Osteoporosis is defined by critically low bone mass or a fragility fracture. Physical activity has been proposed as a necessary lifestyle contributor to bone health, however, few exercise programs have demonstrated an ability to notably increase bone mass. The bone response to exercise is highly dependent on the nature of applied mechanical loads. The most osteogenic activities are those that induce high magnitude strains at high rates or frequencies in bone. Under such conditions, only brief loading bouts are required to stimulate a response. Such strains are typically induced by weight bearing impact loading and high-intensity progressive resistance training. To date, high intensity resistance and impact training has not been investigated in postmenopausal women due to a perceived risk of fracture and/or injury. Consequently, the primary aim of the current work was to develop a novel bone specific high intensity resistance and impact training program (HiRIT) for postmenopausal women to improve bone, physical function and risk factors for fracture.

The thesis comprises of four publications, presented as three published manuscripts and prepared for submission. In the first manuscript (Chapter 4), the preliminary bone and physical performance findings of the Lifting Intervention For Training Muscle and Osteoporosis Rehabilitation (LIFTMOR) trial are presented. In the subsequent manuscript (Chapter 5), the final findings of bone and physical function from the LIFTMOR trial are presented. The LIFTMOR trial was an 8-month exercise intervention of twice-weekly, 30-minute, supervised HiRIT (5 sets of 5 repetitions, > 85% of 1 repetition maximum) program. A home-based, low intensity exercise program served as a positive control (CON). Postmenopausal women with low bone mass were recruited and randomized, stratified on presence or absence of osteoporosis medication use. Pre and post intervention testing included lumbar spine and proximal femur bone mineral density and geometry, and measures of functional performance. We found that 8 months of twice-weekly HiRIT improved lumbar spine and femoral neck bone mineral density and geometry and all physical performance measures compared to losses or minimal change in the low intensity home based exercise program.

Manuscript three (Chapter 6) presents changes in kyphosis and vertebral morphology over the period of the LIFTMOR trial. We found that 8 months of twiceweekly, 30-minute, supervised HiRIT improved thoracic kyphosis more than the lowintensity control exercise program. Furthermore, HiRIT did not induce new vertebral fractures or worsen existing vertebral deformities. The findings of manuscript three challenge traditional concerns that high-intensity exercise loading presents an unacceptable level of risk to postmenopausal women susceptible to fragility fractures from osteoporosis.

The final manuscript (Chapter 7) was a mixed methods qualitative analysis of LIFTMOR participant experiences and perceptions of the HiRIT and CON exercise programs. We observed that 8 months of supervised HiRIT improved physical activity enjoyment and quality of life. The qualitative analysis revealed that HiRIT was received positively, with participants reporting a sense of achievement, enjoyment of the group nature of training sessions and feeling stronger. Furthermore, HiRIT group participants were more likely to participate in the LIFTMOR trial again given the opportunity, to continue HiRIT after trial completion and would recommend HiRIT to a friend.

In summary, the current thesis reports the positive effects of a bone-targeted HiRIT exercise program on bone, kyphosis and physical function. Furthermore, the HiRIT exercise program was enjoyable. Based on these findings, we conclude HiRIT has the potential to be a safe, efficacious and appealing exercise program for the management of osteoporosis in postmenopausal women.