the pavement has long been thought detrimental to bone strength.

Published by the Office of Research.