Age-related bone and muscle loss is a major risk factor for falls, injuries, and fracture and, as Canada's population is aging, prevalence of such health concerns is escalating. Osteoporosis alone is estimated to cost the Canadian health care system $2.3 billion per year or 1.3%, of Canada's total healthcare budget. Postmenopausal women are at high risk of osteoporosis and experience the highest rate of hip fracture, resulting in disability, loss of physical function and premature death. The investigators' study aims to improve bone mass and bone strength at the most clinically relevant bone site, the femoral neck, in order to reduce the risk of hip fracture. Specifically, it will determine the effects of a nutritional supplement (creatine monohydrate) combined with exercise training on bone mineral density (BMD) at the proximal femur in postmenopausal women. .

Creatine monohydrate is found in small amounts in meats and fish and, when taken as a nutritional supplement, increases muscle mass and strength. The investigators have conducted a number of preliminary studies showing that when a creatine supplement is taken during a resistance training program, urinary markers of bone resorption (i.e. bone catabolism) are reduced compared to placebo. The investigators recently completed a small 12-month randomized controlled trial in 33 postmenopausal women who either supplemented with creatine monohydrate (10 g/d) or placebo during a resistance training program. Bone mineral density of the femoral neck decreased by 0.5% in the creatine group, and 3.9% in the placebo group (p\<0.05 between groups). This proposed randomized controlled trial will replicate the investigators' pilot design for longer duration (i.e. 2 years) to determine if sustained supplementation with creatine monohydrate combined with exercise training can induce a clinically significant difference in bone mineral density at the femoral neck (the investigators estimate a 5% difference between creatine and placebo groups capable of predicting a significant reduction in fracture risk).

This trial will use a randomized, double blind, placebo controlled, parallel group, repeated measures design, performed at the Universities of Saskatchewan and Regina. Post-menopausal women (n=240) will be randomized to creatine (10g/d) or placebo groups while participating in an exercise program (resistance training and walking) three times per week for 24 months. The investigators' main dependent variable is femoral neck bone mineral density, which will be assessed at baseline, 12, and 24 months. Secondary variables to be assessed at the same time points include geometric properties of the proximal femur (predictors of bone strength), lumbar spine bone mineral density, ultrasound measurements of bone at the distal radius and tibia (predictive of the architectural integrity of bone), lean tissue mass, muscular strength, dynamic balance, and gait speed. The investigators will assess incidence of falls and fractures at the same time points and also at 12 months post-intervention (i.e. at 36 months). The results of this study have clinical potential, providing physicians and health-care professionals evidence-based advice to give to postmenopausal women interested in taking creatine as a novel strategy to increase bone mineral density and prevent osteoporosis.