One of the most controversial topics in sports medicine is the role of hydration for athlete safety. There is no argument that health is far more important than performance, and the current science of hydration in sport indicates that professionals should not overlook confounding risks to athlete health outside of consuming water and sports drinks. Cramps, heat stroke, athlete sudden death, and even supplementation are all discussion points brought up when dehydration is a possible contributor. In this Academy Guide, we outline the big picture and review both the science and thought leadership on a very conflicting subject. In addition to the monitoring of hydration, we cover the necessary groundwork for applying recommendations that align with the ethical side of sport beyond performance.

Defining Dehydration and Measuring Hydration

The optimal hydration state is a difficult designation, as the scientific literature debates what is normal in health and wellness, and what is potentially problematic in sport. Technically, hydration refers to the water content of a human, but due to its overlap with nutritional needs, electrolytes and sometimes carbohydrates are included. Currently, a wide range of measures of determining hydration are available, but there is no consensus as to which measurements are ideal for athletes. Analog ratings of urine color and thirst, body mass, measures of urine concentration, and blood do provide value, but the identification of an optimal hydration state (euhydration) is far from perfect. In addition to water loss from exercise, sweat rate and composition play a part in fluid intake strategies because daily electrolyte maintenance is important.

Body mass is likely the most practical assessment of water loss during intense training and competition. Due to the need to weigh the athlete nude, privacy issues come into play, but you can make modifications to the weigh-in and weigh-out protocols to ensure athletes are comfortable and the data is accurate. The use of body mass changes or thresholds is also common in the scientific research, so adopting a similar approach is practical for monitoring and supporting athletes. Athletes can towel dry and use identical underwear to provide a reliable body mass change, as the absolute numbers are not as important as the actual change in the entire weight of the player monitored. Connecting weight tracking with hydration metrics streamlines the monitoring process.



As of today, several wearable hydration companies have attempted to monitor consumer hydration, but their systems are not validated for extreme environments with intense training. As they improve, they should gather data that is interchangeable with body mass and other physiological metrics beyond water content of the body. Individual sweat composition profiles require custom support post training for both health and recovery.

“Individual sweat composition profiles require custom support training for both health and recovery.”CLICK TO TWEET

Sweat Profiles and Environmental Conditions

Every athlete has a unique physiology, sweat rate, and sweat composition. In addition to the athlete’s pattern of sweating, environmental conditions and attire will contribute to dehydration. An athlete competing outdoors, such as in soccer, has a higher probability of dehydration than in indoor sports that are intermittent, such as basketball. Therefore, it’s important to monitor and prepare for environmental conditions, as those variables determine drinking rates. It’s necessary to know that cumulative sweat loss is not the same as sweat rate. Using independent measurements to plan and log environmental conditions live is essential for both the accuracy of the data and the legal requirements of protecting an athlete.

“Hydration plays an important role in athlete performance and well-being, but it can’t be isolated into oversimplified suggestions such as how much water to drink based on athlete weight only.”CLICK TO TWEET

Sweat composition, which is mainly sodium loss, is a factor with intense training. While the research is unclear as to the severity of sodium imbalance, athletes should not be exposed to chronic training with an electrolyte imbalance. Other minerals such as calcium, magnesium, and potassium are more stable in the body, but should be replenished with dietary interventions. Generally, most athletes can consume enough electrolytes from typical diets, but athletes are at risk when low sodium intake occurs, as fruits and vegetables are poor options. Thus, registered dieticians familiar with athlete training should be heavily involved.

Humidity and altitude are factors that you should monitor and make adjustments for. Dry heat can be an issue because athletes tend not to notice sweating, so all environmental conditions should be viewed as risk factors to poor hydration. Cold environments are deceptive, as the athlete will usually drink less subconsciously and their attire may increase their body temperature beyond expectations. Cold conditions usually reduce the risk of overheating, but you should monitor athletes regardless of risk as all conditions play a role in hydration.

Maintaining Hydration During Competition and Training

Fluid intake depends on the athlete’s size, work rate, and environmental conditions. A large NFL athlete such as a lineman in Florida during the pre-season will have an entirely different strategy than a professional baseball player during a championship game in Ohio in October. Changing and modifying drinking strategies is necessary to reduce the small risk of hyponatremia, as overdrinking can occur when an athlete is encouraged to drink too much based on unnecessary hydration strategies. This can happen when an athlete chronically drinks only water and their electrolyte consumption is low, and is more common with athletes who have strict diets that are low in sodium.

1. Support staff should encourage the eating of foods, such as fruits and vegetables, that have high water content. While fluids are an obvious solution, athletes need to see how an entire diet facilitates hydration.

2. All staff should be educated and involved in the hydration process. Do not reduce hydration to the athlete’s responsibility or an athletic training requirement.

3. Athlete education is a priority, but compliance should be monitored with hydration testing or evaluation on either a daily basis or during periods of time that are high risk.

4. The thirst mechanism is unreliable, but you should encourage athletes to drink to their liking and not restrict them unless a real risk of hyperhydration exists. The probability of an athlete consuming more water than they lose during intense training is low, but monitoring is suggested.

5. Beverages, whether specific to sport or modified for athletes, should be palatable and encourage drinking. In addition to hydration, it may be necessary to provide carbohydrates if the training or competitive periods are longer than an hour.

6. Coaches should be instructed to plan time periods for hydration breaks and rest. Continual training without water is a technique currently being experimented with, but in team sports it’s recommended that breaks are purposely scheduled.

7. Athletes should have access to properly cleaned and sanitized water bottles if used, as the risk of illnesses such as mononucleosis or the common cold increases when resources are inadequate.

These strategies are designed to facilitate fluid intake, but are far from perfect because athletes cannot always drink on command and they often spend a lot of their time away from the facility or arena.

Cramping and the Influence of Neuromuscular Fatigue

Exercise-associated muscle cramps (EAMC) are not necessarily hydration errors, but more often symptoms of athletes being overloaded from fatigue or exertion. While hydration may interact with fatigue and cramping indirectly, the cramping is not from electrolyte imbalance or lower blood viscosity. Based on the scientific literature, cramping is connected to athlete fatigue and remedies such as sports drinks and other options are simply unproven. Researchers have narrowed the cause of cramping to three variables: neuromuscular control, dehydration, and electrolyte depletion. Clearly, the research is not yet conclusive, but generally the risks of cramping stem from high intensity and fatigue of the neuromuscular system.

Intervention studies demonstrated that static stretching improves muscle function and return to play, thus calling the dehydration or electrolyte depletion theories into question. What remains a mystery is how all of the environmental and perceptual factors interact with hydration and cramping rates. Down the road, more research on the role of hydration with the recovery of both local and perceptual fatigue is needed. New science may help support staff understand what protocols elicit the best responses to both preventative measures to dehydration and what facilitates recovery of athletes.

Monitoring Hydration and Recovery

Repeated measurements done at a high frequency transform testing into optimal monitoring. Monitoring hydration is still relevant, even with the new research on exercise-associated muscle cramps and conflicting data on athlete health and performance. It is known that athletes who are dehydrated in team sport tend to have poor subjective responses to training loads and power drops based on the magnitude of dehydration. Endurance-based sports tend to fare differently, mainly because athlete body mass decreases as hydration levels decrease, cancelling out power losses. Therefore, even if the trade-off is advantageous in extended duration events, support staff guiding athletes who require repeated anaerobic work should reconsider the favorable shift in the power-to-weight ratio and maintain hydration.

“Monitoring player weight is a straightforward and effective way to prescribe the interventions post training or post competition”CLICK TO TWEET

Monitoring player weight is a straightforward and effective way to prescribe the interventions post training or post competition, but strategic hydration before and during those activities is recommended. Compliance with both the programmed drinking and monitoring of body weight determines the success of proper hydration. Successful programs utilize team dashboards to monitor group hydration on a macro scale.

Current and Future Recommendations

Recommending proper guidelines for hydration is a scientific, political, and legal challenge. Due to the lag time between current research and legal requirements in sport, it’s important to be aware of the risks associated with not adhering to best practices in sports medicine. Each league, as well as each country, should have proper recommendations for hydration before, during, and after training or competition. Adhering to those guidelines ensures athletes are safe, performance is optimized, and recovery is facilitated.

In addition to hydration, overall fatigue monitoring and cardiac screening are recommended to protect athletes from possible risk due to a vascular or electrically caused event. Other pathological factors contribute to risk, such as sickle cell anemia, pulmonary diseases, and diabetes. Hydration plays an important role in athlete performance and well-being, but it can’t be isolated into oversimplified suggestions such as how much water to drink based on athlete weight only. Pragmatic solutions are excellent ways to ensure athletes are protected from unnecessary risks in sport.

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