Dr. Graeme J. Connolly
AUGUSTA, GA – Fluid balance is critical for cardiovascular function, regulation of body temperature, injury prevention, and recovery from activity. A body that is not optimally hydrated cannot perform maximally. In addition, most athletes are going to sweat when the exercise. Therefore, fluid needs are always going to be higher in a physically active individual than in someone who is inactive.
An athlete who loses 2 percent of their weight attributable to water loss will see a decrease in performance- as much as an 8 percent decrease in stamina, speed, and strength. Indeed, the most recent American College of Sports Medicine (ACSM) Position Stand on Exercise and Fluid Replacement discusses the performance and health issues associated with dehydration, including the following:
- Increased heart rate
- Impaired body temperature regulation
- Early-onset fatigue
- Increased perceived effort of exertion
- Decrease in sustained attention
Every liter of sweat loss forces the heart to work harder earlier in an exercise bout or activity session, increasing the likelihood of an athlete fatiguing quicker. In addition to having physiological effects, dehydration can affect psychological functioning. Athletes who are dehydrated will have a reduced attention span and will find it more difficult to remain focused, affecting learning and productivity in a variety of settings – their error rate increases, their task accuracy decreases, and as a result they are more likely to be injured. These effects do not contribute to optimal performance.
What, when, and how much athletes should drink?
All liquids except alcohol count towards the daily fluid requirement. Water, milk, juice, sports drinks, coffee and tea count fully as fluids. Foods that have a high water content, such as fruits and vegetables, can also count as part of the daily food intake. Too often athletes say that they are not getting enough fluid because they drink very little water, so they need to be reminded of other choices.
Some beverage choices are better than others, particularly around the time of exercise. Carbonated beverages are not a good choice because they take too long to leave the stomach. This is also true of fruit juice, highly sugared fruit drinks, as well as energy drinks. The goal of drinking fluid before and during exercise is to move fluid out of the stomach fast so it can get to the muscles. That is why water and sports drinks at the top two choices.
Sports drinks (such as Gatorade and Powerade) are appropriate during exercise, perhaps even more so than water. A sports drink supplies not only liquid but also fuel and electrolytes, especially sodium (salt). Electrolytes, which include sodium, potassium, and chloride help to maintain fluid balance so that an athlete will not dehydrate or overhydrate during exercise. More fluid is absorbed into the muscles from a sports drink than from plain water alone, and again, this provides some fuel to the active muscles as well as to the brain. Athletes who consume sports drinks should be discouraged from diluting these beverages- they are already dilute and are not as effective if they are watered down.
Athletes should abide by the following three general guidelines to hydrate properly before, during, and after exercise.
1. Drink 20 ounces (about 0.6 liters) of fluid one hour before practice or competition.
It takes 60 minutes for 20 ounces of fluid to empty from the stomach and be absorbed by the intestine, so drinking ahead of practice or competition makes sense.
2. Drink 14 to 40 ounces (420ml to 1.2L) of fluid, depending on their sweat rate, per hour of exercise or competition.
A large fluid intake during exercise leads to greater cardiac output, greater skin blood flow, lower core body temperature, and reduced perceived effort of exertion.
3. After exercise, drink 24 ounces (480ml) of fluid for every pound (.45kg) lost during exercise or competition.
Because athletes sweat and most don’t drink enough fluid to replace all the losses that occur while they are active, they are going to need to drink enough after exercise to replenish what was lost. The only way to know how much fluid was lost is to weigh before and after exercise. Note: Be careful not to overdrink after exercise, as taking in too much fluid is just as dangerous as not consuming enough, because it usually results in water overload and potential sodium loss.
In addition to losing fluids, some athletes, called salt losers or salty sweaters, will lose significant amounts of sodium during exercise. These athletes are more likely to experience muscle cramps, their sweat stings their eyes, and they may notice salt on their skin or clothes after exercise. Hyponatremia, or low blood sodium, is becoming more common. It is caused by a combination of excess fluid intake, inadequate sodium intake, and excess sweat sodium losses. A hyponatremic athlete can suffer from headaches, nausea, vomiting, swelling in the extremities, and fatigue. It can be fatal in extreme cases.
Salty sweaters should consider the following tips:
- Consume sports drinks rather than water during exercise
- Add ¼ teaspoon of salt to 20 ounces of a sports drink
- Eat salty foods like crackers, pretzels, pickles, soup and broth
- Drink salty beverages like V8 or tomato juice
In summation, athletes should follow fluid strategies before, during and after exercise. So drink early, often, and enough! This will lead to fewer injuries, less fatigue, better concentration, and sustained level of effort and intensity.