Fluids Before, During and After Exercise
Before Exercise
As an athlete or a frequent exerciser it is essential that you begin your workout with your body in water balance to support maximal performance. If you begin your training session in negative water balance you will likely experience an early onset of fatigue, lack of concentration, and experience a lack of motivation or inability to perform at your best.
Keep in mind the following:
- After a hard workout, it may take 8 to 12 hours to rehydrate.
- The pre-hydration goal is to drink approximately 5 to 7 ml per kg of body weight at least 4 hours prior to exercise. For 145 pound athlete (65.9 kg), this equates to 330ml to 460 ml, roughly 11-15 ounces.
- It is important to hydrate several hours before exercise and not right before as this doesn’t allow enough time to eliminate the excess fluid before starting the workout.
- Some athletes think if they overhydrate prior to exercise than they will not have to hydrate during exercise, however keep in mind the body can only absorb so much.
- Too much fluid results in excessive urination during the race or workout.
- Overhydration can also contribute to low blood sodium and if you continue to aggressively hydrate during exercise, you may be increasing your risk of developing hyponatremia (low blood sodium which can be problematic or fatal in some instances).
- Pre-workout coffee/caffeine not only boosts performance, but can also act as pre-exercise hydration. Rest assured, caffeine, in moderate doses~ 12 ounces of coffee or 200 mg caffeine is unlikely to increase your daily urine output or cause dehydration. So go ahead and enjoy that cup of Joe if desired!
During Exercise
Drinking during exercise is often overlooked by many athletes, even at the professional level. What athletes need to understand is the goal of drinking during exercise is to prevent excessive dehydration, defined as more than a 2 percent body weight loss from a water deficit. You put yourself at great risk for dehydration when working out hard every day. If this is your case, you should add in hydration breaks to make sure fluid levels are up to par and you are not digging a deeper hole.
- Endurance athletes who will be working out or competing for more than 3 hours, should be sure they know their sweat rate to aid in the prevention of declining performance. By knowing your sweat rate this helps to prevent a mismatch between how much fluid you are taking in versus how much you are losing.
- Most athletes see measuring their sweat rate as an inconvenience. Athlete or not it is essential to pay attention to your body and drink accordingly. Do not wait until you are thirsty, at this point it may be too late to play catch up.
- If you know your sweat rate this can help you know how much to drink per hour. For instance a 150 pound man has a sweat rate of about 1 pound per hour at a high intensity, indicating that he needs to drink 16-24 ounces per hour (16 ounces = 1 pound). This is typically broken down to 8 ounces every 15 to 20 minutes. At lower intensities this athlete will likely lose 1/2 pound per hour, indicating that they need about 8 ounces per hour. Knowing your sweat rate will only enhance your performance.
- Keep in mind that a large portion of water lost through sweating comes from the blood plasma, so circulatory capacity progressively decreases as sweat loss progresses. Fluid loss coincides with decreased blood volume, reduced skin blood flow for a given core temperature, reduced stroke volume, increased heart rate, and lastly general deterioration in circulatory and thermoregulatory efficiency in exercise.
- Dehydration also contributes to a decreased gastric emptying rate thus increasing cramps and nausea.
The most common question asked among athletes is what to drink. According to the American College of Sports Medicine (ACSM), the recommended fluid replacer should provide a little sodium to stimulate thirst, potassium to help replace sweat losses, and a little carbohydrate to provide some energy. 110 to 170 milligrams of sodium per 8 ounces, 20 to 50 grams of potassium per 8 ounces, and 12 to 24 grams of carbohydrate per 8 ounces (ACSM 2007). The nutrients can be consumed as standard foods such as saltines, pretzels, bananas, apples as well as engineered foods, which may be more convenient for endurance athletes.
If you are exercising hard for longer than an hour, or less intense exercise for several hours, you greatly benefit from consuming approximately 120 to 240 calories (30 to 60 grams) of carbohydrate per hour along with your fluid intake to help maximize your performance. Carbohydrates, as many of us have been told, help maintain normal blood sugar levels helping you to sustain your energy longer. Sports drinks are a great way to get carbohydrates and fluid. Due to the plethora of sports drinks it is up to you as an athlete to find the one that works best for you.
After Exercise
Rehydrating after exercise is just as important as refueling after exercise. Your goal is to thoroughly replace any fluids and electrolytes lost and how aggressive this process is depends on how fast you need to recover for your next exercise session. If you are significantly dehydrated and need to train again within 12 to 16 hours then you need to be much more aggressive than the recreational athlete who has a few days to rehydrate. Drinking 50 percent more fluid than you lost through sweat will help improve recovery from dehydration. Aim to sip fluids over time rather than all at once as this helps maximize fluid retention and prevents unwanted side effects.
“How do I know how much to drink for recovery”, is a common question asked among athletes. This is where weighing yourself before and after exercise is important. If, after a 2 hour ride oe run, you lose 2 pounds even with “adequate hydration” then you need to consume 16 to 24 ounces of fluid for every pound lost. The amount of recovery fluids may be overwhelming, but keep in mind these fluids can be consumed over time. Foods have to be consumed within 30 to 45 min post exercise with some fluids, but the fluids can be consumed over time. Any fluid will do whether it be milk, water, juice, tea, etc. You will replenish a lot of your electrolytes in the foods you will consume for recovery. If you are craving salt afterwards, don’t take salt tablets, rather go for the food sources such as pretzels, chicken noodle soup, etc as your body will more readily absorb these than the tablets. So after workouts/races be sure to eat, drink, stretch, and get enough sleep!
Reference:
American College of Sports Medicine (ACSM(. 2007. ACSM Position stand on exercise and fluid replacement. Med Sci Sport Exer 39 (2):377-390.