A good discussion on the Gym Chat forum:
The temperature was nearly 92 degrees outside and there was no chance of any air conditioning units being turned on in the Gymnastics Revolution gymnasium on Francis J. Clarke Circle.
Gymnastics Message Boards – Gym Chat :: View topic – how to keep cool in the hot gym!
How hot is too hot?
At what point is a hot gym dangerous?
A hot, humid environment seems to be good for the musculature, I feel.
So long as the athletes have good hydration the temperature could be very high before I would start worrying about any health or injury risk.
On the other hand, you could always do as they do in Santa Monica, California. Set up a water slide IN the gym.
more photos – flickr – Wordsmith from Nantucket
Gymnastics Coaching.com 