This approach will allow you to build up an initial picture of what different levels of carbohydrate intake are doing to your ability to perform and to your stomach. Whilst there are some inter-individual differences in the amount of carbs that are needed to sustain performance, there seems to be relatively less intra-individual variance.

Optimal carb intake is reasonably stable once you dial it in, but fluid loss via sweating is significantly more volatile, both between and within individuals. So, hydration requirements can be lot more variable too in no small part due to the huge role that environmental conditions and clothing can have on sweat rates.

Image Credit: Dale Travers ©. One sensible way to approach this issue is to start at the edges and to work inwards by beginning with the lowest amount of fluid intake needed For activities of less than ~60 minutes and even up to 90 minutes in some cases , fluid intake of close to zero is definitely an option if an athlete starts well hydrated and has plenty of access to drinks to top up again afterwards.

This is certainly true in colder conditions when sweat rates are blunted because core body temperature is much easier to manage. When you get into the zone of hours and in hotter and more humid conditions , fluid intake definitely starts to be required to maintain optimal output when you're going as hard as possible.

Without it, sweat losses can result in a decrease in blood volume that manifests in cardiovascular strain and a reduction in performance. It's true that a more structured approach to drinking might be beneficial for this kind of duration in certain situations e.

In these cases, some experimentation starting around ~ml ~16oz per hour and adjusting up or downwards from there as necessary is sensible. For much longer sessions and races i. Whilst that sounds like and is!

a very wide range, it's fair to say that for a large majority of athletes something in the range of mlml ~oz per hour is a decent zone in which to start some experimentation.

And be more aggressive if you have a big sweat rate see this article for details on how to measure your sweat rate or if the conditions are very hot or humid. Be very mindful that hyponatremia is a real risk if you significantly overdrink. This article is a useful resource to look at to understand the topic in more detail.

Image Credit: Jake Baggaley ©. Whilst having a flexible drinking plan and understanding your own requirements is a big part of the process, it's clear that the very best athletes become highly attuned to their own needs and manage intake very dynamically in longer endurance events.

This inevitably leads to the best outcomes when you become skilled at it and there's no real substitute for building up a large database of experience to get to this point. This article describes in detail how pro IRONMAN athlete Allan Hovda has been measuring his own data and is starting to reap the benefits.

For shorter activities under about minutes in duration , it's highly unlikely that even the heaviest, saltiest sweaters need to worry about sodium replacement too much in the context of a single session anyway. When you get to durations of hours at a high intensity and in conditions that drive high sweat rates, sodium replacement can start to be important, especially for those with heavy losses.

So, this is the kind of range to start experimenting in. When stepping up to the really long stuff hours plus the differences in sodium loss really starts to tell and there's potentially quite a large divergence between people who still require very little exogenous sodium input to those whose intake levels need to be very high indeed.

That's based on me having both a high sweat rate 1. Image Credit: dryrobe ©. No decent exploration of hydration and nutrition intake for endurance athletes should gloss over the impact that pacing has on the equation. It gets confusing because going too hard especially in the heat can lead to dramatically reduced blood flow to the gut this is reduced significantly during exercise of any level, but especially if you push too hard and can mean that you're unable to absorb calories and fluids at rates that you could normally tolerate.

The result is a bloated, uncomfortable stomach and it can become unclear whether this is the cause of a slow down or the other way around.

To that end, it's always worth employing a conservative pacing strategy i. Image Credit: Phil Hill ©. Whilst this is not a particularly difficult process per se, it's one that requires trial, error and iteration to work out the ranges of each element that work for you at various durations, intensities and in environmental conditions.

There's a strong interplay between these 3 key factors that adds a potential layer of complexity to the process — if you get 1 or 2 of them way out of whack it can affect the absorption of the others.

If you knuckle down and learn how to pull the levers effectively for yourself, it's a very straightforward way to start to make a positive impact on your performance. Andy Blow is a Sports Scientist with a BSc Honours degree in Sports and Exercise Science from the University of Bath.

An expert in hydration, he has co-authored a number of scientific studies and books. Things like: How long is the program? How Hydration Affects Performance.

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Wall Justin Price Billie Frances Amanda Vogel. This interference, in turn, negatively affects both performance and recovery. Fluid helps to regulate blood pressure. Effectively regulated blood pressure normalizes heart rate and, therefore, manages stress on the body during training and recovery.

Excessive stress can lead to inflammation and other processes that can interfere with both performance and recovery. Fluid helps in the movement and transport of essential energy nutrients.

Essential macronutrients such as carbohydrate, protein, fats and supporting nutrients that are used as energy for the body are all transported by fluid in the body. In addition, fluids help to remove the metabolic waste that is produced during intense exercise.

Consider exercise intensity and duration, breaks and sweat rates as well as these recommendations from ACE on how to maintain optimal hydration: Pre-workout Drink 17 to 20 fl oz of water two to three hours before exercise Drink 8 fl oz of fluid 20 to 30 minutes before exercise During workout Drink 7 to 10 ounces of fluid every 10 to 20 minutes during exercise Post-workout Drink an additional 8 ounces of fluid 30 minutes after exercise Drink 16 to 24 ounces of fluid for every pound of body weight lost during exercise As with meal plans , a hydration protocol should be consistently followed for best results.

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Backes TP, Fitzgerald K. Fluid consumption, exercise, and cognitive performance. Biol Sport. Savoie FA, Kenefick RW, Ely BR, Cheuvront SN, Goulet EDB. Effect of hypohydration on muscle endurance, strength, anaerobic power and capacity and vertical jumping ability: a meta-analysis.

Sports Med. Drozdowska A, Falkenstein M, Jendrusch G, et al. European Hydration Institute. Forootan M, Bagheri N, Darvishi M. Chronic constipation: A review of literature.

org, Fit Facts, Healthy Hydration ,. gov, Water and nutrition basics ,. By Rachel MacPherson, BA, CPT Rachel MacPherson is a health writer, certified personal trainer, and exercise nutrition coach based in Halifax.

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Table of Contents. Helps With Weight Balance. Supports Healthy Skin. Increases Aerobic Capacity. Enhances Power and Strength. Boosts Cognition. Improves Digestion. Frequently Asked Questions. It also results in constriction of blood vessels to maintain blood pressure and elicits feelings of thirst, inducing fluid intake.

In conjunction, pressure-sensitive receptors in blood vessels called baroreceptors sense the decreased blood volume and respond by triggering the release of aldosterone, a corticosteroid. When blood osmolality decreases or there is a large influx of water from the small intestine, AVP drops, thirst disappears, and the kidneys produce a greater volume of dilute urine.

While occasional mild hypohydration is not a problem, being chronically dehydrated may be a threat to long-term health and well-being. Low TBW keeps the RAAS in a constant state of activity, with high circulating levels of the hormone cortisol.

In terms of exercise, fluid is important not just for aerobic performance but also for maintaining optimum muscle tissue. Dehydration leads to increased production of urea a crystalline compound in urine , suggesting that water deprivation is accompanied by body tissue catabolism breakdown.

Also check out: Monitoring Hydration Levels. There is evidence that those with persistently low body water are at higher risk of serious chronic conditions, including type 2 diabetes, kidney disease and metabolic syndrome abdominal obesity, insulin resistance, hypertension and persistent inflammation.

AVP apparently alters liver glucose production and its breakdown of stored glycogen, while also impairing insulin secretion and insulin sensitivity Qian In people diagnosed with type 2 diabetes, low TBW deteriorates glucose regulation. Diabetes is already a challenge to TBW because excess glucose in the blood acts as an osmolyte, pulling water from cells to counteract the higher osmotic pressure in the ECF.

The kidney glucose transporters become saturated, so glucose is lost in the urine, pulling excess water with it. Thus, the water never gets to the ICF, where the thirst was triggered—hence, the diabetes symptoms of excessive thirst triggered by cellular dehydration and large volumes of urine following glucose loss in the urine.

Although it may seem counterintuitive given the excessive urine production , restricting water will only exacerbate the problem for people with diabetes. Blood glucose clearly needs to be controlled, but optimal hydration will help the body better manage the condition overall.

A broad range of other diseases are also associated with markers of hypohydration: heart failure, vascular dementia, cognitive impairment, inflammatory bowel disease, cancer and premature mortality Lang et al.

Obviously, many of these illnesses are multifactorial, and association is not causation. These recommendations are lower than those from the National Academy of Medicine. For adults, EFSA recommends water intakes of 2. Many factors affect how quickly the body takes in fluids consumed in food and beverages.

Water absorption, which occurs mainly in the small intestine, is important for everyone but may be particularly of interest to athletes wondering how much and what to drink before, during and after various levels of energy expenditure.

Whether we absorb the water from fluids we consume depends on our gastric emptying rate, or how fast fluid leaves the stomach.

Following are some factors to consider when seeking to speed up gastric emptying rate and get fluids to the body parts that need them most. In general, the greater the volume of fluid in the stomach, the faster it exits. This is true up to about mL, at which point the rate may level off.

Personal tolerance varies, of course. Interestingly, refilling the stomach regularly with a larger volume, rather than drinking slowly and continually, will enhance gastric emptying Leiper ; however, drinking a large volume in a short time right after working out is not recommended.

Beverage temperature, contrary to a popular myth, does not affect water uptake. Plain water is emptied from the stomach and absorbed in the intestine faster than fluids containing electrolytes or calories. Here are a few types of beverages and their notable characteristics:.

FRUIT JUICE AND SOFT DRINKS. Solute concentration in fluids osmolality is measured in milliosmoles per kilograms. The problem with hypertonic beverages, which include fruit juice and soft drinks, is that they draw water out of the body-water pool into the intestine to make them isotonic; this delays absorption of their water content and makes them ineffective for rapid rehydration, especially during or following competition Leiper SPORTS DRINKS.

Carbohydrate-electrolyte solutions aka sports drinks that have a carbohydrate concentration of 2. However, sports drinks can have their problems. Also, many store-bought versions contain fructose, which has been shown to enhance carbohydrate oxidation at low-to-moderate exercise intensities but can be difficult for some people to digest Jeukendrup Incidentally, fructose is found in fruit juices and many other sweetened beverages, too.

If someone gets gassy or uncomfortable after drinking a commercial sports drink, fructose may be the culprit. For context, a Starbucks ounce black coffee has about mg, a double espresso about mg.

When exercise will last longer than 2 hours or take place in high heat, exercisers should arrive optimally hydrated—neither hyperhydrated with an excess of TBW nor hypohydrated at a deficit. This is particularly important if fluid loss from sweat will be high in which case sodium losses via sweat will probably also be high.

Beginning an endurance event hypohydrated compromises performance: The water deficit increases cardiovascular strain, raises heart rate and rating of perceived exertion for the same relative effort, and amplifies the thirst sensation. High temperatures increase the degree of impairment and discomfort.

Anaerobic endurance, muscle strength and power all decrease, as well. Further, such dehydration can induce plasma hyperosmolality, which increases heat storage by delaying and decreasing sweating in an attempt to conserve water Paull et al.

Overhydration does not enhance performance, either. Hyperhydration higher than optimal TBW does not improve aerobic or anaerobic performance and can, at extremes, be fatal McDermott et al.

If blood levels of sodium become hypotonic too dilute , osmotic pressure in the extracellular compartments decreases. This becomes particularly dangerous in the brain because cell swelling there will lead to increased intracranial pressure, a dangerous condition called cerebral encephalopathy.

Exercise also results in the shunting of blood to active muscles, leading to decreases in kidney filtration and urine production and making it harder for the body to counter a fluid overload.

Because a lower TBW is more easily diluted, women are at higher risk of hyponatremia Almond et al. Use of medications such as nonsteroidal anti-inflammatory drugs NSAIDs and selective serotonin reuptake inhibitors SSRIs confer additional risk Cotter et al.

Clients may benefit from being made aware of the potential effects of these common medications. If you are overhydrating as a result of rhabdomyolysis , see a professional! Looking at individual losses is important because sweat rate ranges from 0.

This does not mean you should attempt to consume that amount of fluid during each hour of exercise; it is unlikely you could absorb that much, and overhydration puts you at risk of exertional hyponatremia. Additionally, while negative consequences can ensue from drinking too much before or during exercise, consuming large amounts of fluid over a short time post workout is not advisable, either.

This practice will overstimulate the kidneys, producing large volumes of urine, which undermines rehydration Jones et al. If you are able to absorb more than 1. Generally speaking, the best strategy is to drink to thirst or comfort, but not beyond.

Remember that heat factors into getting properly hydrated as well! In situations when complete rehydration between events particularly those of longer duration is limited by time or availability, athletes should consume fluid as they can and then restore full TBW when possible overnight, for example.

In such cases, sports drinks can aid in replenishing electrolytes and carbohydrates as well as fluids Leiper ; Shirreffs Metered consumption increases hydration efficiency—the amount of water retained by the body—without prolonging dehydration. Of course, post workout is not the only time when it is important to counter dehydration.

If your self-checks indicate dehydration at any time, increase your water intake by about 1. Your urine should be about two shades lighter within about 24 hours Perrier et al. This may be a topic to discuss with clients, too, as some may be experiencing chronic hypohydration and not be aware of it.

Barring medical contraindication, striving for consistent adequate intake of plain water can only enhance health now and in future years. As fitness professionals, we provide all kinds of lifestyle improvement suggestions to our clients and gym members.

Advising them of ideal hydration habits is another service we can provide that will enhance health. Further, the recommendations are simple and inexpensive, so barriers to improving hydration other than the inconvenience of frequent urination are typically low.

As always, our suggestions are most powerful when we model them, so hydrate thyself—and then help others soak up some knowledge, too. diuretic: spurring extra urine production by kidneys to maintain TBW balance; a substance causing this effect.

electrolyte: an electrically charged particle anion or cation resulting from salts dissolved in water. euhydration: the ideal amount of body water; necessary to sustain normal physiological functions of the body.

osmotic gradient: the difference in concentration between two solutions on ­either side of a semipermeable ­membrane. rehydration: the process of restoring normal TBW from a hypo- or dehydrated state.

tonicity: effective osmotic gradient; relative concentration of solutes; drives movement of water between body ­compartments. In people over the age of 65, TBW decreases. This is partly because water is dependent on fat-free mass, so age-related muscle loss, known as sarcopenia, causes TBW levels to drop.

Osmo- and baroreceptors also become less sensitive in older adults, so thirst tends to be less pronounced and the kidneys become less effective at concentrating urine. There are several ways to gauge hydration levels without doing lab work: They involve measures that are easy to check at home, including thirst, body weight, and urine volume and color.

This thirst perception rating can serve as a good baseline throughout the day Armstrong et al. Unless you are actively losing or gaining weight, most day-to-day variations in weight are from fluctuations in total body water. To establish a baseline, weigh yourself nude, first thing in the morning after using the bathroom, 3 days in a row.

The average of these three weights is a pretty good representation of your weight. Keep a record of this number and use it for comparison with your postworkout weight. Then rehydrate accordingly. Caveat: This is not a good gauge in the days after a high salt intake, which will cause fluid retention that does not correspond with good hydration.

Urine color can also help you assess your hydration level. A pale-yellow color indicates good hydration, and a darker, sunflower-yellow color shows normal hydration or slight dehydration.

If the color shifts to a mustardy or brownish color, you are exhibiting a sign of dehydration see the color chart below. Caveat: Many things can affect urine color, including drinking a large quantity of water soon before urinating which can lighten it or taking B vitamins which can darken it.

Using at least two methods to gauge hydration will give you a clearer picture of where you stand. Knowing how much water you lose to sweat can be helpful in sustaining hydration or at least in not losing too much fluid during a practice or event. It will also help you restore euhydration later.

Here is an assessment that can help you approximate your average sweat rate SR. THE MINUTE SWEAT RATE TEST. Note: The minute test is easiest if you avoid eating or drinking anything during the exercise.

If you drink any fluids beforehand, add that amount to the difference in weights in step 4. If the weight difference is grams and you drank mL of fluid beforehand, add that to the g for a loss of g, or an SR of 1.

Almond, C. Hyponatremia among runners in the Boston Marathon. D Debra Wein Meg Root Cassandra Padgett Graham Melstrand Margarita Cozzan Christin Everson Nancy Clark Rebekah Rotstein Vicki Hatch-Moen and Autumn Skeel Araceli De Leon, M. Avery D. Faigenbaum, EdD, FACSM, FNSCA Dominique Adair, MS, RD Eliza Kingsford Tanya Thompson Lindsey Rainwater Ren Jones Amy Bantham, DrPH, MPP, MS Katrina Pilkington Preston Blackburn LES MILLS Special Olympics Elyse Miller Wix Blog Editors Samantha Gambino, PsyD Meg Lambrych Reena Vokoun Justin Fink Brittany Todd James J.

Annesi Shannon Fable Jonathan Ross Natalie Digate Muth Cedric X. Bryant Chris Freytag Chris McGrath Nancey Tsai Todd Galati Elizabeth Kovar Gina Crome Jessica Matthews Lawrence Biscontini Jacqueline Crockford, DHSc Pete McCall Shana Verstegen Ted Vickey Sabrena Jo Anthony J. Wall Justin Price Billie Frances Amanda Vogel.

This interference, in turn, negatively affects both performance and recovery. Fluid helps to regulate blood pressure. Effectively regulated blood pressure normalizes heart rate and, therefore, manages stress on the body during training and recovery.

Excessive stress can lead to inflammation and other processes that can interfere with both performance and recovery. Fluid helps in the movement and transport of essential energy nutrients. Essential macronutrients such as carbohydrate, protein, fats and supporting nutrients that are used as energy for the body are all transported by fluid in the body.

In addition, fluids help to remove the metabolic waste that is produced during intense exercise. Consider exercise intensity and duration, breaks and sweat rates as well as these recommendations from ACE on how to maintain optimal hydration: Pre-workout Drink 17 to 20 fl oz of water two to three hours before exercise Drink 8 fl oz of fluid 20 to 30 minutes before exercise During workout Drink 7 to 10 ounces of fluid every 10 to 20 minutes during exercise Post-workout Drink an additional 8 ounces of fluid 30 minutes after exercise Drink 16 to 24 ounces of fluid for every pound of body weight lost during exercise As with meal plans , a hydration protocol should be consistently followed for best results.

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