New research suggests that exercise could improve bone density in middle-aged men, UPI reported.

Researchers at the University of Missouri-Columbia found that certain types of weightlifting and jumping exercises, when completed for at least six months, improve bone density in active, healthy, middle-aged men with low bone mass. These exercises seem to help prevent osteoporosis by facilitating bone growth.

Men gradually lose bone mass as they age, which puts them at risk for developing osteoporosis, a condition that makes bones weak and prone to breakage. Nearly 2 million men in the U.S. have the condition, and 16 million more have low bone mass, studies have shown.

"Our study is the first to show that exercise-based interventions work to increase bone density in middle-aged men with low bone mass who are otherwise healthy. These exercises could be prescribed to reverse bone loss associated with aging," researcher Pam Hinton said in a statement.

For the study, researchers recruited 38 physically active, middle-aged men who completed either a weightlifting program or a jumping program for a year. Both programs required participants to complete 60 to 120 minutes of targeted exercises each week, UPI reported. The participants took calcium and vitamin D supplements throughout their training programs. The researchers measured the men's bone mass at the beginning of the study and again at six and 12 months using specialized X-ray scans of the whole body, hip and lumbar spine.

They found that the bone mass of the whole body and lumbar spine significantly increased after six months of completing the weightlifting or jumping programs, and this increase was maintained at 12 months. Hip-bone density only increased among those who completed the weight-lifting program.

"Only the bone experiencing the mechanical load is going to get stronger, so we specifically chose exercises that would load the hip and the spine, which is why we had participants do squats, deadlifts, lunges and the overhead press," Hinton said. "Also, the intensity of the loading needs to increase over time to build strength. Both of the training programs gradually increased in intensity, and our participants also had rest weeks. Bones need to rest to continue to maximize the response."

The findings are detailed in the journal Bone.