“That’s stupid!” we hear you cry – but there’s a difference between core temperature and how hot or cold you feel.
Of course a cold shower will make you feel instantly cool.
But this feeling may not reflect your core temperature because your perception comes “exclusively from skin temperature sensors”, according to three experts from Swinburne University of Technology.
In fact, as you stand shivering under your cold shower, your body reacts by reducing blood flow to the skin to preserve heat.
“Because there is less blood flowing to the skin, we’ll actually keep more heat inside, thus leading to an unintended overall increase in core temperature,” the Swinburne experts write.
“Some minutes later, we feel hot again. But [that] warm sensation on the skin will lead to increased blood flow to the skin, increasing heat loss from the body.”
So, if you’ve just run up a desert sand dune while wearing a duffle coat and Ugg boots (this is not advised) your body will be pumping blood to your skin to cool you down.
By jumping under a cold shower, you stop this and put your body in heat conservation mode.
It’s therefore better to have a warm shower which is cooler than your hot skin than a shockingly cold dousing, says Mike Tipton, professor of human physiology at the University of Portsmouth.
But how warm should your shower be?
Professor Tipton recommends using water in the 20s Celsius (68-86F) rather than the 10s (50-67F).
The Swinburne experts suggest a warmer “cool down” shower – saying water at about 33C (91F) will work better than 20-25C (68-77F).
“It will seem warm initially but after a few minutes will provide better comfort in the long term,” they say.