this has been what works best for me. i find it's easier in training than racing, though - on a race course you can usually only get what they give you, though probably possible to have a water bottle on your bike start out frozen and still be cold when you pull out of T1. when I ran the Boston Marathon spectators were giving out those freez pop things which can really hit the spot.

I think rappstar said something about this after he did Kona, though I coudl be mis-remembering that.

and man, what i wouldn't give for a snow cone some days... i'm living in Hong Kong, it's hot and humid and you can't get anythign like that. I don't know where the Aussies put their machine but it isn't here.

Not to be pedantic, but some do better than others in humidity. Usually those "some" are skinny folks with high surface/volume ratio, whose loss of evaporative cooling is not as catastrophic. The "others" end is composed of the weightlifters, fatties and other low surface/volume ratio types, who will run into their already lower limits of cooling ability much sooner in a humid climate, all other things being equal.

There is also some element of trainability, which Tucsonians can possibly simulate, or possibly not. But in any case, there are limits.

FWIW, should I as a lower surface/volume type ever race hot/humid, I will have a comprehensive acclimation and ice plan.

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Hard work beats talent when talent doesn't work hard.

When you think about it humidity might actually favor "heavy" athletes.

In hot dry weather people with a low body mass and a large surface area- will have an advantage over denser people.
More surface to radiate heat from.

But when there is very high humidity, there is little evaporation. The body thus looses much of its' ability to cool itself through the skin.

This would mean that the key to success in humidity is to avoid producing a lot of heat in the first place.

Heavy athletes are generally less effective at getting rid of heat. It would thus not be surprising if they had learned to produce less heat in the first place.

Echoing what jackmott said, I rode 7w under my power target on Sunday, adjusted due to the climate and a HR that was higher than I wanted. It then PR'd the run by a few minutes. I benefited from going off earlier than some, as I dealt with less sun and heat on the run, and finished the bike before the winds shifted a bit. There wasn't much wind anyway, but I'm told those that started later dealt with more of a headwind coming back.

I'm a relative lightweight (140-145lbs) and am quite convinced that also helps.

High surface/volume ratio will always favor heat transfer. Radiant heat loss, as you mentioned.

You may be right about big units producing less heat per Kg in general while in a humid climate. But in this context we're talking about bodies performing maximum tolerable exertion, not basal metabolic rate. Producing a given amount of energy to move the body creates a constant amount of heat waste per unit of energy expended, and the smaller athlete will always be better at shedding it.

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Hard work beats talent when talent doesn't work hard.

I've read before that body fat% and overall size of a person can be significant factors in a person's ability to race in heat.

I believe someone with a lower body fat% has an easier time dissipating heat. And smaller people apparently also can dissipate heat more efficiently because they have a higher ration of surface area (which dissipates heat) to volume (which generates heat). I'm no doctor or scientist, so I cannot confirm either of these. But they seem to make sense.

From personal experience I can say that I once did a 70.3 in 102 degree heat and fell apart on the run. I now weigh substantially less (5'10" and 135 lbs race weight) and have a MUCH easier time running in the heat.