[rifung]

I also wonder though how much of a difference it makes that the Williams sisters presumably only train with or to play against other women.

Let me say that I don't disagree in the advantages of genes and sex, but from my own experience competing at a moderately high level and knowing players who competed at the highest levels, you more or less train with an expectation of what your opponents will do in mind.

At least in badminton, the way men and women play the game is completely different, but I would be very surprised if it's merely due to physical differences. I don't think it's due to physical differences because the difference in style shows up across the skill level, and I imagine a professional female player who consistently did weight training should be able to achieve the same level of strength as a male who isn't nearly as serious.

[mannykannot]

I am a bit skeptical that any such effects have not already been mined out in the relentless search for competitive advantage.