2.1.1. The Pulmonary System

Although data on the breathing reserve (BR; maximal voluntary ventilation related to minute ventilation during maximal exercise) do not indicate a considerable ventilatory limitation of VO2max in healthy older individuals [11], it can become a limiting factor in some highly trained aged athletes [12]. In addition, diffusion capacity of the lung is predictive of marathon performance, and it decreases markedly with age, an effect from which masters athletes are not exempt [13]. Probably as a consequence of this, exerciseinduced hypoxemia is more prevalent in highly fit older individuals compared to the healthy general population and fatiguing work of the respiratory muscles may provoke vasoconstriction in the leg muscles and compromise Q [14]. Thus, VO2max restriction by the pulmonary system depends on the level of fitness (the higher the more likely) and the age-related degree of decrease in respiratory function along with structural changes, i.e., declining respiratory muscle strength and endurance, enhanced rigidity of the chest wall, loss of elastic recoil, reduction of the alveolar surface area and the number of capillaries perfusing the lung [11,15,16]. A low BR, reduced forced expiratory volume in one second (FEV1) and exercise-induced hypoxemia are potential markers for pulmonary limitations of VO2max in the older athlete [17] (Figure 2).
