Gender differences in the cardiovascular response to exercise.

During an acute bout of dynamic exercise, cardiac output increases in direct proportion to the increase in oxygen uptake. The mechanisms by which the cardiac output is increased during exercise may differ between men and women. The increased blood flow is distributed to the exercising skeletal muscle, to the myocardium, and, if exercise lasts longer than 5 minutes, to the skin. Blood flow to tissues whose metabolic rate has not been increased is reduced as a result of a general, sympathetically mediated vasoconstriction. During dynamic exercise, muscle blood flow, degree of peripheral vasoconstriction, increase in heart rate, and increase in myocardial blood flow and oxygen uptake are all functions of relative workload, often expressed as a %VO2 max. During an acute bout of resistive exercise, the increase in oxygen uptake and cardiac output is small, at least partially because perfusion of the exercising muscles is difficult as a result of high intramuscular pressures. The heart rate increase is also small. Blood pressure increases markedly as a result of increased total peripheral resistance. Dynamic exercise training results in cardiovascular adaptations both at rest and during exercise. At rest, myocardial hypertrophy of the volume overload type is the most common, but not universal, finding. Dynamic exercise that involves a sizable resistive exercise component may produce changes in myocardial structure and function similar to those resulting from static exercise. The effects of dynamic exercise training on myocardial function at rest need further investigation. The cardiovascular effects of dynamic exercise training are manifest during submaximal exercise by reduced heart rates, blood pressures, and less vasoconstriction in nonexercising tissues; increased stroke volumes; and unchanged cardiac outputs and oxygen uptakes at any given exercise load. During maximal exercise, VO2 max, maximal cardiac output, and maximal stroke volume are all increased. Maximal heart rate and blood pressure at maximal exercise are unchanged. Redistribution of the cardiac output to better perfuse the exercising muscles also occurs. Certain other factors that may modify the cardiovascular response to exercise include phase of the menstrual cycle, pregnancy, age, exercise mode, length of the exercise session, and environmental conditions such as heat stress. Although there are some physiologic differences that may affect the mechanism of the changes, the overall response of the cardiovascular system to exercise is similar in men and women.