Acquiring the ability to maintain whole-body integration of physiological-system functions during exercise enabled human beings to evolve exercise tolerance and adaptability to environment, with those who possessed this capability being able to accelerate in an integrated manner their physiological functions whose habitual status is so strongly correlated with health. In modern developed nations, however, the spread of artificial environments and comfortable living and working environments has reduced the adaptive capacity and in particular the endurance work capacity as well as adaptability to environment that human beings had historically acquired, resulting in hypokinetic diseases and maladaptation to heat.
