The effects of a two year randomised exercise intervention on markers of bone turnover in postmenopausal women

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Osteoporosis is a condition where the bones become more fragile and can break more easily. In Australia after age 60, three out of every five women and three out of every ten men will fracture a bone. When people fracture a hip they lose their independence and become much less mobile. Exercise is one lifestyle approach which may help in preventing osteoporosis by slowing bone loss and keeping the muscles strong. Previous research has not been able to clearly demonstrate the usefulness of exercise due partly to the difficulty in getting people to exercise for a least one year, which is how long bone studies must be carried out for. We have conducted two large research studies in women past the menopause where they have done weight training exercises. In the previous study we showed the greatest increase in bone mass occurred in those women lifting the heaviest weights. In a recently completed two year study in 126 woman, which forms the basis of this proposal, we found a weight training program was effective at increasing the bone mass at the hip, a common fracture site. The fitness group did not show any increase. So although we have been able to show this type of exercise helps increase bone mass we don't know how the bone is able to respond to this. The question we wish to address with this proposal is does exercise slow the breakdown of bone or does it help form new bone? The best way to be able to answer this question is by measuring certain products in blood, known as bone markers. Bone is continually turning overthese markers are released from bone into the blood. By studying these bone markers in blood samples taken from the subjects over two years it will helps us determine how exercise is affecting bone. From our previous studies we know that weight training can help slow bone loss. By measuring the bone markers we will then be able to make recommendations to people on how exercise will help prevent bone loss.