Water and salt balance: How much should you drink during summer training sessions?

When the weather gets hot, runners need to pay closer attention to their bodies, particularly to their water and salt balance. Certified health coach and marathon runner Madi Aitimov explains what and how much should you drink.
Why is dehydration dangerous for runners?
It is evident that physical activity affects the body’s water balance. During running activities, metabolic reactions are accelerated and energy is released: up to 60–70% of the energy is dissipated as heat, while the remaining 30–40% is utilised for muscular activity. As body temperature rises, the sweating is activated to normalise the temperature; when sweat evaporates from the skin’s surface, heat is released. The intensity and rate of sweating are contingent on the nature of the training and environmental conditions (e.g., temperature). In any case, the electrolyte composition of the blood, urine, sweat and saliva will undergo alteration during the running.
When the body does not receive enough fluid, the following symptoms are observed:
- decreased performance,
- accumulation of metabolic products (uric acid, salts),
- increased heart rate and body temperature.
How can you find out if you are dehydrated?
The more water the body loses, the worse the consequences:
- a loss of 1% of body weight causes thirst,
- 2% —decreased endurance,
- 3% — decreased strength,
- 5% — decreased salivation, urine production, increased heart rate, apathy, muscle weakness, nausea,
- a loss of 20% results in irreversible consequences.
How can you avoid dehydration?
There are a few basic recommendations that can help you stay healthy in the heat and continue running without harm.
First, avoid any training activities in direct sunlight and look for shade. You should run outdoors when the temperature is below 20°C. In other weather conditions, please use a ventilated gym as an alternative.
Secondly, drink water throughout the day. The formula is simple: 30 ml per 1 kg of body weight per day. If you weigh 62 kg, you should drink around 1.8 litres of water per day (not all at once, but in portions over the course of the day). If you are an active runner and exercise for 60 minutes a day, add 0.5 litres of water or more to your daily intake (depending on weather conditions and training intensity).
If, you like drinking coffee and tea like I do, you should know that these drinks ‘take away’ moisture. Afterwards, it is recommended to replenish your water balance.
Thirdly, keep in mind that it is not enough to just drink water during training sessions — it is better to dilute your drinking water with electrolytes. It is best to drink water when you wake up and before meals, but do not drink too much before bedtime.
Let’s take as an example a 60-minute recovery run at a low heart rate. We lose 700 kcal, 70 g of carbohydrates, 55 g of fat, 0.75 l of water, 126 mg of magnesium, 63 g of calcium, 211 g of potassium, 253 g of chlorides, 421 g of sodium. All of these elements can and should be replenished during training with the help of a sports isotonic drink.
Unlike hunger, we rarely feel thirsty. That’s why it’s important to drink enough fluids and not let yourself get to the point where your throat feels dry. Set a reminder, use a tracker, or just carry a water bottle with you. Stay healthy.