The heart, lungs, and bones of males are larger than those of women. Men have a slower heart rate which, coupled with their larger hearts, enables them to pump more blood with fewer beats. The stroke volume of a well conditioned woman can still exceed that of a deconditioned man. The blood of a typical male is thicker then a woman's. It carries 6 percent more red oxygenated blood cells per cubic millimeter.
Men also have more and bigger muscle fibers then women.
In addition, the male hormonal system produces testosterone that increases the growth of muscle size. Because of this, the muscles of women who lift weights do not hypertrophy to the extent that a man's does. On the other hand a woman's muscles grow stronger from regular exercise just like a man. A woman's heart rate, cardiovascular capacity, strength and endurance will improve from regular exercise just like a man's will. She stands to gain as much as any man from exercise.