Hydration is fundamental both for our body’s health and sports performance.

Our musculoskeletal performance is linked not only to their fitness but to their food and fluid intake. 

Considerable care should be taken by all athletes to ensure adequate hydration before, during, and after exercise to avoid thermal distress.

Dehydration can increase perception effort and compromise performance, particularly in hot and high-altitude conditions, and may also impair cognitive performance.

Body Fluid Balance 

Sweat rates for any given activity, and therefore fluid losses, will vary according to ambient temperature, humidity, body mass, genetics, metabolic efficiency, muscules’ efficiency, and even clothing.

The sweating process can range from as little as 0,3L/hour to typically maximum rates of 2-3L/hour with high-intensity exercise in a hot and humid ambient.

Where sweat losses greatly exceed replacement, the circulatory system is unable to cope, and skin blood flow slows. This is accompanied by a reduction of sweating and the ability to lose heat. Thus, body temperature will rise, with potentially fatal consequences. 

The main function of the sweating process is to lower the body temperature when It goes above 36° Celsius. The high temperature of the body compromises all its metabolic functions including muscle performance and therefore sports performance as well.

Body Fluid Intake

Acute changes in body mass generally reflect shifts in body water, assuming the athletes are in energy balance. To improve sports performance we need to take care of our body hydration before, during, and after exercising or a competition.

Hydration before exercise

Good hydration should be strived for before training or competition.

This can be achieved by drinking 5-10ml/Kg body mass of water or sports drinks 2-4 hours before exercise to achieve urine that is pale-yellow in colour while providing sufficient time for any excess fluid consumed to be voided.

We should choose Sports Drinks that contain carbohydrates and electrolytes at levels that will be acceptable for use before, during, and after most sports. These sports drinks will typically be labeled as Isotonic.

The addition of sodium to sports drinks aids the absorption of water and thus the process of rehydration. Further, the sodium prevents a drop in plasma sodium concentration and plasma osmolality that would occur during exercise with the ingestion of large volumes of plain water. 

A drop in plasma sodium concentration and plasma osmolality would result in dieresis, with an accompanying decline in desire to drink, resulting in lower fluid consumption.

Hydration during exercise

The achievement of fluid balance during exercise is not always possible as a result of maximal sweat rates exceeding maximal gastric emptying.

The aim of drinking during exercise is to limit hydration to <2% of body mass.

Athletes participating in endurance events can be at risk of hyponatremia ( decreased plasma sodium ) if they drink copious amounts of plain water.

 The use of beverages containing carbohydrates and electrolytes can help to maintain fluid and electrolyte balance, especially during the performance of endurance exercise.

Without the presence of other factors that alter body mass during exercise, such as a sizable loss of substrate, which may occur during very prolonged exercise, a loss of 1Kg body weight represents approximately 1L of sweat loss.

 When exercise lasts less than an hour and the temperature is not too high, fluid may not be needed during the exercise period.

However, when exercise is of long duration (2-3 hours) or results in excessive sweating, it is advisable to dring during exercise. 

Hydration strategy during exercise should aim to:

• Match fluid losses through sweat with fluid intake with an average of 0.4-0.8L/Hour.
• Minimize body weight losses to 1-2%, especially in hot and humid conditions.
• Use palatable drinks as the presence of flavor in a drink may increase voluntary fluid intake.
• Use training sessions to practice drinking during exercise to increase gastric tolerance.

Hydration Post-Exercise

Athletes will complete most exercise bouts with some degree of dehydration.

 The volume of fluid consumed following the exercise needs to replace that lost as sweat, but should also take account of the ongoing sweat losses during the immediate recovery period.

 Therefore, fluid intake during this period should exceed losses, with athletes aiming to consume around 125-150% of the fluid deficit, i.e. for every liter lost, 1,25-1,5L should be drunk.

Strategies implemented following exercise should ensure that:

• Rehydration starts immediately after the exercise.
• Drinks contain some sodium to assist in rehydration stimulating thirst.
• Drinks contain more carbohydrates as they are useful where the focus is on refueling (Hypertonic Sports).
• If you get a sports therapy such as Sports Massage after exercising or competition you should drink some extra water to replenish the extra fluid lost for the drainage effect of the massage therapy.

Be aware that correct hydration is complementary to an optimal food intake to reach your best sports performance.