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Weight-bearing Exercise Helps Strengthen Bones

Posted: June 12, 2009

Physical activity, exercise and sport all provide a variety of benefits to our heart, lungs and other vital organs. Researchers at the University of Michigan have confirmed that exercise is just as important for a healthy skeletal system. Ronald Zernicke, director of the University of Michigan Bone & Joint Injury Prevention & Rehabilitation Center, concluded that exercise, specifically weight-bearing activities, such as running, gymnastics, basketball and dancing, are effective in building and enhancing overall bone health. Zernicke’s scholarly review, to be published in the July/August issue of Sports Health: A Multidisciplinary Approach, synthesized information over the last 50 years on the role of exercise on skeletal tissue and overall bone health.

A combination of collagen (protein) and calcium phosphate (mineral) make bone strong and flexible and provides the framework to withstand the stresses of physical activity. During an individual’s childhood and teenage years, new bone is added to the skeleton faster than old bone is removed. Bone formation and bone mass density (BMD) also continues at a faster pace than it is removed until about 30 years of age. Bone mass density increases are possible across all age groups; however, the most beneficial time to improve BMD with exercise is before and during puberty.

Bone deformation rates and magnitudes, the amount of pressure put on bones, bone mass composition (BMC) and BMD in physically active populations were all important components of the review. Past research has shown, for example, female gymnasts will have greater total BMC and higher bone strain rates while in training and during pre-pubertal to post-pubertal stages of life. Other activities, such as ballet and competitive jump rope, will also produce higher total BMC and increase bone strength in this population. Non-weight bearing sports and activities like cycling and swimming are healthy activities and have excellent cardiovascular benefits, but are not as effective as weight bearing activities in adding bone.

“Our skeletons respond to a combination of weight-bearing activities and muscular movements. The review found the most bone friendly exercises are those that have high deformation rates, such as jumping for the lower body, and racquet sports, like tennis, for the upper body,“ Zernicke said. He went on to say, “This evidence makes a strong case for physical activity being one of the best, non-pharmacological ways to develop and maintain healthy bones.”

Bone is dynamic tissue. Physically demanding, continuous exercise regimes are not necessarily the best activities to build and enhance bone health. Zernicke says “rest” periods within exercise plans can help stimulate bone growth as much, if not more than activities executed without rest. For example, bones can respond to strength building from jumping sessions three shorter times a day better than a longer continuous jumping session — think jumping rope three minutes per day three times a day versus jumping rope for 10 solid minutes. The bottom line: Exercise may help increase bone density and protect against bone mass decline when performed properly.