Performance and energy expenditure in cold environments.

This paper reviews the associations between physical performance and energy expenditure in cold environments. The basic question in cold is how to maintain adequate thermal insulation without marked cold or heat strain and with minimal impairment on physical performance. 24-hour energy expenditure is increased by 105-156 kJ when ambient temperature decreases by 1 degrees C either due to increased clothing, lowered body temperatures or environmental conditions like snow, ice or darkness. Clothing and other protective garments decrease performance due to the weight, bulkiness and friction, and by covering body areas which are important for sensory functions. Each additional kg in clothing weight increases energy costs approximately by 3% and each additional layer by 4%. Increased energy costs are associated with a decrease in physical performance: the decrease is task specific, and roughly comparable to the changes in the energy costs. The decrement in performance can be minimized by decreasing clothing weight and bulkiness as well as the friction between the clothing layers as well as the number of clothing layers. Minimal friction is important in sites where large range of movements is expected like in trouser legs and sleeves of jackets.