Why do we shiver when it’s cold?

Ever wonder what’s going on in your body when you shiver?  One reason you shiver is your core body temperature is too low.  Your nervous system senses when you get too cold and it initiates the shivering reflex.  The result is repeated muscle contractions characteristic of shivering.  But, why?  What does this accomplish?  Muscle contraction is a relatively inefficient process.  Some sources say (https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1805800/) muscular efficiency ranges from 20-30%.  This means that 70-80% of the energy that goes into making a muscle contract is not used for contraction.  It’s wasted!  So what happens to that energy?  Energy can’t be created or destroyed, just converted to a different form.  So, where does it go?  That ‘wasted’ energy is converted to heat!  So, along with producing skeletal movement when they contract, skeletal muscles produce heat.  The heat produced by the repeated contraction of the muscles when you shiver, will warm the body.  Once normal core body temperature has been reestablished, and homeostasis has been restored, the shivering stops.  So, keep moving and stay warm my friends!  Cheers 🙂

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