On a sweltering evening in Chennai in April, cricketer Sachin Tendulkar, playing for the Mumbai Indians in the Indian Premier League, had to suddenly retire from the field in the middle of chasing a modest total by Chennai Super Kings. The reason? Dehydration had made him too weak to continue. By the time he came back to the crease after a 20-minute break, Mumbai had lost six wickets and Chennai were galloping to a win. Cricket analysts jokingly suggested that it was difficult for any team to beat Chennai on their home ground because of the hot, sweltering weather there.
In a study published in 2007 in the Journal of the American College of Nutrition, Bob Murray, president of Sports Science Insights, a US company specializing in providing scientific insights into performance, says athletes who perform vigorous physical activity, especially in a warm environment, put their cardiovascular and thermoregulatory functions under severe stress. In simple terms, sweaty exercise is dehydrating and places great strain on the body as it strives to deliver blood to the heart and muscles as well as the skin for sweating. This competition between muscle and skin for your limited blood supply leads to fatigue, irritability, inability to focus mentally, heat exhaustion, and in some cases, a heat stroke, which can be fatal, according to Pratip Mandal, consultant, sports medicine, Moolchand Orthopaedics Hospital, Moolchand Medcity, New Delhi.
Though Murray’s study was based on athletes and the effect on their performance, it rings true for anyone who’s exercising hard—be it cardio, lifting weights, or playing a sport. “Dripping excessive sweat in the gym or on the field can lead to serious dehydration in your body,” says fitness expert Vesna Jacob, a Delhi-based trainer who runs Vesna’s Wellness Clinic in Panchsheel Park. “Especially at risk are people who do cardio for more than an hour every day. Even people who have a tendency to sweat profusely are at risk,” she says.
Don’t wait till thirsty
The saying that you can lead a horse to water but you can’t make it drink has scientific backing. Horses lack a sensitive thirst mechanism and this makes dehydration and loss of appetite common among them. Humans also routinely resort to what scientists term “voluntary dehydration”—when exercising, we tend to ignore sweating as a sign to rehydrate, and drink only when we are very thirsty. “(But) thirst is an inaccurate signal of water needed in your body,” says Dr Mandal. “To remain hydrated, you need to follow a scientific hydration routine.”
As the body loses its water through sweat, performance drops drastically. This deterioration starts even with as little as 1-2% fluid loss. “Besides water, sweat also contains electrolytes like sodium and potassium,” says Deepshikha Agarwal, a Mumbai-based dietician and sports nutritionist. “Potassium is involved in many vital processes such as muscle contraction, heart function, and maintaining fluid balance. Sodium, which is a component of (common) salt, is involved in (the) maintenance of fluid balance.” The loss of these salts expedites the process of dehydration, leading to exhaustion faster. Without proper rehydration, the body is also unable to repair muscle cells that are damaged during a workout.
How much, how soon?
Since you cannot just rely on your thirst as a sign that you need to rehydrate, a good way of gauging fluid loss during an exercise session is by measuring body weight before and after a strenuous workout.
If the loss in weight is more than 2% of your body weight, you need fluids. “During heavy exercise, sweating can easily (cause loss of) about 1-2 litres per hour, depending on intensity and duration, temperature, and humidity,” says Ishi Khosla, a clinical nutritionist and director, Whole Foods, New Delhi. You need to drink the same amount during and after a strenuous session to rehydrate.
Sports drinks vs water
The needs of your body differ according to your exercise routine.
Half an hour of yoga a day in a pleasant environment requires nothing more than water to replenish your body. “But heavy cardio or weight training needs more serious rehydration. Irrespective of thirst,” says Dr Mandal, “you need to sip about 200ml of water in half-hour of a high-intensity workout.”
The rule of thumb is that if you perspire a lot doing anything, you need to replenish your body’s lost fluid, which includes not only water but also sodium and potassium salts, says Jacob. Professional athletes sip sports drinks while playing, which are a mix of water, simple carbohydrate (sugar), sodium and potassium, with an attractive flavour, to help overcome our tendency to “voluntary dehydration”.
“Consuming sports drinks in addition to water helps athletes stay hydrated and energize their muscles,” says Agarwal. “Another benefit is that by drinking carbohydrates during exercise, you are getting energy that can potentially help you think more clearly and make better decisions on the field.” The ideal level of carbohydrate in a sports drink is about 6-8% of its total amount.
However, a sports drink is meant for those who are professional athletes or performing high-intensity workouts for more than an hour every day. For others (read that as those who are exercising less than an hour), “water is your best bet”, Agarwal adds.
Go easy on the juice
Carrot juice, orange juice, cranberry juice and grape juice are other natural alternatives for lost fluids. “Since these juices contain glucose and fructose sugars, as well as potassium, you replace what you lost during sweating, while giving your muscles the glycogen they need to energize,” says Agarwal.
But juices, though refreshing, can put too much sugar into your body if taken in large amounts (one small glass of juice has as much as 100-170 calories) and soon stop being a recipe for fitness.
Make your own drink
Though a little bit of sugar is good for your body during hard exercise, it’s not a good idea if you are sweating it out to lose weight. Water is a zero-calorie drink. Otherwise, the best way to control calories is to make your own sports drink or have a glass of coconut water.
“Nariyal paani (coconut water) is natural Gatorade,” says Jacob. The water of a young green coconut, which is between six months and nine months old, contains around 750ml of water. “It’s a natural isotonic beverage, with the same levels of electrolytic salts as we have in our blood as well as a healthy dose of calcium, potassium and magnesium,” Jacob says. However, since fresh coconuts are not always available and packaged coconut water stays good only for a few days before fermenting, a good natural alternative is a nimbu paani (lemonade) with both sugar and salt added. Lime contains the right dose of potassium and magnesium that your body requires, according to Agarwal. “Half a lemon, a teaspoon of salt for sodium and a pinch of sugar in a 200ml glass of water make a perfect rehydrating solution,” says Jacob.
Agarwal offers another quick solution: “Add one teaspoon of salt (to replace the sodium lost while sweating) to a 250ml glass of diluted natural (unsweetened) juice, and you’ve made your own sports drink.”
Vesna Jacob, of Vesna’s Wellness Clinic, points out a dangerous aspect of sports drinks—that of mistaken identity. “Energy drinks...are commonly confused with sports drinks since they are marketed in a similar fashion,” she says. Sports drinks such as Gatorade have nothing in common with energy drinks such as Red Bull and Cloud 9. Energy drinks have a high caffeine content (equal to a cup of coffee in one can) and other caffeine-like stimulants, which actually accelerate dehydration. In fact, consuming energy drinks during cardio can lead to extreme dehydration. Energy drinks are meant to give you a rush, much like a cup of coffee would do.
Read the label carefully while choosing a sports drink to avoid grey areas: The beverage should not contain caffeine or caffeine-like stimulants such as guarana, ginseng or taurine.
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