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The Physiology of Hydration, and When to Use Sports Drinks,
Sports drinks, electrolyte drinks, plain water — have you ever wondered which of these to use, when, and why? Well, you’re not alone. When trying to understand what will hydrate you best, it helps to have a basic understanding of the physiology of hydration and the critical role that fluids and electrolytes play in keeping you hydrated and performing at your best.
Hydration is your coolant system
Your body operates best within a fairly narrow internal or core temperature range. When you are at rest in a comfortable environment, the conditions are perfect for optimal function. But, walk outside in the blazing sun, and you’ll make a beeline toward shade. Open the front door in the dead of winter, and you’ll immediately grab a coat. These instinctive reactions occur because your body inherently knows that it operates most effectively when it’s not too hot or too cold.
The same principle applies when you train or compete. During exercise, your muscles generate heat. This heat boosts your core temperature. If that temperature rise isn’t effectively blunted, you can overheat, and exercise will come to a grinding halt. Fortunately, you have a well-designed system for keeping your core body temperature in check. The most critical component of this cooling system is the water found within and between your cells and tissues. This shouldn’t come as too much of a surprise: Water is far and away your primary internal ingredient. In fact, the typical 150-pound (68-kg) athlete is packing a solid 90 pounds (41 kg) of the wet stuff — equivalent to 41 1-liter bottles of fluid!
With all that fluid around, you may not think that running short a few liters or quarts here or there would be a problem. But in fact, fluid balance is incredibly important to how well you function, and that includes how well you function when training or competing. A testament to the importance of fluid balance to physiologic function is the fact that even when you’re resting in very comfortable conditions in which you’re not sweating at all, your body maintains a near-constant fluid balance that only fluctuates up or down by a few fluid ounces.
Leaks in the system
You’re constantly losing fluids. The obvious routes are through urination and sweating, but you can also lose fluids through your skin, every time you exhale, and when you excrete solid waste. However, while fluids are leaking out continuously, you’re also spontaneously taking in fluids, such as with meals and snacks. If fluid loss starts to seriously outpace fluid intake, you have a backup system. Fluid balance is maintained by receptors in your brain that monitor the concentration of dissolved particles in the bloodstream and receptors in the circulatory system that monitor blood pressure. These receptors pick up on fluid imbalances; then, in response, your kidneys receive a message to begin conserving water and electrolytes, and you quickly start to feel thirsty and begin to search out something to drink. If you happen to consume too much fluid, the receptors again detect the imbalance and send a signal to the kidneys to eliminate the extra fluid through the formation of urine.
It’s a complex and intricate system that works well to maintain fluid balance over the course of 24 hours. But, all bets are off during those acute periods when you’re training or competing, especially in hot or humid conditions. In these more severe conditions, what was once a small leak in the system can become a comparative gusher. You typically lose 1 to 2 liters (about 1 to 2 quarts) of fluid per hour as sweat when training or competing, and you may even be one of those who sweat at the rate of 3 liters (about 3 quarts) or more per hour. With sweat literally dripping off your body, it’s simply too much, too fast. Your body tries desperately to compensate by decreasing urine production, but your thirst mechanism isn’t nearly sensitive enough, and you end up out of fluid balance — in other words, dehydrated.
What’s a little dehydration, you ask? Well, do you remember your number-one ingredient? It’s water, and that fluid is present because you operate best with plenty of it. Suffer a fluid deficit of just 1% of your total body weight — that’s about 680 ml, or just less than 3 cups of fluid for a 150-pound (68-kg) athlete — and your ability to train or compete can already start to suffer. Lose 2% of your total body weight due to sweating, and you’ve officially joined the ranks of the dehydrated, suffering measurable performance-robbing consequences. These ill effects can include higher heart rate, slower reaction time, decreased coordination, impaired concentration, and a greater perceived sense of the difficulty of the exercise or activity you are doing.
The bottom line is, if you’re dehydrated, you’re not as sharp mentally or physically, and so you won’t be training or competing at your best.
How to derail dehydration
You can head off dehydration and its baggage by replacing those lost fluids as you exercise. Don’t wait until you’re thirsty. By the time you start to feel thirsty, it’s too late — you’re already well on your way to dehydration. Instead of relying on thirst, rely on a hydration plan. The perfect plan is to consume fluids at or near the rate at which you are sweating them out of your body. That’s the consensus recommendation of organizations like the American College of Sports Medicine. PowerBar® makes it easy for you to determine your sweat rate and to develop a hydration plan specific to your hydration needs with the POWERBAR® Sweat Rate Calculator.
What type of fluid is best?
So, consuming fluids is critical to achieving fluid balance and optimal performance during exercise. The obvious next question is, what kind of fluids? Here is where applying some physiology basics can pay off.
Let’s start by addressing good old plain water. No doubt the stuff is incredibly thirst-quenching, but in many cases, it’s not your best choice for rehydrating. The reason is that it lacks electrolytes — most importantly, the specific electrolyte sodium. Electrolytes are dissolved minerals found in cells and in the fluids between your cells. In the same way that fluid balance is tightly regulated, electrolyte balance in and between cells is also under strict control. When you’re in electrolyte balance, nerve impulses and muscle contractions occur as intended. But, when electrolyte concentrations in the blood are out of kilter, cell function deteriorates, physiologic function suffers, and athletic performance is impaired.
One of the factors that can bring about an electrolyte imbalance is a large volume of fluid loss due to sweating. So far, we have focused on sweat as fluid, but sweat also contains electrolytes such as sodium, potassium, calcium, and magnesium. Of all these electrolytes, sodium is present in the greatest abundance in sweat, and, along with chloride, forms salt. This is why, after a long exercise session in the heat, you’ll often find a powdery-thin layer of white crystals caked on your skin, sunglasses, or hat. These powdery crystals are salt left over from the sweat that’s evaporated from your skin.
Because sodium is present in high concentration in sweat, it needs to be replaced during exercise when you’re losing large volumes of fluids. Replacement of potassium, calcium, and magnesium doesn’t demand the same urgency because these electrolytes are present in much lower amounts in sweat, and their losses can be easily replaced after exercise through meals and snacks.
Sodium losses vary greatly from individual to individual, and can change as your training progresses. This can range anywhere form 460 to 1840 mg sodium lost per liter of sweat. Frequently you will see a range of 500 to 1000 mg per hour as a starting point to gage sodium intake per hour for more intense endurance events, even though there is no exact intake of sodium to recommend during exercise. Instead, make sure that your sports drink and energy gels contain substantial quantities of sodium. As a point of reference, POWERBAR® Endurance sports drink provides 400 mg of sodium and 42.5 g carbs in 20 fl oz.(600 ml) POWERBAR® Gels provide 200 mg sodium and 27-28 g carbs in each packet, and POWERBAR® Electrolyte drink mix provides 260 mg per 16.9 ounce (500 ml) serving, with 2 grams of carbs. The sports drink and gel-water combination is designed so that they can be substituted for each other during training and competitions, without sacrificing sodium or carbohydrate intake. Electrolytes drink mix provides a low calorie option, when carbs are not required or are obtained through other sources.
Back to plain water. It’s great as a thirst quencher because it’s rapidly absorbed into the bloodstream. However, absent any significant sodium, a sudden influx of fluids can dilute the sodium concentration in your blood. The receptors in your brain then erroneously interpret this dilution effect as a sign that you’re now fully rehydrated. Thus, your brain sends out a message to suppress your drive to drink, yet, in reality, you’ve not met your fluid or electrolyte needs. Your athletic performance can suffer as a consequence.
By consuming a sodium-containing electrolyte drink or sports drink, you’re not just flooding your system with plain water. You’re giving back more of what your body is losing — fluids and electrolytes — and helping to avoid the dilution effect. Therefore, your drive to drink fluid is maintained. So, consuming a sodium-containing sports or electrolyte drink during exercise can help your body to better gauge your true fluid needs.
Another distinct advantage of sports or electrolyte drinks over plain water is the fact that they’re flavored. Studies show that when athletes are offered the choice of plain water or a flavored beverage, they consume more of the flavored fluids.
Finally, the diluted carbohydrate concentration in a sports drink can actually help to promote fluid absorption from the digestive tract. As the carbohydrates are transported into cells, water follows along as well. So, this is an extra advantage that a carbohydrate-containing sports drink can offer.
Putting the physiology into practice
With the physiology basics covered, you can now put all of this information into practice when choosing your hydration strategy:
If you’re training or competing for less than an hour per day in comfortable conditions, fluid and electrolyte losses from sweat may not be that high, and so you can probably get away with consuming plain water during exercise.
If conditions are hot or humid, or you’re training or competing for 60 minutes or more, you’ll probably be losing a substantial volume of fluids and sodium in the form of sweat. In this situation, a sodium-containing electrolyte or sports drink is a better hydration option. Use an electrolyte drink if the intensity and duration of your exercise doesn’t require refueling, and opt for the carbohydrate- and sodium-containing sports drink if you need to be refueling while you rehydrate.
It’s not an all-or-none proposition when it comes to choosing rehydration options. With the advent of the electrolyte drink, many endurance athletes switch off between a sports bottle with an electrolyte drink and one with a carbohydrate- and sodium-containing sports drink.
Finally, to rehydrate between or after workouts, select the appropriate beverage based on the volume of fluid losses during exercise, as well as the need for carbohydrate and protein for recovery. For short workouts in moderate conditions, rehydrating with water is probably fine. But, for workouts where fluid and sodium losses are heavy, make sure you take in sodium along with your fluids.
By attending to your fluid and electrolyte balances during and after exercise, you can hydrate more effectively. That translates to better workouts and stronger performances.
Sports drinks, electrolyte drinks, plain water — have you ever wondered which of these to use, when, and why? Well, you’re not alone. When trying to understand what will hydrate you best, it helps to have a basic understanding of the physiology of hydration and the critical role that fluids and electrolytes play in keeping you hydrated and performing at your best.
Hydration is your coolant system
Your body operates best within a fairly narrow internal or core temperature range. When you are at rest in a comfortable environment, the conditions are perfect for optimal function. But, walk outside in the blazing sun, and you’ll make a beeline toward shade. Open the front door in the dead of winter, and you’ll immediately grab a coat. These instinctive reactions occur because your body inherently knows that it operates most effectively when it’s not too hot or too cold.
The same principle applies when you train or compete. During exercise, your muscles generate heat. This heat boosts your core temperature. If that temperature rise isn’t effectively blunted, you can overheat, and exercise will come to a grinding halt. Fortunately, you have a well-designed system for keeping your core body temperature in check. The most critical component of this cooling system is the water found within and between your cells and tissues. This shouldn’t come as too much of a surprise: Water is far and away your primary internal ingredient. In fact, the typical 150-pound (68-kg) athlete is packing a solid 90 pounds (41 kg) of the wet stuff — equivalent to 41 1-liter bottles of fluid!
With all that fluid around, you may not think that running short a few liters or quarts here or there would be a problem. But in fact, fluid balance is incredibly important to how well you function, and that includes how well you function when training or competing. A testament to the importance of fluid balance to physiologic function is the fact that even when you’re resting in very comfortable conditions in which you’re not sweating at all, your body maintains a near-constant fluid balance that only fluctuates up or down by a few fluid ounces.
Leaks in the system
You’re constantly losing fluids. The obvious routes are through urination and sweating, but you can also lose fluids through your skin, every time you exhale, and when you excrete solid waste. However, while fluids are leaking out continuously, you’re also spontaneously taking in fluids, such as with meals and snacks. If fluid loss starts to seriously outpace fluid intake, you have a backup system. Fluid balance is maintained by receptors in your brain that monitor the concentration of dissolved particles in the bloodstream and receptors in the circulatory system that monitor blood pressure. These receptors pick up on fluid imbalances; then, in response, your kidneys receive a message to begin conserving water and electrolytes, and you quickly start to feel thirsty and begin to search out something to drink. If you happen to consume too much fluid, the receptors again detect the imbalance and send a signal to the kidneys to eliminate the extra fluid through the formation of urine.
It’s a complex and intricate system that works well to maintain fluid balance over the course of 24 hours. But, all bets are off during those acute periods when you’re training or competing, especially in hot or humid conditions. In these more severe conditions, what was once a small leak in the system can become a comparative gusher. You typically lose 1 to 2 liters (about 1 to 2 quarts) of fluid per hour as sweat when training or competing, and you may even be one of those who sweat at the rate of 3 liters (about 3 quarts) or more per hour. With sweat literally dripping off your body, it’s simply too much, too fast. Your body tries desperately to compensate by decreasing urine production, but your thirst mechanism isn’t nearly sensitive enough, and you end up out of fluid balance — in other words, dehydrated.
What’s a little dehydration, you ask? Well, do you remember your number-one ingredient? It’s water, and that fluid is present because you operate best with plenty of it. Suffer a fluid deficit of just 1% of your total body weight — that’s about 680 ml, or just less than 3 cups of fluid for a 150-pound (68-kg) athlete — and your ability to train or compete can already start to suffer. Lose 2% of your total body weight due to sweating, and you’ve officially joined the ranks of the dehydrated, suffering measurable performance-robbing consequences. These ill effects can include higher heart rate, slower reaction time, decreased coordination, impaired concentration, and a greater perceived sense of the difficulty of the exercise or activity you are doing.
The bottom line is, if you’re dehydrated, you’re not as sharp mentally or physically, and so you won’t be training or competing at your best.
How to derail dehydration
You can head off dehydration and its baggage by replacing those lost fluids as you exercise. Don’t wait until you’re thirsty. By the time you start to feel thirsty, it’s too late — you’re already well on your way to dehydration. Instead of relying on thirst, rely on a hydration plan. The perfect plan is to consume fluids at or near the rate at which you are sweating them out of your body. That’s the consensus recommendation of organizations like the American College of Sports Medicine. PowerBar® makes it easy for you to determine your sweat rate and to develop a hydration plan specific to your hydration needs with the POWERBAR® Sweat Rate Calculator.
What type of fluid is best?
So, consuming fluids is critical to achieving fluid balance and optimal performance during exercise. The obvious next question is, what kind of fluids? Here is where applying some physiology basics can pay off.
Let’s start by addressing good old plain water. No doubt the stuff is incredibly thirst-quenching, but in many cases, it’s not your best choice for rehydrating. The reason is that it lacks electrolytes — most importantly, the specific electrolyte sodium. Electrolytes are dissolved minerals found in cells and in the fluids between your cells. In the same way that fluid balance is tightly regulated, electrolyte balance in and between cells is also under strict control. When you’re in electrolyte balance, nerve impulses and muscle contractions occur as intended. But, when electrolyte concentrations in the blood are out of kilter, cell function deteriorates, physiologic function suffers, and athletic performance is impaired.
One of the factors that can bring about an electrolyte imbalance is a large volume of fluid loss due to sweating. So far, we have focused on sweat as fluid, but sweat also contains electrolytes such as sodium, potassium, calcium, and magnesium. Of all these electrolytes, sodium is present in the greatest abundance in sweat, and, along with chloride, forms salt. This is why, after a long exercise session in the heat, you’ll often find a powdery-thin layer of white crystals caked on your skin, sunglasses, or hat. These powdery crystals are salt left over from the sweat that’s evaporated from your skin.
Because sodium is present in high concentration in sweat, it needs to be replaced during exercise when you’re losing large volumes of fluids. Replacement of potassium, calcium, and magnesium doesn’t demand the same urgency because these electrolytes are present in much lower amounts in sweat, and their losses can be easily replaced after exercise through meals and snacks.
Sodium losses vary greatly from individual to individual, and can change as your training progresses. This can range anywhere form 460 to 1840 mg sodium lost per liter of sweat. Frequently you will see a range of 500 to 1000 mg per hour as a starting point to gage sodium intake per hour for more intense endurance events, even though there is no exact intake of sodium to recommend during exercise. Instead, make sure that your sports drink and energy gels contain substantial quantities of sodium. As a point of reference, POWERBAR® Endurance sports drink provides 400 mg of sodium and 42.5 g carbs in 20 fl oz.(600 ml) POWERBAR® Gels provide 200 mg sodium and 27-28 g carbs in each packet, and POWERBAR® Electrolyte drink mix provides 260 mg per 16.9 ounce (500 ml) serving, with 2 grams of carbs. The sports drink and gel-water combination is designed so that they can be substituted for each other during training and competitions, without sacrificing sodium or carbohydrate intake. Electrolytes drink mix provides a low calorie option, when carbs are not required or are obtained through other sources.
Back to plain water. It’s great as a thirst quencher because it’s rapidly absorbed into the bloodstream. However, absent any significant sodium, a sudden influx of fluids can dilute the sodium concentration in your blood. The receptors in your brain then erroneously interpret this dilution effect as a sign that you’re now fully rehydrated. Thus, your brain sends out a message to suppress your drive to drink, yet, in reality, you’ve not met your fluid or electrolyte needs. Your athletic performance can suffer as a consequence.
By consuming a sodium-containing electrolyte drink or sports drink, you’re not just flooding your system with plain water. You’re giving back more of what your body is losing — fluids and electrolytes — and helping to avoid the dilution effect. Therefore, your drive to drink fluid is maintained. So, consuming a sodium-containing sports or electrolyte drink during exercise can help your body to better gauge your true fluid needs.
Another distinct advantage of sports or electrolyte drinks over plain water is the fact that they’re flavored. Studies show that when athletes are offered the choice of plain water or a flavored beverage, they consume more of the flavored fluids.
Finally, the diluted carbohydrate concentration in a sports drink can actually help to promote fluid absorption from the digestive tract. As the carbohydrates are transported into cells, water follows along as well. So, this is an extra advantage that a carbohydrate-containing sports drink can offer.
Putting the physiology into practice
With the physiology basics covered, you can now put all of this information into practice when choosing your hydration strategy:
If you’re training or competing for less than an hour per day in comfortable conditions, fluid and electrolyte losses from sweat may not be that high, and so you can probably get away with consuming plain water during exercise.
If conditions are hot or humid, or you’re training or competing for 60 minutes or more, you’ll probably be losing a substantial volume of fluids and sodium in the form of sweat. In this situation, a sodium-containing electrolyte or sports drink is a better hydration option. Use an electrolyte drink if the intensity and duration of your exercise doesn’t require refueling, and opt for the carbohydrate- and sodium-containing sports drink if you need to be refueling while you rehydrate.
It’s not an all-or-none proposition when it comes to choosing rehydration options. With the advent of the electrolyte drink, many endurance athletes switch off between a sports bottle with an electrolyte drink and one with a carbohydrate- and sodium-containing sports drink.
Finally, to rehydrate between or after workouts, select the appropriate beverage based on the volume of fluid losses during exercise, as well as the need for carbohydrate and protein for recovery. For short workouts in moderate conditions, rehydrating with water is probably fine. But, for workouts where fluid and sodium losses are heavy, make sure you take in sodium along with your fluids.
By attending to your fluid and electrolyte balances during and after exercise, you can hydrate more effectively. That translates to better workouts and stronger performances.