Through a complex system of hormones and cell receptor molecules, your body is primed to respond to changes in your physical activity; these adaptations are commonly observed during aerobic exercise, in which your heart and breathing rate increase for a recommended minimum of 30 minutes, five to seven days per week, according to Cleveland Clinic.
The Physiology of Exercise
As your skeletal muscle increases its contractile activity, this change alone will increase the circulation of blood simply due to the increased pressure within the muscular capillary networks. Additionally, the increased metabolism that fuels your exercise will increase the production and release of acid into the blood stream in the form of lactic acid. The cardiopulmonary system, or the heart and lungs, must work to adapt to the metabolic effects of exercise by increasing cardiac output as well as pulmonary circulation.
Cardiac and Vascular Adaptations
Heart muscle will change its properties in response to exercise; the adaptations all serve to increase cardiac output, which is controlled by stroke volume and the rate of contraction. Changes occur on both the molecular and gross level of the heart; changes in ion permeability in pacemaker cells will increase the rate of heart contraction, for example. Meanwhile, the ventricular volume is actually expanding on a large scale, increasing the stroke volume thus raising the cardiac output to the level demanded by the body.
Pulmonary Physiology
Not only must the heart pump more blood to the systemic circulation, this blood must be maximally oxygenated; changes in lung physiology during exercise enable the cardiopulmonary system to meet the metabolic demands of skeletal muscle. Dilation of pulmonary arteries increases blood flow; the deep breathing that accompanies exercise acts as a secondary pump, facilitating the flow of blood through the circulation, much like any other pump would. Microscopic structures, known as alveoli, manage the process of gas exchange, releasing carbon dioxide into the environment while simultaneously absorbing oxygen.
Applications
Evolution has encouraged the development of a cardiopulmonary system that is appropriately responsive to changes in your activity, metabolic demands and energy output. During exercise, the homeostasis of your system is disturbed; by increasing energy consumption, acid production and temperature, the balanced equilibrium is thrown off and your system must promptly react. These innate systems are essential to your survival in a highly variable environment, such as the Paleolithic period, when your ancestors rapidly evolved. Dr. O'Keefe from the Mid America Heart Institute suggests that a return to the Paleolithic, hunter-gatherer lifestyle would solve many of the modern epidemics such as obesity, diabetes and heart disease.
References
- Mayo Clinic - Discovery's Edge: The Science of Exercise; Tony Fitzpatrick; May 2009
- Cleveland Clinic: Aerobic Exercise; 2011
- Mayo Clinic Proceedings: Cardiovascular Disease Resulting from a Diet and Lifestyle at Odds With Our Paleolithic Genome: How to Become a 21st-century hunter-gatherer; JH O'Keefe and L Cordain; January 2004
