Exercising? Don’t forget to drink

Few pointers on how much water we should drink when we exercise and why

Drinking water while cyclingWater is the largest component of the body. It affects activity and athletic performance more than any other nutrient.

Our muscles are around 75 per cent water. Water makes up about 45-70 per cent of a persons body weight – a 60 kg person is made up of more than 30 kg of water – depending on his or her body composition [the proportion of muscle and fat in the body].

How do we lose water?

Water leaves our body through the following ways

  • Urine
  • Faeces
  • Sweating
  • Exhalation.

We lose about 1.5-2 litres of water on a daily basis. This is replaced by fluid intake with water present in milk and milk products, beverages like tea or coffee, fruits and vegetables and most cooked food.

When we exercise, water loss through sweating and exhalation increases several times and so does our fluid requirement.

Furthermore, a hot and humid environment will affect water loss adversely. In prolonged and intense exercise, when we sweat profusely, our fluid requirement may go up to 10 litres per day!

The average fluid requirement is around two litres per person, including both water and water in foods and beverages. Consuming greater amount of calories [more than 2500], working in dry and hot climate [where sweating may be absent], being involved in vigorous activity, consuming a high-fibre or high-protein diet, and conditions such as pregnancy, infections and fevers require higher fluid replacement, which would have to be individually adjusted.

What happens if we don’t drink enough water?

In prolonged exercise, if the water lost is not replaced, it will lead to dehydration and electrolyte imbalance. Electrolytes like sodium, chloride and potassium are lost in sweat as well, and therefore need to be replaced.

Fluid loss of as little as one per cent of body weight can cause body temperature to rise while exercising. Also, the fluid loss decreases the ability to cool off the extra heat being produced in the body and causes a strain on the heart. This is known as heat exhaustion and can severely limit performance among athletes. Fluid losses exceeding 6-7 per cent of body weight signal an impending collapse [heat stroke], which can also lead to death.

Unfortunately, when it comes to exercising, thirst is not a reliable indicator of fluid requirement.

Tips on drinking water

  • Make it a point to drink fluids throughout the day. Half a glass [around 90-100 ml] every hour that we are awake is better than consuming large quantities at one go, as quite a bit will simply be lost through urination.
  • Two hours before workout, approximately 500ml of water or a cool beverage is recommended.
  • During the activity, we should consume around 150 ml every 15 minutes.
  • After the workout, we should consume 500ml for every ? kg of weight lost as compared to the weight before workout. To be exact, one must weigh without clothes which may be drenched in sweat after the workout.

Some other indicators of dehydration – particularly over a longer period – are dark yellow, strong-smelling urine [rule out supplemental vitamins or other medications that could cause similar changes in the urine], rapid heart rate at rest, and prolonged muscle soreness. Urine should be light yellow in colour and the frequency should be 3-4 times per day. The normal range for resting heart rate is 40-100 beats/min. Most exercisers would be aware of their own resting heart rates and an elevation of the same by 10-15 beats/ min signifies dehydration.

Muscle soreness [usually just a persistent ache in the muscles] which lasts for longer than 24 hours, in the absence of a vigorous workout, may be indicative of dehydration when co-related with the history and other signs and symptoms of the individual.

Is water the best drink for a workout?

In most cases, yes. Unless your workout is continuous and prolonged beyond an hour, sports drinks give no additional benefit over water. Sports drinks contain 5-8 per cent carbohydrates as well as necessary electrolytes. Apart from the commercially available ones, sports drinks can be made at home by diluting fruit juice 2:1 and adding a pinch of salt. If the workout is moderately intense and under an hour, cool water is better absorbed in the gut and is therefore preferred over lukewarm or warm water. Beware of consuming concentrated juices or beverages immediately before, or during the workout, as it can cause nausea, abdominal bloating and discomfort or abdominal cramps.

So, to maximise performance and safety in the workout, drink up.


Excess water [also known as water intoxication] can also cause problems. Though it is not common, it is something we should be aware of.

If the water content of the blood increases, the salt content gets diluted. Hence, the quantity of salt available to body tissues decreases, which can lead to problems with brain, heart and muscle function. Symptoms like dizziness, nausea, apathy are observed. Confusion can result from over-hydration. Since dehydration can also cause these symptoms, it is important to know your body and how much you are drinking.

Team CW

Ruchira Tendolkar
Dr Ruchira Tendolkar, MBBS, is an A.C.S.M certified health and fitness instructor. She is also an A.C.E certified clinical exercise specialist and a consultant, practitioner and educator for exercise science.


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