Some mentioned the fact the cold tends to slow down the body. No dobt air densities are culprits to. Also important is that when you are cold, you tend to wear more clothing, which slows down the body turns. When I play golf, I put my wallet, keys, phone in the bag, since I feel they add up to extra weight that would interfere my body turn. Even my watch I'll take off because i figure it is just another 30 grams that gets added to the 170 grams that I'm trying to throw.
I suspect that the added weight is more significant than air densities. Now, if you wear t-shirts in a blizzard, like some do, than the density arguement might be stronger. But I would suspect that a t-shirt only person is also slowing down because of the cold muscles, not matter how young they may be.