Increasing age is associated with substantial change in cardiovascular structure and function, the cause and permanence of which are unknown. Diastolic function in particular alters appreciably in older adults but non-invasive measurement of cardiac function during diastole has significant limitations. Magnetic resonance imaging with tagging was used to identify changes in three dimensional myocardial strain in older compared to young normal volunteers. This technique identified significantly delayed myocardial relaxation with more myocardial strain persisting in early diastole in older compared to younger individuals, which was brought to be due to the aging process. Epidemiological studies and small, non-randomised trials suggest that physical activity might slow cardiovascular aging and improve diastolic function in older adults. A randomised controlled trial was therefore performed to assess whether exercise training could modify age-related changes in older, normal volunteers who had undergone screening tests to exclude significant cardiovascular disease. The intervention group underwent six months of supervised exercise training whilst participants in the control group were asked to maintain their pre-trail levels of activity. Measurements made at baseline and after six months included transthoracic echocardiography, cardiac MRI, body composition, blood lipid concentrations, applanation tonometry, quality of life and maximal exercise capacity. Despite significant increases in exercise capacity following exercise training in the intervention group, no other significant changes in the cardiovascular structure or function, body composition, cholesterol concentration or quality of life were observed when compared to changes seen in the control group. Six months of exercise training in previously sedentary older adults are insufficient to modify cardiovascular function and structure despite causing marked improvements in exercise capacity. These findings contrast with previously reported non-randomised trials of exercise training in older people. However, they add important, robust information regarding the likely effects of short periods of exercise training on cardiovascular function and structure in older normal adults.