Pre-dawn patrol

Is it a good idea to trade sleep for training time right now? I have no real loss to conisder. It will pay off in the end and might even add up to more sleep. I can be out on the skis at 5 or 5.30 am and perhaps ride a bit if properly bundled. Skis would be better, slow=warmth=good. Yesterday is on my mind, it was that good.