ABSTRACT
Within the lifespan of an individual there are several discrete stages that include periods of rapid growth, adolescence and maturation followed by adult life leading to senescence and eventually, death. During growth and maturation the different organs and physiological systems develop and increase their capacities, for example, to perform physical work. Later in adult life with approaching senescence these same organs and systems experience a reduced integrity and capacity and the tolerance for physical work is reduced. In this text, it has been stressed that several organ systems – cardiopulmonary, vascular and muscular – must operate in a highly coordinated fashion to effectively conduct O2 from the inspired air to its site of utilization within the mitochondria. The effect of advancing age in reducing V̇O2 max, has been well described (Docherty, 1990; Folkow and Svanborg, 1993; Lakatta, 1999; Conley et al., 2000a; McGuire et al., 2001), however, apart from contrived laboratory tests and a select few athletic events, humans rarely exercise at V̇O2 max, and this is even more true for children and aged individuals.
