Bone Health : Exercise Builds Stronger Bones

Caroline Dohack

I's common knowledge that calcium and vitamin D are crucial to maintaining strong bones, but exercise also plays an important role.

In study published in February's issue of the Journal of Strength Training, Pam Hinton, assistant professor in the Department of Nutrition and Exercise Physiology in the MU College of Environmental Sciences, examined bone densities in men ages 21 to 45 who maintained regular cycling, weight lifting and running routines.

The results of the study indicate areas of the body that get exercised the most have higher bone densities. According to the National Osteoporosis Foundation, the most commonly broken bones are the hip, the spine and the wrist. A full-body workout following the American College of Sports Medicine's recommendations of three to five weight-bearing and two to three resistance-training workouts per week is crucial in preserving bone density and protecting against fractures like these.

Hinton's research was based on the theory that bone mass increases when exposed to pressure to prevent fracture.

In the study, those who cycled or lifted weights had more lean muscle mass, which contributes to bone density.

"If your skeleton has to carry around a lot of extra weight, it has to be stronger," Hinton said.

Furthermore, lifting weights or cycling causes the muscles to contract around the bone, which further contributes to bone density by stressing the bone.

But the cyclists and the weight lifters differed in the distribution of bone density.

Because cyclists primarily use their lower bodies, the bones in their legs and hips were denser than the bones in their upper bodies. The weight lifters, meanwhile, had the highest whole-body bone density.

"It can be very site-specific," Hinton said.

Though the runners in the study didn't have as much muscle mass as the cyclists and weight lifters, they had higher bone densities because their bones absorbed more impact, particularly in the legs, hips and spine, Hinton said.

The runners' relative lack of muscle mass might have further contributed to their bone density because muscles absorb impact, lessening the impact on the bone.

The study participants' high bone densities can be attributed to their dedication to exercise. To qualify for the study, participants had to work out a minimum of six hours a week for the past two years.

"The importance of exercise or mechanical loading of the skeleton becomes very obvious when you look at the effects of weightlessness," Hinton said.

Astronauts in space or patients on bed rest tend to lose bone density in a short period of time because, like muscles, bones start to atrophy with disuse, Hinton said.

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