FOOD FOR THOUGHT
It is going to be a very hot summer. I predict an energy-sapping time for athletes over the next quarter. The world is talking about climate change. It is getting worse. Temperatures are higher than they have ever been. The average temperature in Indian summer ranges from 25 °C to 52 °C.
With heatwaves and humidity causing record temperatures across the country, you may be wondering how to safely stay cool this summer, especially if you’re training outdoors. Without a working air conditioner for training, you are deep-fried!
But first, let’s understand how summer heat changes body temperature.
The average human body core temperature is 37.5 °C and is maintained by heat loss and heat production, also known as thermoregulation. In warmer climates or during strenuous activities, the core temperature rises due to heat production, and this heat is released from the body in the form of sweat, which then evaporates in the air to cool off the body.
It seems like we have an inbuilt air conditioner to maintain core body temperature, but then why do we still feel uncomfortable and icky with the thought of working out in summer? There is a simple explanation for this. It is called “humidity.”
Have you ever observed that you sweat more in Mumbai/chennai/goa as compared to drier regions like Delhi/pune/bengaluru at the same temperature? That’s because the higher the humidity, the slower is the sweat evaporation rate. There is already water present in the air, so the sweat on your skin stays put for longer.
This is dangerous for an athlete training in humid regions because your body tends to overheat and puts extra load on the body to cool down, leading to excessive sweating, increased heart rate, increased blood circulation, and thus you feel out of breath faster. All of this, if not looked into, may lead to heat-related illnesses like heat exhaustion and heatstroke.
So is it good to sweat or not during exercise?
Sweat is produced by sweat glands on the skin and primarily consists of Nacl ( sodium chloride salt), small amounts of urea, lactic acid, etc. Unlike the kidneys, where during excretion, the water loss is conserved, the sweat glands do not do the same. Thus we become dehydrated.
You can estimate your sweat loss rate by a simple formula: pre-exercise body weight — post-exercise body weight + fluid intake — urine volume/exercise time in hours.
To simplify this, if you weigh more before one hour of exercising as compared to after, you are losing more fluids; therefore, you need to increase fluid intake during exercise and work on rehydration. If you weigh more after, then you are over-hydrating.
How do you hydrate correctly?
Replenishing sweat loss during and after exercise is an important part of recovery and is often overlooked. The electrolytes lost in the sweat vary for each athlete, depending on the sport and other factors.
An optimum rehydration beverage should consist of:
• High levels of sodium (>= 50 mmol l-1 ) and some potassium.
• A small amount of carbohydrate ( < 2%) to improve the rate of intestinal uptake of sodium and water.
Since the quantity of beverage consumed would be greater than the volume of sweat loss, it also has to be palatable.
So are we taking the right sports drink? Do we even know what exactly a sports drink comprises? Human body is made up of 70 per cent water, so when it doesn’t replenish the lost fluids, the athletes feel dizzy, tired, fatigued, their response rate falls, and they make poor decisions.
The loss of as little as 2% of body weight through sweat might impede an athlete’s performance capacity due to poor utilisation of nutrients & oxygen and a low blood volume.
The oral rehydration solution recommended by the World Health Organisation for rehydration has a sodium content of 90 mmol l-1, whereas the sodium content of most sports drinks is in the range of 10-25 mmol l -1; therefore,, these drinks are unsuitable when the need for rehydration is crucial. I have always pointed out to athletes that most of these oral rehydration products are designed for dehydration from diarrhoea and not designed for dehydration from sweating. So they really underperform for the athlete. Even nimbu pani (lemonade) or coconut water is not the pristinely balanced formula to work for an elite athlete.
It is also claimed that consumption of 6% carbohydrate solution in rehydration beverages improves physical performance in high-intensity endurance activities. The mechanism is that glucose is absorbed via a sodium-dependent transporter (SGLT1), which becomes saturated at a carbohydrate intake of around 60 g/h. The 6% solution may contain glucose, maltodextrin (chains of glucose), fructose, and sucrose. As carbohydrates are the primary energy source for muscles, the quantity of carbohydrates consumed during and after exercise is crucial. Thus, it is important to make it available in rehydration beverage for glycogen sparing