I was reminded of this fact on Saturday morning when my alarm went off at 4:00 AM (yes, on a Saturday) and it was 17F degrees outside. I had a 90 minute bike ride with an hour at or near threshold followed by a 20 minute brick run. My pain cave is the uninsulated garage and I forget to get the propane heater refilled. Alas, I was left to battle the workout plus the frozen temperatures. Good mental training, right?