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So, how much water should you actually be drinking?

Summer is almost here. Here is how you can stay cool and hydrated, especially if you exercise regularly.

Most of us can stay hydrated without overthinking it because thirst drives our need for fluid replenishment
Most of us can stay hydrated without overthinking it because thirst drives our need for fluid replenishment (Pexels)

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We all have that friend who doesn't sweat when exercising. Imagine this: you are both doing burpees. You end up drenching your mat with sweat and, embarrassingly enough, probably splashing some onto your neighbour's mat (hoping that he doesn't notice). Your friend, on the other hand, is breezing through the workout as casually as if they were reading a book.

I must admit, even though I sweat so much, I don't like sipping water throughout a high-intensity session: the slosh of fluid in my stomach makes me feel seasick. Instead, I chug back water post-session.

Sounds familiar? Then, I presume your next question will be: how much water should I actually drink when I work out?

The answer is not that straightforward. 

Also read: Why women should avoid fasted cardio

You’ve probably heard people say that you should replace the water lost by the body during exercise. Aside from weighing yourself before and after each high-intensity exercise class, the average person won't know how much fluid they have lost. And no, that isn't as unreasonable as it sounds: many athletes do weigh themselves before and after a training session to optimize their fluid intake. However, I'm not a big fan of getting people to act like scientists in the gym. So, let's look at simpler ways to gauge your thirst and fluid intake; this way you can perform at your best and lose weight. 

We all know that we need water to survive, depending on our bodies and climate, up to three litres of water each day. Water is so vital to our existence that according to Medical News Today, the human body can live one to two months without food, yet only a few hours (young kids or elderly) to a week without it. According to Precision Nutrition's article titled Water and Weight Loss, water has a great many vital roles in our bodies, such as the transportation of nutrients and oxygen to our muscles. This is handy for exercise and sports recovery, shuttling out waste such as carbon dioxide, padding our joints from shock, assisting in chemical reactions, lubricating our gastrointestinal tract and allowing us to sweat and cool our skin.

 If we experience mild dehydration, our bodies start sending up little warning flares that it's time to refuel our fluid supply: first, thirst or a primal desire to drink something, followed by other physical discomforts. Our skin will start to dry; we may experience muscle cramping, headaches, nausea, and dark-coloured urine. Over time, the more serious the dehydration gets, some of our most valuable mechanisms fail, resulting in unpleasant situations involving kidney stones, vision problems, urinary tract infections, and poor mental and physical health performance.

But don't be alarmed; most of us can stay hydrated without overthinking it because thirst drives our need for fluid replenishment. However, if you regularly exercise, your thirst mechanism is less effective, which, in turn, can cause mild chronic dehydration. 

Now let's return to the burpees. If you were doing those burpees while perfectly hydrated, your muscles would be shuttling nutrients and oxygen around, and your blood would effectively sweep up the heat your burpees are creating and bring it close to your skin. Then, the most amazing thing happens, water from your blood will transport the heat to above the skin's surface, acting as a cooling layer on your skin, so you can keep pushing out those burpees while keeping your core temperature down. 

Now let's say your body is low on hydration. This means that your blood is more viscous, which means it is denser with the lack of water volume. Dr Stacy Sims, a nutritional scientist (who did her PhD in sex differences in hydration in the heat), tells us that the cascading effect of not having enough water in your blood means that your heart has to work harder to pound this sludge around your body, making your heart rate goes up, your overall power goes down, core temperature rises, which means your overall performance suffers.

To replenish our lost fluids, most of us are told to drink according to our thirst mechanism, and this is true for a substantial amount of people. But, like with everything, there are caveats.

There are several populations of people, such as the elderly, who don't have the exact, reliable thirst mechanisms as their younger selves. This can be from numerous things, such as a decreased perception of thirst, reduced kidney function, and the interaction between medications. Drinking according to their thirst may not be a reliable practice and may require prompting to drink more fluids throughout the day, such as every two hours, or to have a glass or two of water with every meal. If you're over 65, a good practice is to drink at least one more glass of water over your thirst level daily and increase that amount with exertion.

Also read: Can the age gap in a relationship affect your mental health?

Another group of people who may be unable to rely on their thirst mechanisms for hydration is – surprise, surprise, women. According to Sims, a woman's body has less available water (50% compared to 60% in men), we tend to sweat less than men, and our core body temperatures, therefore, rise twice as quickly when we exercise. This means we are more susceptible to the strain of high-intensity exercise. Where a woman is in her cycle also affects her core temperature, as it can increase 0.3-0.5 degrees Celsius in the luteal phase (second half, towards menstruation). 

A study conducted in the Journal of Applied Physiology on the sex differences in physiological responses to exercise-induced dehydration tells us that our blood osmolality and volume drive our thirst mechanism. In the case of women, though, since our hormones play a role in our hydration, it is possible for our body temperature will rise without an uptick in our thirst. Women who are also edging towards menopause and are in their perimenopause phase of life may experience this diminished sense of thirst even more acutely due to widely fluctuating hormones. For women currently in a natural menstrual cycle, pay attention to your hydration a week or two before your period starts. Drink an extra glass of water or two to help keep your body cool and operating at its best. The same goes for women who are over 45.

If you're training in hotter climates, as most of us will be in the next couple of months, aim to drink one litre of water in the morning, afternoon, and night to achieve your three litres daily. And yes, if you are exercising in the heat, offset your dehydration by including at least two glasses of water per hour of exercise in addition to your daily requirements.

Adjusting for age, gender, and climate, how do we now ensure we are hydrated enough? The most practical advice is to check your toilet after urinating. Light straw colour urine is a sign of being adequately hydrated, while urine with a more orangey or light brown colour tells us that you need immediate hydration. 

Aim always to keep your urine in more lightly golden hues. Secondly, know the signs of dehydration and don't try and pass them off as something else. They include fatigue, dizziness, headaches, and dry mouth. So, before you pop a pain killer, drink a glass or two of water to see if your symptoms alleviate.

Jen Thomas is a Chennai-based weight-loss coach

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