At what body temperature do we shiver, is running effective in terms of heat loss, and what do people need to keep warm?
Answered by: cardiovascular surgeon
Shivering is the body’s defense reaction to a drop in body temperature. By the way, it is characteristic of all warm-blooded animals, not just humans.
The fact is that the range of temperatures in which biochemical reactions that ensure our vital activity can take place is quite narrow. At elevated body temperatures, proteins lose their catalytic activity, meaning that they no longer accelerate chemical reactions in the body. At a lower temperature, biochemical reactions slow down, and the lower the temperature, the more likely they are to stop altogether. In this case, the person will die.
Shivering is the most effective way to “warm up” the body. The skeletal muscles of any warm-blooded animal, when contracted, perform a certain work, which results in heat generation. Shivering makes it possible to correlate the energy expenditure and the heat generated. In other types of skeletal muscle activity, such as running, this balance is shifted toward energy expenditure. That’s why dogs that are freezing don’t run in circles to keep warm, but curl up and shiver – this is how they minimize heat and energy loss.
In the event of a sudden cold snap, heat is transferred from the body surface to the environment. Up to a certain point, this situation is not considered critical by the body. But if the heat loss continues, the first of the defense mechanisms is activated: the subcutaneous capillary network sharply narrows, reducing the subcutaneous blood flow. The body tries to preserve heat for vital organs – internal organs, sacrificing less important ones – superficial organs. We feel cold. If heat loss does not stop at this stage, the body temperature drops. Usually, a person starts shivering when their body temperature drops to about 35°C. But it happens that shivering occurs even at lower temperatures.
In any case, to calm it down, it is necessary to limit the body’s heat loss, for example, by dressing warmer.
