The Art and Science of Fitness | Busting myths of exercising in the heat

Aug 19, 2022 08:43 PM IST

We’ve been told not to drink cold water, pour it on our heads or sit in an air conditioned room right after a workout on a hot sunny day and that playing in the sun makes us stronger. Is that so?

300, a 2006 Hollywood blockbuster film, showcased that in Sparta stunted and sickly newborns were thrown off the cliffs. Well-built and sturdy boys were allowed to live, who at the age of seven were turned over by their parents to the state to undergo rigorous education and military training. They weren’t fed well and were encouraged to fight each other. And sleep was for the weaklings. They had to train in all kinds of extreme conditions, especially heat.

When the body's temperature increases because of exercising, more so in hot and humid conditions, receptors (sensors) in the hypothalamus portion of the brain and also in the skin trigger a series of events that lead to sweating to cool the body down. (HT Gallery/Representative Image) PREMIUM
When the body's temperature increases because of exercising, more so in hot and humid conditions, receptors (sensors) in the hypothalamus portion of the brain and also in the skin trigger a series of events that lead to sweating to cool the body down. (HT Gallery/Representative Image)

A decade after the release of 300, i.e. in 2016 at the Rio Olympics, OP Jaisha was representing India in the marathon. She too was treated no lesser than the Spartan male warriors. Jaisha had collapsed after crossing the finish line and had to be rushed to the hospital. She alleged that she was not provided water and energy drinks by the Indian officials at the designated stations and could have died.

We don’t have to be elite athletes or be in the army to relate to Jaisha or 300. Most of our physical education teachers and even parents told us not to drink any water, definitely not cold, after doing strenuous physical activity in hot and humid conditions. Pouring cold water on our heads was simply out of the question. Then there were the coaches who made us play in extreme heat as it supposedly made us strong and ready for any condition. It still happens today, even in some top sports academies across the world.

Humans have known about heat-related illnesses – including heat stroke – since 400 BC, when Hippocrates documented it in The Aphorisms of Hippocrates and acknowledged that sweating is important for cooling down. It was around the same time that Herodotus made an observation on the good old Spartans that physical exertion in the heat led to thirst and water was crucial to address it. And about 70 years later, Alexander the Great advised his army not to march when it was extremely hot, definitely not without ample water supply.

How then did the consensus to address heat stroke take a 180° turn?

A thousand years ago, The Canon of Medicine of Avicenna in 1020 first documented that swallowing cold water could lead to sudden death. It strongly recommended that cold water should only be used for rinsing the mouth, that too in moderation. Soon enough, people were getting diagnosed as ‘hurt by drinking cold water.’ There were warning signs next to public hand pumps in Europe and North America, stating that drinking cold water could lead to sudden death. Courtesy of colonialism and trade, this approach to managing heat strokes seeped into all the cultures around the world. This ‘wisdom’ was passed down the generation, soon becoming “common knowledge”.

Even though there has been a difference of opinion in managing heat stroke, there has been a consensus throughout the last two and a half millennia that there is an urgent need to cool the body down when the core temperature exceeds 40°C. Sweating happens to be the most efficient way to cool down.

But where does the sweat come from? It is a question worth asking to understand what we need to do to safely exercise in heat and perform to our optimal levels. Yes, you guessed it right. Sweat comes from the water we drink, but no, it’s not as straightforward as that. When we drink water and other liquids, they get to the stomach through the food pipe and are absorbed there. Now blood has two major components, the liquid portion that constitutes 55% of the blood is called plasma. It primarily has water – which has electrolytes, nutrients, proteins etc. The other component has red blood cells, white blood cells, platelets etc.

When the body's temperature increases because of exercising, more so in hot and humid conditions, receptors (sensors) in the hypothalamus portion of the brain and also in the skin trigger a series of events that lead to sweating to cool the body down. There is an increased amount of blood pumped with every heartbeat and the heart rate also increases to get the blood rushing to the skin. It is the liquid portion of the blood from which sweat is formed, reducing the fluid portion of the blood, as a result increasing the blood’s viscosity. There is an overall reduction in blood volume that is circulating in the body. Loss of fluids and electrolytes leads to the sensation of thirst.

When we continue to exercise in hot and humid conditions, the body’s core temperature increases further. This puts further pressure on the heart to pump more blood, but it starts to struggle to keep up with the demand. Blood flow to the skin starts to fall and sweating reduces. There is also a compromise in blood flow to vital organs like the brain, heart and gut. As much as there is thirst, widespread cellular injury, especially to the stomach and the intestines, causes the inability to drink, failure to correct fluid balance and electrolyte loss.

Busting Myths

> Don’t pour cold water, rather any water, on your head after exercising in the heat

When you are unable to drink water, it becomes even more important to pour cold water over your neck, head and limbs, along with splashing ice cold water on your face to reduce your internal body’s temperature. It is recommended after all exercising sessions in the heat. One feels refreshed pretty soon and not tired and lethargic throughout the day.

> Don’t drink cold water after exercising in the heat

Utter rubbish. As explained above, it is important to quickly bring down the body’s internal temperature and it is safe. Just drink it in small sips.

> Drink only plain water after exercising in the heat

Both water and electrolytes are lost through sweat, so always have electrolytes. Having excess plain water is also dangerous.

> Don’t have any water before starting your exercise

When you are going to be exercising in the heat, it is best to start slightly more hydrated. A glass or two of electrolyte-mixed water over 2-3 hours before exercising is ample. It is important to repeat that the water should be consumed in small sips.

> Exercising in hot and humid conditions makes you stronger for all conditions

There is an advantage to acclimatising to training in hot and humid conditions, but the benefits of it only last for 1-2 weeks. It is detrimental to train at the hottest time of the day throughout the year. There is early muscle fatigue, reduced coordination and poor metabolism, leading to poor performance. It also has a direct mental impact as, despite the higher perceived effort, the results are worse. Indirectly, exercising in hot and humid conditions leads to conditions like depression, stress and anxiety, leading to worse performance and unnecessary injuries. There is a delay in recovery, making sleep uncomfortable. One of the biggest reasons for heat stroke is excessive motivation from self, peers and coaches to carry on and push oneself in extreme conditions.

> Practice sleeping in hot conditions without putting on the air conditioner

Not using air conditioners during summer nights adds to the woes. The core body temperature is already high, even before you begin to exercise in the heat. At least for the last hour of sleep, have your air conditioners at a degree or two lower than you usually do. This helps in delaying heat-related illnesses and better performance too.

It is important to make ourselves aware of this information and question the status quo. At the end of the day, the idea is to enjoy the sports and exercise we do, and do them safely, so you can enjoy them for as long as you possibly can.

Keep miling and smiling.

Dr Rajat Chauhan is the author of MoveMint Medicine: Your Journey to Peak Health and La Ultra: cOuch to 5, 11 & 22 kms in 100 days

He writes a weekly column, exclusively for HT Premium readers, that breaks down the science of movement and exercise.

The views expressed are personal

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