Acute Responses
What immediate cardiovascular response reduces heat loss from the skin?
Peripheral vasoconstriction
What is the core temperature threshold for hypothermia?
Below 35°C (95°F)
What adaptation improves insulation in chronically cold-exposed populations?
Increased subcutaneous fat or improved vasoconstriction efficiency
Why does cold air make breathing feel harder?
Cold, dry air irritates airways and increases resistance
A skier’s fingers turn white and numb. What condition is developing?
Frostnip or early frostbite
What involuntary muscular activity increases heat production?
Shivering thermogenesis
What cold injury occurs when tissue freezes and ice crystals form?
Frostbite
What metabolic adaptation increases heat production without shivering?
Enhanced brown adipose tissue activity
How does cold affect VO₂ max?
Minimal change, but performance may drop due to muscle stiffness
A swimmer falls into 5°C water. What response happens first?
Cold shock response (gasping + hyperventilation)
Why does cold exposure increase urine production (cold diuresis)
Vasoconstriction increases blood pressure → kidneys excrete more fluid
Why is wind chill dangerous?
It increases convective heat loss, making the body cool faster
Why do some Arctic populations maintain higher resting metabolic rates?
To generate more internal heat in cold climates
Why do athletes burn more carbohydrates in cold conditions?
Carbs provide faster heat-producing energy than fats
A mountaineer stops shivering and becomes confused. What stage of hypothermia is this?
Moderate to severe hypothermia
What happens to nerve conduction speed in cold temperatures?
It slows down, reducing reaction time and dexterity
Why does dexterity decrease in cold environments?
Reduced blood flow to extremities impairs muscle and nerve function
What adaptation helps protect extremities from frostbite during repeated cold exposure?
Cold-induced vasodilation (CIVD)
Why does cold reduce muscle power output?
Slower enzyme activity and reduced muscle temperature
A cross-country skier maintains performance despite cold. What adaptation helps?
Improved metabolic heat production + efficient clothing strategies
What is the purpose of non-shivering thermogenesis?
Increase heat production via brown adipose tissue metabolism
What is the main physiological reason cold-water immersion is more dangerous than cold air?
Water conducts heat away 25× faster than air
Why do experienced cold-weather athletes show reduced shivering over time?
Improved metabolic heat production and insulation reduce need for shivering
What clothing principle helps maintain performance in cold environments?
Layering to trap warm air and manage moisture
An Arctic researcher shows strong CIVD in fingers. What advantage does this give?
Better protection against frostbite through periodic blood flow increases