Hot Foot

The military has been using exothermic reactions triggered by adding water to magnesium and iron to heat rations for a long time. The Russians have now come up with a set of self-heating shoe insoles that act in a similar way. The Russians certainly understand cold feet. The new insoles are "powered" by ordinary sweat, and can keep feet at about 18-20 C (70F) for approximately 5-6 hours.