The psychology and physiology of heat…

As I stood under a really hot shower the other day, I let out a contented relaxed sigh at the heat and wondered why I did that, what does heat actually do to our muscles and its it on a physiological or psychological level?

So I decided to do a bit of research…and it went down a rabbit hole.


What does the application of heat do to our bodies?

Both stress and the cold causes us to hunch and contract our muscles, decreasing blood flow to them.

Heat increases blood flow, by allowing the blood vessels to expand, which can aid the ‘flushing out’ of waste products like lactic acid.

It relaxes the muscle fibres making them longer and increasing mobility. It accelerates tissue metabolism and healing by increasing oxygen uptake and can also reduce joint stiffness.

Endorphins are released when we feel the warm sun and heat on our skin and the same effect happens when we bathe in warm water.


How can heat reduce pain?

The application of heat can aid the management of chronic pain, but how?

It’s a bit complicated…Heat increases stimulation of sensory nerve fibres (thermo receptors) which are connected to blood vessels close to the surface of the skin, this signals a substance that to be released that relaxes blood vessels called bradykinin (a vasodilator) reduces the threshold at which the muscle fibres fire, and relaxes the muscle, decreasing the tone.

Heat also stimulates sensory receptors that directly inhibit pain receptors. If pain is deep, then heat can reduce pain by altering the way the spinal cord talks to the brain.  

Going even more technical; Heat and cold are purported to alter calcium and sodium exchange in neural cells which positively affects pain tolerance and thresholds.


The benefits of taking a hot bath

A hot bath increases skin temperature and superficial blood flow, which allows for improved removal of waste products and relaxing muscle. The pressure of the water is thought to help reduce pain by assisting the removal of swelling (oedema).

Winston Churchill, who suffered from depression, was known for doing a great deal of his writing in the bath.

Immersion in hot water activates the parasympathetic nervous system (the bodies brake pedal). Heat and hydraulic pressure increase the metabolism allowing lactic acid and other substances to be removed from the muscles easier and decreasing fatigue. The buoyancy aspect aids relaxation and be good for the body on a physiological and psychological level.

Immersion in hot water is instantly relaxing and been shown to decrease the sympathetic nervous system (the bodies accelerator pedal).

Deep muscle structure blood circulation also increases significantly when the body is immersed in warm water, which aids oxygen flow and leads to improved healing.


Having a bath with Epsom salts

I told you I went down a rabbit hole…

Epsom salts, named after the town of Epsom, isn’t actually a salt but magnesium and sulfate (sulfur).  Magnesium is used for over 120 physiological processes within the human body, including heart function, nerve and muscle regulation, joint proteins, brain tissue and also helps line the digestive tract.

Having a couple of cups of Epsom salts in your bath can help with muscle soreness, relax you and help reduce the effects of stress.

How? The warm water increases circulation, allows the blood vessels to open up enabling the magnesium to be absorbed into your body, aiding the removal of toxins. It’s good for recovery post exercise. It’s known to be beneficial for arthritis as the magnesium possesses anti-inflammatory properties.

Magnesium deficiency in the body can cause mental fog and confusion, low mood, poor sleep, muscle weakness and twitching and even seizures.

So, I had a nice hot Epsom salts bath tonight. A much-needed bit of self-care for my tired muscles.


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