Ha. Your theory makes sense to me. I think standing around (or walking slowly) in the cold would be very trying indeed.
The replies to this thread are reassuring. I did bike last winter, but didn't have enough experience to detect the slowing I'm finding this year.
Skhill, your food theory is interesting. I'm as locavore as possible, so winter food is very different. And of course the extra clothes are a factor.
I'm taking a week off to avoid burnout. I plowed through a 32 mph wind last week which just about finished me mentally (and damn near knocked me off the bike, too).
Now that I know this happens to everybody and it's not just me being a wimp, I hope to regain my usual cheery attitude.

