Development and evaluation of an exercise intervention to improve risk factors for vertebral osteoporosis in postmenopausal women

Osteoporosis is defined by low bone mineral density (BMD), which in combination with other risk factors can increase the risk of osteoporotic fractures. Vertebral fractures (VFs) lead to back pain, kyphosis and inability to perform physical activity of daily life. As well as low BMD, kyphosis and low back muscle strength can increase risk of vertebral fracture. Physical exercise is recommended as preventive strategy to reduce the incidence of vertebral fracture, so it is important to develop an effective exercise programme; however, the interventions thought to be most effective may not be available or acceptable for postmenopausal women. The primary aim of this thesis was to develop an acceptable exercise intervention to improve lumbar spine BMD and risk factors for vertebral fracture for postmenopausal women.

The thesis comprises of three studies. The first study was a systematic review of the current literature to identify which type of exercise is the most effective on vertebral bone density, spine posture and strength of trunk. The results of the review indicated that resistance training (work against an external load, e.g. lifting weights), alone or in combination with high impact loading (generating high ground reaction forces, e.g. jumping) may be effective to reduce risk factors for vertebral fracture.

Study two investigated the feasibility of developing an exercise programme using the behaviour change wheel framework. Twenty-six postmenopausal women were recruited and face to face interviews were used to explore behaviour and attitudes to exercise. Results of this study identified 11 behaviour change strategies addressing exercise mode (e.g. improve knowledge of benefits of resistance exercise), individual barriers (e.g. limited physical ability due to injury), motivation (e.g. group exercise), and opportunity (e.g. supervision by an specialist) to encourage bone strengthening exercise programme and suggested strategies to develop an exercise programme for main intervention.

Study three evaluated the effects of a resistance band exercise intervention on lumbar spine BMD, spinal curvature, and back strength in postmenopausal women. Forty-one participants were recruited and were randomised to either exercise group (EG) or control group (CG). The EG completed 6 months of 30 min, weekly supervised exercise sessions with twice weekly home-based exercise session. Habitual physical activity was maintained in the CG. Dual X-ray absorptiometry (DXA) scans were acquired at baseline and follow up to assess BMD at lumbar spine and femoral neck and thoracic kyphosis. Back extensor muscle strength was measured by hand-held dynamometer at baseline, middle and follow up. Thirty-four participants completed the exercise intervention: 22 in EG and 12 in CG. Lumbar spine (L1-4) BMD decreased in both groups (EG:1.9% vs CG:1.3%, main effect of time P=0.001). Back strength improved in EG compared to CG (EG: 15.3% vs 2.5%, time x group interaction effect P=0.006), and kyphosis angle improved in EG relative to CG (EG:4.6% vs CG:5.2%: time x group interaction effect P=0.001).

This research is the first to evaluate the effect of a resistance band exercise intervention on multiple risk factors for vertebral fracture in postmenopausal women. The intervention improved kyphosis angle and physical function; however, there were no benefits to lumbar spine or femoral neck BMD. Resistance band training is feasible and safe in healthy postmenopausal women.