In primitive times, mankind still had a much stronger body hair as protection against adverse climatic conditions. The lush body hair acted as a warming air cushion for the entire organism. Nowadays we lack this “warming fur” and the body must help itself differently. If the temperature drops in winter and we get cold, the small muscles in the skin contract involuntarily. This reflex ensures that the hairs on our skin stand up and – as in the past – an air cushion is formed. However, this reflex has long since ceased to be sufficient.
What happens in the body?
The body has different mechanisms to keep heat loss as low as possible. In addition to the contraction of the small skin muscles, the muscles of the arterial skin vessels also contract, causing less blood flow to the skin. Instead, blood flows more to the internal organs, spinal cord and brain, keeping the core body temperature constant. In addition, the body stops producing sweat, since sweat on the skin is known to cause evaporative cooling. Furthermore, the muscles under the skin tense up in an attempt to produce heat. If all these measures are unsuccessful, the body tries to heat up again by contracting the muscles more strongly.
How does this work?
Over one-third of our body mass is made up of muscles that enable us to move. When the ambient temperature is cold, the muscles contract (contraction). Muscle contraction, however, also means movement, and from movement comes heat. Because everything that the muscles do not need themselves in terms of energy becomes body heat. Anyone who rides a bike for a few minutes or goes jogging will notice that this is the case. This is why we start to shiver when we are cold. And the more we freeze, the more we start to shiver. Our body tries to help itself in this way. So shivering violently is the best way to raise the body temperature quickly.
