Fluid replacement is an important part of any athletic regimen, but proper hydration is one of the most neglected aspects of the athlete’s diet. Now that podiatrists are active members of the medical teams servicing many types of athletic events (and often act as medical directors and co-directors), it is vital to have a working knowledge of the signs and symptoms of dehydration. Active sports medicine podiatrists should also be able to develop a plan for establishing hydration protocols at sporting events.
When athletes engage in sport, they will lose a percentage of body weight through water loss. When their sweat loss exceeds fluid intake, athletes become dehydrated during activity. Dehydration of 1 to 2 percent of body weight begins to compromise physiologic function and negatively influences performance. Dehydration of greater than 3 percent of body weight further disturbs physiologic function and increases the athlete’s risk of developing heat cramps or heat exhaustion. Loss of 5 percent or more body weight can result in heatstroke.
These levels of dehydration are common in sports and can occur in just an hour of exercise or even more rapidly if the athlete is dehydrated before exercising or participating in a sports activity.
When supervising the medical care of athletes, it is important to recognize the basic signs of dehydration. These include thirst, irritability and general discomfort followed by headache, weakness, dizziness, cramps, chills, heartburn, vomiting, nausea, head or neck heat sensations and decreased performance. Thirst is a notoriously poor indicator of dehydration because it is a delayed response. An athlete can lose over 1.5 liters of body water before becoming thirsty.
The athlete’s level of hydration is influenced by many factors. The energy level or intensity of the sport (e.g., badminton vs. football) is a major factor in how much fluid is lost. If the sport requires helmets and padding, this will increase the amount of perspiration and result in greater fluid loss. Rest breaks and fluid access are important factors that affect hydration. If hydration opportunities are frequent, as in baseball, football and track and field, the athlete can consume smaller volumes of liquid at a convenient pace. In sports such as soccer, lacrosse and distance running, athletes must consume fluids at specific times, making it more difficult to rehydrate.
Another important factor in dehydration is the environment of play. Hot, humid areas and high-pressure altitudes will also influence physiologic response and increase fluid loss. Children involved in sports activities are more susceptible to dehydration and heat illness in hot weather than adult athletes. Therefore, it is necessary to consider the athlete’s age, sport and climate conditions when developing a plan to prevent dehydration.
One should evaluate the hydration status of athletes before starting any rigorous sports activity. Athletes should begin all exercise sessions well hydrated. A recent study found two-thirds of the pediatric athletes evaluated were dehydrated before practice.
There are several ways to approximate hydration status. Assuming the athlete is properly hydrated, pre-exercise body weight should be relatively consistent throughout the entire exercise session. One should determine the percentage difference between the post-exercise body weight and also determine the baseline hydrated body weight. The post-exercise weight should be no more than 2 percent less than the pre-exercise weight.
A simple method to determine hydration status is to compare urine color (from a sample container) with a urine color chart. A light “straw” color (1 or 2) is indicative of being well hydrated while a dark color (5 or 6) represents significant dehydration. Measuring urine specific gravity with a refractometer is less subjective than comparing urine color and can also be used. For color analysis or specific gravity, midstream urine should be collected for consistency and accuracy. Since body weight changes during exercise give the best indication of hydration status, one should determine an athlete’s weight and urine measurement before the exercise session and then determine their weight after exercise to estimate fluid balance.
All athletes participating in sports requiring weight classes such as wrestling or rowing should have their hydration status checked at weigh-in to ensure they are not dehydrated. A urine specific gravity less than or equal to 1.020 or urine color less than or equal to 4 should be the upper range of acceptable on weigh-in. Procedures such as taking diuretics, exercising in rubber suits or in a sauna to reduce body weight can produce dramatic dehydration.
The best way to prevent dehydration is to establish a good hydration protocol for the athletes. Fluid replacement beverages should be easily accessible in individual fluid containers. Individual containers make it easier to monitor the athlete’s fluid intake. The containers should also be marked in 100 ml or in 3- or 4 oz. increments, providing visual reminders to athletes to drink beyond thirst satiation. When it is practical to do so, carrying fluid bottles during exercise encourages greater fluid ingestion.
To ensure proper pre-exercise hydration, the adult athlete should consume approximately 16 to 20 fl. oz. of water or sports drink two to three hours before exercise and 8 to 10 oz. of water or sports drink 10 to 20 minutes before exercise. Adjust fluid intake for children for differences in body weight and physiology (see “Recommendations For Fluid Intake For Children” below). Fluid replacement should approximate sweat and urine losses, and at least maintain hydration at less than 2 percent body weight reduction. This generally requires 8 to 10 fl. oz. every 15 to 20 minutes of rigorous exercise.
Post-exercise hydration should aim to correct any fluid loss resulting from the practice or event. One should ideally complete rehydration within two hours with a fluid that contains water to restore hydration status, carbohydrates to replenish glycogen stores and electrolytes to speed rehydration. The primary goal is the immediate return of physiologic function. When rehydration must be rapid, as in cases where an exercise bout will follow, an athlete should drink about 25 to 50 percent more than sweat losses to assure optimal hydration four to six hours after the event.
The type and temperature of the fluids used in a sporting event are important in the promotion of the rehydration process. This is especially true in events that involve children and adolescents. One should ensure the most palatable beverage possible is available.
Sports drinks appear to outperform water in preventing dehydration, especially in young athletes. A study that offered water, flavored water and a sports drink to active children ages 9 to 12 showed they drank 90 percent more of the sports drink and stayed better hydrated than when drinking plain water. Sports drinks served cold (50º to 59ºF is recommended) have flavor (sweetness) and sodium that encourage athletes to drink more.
When fluids have the correct mixture of carbohydrates and electrolytes, athletes absorb them quicker into the bloodstream and the fluids help refuel muscles and speed rehydration. Carbohydrates also aid in performance by facilitating an increased feel of energy for power and endurance enhancement. Though carbohydrate concentrations greater than 8 percent increase the rate of carbohydrate delivered to the body, they compromise the rate of fluid emptying from the stomach and absorbed from the intestine.
Fruit juices, carbohydrate gels, soda and sports drinks that have carbohydrate concentrations greater than 8 percent are therefore not recommended during an exercise session as the sole beverage. Most carbohydrate forms such as glucose, sucrose and glucose polymers are suitable and the absorption rate is maximized when multiple forms are consumed simultaneously. Fructose ingestion should be limited since it may cause gastrointestinal distress.
Substances to be avoided include caffeine and alcohol, which increase urine output and reduce fluid retention, and carbonated beverages, which reduce voluntary fluid intake due to stomach fullness.
Consider adding sodium chloride to fluid replacement beverages for physical activity exceeding four hours or during the initial days of hot weather. This can offset the salt loss in sweat and minimize the medical problems associated with electrolyte imbalances such as muscle cramps and hyponatremia. Hyponatremia has been associated in sporting events with overhydration, both orally and IV, with hypotonic (relative to sweat) solutions. There have been reported cases in which individuals had been overhydrated with as much as 6 to 7 liters of free water. Given this, providing hydration beverages that contain a small amount of salt would be desirable and should cause no harm.
Dr. Caselli (pictured) is a staff podiatrist at the VA Hudson Valley Health Care System in Montrose, N.Y. He is also an Adjunct Professor at the New York College of Podiatric Medicine and a Fellow of the American College of Sports Medicine.
Dr. Brummer is in private practice with the Metropolitan Foot Group, New York City. He is an Associate of the American College of Foot and Ankle Surgeons.
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