Osteoporotic fractures are an extremely common and serious public health issue which contribute substantially to pain, impaired mobility and morbidity in the elderly. Declines in bone strength combined with an increase risk of falls (associated with decline in muscular function with age) are the main determinants of fracture risk. Exercise that is novel and involves impact loading has the potential to improve bone strength and neuromuscular function (strength, power and balance). It is thus imperative to evaluate potential benefits of exercise in older people. The musculoskeletal responses to exercise may also be influenced by vitamin D status. It is the purpose of this study to consider the influence of a one year unilateral (one limb) high impact exercise programme on musculoskeletal health, specifically bone structure, muscle strength and power in older caucasian men. It is also the purpose of this study to determine whether this differs according to vitamin D status. The findings will reveal whether exercise can improve bone health and/or neuromuscular function, and whether improvements are dependent upon vitamin D status.