24.20: Exercise and Cardiovascular Response
Exercise significantly impacts cardiovascular response, which is crucial for understanding patient health and designing effective treatment plans.
Light to moderate physical activity initiates a series of interconnected responses in the body. The heart rate modestly increases in anticipation of the workout, followed by widespread vasodilation as oxygen consumption by skeletal muscles increases. This results in decreased peripheral resistance, increased capillary blood flow, and accelerated venous return. The latter is further enhanced by skeletal muscle contractions and rapid breathing. As a result, cardiac output rises, maintaining arterial pressure despite lower peripheral resistance. This leads to a gradual doubling of cardiac output, which supports increased blood flow to skeletal muscles, the cardiac muscle, and the skin.
When one engages in strenuous exercise, additional physiological adjustments occur due to the activation of the sympathetic nervous system by the cardiac and vasomotor centers. The blood flow redistributes to prioritize active skeletal muscles, and with intense sympathetic stimulation, cardiac output can skyrocket to 20-25 L/min. However, to meet the demands of exercising muscles, blood flow to non-vital organs, such as those in the digestive system, may be curtailed. In such strenuous workouts, blood essentially shuttles between the skeletal muscles and the lungs and heart, with skin perfusion increasing for body cooling. The brain's blood supply remains stable.
Engaging in regular exercise can boost cardiovascular performance and lower the risk of heart disease. Athletes, compared to non-athletes, generally have a slower heart rate due to their larger hearts and greater stroke volumes. Regular exercise can reduce blood cholesterol levels, thereby decreasing the risk of atherosclerosis, cardiovascular disease, and strokes. It accomplishes this by stimulating enzymes that facilitate the movement of low-density lipoproteins (LDL, the "bad cholesterol") from the bloodstream to the liver for conversion to bile and excretion. A balanced lifestyle, with regular exercise, a healthy diet, weight management, and abstaining from smoking, can reduce stress, decrease blood pressure, and slow down plaque formation. Regular, moderate exercise can significantly reduce heart attack incidence rates and aid in faster recovery post-heart attack. However, exercise does not remove existing medical issues, and intense athletic training does not have proven benefits in reducing cardiovascular disease incidence. In fact, extreme athletic events can place severe strains on all body systems, including the cardiovascular system. Individuals with pre-existing heart conditions, or even healthy individuals, could face severe physiological disorders like kidney failure following extreme exercise.
