Why, when, and how much water to drink during workouts?

Author: Sergey Yezhov - sports medicine physician.
2017-01-12

Every athlete knows the importance of restoring water homeostasis (homeostasis is the stability of the body's internal environment), which is lost during training. It is well known that water makes up to 80% of a person's mass and plays a key role in their vital functions. It facilitates the transport of nutrients through the cell membrane, maintains blood volume, and regulates body temperature.

Daily, to replenish our basic fluid losses, it is necessary to consume at least 2 liters of water (water intake calculator). Naturally, this need is significantly higher for those who are actively engaged in physical exercise. Even a slight deficit in the body's fluid balance can lead to a slowdown in metabolism and substantially reduce both work capacity and recovery after physical exertion.

Rehydration after exercise should exceed the amount of fluid lost. This can be easily achieved by comparing your body weight before and after the session. A reduction in body weight of 1 kilogram should be compensated with at least 1200 ml of water. This is the amount needed by the body to maintain a high level of performance. It’s also important to drink water after, during, and even before the workout.

Professional athletes begin consuming electrolyte solutions before training starts to reduce blood viscosity and increase sodium and potassium ion content in the body. A decrease of just 2% in serum electrolyte levels can impair aerobic metabolism and consequently reduce the cell's energy supply.

When and How Much Water to Drink

Key recommendations for fluid consumption during physical activity:

1. Two hours before the workout, it is essential to drink 500 ml of water with dissolved sodium and potassium salts, as the body needs to store electrolytes before the exertion.

2. It is recommended to consume 150–300 ml of water every 15–20 minutes during training since the average fluid loss for the body is about 10-15 ml per kilogram of body weight per hour. Accordingly, training in conditions of elevated temperature and humidity requires increased fluid intake.

3. During exercise, consume drinks containing simple carbohydrates (4–8%, i.e., 40–80 g of carbohydrates per 1000 ml). This will provide the body with extra energy, protect muscle protein from breakdown, stimulate the brain, and enhance mental performance and coordination.

4. After training, rehydrate at a rate of 1 liter of fluid for every 1 kg of "lost" body weight, plus an additional 250–500 ml to compensate for fluid losses through urine.

5. Avoid consuming overly sweet, carbonated, chilled, or flavored drinks during training. They can stimulate additional voluntary fluid intake.

The key micronutrients lost with sweat are sodium, potassium, and chloride ions. To restore electrolyte balance, specialized sports drinks (isotonic drinks) should be used, or you can add a little table salt to the water (5 grams per 1 liter of fluid).

6. After training, eat potassium-rich foods (bananas, citrus fruits, potatoes, cottage cheese).

7. Avoid consuming beverages that contain alcohol or caffeine after physical exertion. These substances increase urination, exacerbating dehydration.

8. With adequate fluid replenishment, the urine produced in large quantities should be clear, pale yellow, and transparent.

9. Avoid drinking large amounts of water all at once. It is better to divide the total volume into several portions, sufficient only to quench your thirst.