Many people know the excruciating pain that comes in the winter when you are trying to hike, snowmobile, ski, or cycle, and the biting cold cuts through your shoes and numbs your toes. A simple solution to this comes in the form of chemically activated heat packs that can be inserted into the shoe, called heated insoles.

Bending the metal disk inside the pack starts the crystallization process, and you the crystallization proceeds through the liquid and makes a solid and heat as a byproduct. You can then insert the insole in your shoe and feel the warmth!

Some of the packs are reusable. When you boil the solid, you melt it back to the liquid state. You have to completely melt every crystal, by the way, or the liquid will quickly re-solidify. You can repeat this cycle forever, theoretically, just as you can freeze and melt water as many times as you like. The plastic pouch eventually wears out and leaks, though.

They keep your toes warm and toasty for up to 6 hours. I've always had problems with my toes going numb, even with sock liners, wool socks, and neoprene booties (used with a pair of shoes one size up from my normal size.) These really work. (And after the ride, keep your toes toasty for the drive home!)

If you don't want to use a throw-away insole, and would like to be safe from tearing the pack and having it leak on you, a battery rechargeable insole may be right for you.

I've only used them on 5 hour rides in the 40's, but with enough other insulation, they really seem to help. Insoles will take up some space inside the shoe, so you may want to consider wearing a pair that are roomy enough to still be comfortable on your feet, but even buying another, bigger size winter shoe would be worth it if it means feeling your feet during a bike ride.

Take the opportunity to make winter cycling and outdoor activities that much more pleasurable and comfortable, and pick yourself up some heated insoles!