Thermal Equilibrium – the point at which your body no longer loses heat to the outside, a more comfortable level of thermal equilibrium can be reached by wearing suitable outdoor clothing and dressing in layers
 
Thermal Underwear – the thin absorbent lowest clothing layer (“Base Layer”) in the “Three Layer System” aids in reaching Thermal Equilibrium by keeping the skin dry

Three Layer System – a dressing strategy for outdoor activities that allows for maximum heat retention in cold weather while allowing flexible adaptability for warmer weather. See “Base Layer,” “Insulation Layer,” and “Outer Shell”

 Tongues – protective flaps between the laces and upper feet, often with gussets attaching them to the boots in order to keep out moisture and debris
 
Trail Running Shoes – footwear constructed for off-road running, and can also be used for light terrain hiking.