Women and men vary in their cardiovascular fitness abilities. Women are limited in fitness, as compared to males, in their anatomy and physiology. Gender differences regarding heart size and function and lung function produce varying levels of cardiovascular fitness. These differences mean a lower maximum heart rate and overall lower maximum work capacity 4.

Heart Rate

Women are not able to achieve as high a heart rate as a man. This limits a woman's cardiovascular fitness. According to a study published in "Circulation" in June 2010, the current age-predicted maximum heart rate equation overestimates a woman's heart rate, when testing the heart rate response of 5,437 women 34. A lower maximum heart rate means a lower level of cardiovascular fitness 4. A man can use the equation of 220 minus age, for age-predicted heart rate. However, a woman must use the equation 206 minus (0.88 times age) for her maximum heart rate 4.

VO2 Max

VO2 max is a measurement of the maximum amount of oxygen your heart and lungs can deliver to your working muscles. It is the best way to judge a person's cardiovascular fitness. For men and women, VO2 max differs. Absolute VO2 max is, on average, 40 percent greater in a man than a woman, according to the book "Exercise Physiology" by Brooks, Fahey and Baldwin. Even when measuring relative difference, when taking into account body weight, men have a 20-percent greater VO2 max.

Heart

The size of the heart is one compelling difference between genders. Men have a larger heart than women do, according to "Exercise Physiology." In general, the size of the male left ventricle is larger than a woman's. This means that a man's heart is capable of holding and pumping more blood per beat than a woman's. The ability to pump a larger amount of blood makes it possible to deliver more oxygen and thus produce a larger amount of energy. This difference may account for the disparity in VO2 max between a male and female.

Respiration

Gender affects respiratory capabilities 5. In general, women have a smaller lung capacity not just because of the size of their lungs and torso, but also because of certain hormones. Estrogen and progesterone, found in larger amounts in women, can reduce ventilation and function, specifically during exercise, according to a review published in "Respiratory Physiology and Neurobiology" in October 2005 5.