Originally Posted by
Wolfhaven
I paid closer attention to the pressure points and noticed that's where my feet started getting cold and quickly went to the toes. I don't think the pedal is going to draw much heat from the foot, not near as much as the convection of the wind.
The pressure points were of interest because I've x-ctry skied in boots with far less protection while wearing thin cotton socks in -20 degree temps for a few hours on several occasions and never experienced cold feet. Full moon, clear skies, freezing temps is my favorite time to ski in the backwoods trails. Feet rarely get cold walking in sub zero either. Both have a rolling foot motion that doesn't concentrate pressure one on point, while biking it's pretty much continuous on one concentrated area.
Before you blame the problem on "pressure points", you should consider other factors. Assuming that you are using clipless pedals, the hole for the cleat is a large area for cold air infiltration. The cleat itself
is a heat sink but that pales in comparison to the air that can flow in and out of that hole. The act of pedaling acts as a "pump" as well because you are pushing down on the downstroke and pulling up (or at least relieving the pressure) on the upstroke. If the hole isn't sealed, cold air is just going to be pumped in and out.
I always seal the cleat hole on my winter shoes with aluminum furnace tape to reflect heat back and to keep air from being pumped into and out of the shoe. I then use the aerogel insoles to add a thin but very efficient layer of insulation to the shoe.
There is another factor to consider as well. If you are using a true winter shoe like a Lake MXZ 303 boot or 45nrth Wölvhammer or Japather, there is a lot of area for the shoe to radiate heat. Bicycle shoes are made for warm to hot weather riding and thus are very open. Finding a bike shoe that works well in winter is difficult and expensive.
Another thing to think about when comparing bicycling to cross country skiing is the movement of the feet. In particular, the flexing of the foot just above the toes. Bicycling doesn't encourage flexing so the toes don't get a boost in circulation. Cross country skiing is constantly flexing the toes which pumps blood to them. Think of how cold your feet can get on a long downhill run in XC boots. Or think of how cold your feet get when downhill skiing. It's the same mechanism, no flexing of the toes.
You are also moving your foot through open air. While skiing, your foot is in contact with the snow which may not be as cold as the air surrounding it...think snow cave. But when bicycling, your foot is moving through cold air and radiating heat at a constant rate. The radiation is also fairly rapid. This cools the foot faster.
All of these are contributing factors with at least as much impact as pressure points and probably more. You may just notice the pressure point more because, well, it's a pressure point and it's giving your brain feedback. But all this other stuff is going on as well but you just don't notice it until the pressure point reminds you.