I have an upcoming 70.3 that always seems to take place on the first really hot weekend of the year up here in New England, so, with the sauna and steam rooms open in my gym again, I’m playing with heat adaptation
My normal swim sets end with a 300m cool down. After, I’ve gone straight into the hot room. Would you do that cool down set? Or would you finish your work set and go straight into the heat? Or is the difference less helpful than the 900 extra meters covered in a week?
I think one important consideration here is whether the additional 10(?) minutes dedicated to your cooldown will be coming out of the time you spend in the sauna.
With heat acclimation training, the adaptations you trigger in the sauna depend on:
Generally, you’ll get more bang-for-your-buck if you’re in the sauna for a little longer and get a little warmer (provided, of course, that you’re in a reasonable heat range and not on the verge of passing out).
So, if completing your cooldown means spending less time (say, 10-15 minutes less) in the sauna, then you’re going to be losing out on the greatest benefits that would have occurred in the final minutes of the sauna session (i.e. when your core temperature is at its highest). This might be a decent argument to skip the cooldown. On the other hand, if you’re planning to do the same amount of time in the sauna regardless of whether you do the cooldown or not, then I think the decision might not matter all that much.
One last thought: the point of a cooldown is literally to ‘cool down’ your body and decrease your core temperature after a workout (among other functions). The goal of heat acclimation training is to increase your core temperature to a higher level for a prolonged period of time. If you want to get nice and hot, then spending extra time ‘cooling down’ in the pool before your sauna session might be counterproductive (especially if the water temperature in the pool is relatively cold). But, then again, the drop in core temperature over a 10-minute cooldown could be negligible—I’m not really sure… I’ll leave that to the exercise physiologists on here to discuss. 
Good luck with your training!
Thanks for clarifying what I was feeling. I planned the same time in the sauna regardless of cool-down, however, I found it much more difficult after trying it yesterday directly after my workout…sans cool down.
I’ll try it that way for a little bit and see how I adapt. Thanks for helping me think it through.
…now to convince my wife that we need a sauna in the pain cave…
@Stephensjer
Now there’s a whole thread of conversations to read through…send your suggestions to…Forum , Trainerroad