The decline in function of muscle, heart and lungs combine to reduce cardio-respiratory performance and as a consequence of that there is a decline in the Activities of Daily Living (ADL). Because most ADL require a combination of force with power or speed of movement and with cardio-respiratory fitness, it is imperative to preserve these qualities in old age to reduce the risk of disability and loss of independence. Those who maintain a reasonable level of physical activity throughout life will reach the threshold for independence as is illustrated in figure 4 below.