Ageing is associated with major changes in almost all physiological systems. These age-related changes influence both the health and exercise capacity of the masters athlete. On one level, many of these age-related changes affect appetite, food intake and nutrient absorption and thus the potential to affect substrate availability at the exercising muscle. On another level, age-related changes to the cardiovascular and musculoskeletal systems affect the energy systems used during exercise in addition to the force-generating capacity of the muscles. This chapter reviews a number of age-related changes that occur to several physiological systems and the affect these changes may have on the nutritional needs of masters athletes. Furthermore, the chapter will examine the extent to which regular physical activity across the lifespan is likely to impact on these changes.