From Are Women More Suited To Endurance Sports Than Men?.

An interesting article. Might become heated, but well worth a read, here’s some excerpts:

Women, it now seems, might have been better equipped all along than men! At least that may be true as far as fuel is concerned when female endurance reserves are compared to those of the stronger men who were protecting the “weaker sex” as too delicate for such a grueling distance.

Whatever advantage women may possess probably doesn’t kick in until a running event gets at least as long as the marathon—anything 26.2 miles or over, or its equivalent in another sport. And if our theories are correct, the longer the event is, the greater the possible advantage is.

It may be a simple matter of fat stores—the increased body fat so many women athletes resent in themselves as some kind of deadweight, wishing it were muscle instead. We know that after about 18 miles of steady running, the body begins to get low on glycogen— hitting the famous “wall”—and turns increasingly to other energy stores to keep going. But only recently, thanks in part to increasing numbers of women ultra-athletes and the times they’re turning in, have we begun to suspect women may be more efficient at using that body fat early in a race and saving the glycogen for the long haul. A bigger tank and a more efficient fuel injection system? That could be.

Until now we’ve had only two major studies on the subject, and they conflict. But a recent one suggested that women may in fact have some way, not yet understood, of preferentially burning fatty acids better than men do. If that’s the case, and we factor in that ability with women’s greater body fat reserves, the implications are obvious. Assuming there is some glycogen sparing going on along the way, women might be able to get more out of that premium fuel than men do.

Even bottomless energy reserves wouldn’t do much good for the athlete who is too pooped to access them, however. Muscles get tired as they run out of fuel, but the brain also has a mechanism by which it tells our body that we are weary. And if some recent studies are correct, estrogen attaches to a neurotransmitter in the brain, and the combination may delay the fatigue message. The result: The body doesn’t feel as tired, so it doesn’t race as tired.

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So, a word of warning to marathoning men: Even postmenopausal women have more estrogen than you do! Remember that the next time you’re planning a really long workout and wonder whom to ask along to make you look good. Your female running friend may be slower, but she’s probably a bundle of potential energy. When it’s all over, you might be surprised to find that the “weaker sex” is you.