Yup... aerobic capacities are definately a factor.

(2003) the highest VO2 max ever recorded for a man was 94ml/kg/min... the highest women's aerobic power measured was 77ml/kg/min... both were Nordic skiers.

Absolute muscle power outputs also vary significantly with women being well below men.

Women have a higher fat percentage than men (cause our bodies are designed to carry and sustain children)

Men have a higher muscle mass.

Because women have less muscle mass, they cannot generate as much force as a man.

The average women's total body strength is about 1/3 less than the average man's. Women are relatively stronger than men in their legs and weaker in the abdomen and arms.

There is a common figure used as a guideline to describe the difference between elite female atheletes and elite male atheletes of about 10% regardless of the sport... cycling, weight lifting, sprinting...

HOWEVER... despite the physiological differences, women are still capable of training at comparable levels and intensities... only the volume of training may vary slightly.