Osteoporosis is characterized by low bone mineral density (BMD), bone fragility, and an increased risk of osteoporotic fracture. The disease is systemic in nature but potential solutions include exercises prescriptions that target the clinically relevant sites of osteoporosis (hip and spine) to improve bone mass. The aim of this dissertation was to determine if atypical loading and load magnitude increased bone mass at the hip and spine, respectively, in young athletic women. The first study sought to determine if six months of uncustomary loading in the form of a "hip drop", increased BMD at the hip in young women (n=39, aged 20.2 �� 1.3 years). The hip drop applied a direct side impact to the right greater trochanter, the left hip was the control. The second study compared the spine BMD response after six months of rowing training in experienced (n=16, aged 21.2 �� 1.2 years) and novice rowers (n=19, aged 19.5 �� 0.8 years) with a control group (n=14, aged 19.2 �� 1.6 years). Bone mineral density at the hip and spine were measured in the first and second studies, respectively. Results from the first study showed a significant difference in BMD between hips at the femoral neck but there were no side-to-side differences at the greater trochanter or the total hip. The second study revealed that six months of rowing training increased spine BMD in the experienced rowers (2.1%) but not in the novices (-0.05%). / Graduation date: 2002

Age-related bone loss is a serious public health problem affecting 15 to 20 million people in the United States (1). In the last decade, several studies have investigated the effects of repeated bouts of exercise on bone density. Although this increase in bone density is mediated via hormones and/or cellular metabolites few studies have linked the increase in bone density with changes in these hormones or metabolites. Therefore, the purpose of this study was to determine the effect of a single bout of weight bearing exercise on the growth factors that alter bone metabolism. Seven healthy female subjects (age 23 ± 5 yrs.) agreed to participate in this study. A V02 max test was administered to each subject to determine their overall fitness level. A treadmill speed corresponding to 70% of their V02 max was then developed and the subjects ran for 40 minm on the treadmill at that speed. Blood samples were drawn pre and 1, 2, 3, 4, 5, 10, 15, 20, 30, 45, and 60 min post-exercise and assayed for serum growth hormone, calcium, parathyroid hormone, and alkaline phosphatase. No significant change was found in parathyroid hormone, calcium, or alkaline phosphatase serum levels. Growth hormone was found to be significantly decreased 30, 45, and 60 min. post-exercise as compared to pre-exercise levels (7.089, 5.399, 4.728, and 11.28 ng/mL, respectively). While this indicates that exercise may cause a depression in growth hormone levels during recovery, the elevated pre-exercise levels of three of the seven subjects masked the exercise stimulated release of growth hormone. Growth hormone stimulates bone absorption via insulin-like growth factors and the GH data suggests that these hormones may have been released well after our last measurement time point. In conchusion, 40 minutes of running exercise at 70% of V02 max does not produce a change in any of the hormones or metabolic factors directly associated with calcium turnover in the bone, suggesting that acute exercise has no immediate effect on bone metabolism. However, the exercise protocol did stimulate GH release which influences bone growth indirectly by its ability to regulate IGF release. Therefore, even though no acute effects were evident, a single bout of exercise may alter the long term control of bone metabolism. / School of Physical Education

Diss. (sammanfattning) Linköping : Univ., 2003. / Härtill 6 uppsatser.