There is a phrase in a classic Traditional Chinese Medicine text that accompanies me every summer.
When I read it almost 30 years ago, it had a more complex, more elaborate meaning — and over time it has become increasingly clear and simple. Because in the past, the mindset of those who wrote these texts was focused on the essential, on something with as little noise as possible.
The Yellow Emperor’s Classic — the founding text of Traditional Chinese Medicine, written over two thousand years ago — describes summer with a phrase that remains relevant today:
“You must not let the sun cause you fatigue.”
The fatigue that heat can cause is not inevitable. It is a response of the body to an inadequate management of energy in this season.
At the same time, an observation that can help us understand how we are more or less in harmony with this season.
What the classics suggest — without using the language of modern physiology — is that there is a way to get through summer without being exhausted by it.
What summer asks of the heart
In Traditional Chinese Medicine, summer is the season of the heart.
The same text is clear about what happens when we do not respect this season:
“Opposing it will result in imbalances in the heart.”
This is not a metaphor. It is physiology.
Modern data confirms what the classics observed: during heat waves, deaths from cardiovascular causes increase significantly. Heat demands more from the heart — and when this effort is not managed, the body may suffer or even collapse in more extreme cases.
What is rarely brought to the table is that much of this additional effort doesn’t come only from the external heat. It comes from how we respond to it.
When the heat rises, the body tends to breathe faster — an instinctive attempt to dissipate the heat. But this acceleration has a cost: the heart works harder, blood vessels constrict, and the nervous system goes into alert mode. The heat inside increases instead of decreasing.
It is exactly the opposite of what the season asks for.
The reverse path also exists and is available at any moment.
When breathing slows down — especially when the exhale is prolonged — the heart slows down as well. The vagus nerve is activated. The body’s natural anti-inflammatory process is triggered. And the system begins to regulate temperature from the inside out.
This is not magic. It is what the body does when we give it the right conditions.
The Yellow Emperor’s Classic describes this principle in a way that modern physiology would confirm:
“The flow of vital energy must be assisted, its communication with the outside world must be allowed.”
Breathing is this assistance. It is the most direct way to communicate to the body that it can slow down — even when the heat outside does not.
“You must not let the sun cause you fatigue.”
There is still time for this summer to be different and truly nourishing.
See you next week.
Best practices
Lourenço de Azevedo