Personalized fluid intake enhances performance, reduces heat induced dehydration: Study

Water is the most essential substance, forms the basis of blood, digestive juices, urine, and perspiration, and is contained in lean muscle, fat, and bones. Water loss or dehydration is most common in athletes and people who work out and exercise. A review by Samuel N. Cheuvront and colleagues talks about how the majority of professional sports medicine and nutrition organizations recommend drinking during exercise to replace sweat losses and prevent dehydration, while also avoiding over-hydration. The review is published in the Journal of Science and Medicine in Sport.

Personalized drinking strategies

The metabolic rate depends from person to person the review addresses the knowledge of sweating rate, which is highest in case of heat and the key to managing dehydration. proper drinking strategy minimizes dehydration while also keeping a check on overdrinking. The physiological mechanisms to explain the performance impairments have been well studied but are not yet precisely resolved.

Personalized drinking strategies vary as per an athlete's personal goals as well as the rules and conventions of a particular sport which govern the availability of fluid and fuel in competition. Reviewers found that upon adopting a meaningful dehydration avoidance threshold of > 2%body mass i.e., > 2% loss of body water expressed as a percentage of mass. Reviewers reported the impact of anticipated, sustainable sweating rates was 0.5, 1.0, and 1.5 L/h on dehydration and required drinking rates.

Hot environments are susceptible to dry heat loss under these circumstances, body cooling becomes increasingly dependent on evaporative sweat loss. The reviewer said the complete evaporation of 0.5, 1.0, and 1.5 L/h of sweat can remove 337, 675, and 1012 W of heat energy, for the same running distance and running duration, a larger person will require a larger sweating rate. Even though dehydration takes time to develop for all, it is meant to occur faster in smaller runners than in larger runners when it was assumed sweating rates are identical for both. Therefore, exercise duration is said to be also critical.

Benefits of fuel intake

Athletes require energy and competitive athletes have been updated from time to time, popular recommendations by Jeukendrup (2014) have been adopted by sports medicine and sports dietetics organizations that state the importance of exercise duration.

The review recommended up to 30g, 60 g, and 90 g of carbohydrates (CHO) to be ingested when exercise is 1–2 h, 2–3 h, and > 2.5 h duration. Reviewers selected 1 h, 2 h, and 4 h exercise durations to represent running distances of 10 km,21 km, and 42 km based on median finishing times for large road races represented by these distances. The consumption of a typical sports drink was supposed to deliver 60 g/h CHO in a 1 L volume of fluid.

Drink to thirst strategy

Thirst, an alternative to personalizing exercise fluid replacement based on knowledge of individual sweating was used as a different form of personalization based on individual. Drinking to thirst has been recommended specifically as a means of reducing the risk of hyponatremia. As a strategy for satisfying fluid needs for the exercise of any duration this approach is needed for satisfying both fluid and fuel needs however it should not be overlooked that there are reported incidents of individuals becoming hyponatremic when consuming fluids according to thirst.

The scenario of fluid and fuel benefits requires an estimate of thirst-driven drink volumes, which was set to 50% of sweating rate for this exercise. It has to be noted that 50%replacement of fluid losses is at the higher end of thirst-driven fluid intake and others have known to report lower intakes(~20%).

The reviewers concluded that " Exercise fluid and fuel needs depend heavily on exercise intensity, environment, and exercise duration, as outlined above. Our analysis indicates that knowledge of individual sweating rates can be used to closely gauge drinking needs for optimizing fluid replacement. However, the trade-off between fluid and fuel will often require the use of food products other than sports drinks to satisfy energy needs and avoid over-drinking when exercise is ≥ 2 h"

For further information: https://doi.org/10.1016/j.jsams.2021.01.004