Focus on Fluid Provision
Emilia Szymańska
2026-03-22
3 min. read
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During physical exertion, muscle contractions create heat. The body eliminates accumulated excess heat through thermoregulation processes. The acceleration of sweating and the enhancement of breathing lead to a disruption of water balance (loss of water and electrolytes). The total amount of water lost depends on gender, body weight, level of physical activity, attire, and environmental conditions (temperature, humidity). Fluid loss can manifest in painful muscle cramps, deterioration of performance, decreased concentration, increased blood pressure, and body temperature. Is water alone enough? How to control body hydration? How much fluid should be ingested during activity to prevent dehydration?
Recommendations regarding fluid intake
The new position of the Academy of Nutrition and Dietetics, Dietitians of Canada and the American College of Sports Medicine regarding the nutrition of physically active individuals and athletes is known. Published studies emphasize the importance of an individual approach to nutrition and hydration. In order to determine fluid requirements, lifestyle, environment (temperature, humidity), type and intensity of additional activities, and anthropometry should be taken into account. There are various hydration strategies. The European Food Safety Authority estimates the daily fluid requirement, i.e. the amount of water from drinks and food, to be around 2 l for women and around 2.5 l for men (assuming moderate physical activity and moderate environmental conditions). Converted to body weight, it is: 30-45 ml/kg body weight, e.g. 70 kg x 30 ml = 2100. Additional fluid losses must also be replenished after activities.
Can one genuinely forecast the fluid requirement during the period of strenuous physical exertion?
The provision of the suitable amount of fluids is of paramount importance for individuals actively involved in sports. It is necessary to ensure the appropriate degree of hydration before commencing exercises, during their course, and following their completion.
Before commencing physical exertions
A significant number of athletes initiate their physical activity with an inadequate quantity of fluid in their body, which negatively impacts their exercise regimen. To attain an appropriate level of hydration, it is necessary to consume between 5 and 10 ml/kg of body weight of fluids within a 2-4 hour period prior to training in order to achieve a light urine hue.
Throughout the execution of activities
The goal of hydration during activity is to prevent dehydration exceeding 2% of body weight. It is estimated that during exercise fluid loss could range from 0.3 l/h to as much as 2.4 l/hr. Routine body weight assessments prior to and after exercise provide an indication of the amount of fluid to be consumed during exercise. In certain sports, due to their distinctiveness, hydration is limited (football, long-distance running). Therefore, it is essential to ensure proper hydration before the activity and replenish fluids during breaks. Most athletes typically consume from 0.4 to 0.8 l/h during training. However, the amount of fluid to be supplied should be adjusted according to environmental conditions, sweating rate, type of sport, and duration and intensity of the training. For a training lasting up to an hour, water should compensate for fluid loss, while for longer or high-intensity training, an isotonic drink should be chosen.
Upon finishing the exercise session
Most physically active individuals finish their exercise sessions with a deficit of sufficient fluid quantities. The strategy for restoring body hydration should include water and electrolytes that decrease the diuresis level. Electrolytes can be present in the form of isotonic beverages or derived from food. Fluids should be balanced in amounts ranging from 125 to 150% of lost fluids, for example, for every 1 kg of body weight, from 1.25 to 1.5 l of fluid. Completion of fluid losses should be distributed over time. In case of small losses, this can take up to about 2 hours, but if the losses exceed several liters, the replenishment can take up to 4-5 hours, about 700-600 ml for every 450 ml of lost fluid. After activities, when dehydration is significant (>5% body weight) or rapid rehydration is necessary
Supervise your body
Numerous methods for estimating the body's hydration level can be utilized during daily activities. The simplest ones include the volume and color of urine, experiencing thirst, and body mass. Body weight in active individuals maintaining energy balance can indicate fluid fluctuations. Regular monitoring of body weight in the morning can aid in observing fluid losses. This parameter is perfect for measuring fluid loss during activity. Weighing before and after physical activity reveals how much fluid has been lost. The color of urine correlates well with hydration status. Yellow color signifies dehydration, while a straw-like color indicates good hydration. It is important to note that certain medications and food components can affect urine color. The body is already dehydrated when we feel thirsty.
Excessive fluid volume in the body
Dehydration is a common occurrence among active individuals. An intake of fluids exceeding their loss through sweat and urine, along with the replacement of them with low-sodium beverages, results in hyponatremia (< 135 mmol/l). Recreational athletes are more likely to develop hyponatremia than professional athletes due to lower physical activity and less fluid loss through sweat. Women are also more susceptible to hyponatremia due to lower body weight (low body mass index). Symptoms of hyponatremia (< 130 mmol/l) include weight gain and headaches.
Practical guidelines
– Consume fluids regularly, even if you do not feel thirsty. – Introduce water-rich products (watermelons, cucumbers, pineapples) to your diet, avoid excessive alcohol consumption. – Familiarize yourself with signs of dehydration:.
"It's extremely tender to touch"
("approximately 12% of body weight"): experiencing thirst, head pain, loss of strength, feeling of dizziness, sensation of exhaustion and sleepiness;
"Located in the middle"
(approximately 4% of body weight): aridity in the oral cavity, scarce urination or its absence, drowsiness, accelerated cardiac pulsations, diminished skin flexibility;
Substantial Hardship
(Approximately 10% of body weight): extreme thirst, lack of urine, accelerated breathing, dizziness, changes in mental state, cold, moist skin. Profuse vomiting can be life-threatening. Monitor body weight. In the short term (1-2 days) every lost kilogram is likely to be water. Weigh yourself before training, monitor body weight every quarter in every season. The ambient temperature and humidity can affect the sweating. Maintain adequate hydration during car driving. Driving in a heated car can increase sweating. Even in an air-conditioned car, water losses can be high. It has been shown that dehydration in drivers contributes to a higher error rate. Start the day with a glass of water with lemon, and if your immunity is weakened, add ginger. In daily consumption, choose medium-mineralized water (mineral content 500-1500 mg/l), on hot days choose water with a high degree of mineralization (>1500 mg/l). Pay attention to electrolytes on training days and also use salt, e.g. Himalayan salt.
