Cardiovascular adaptations to physical training.

The role of physical activity in cardiovascular health has received increasing atten­ tion in recent years. A large number of reports have indicated that populations or individuals with high levels of physical activity tend to have a lower prevalence of symptomatic coronary artery disease and lesser death rates from cardiovascular diseases (69, 139). Although no single report provides complete proof that physical activity has a protective effect, the evidence heavily favors that conclusion. The extent of physical training or detraining also obviously has profound implica­ tions with regard to the ability of normal persons to participate comfortably, safely, and successfully in recreational or competitive athletic activities. This matter as­ sumes more importance with increased participation in sports and physical exer­ tional activity by middle-aged and older male and female populations. Thus an understanding of the adaptations that the cardiovascular system un­ dergoes during chronic exercise programs and the effects of different types and intensities of such programs upon cardiovascular responses have been of consider­ able interest to physiologists, clinicians, public health workers, and sports profes­ sionals. This article reviews the cardiovascular adaptations that occur during exercise in experimental animals and in man and how they contribute to the trained state. Whenever possible, the mechanisms underlying these adaptations are discussed.