Exercise limitations by the oxygen delivery and utilization systems in aging and disease: coordinated adaptation and deadaptation of the lung-heart muscle axis - a mini-review.

Cardiorespiratory fitness (aerobic exercise capacity) is one of the most important prerequisites for successful aging in human beings and depends on adequate oxygen transport by the respiratory and circulatory systems from environmental air to the working muscles and the efficient utilization of oxygen by the mitochondria. A linear dose-response relation between aerobic exercise capacity, morbidity, mortality, and quality of life is well documented. The process of normal aging is associated with a variable reduction in functional capacity of the main organs involved in oxygen delivery and utilization. Integrated changes of the heart-lung muscle axis are termed here 'coordinated deadaptation', e.g. due to aging and disease, in contrast to the beneficial effects of 'coordinated adaptation', e.g. resulting from exercise training. Physical inactivity in aging persons initiates a circulus vitiosus resulting in coordinated deadaptation of the oxygen delivery and utilization systems mainly affecting the heart-muscle axis. Whereas in the healthy elderly the deadaptation process starts from inactive locomotor muscles, the lung or the heart represent the origin in patients suffering from respiratory or cardiovascular diseases. Specific exercise training programs, considering the state of cardiorespiratory health and physical activity, are the most important and almost the only effective intervention to avoid or to break the circulus vitiosus, thereby promoting quality and expectancy of life in aging humans.