WATER and performance

Expert Discussion Recovery and Regeneration
1

HERE ARE SOME BASICS ON WATER AND ITS ROLE IN DEVELOPING AND MAINTAINING ATHLETIC PERFORMANCE

The body’s need for water is second in importance only to its need for oxygen. Adult body weight is approximately 55 - 65% water so a 10% loss of body water poses significant health risks and a 20% loss may result in death.

Water plays an essential role in the human energy system. The more we expend, the more we need.
During running only 25% of the energy generated by the body is turned into mechanical work where as the balance is actually turned into heat. The heat must be removed by sweating to avoid dangerous increases in body temperature.

During intense running the body can lose up to two liters of water as sweat. A marathon runner can actually lose 13 lbs of body weight in the form of water during a race. Dehydration due to water loss during running can have a significant effect on the body’s performance. When water is drawn away from the working muscles, blood volume is decreased so the heart must pump harder to supply the same amount of energy.

The effects of dehydration can be profound. They are:

  1. A loss of just 1% to 2% of body weight begins to compromise cardiovascular, body temperature regulation, and muscular function, and can lead to decreases in aerobic power. For example, heart rate rises an additional three to five beats per minute for every 1% of body weight loss.

  2. Muscle endurance and maximal aerobic power decreases when 3% to 4% of body weight is lost. Slightly more than 2% loss of body weight can result in as much as a 35% to 48% reduction in physical work capacity.

  3. Dehydration of greater than 3% of body weight increases the risk of developing exertional heat illness (heat cramps, heat exhaustion, or heat stroke). Heat illness is common in sports and can occur after just one hour of intense exercise in the heat.

The National Athletic Trainers’ Association recommends the following hydration guidelines for exercise:

  1. Two to three hours pre-exercise: 17 to 20 fluid ounces of water or sports drink.

  2. Ten to 20 minutes pre-exercise: 7 to 10 ounces of water or sports drink.

  3. During exercise: Fluid replacement should approximate sweat and urine losses and at least maintain hydration at less than 2% body weight reduction. This generally requires 7 to 10 ounces of water or sports drink every 10 to 20 minutes. Include carbohydrates in the beverage if the exercise is intense or lasts more then 45-50 minutes. Water alone will suffice, and save calories, if the exercise is moderate or less than 45-50 minutes.

  4. Post-exercise: Athletes should weigh themselves nude before and after workouts to learn how much weight is lost from sweat (water and salt) and then ingest fluid equal to 150% of the weight loss, ideally within two hours, and no more than four to six hours after the event. Including sodium in the drink allows fluid volume to be better conserved and increases the drive to drink, and carbohydrate in the drink will improve the rate of intestinal absorption of the fluid as well as replenish glycogen stores in the muscles and liver.

2

Interesting. Where is this taken from?

There has been alot of debate about hydration and its effect on performance of late - I think most people are now acknowledging that the ‘conventional wisdom’ in regards to the need of fluid uptake has been an extreme exaggeration.

The validity of most of the previous studies addressing this topic is questionable when considering physical performance. ie. how were the athletes dehydrated, what effect does the depletion of muscle glycogen have on the optimal ‘level of hydration’, the difference between water and sports drink is massive (sports drink is still along way off the salinity of the body
), etc.

3

I beg to differ. I’ve always found drinking 3-4 liters worth of bottled water has had more positive effects on peak performance then cutting back ever would. It’s all relative to the person, these studies are too general…

4

My son’s basketball reps team coach flogged them at training for a two-hour session a couple of weeks ago and refused to let them drink anything, saying it would make them tougher. It was real old school bullshit.

So I just did a google search on the subject and came up with the listed statements. Thereactually wasn’t that much meaty info on the topic; a lot of basic, opinion-style material and then a great leap into the research documents which was too long-winded and often didn’t come up with anything solid.

Therefore, I cannot guarantee the truth of the statements, nor their source, but they sounded ok and appeared to come from sources who were “experts” on the issue.

5

Was the coach receptive to your input? (Did you give him your input?)

6

The body’s need for water is second in importance only to its need for oxygen.

This is the key point.

CNS and specially limbic system control and regulate the reaction to water variation.
With Omega Wave system i.e. you can see when you are out of balance for dehydration.

Glucose/insuline changes are another type of reaction, more correlated to “fight or flight”.

Food has much implications, but we’re speaking now about a deep survival system.

7

hi Herb,
I have to give credit to the coach because he immediately amended his ways and thanked me, a lot, for the advice. The next session he built in water breaks at reasonably obvious moments and used them to divide the segments of his session.

He’s a good guy, a Vietnamese school teacher who has done psychology and physiology but he’s so excitable and passionate about the hoops that all sense flies out the window unless he’s prompted. So now the older hoops coaches and me, we keep an eye on him and keep it sane.

I was actually searching to find out how long it takes to recover homeostasis - for want of a better word - once hydration starts in a dehydrated athlete.

I couldn’t find any info on that at all. Not even whether restoration is instantaneous, or whether - like in the case of CNS blow-out or serious “over-training” - it can take days.

The same coach, who as I said is really a lovely, caring guy, the week earlier did a 2hr 30min session including scorpions and monkey hops, on the Saturday morning from 8-10:30am. They tipped off at 8:30am the following day and a lot of the boys (U18s) were dead in the legs and couldn’t sustain the (vertical jumps) rebounds and were a half-step slower getting around the court.

I wrote him a note, talking about the paradoxes of training: including the one where, when you train for endurance you don’t get it until you stop training for it, freshen up and super-compensate. Like, while you’re actually training for endurance (or strength) all you end up with for the next day or so is the opposite due to the fact that you’re all torn down.

He was really good about that too and promised to be more sensible in future, which to his credit he has been. He actually admitted in writing to the squad that he had made a mistake and felt he had cost his guys the W. That’s pretty honest and self-effacing of him. :slight_smile:

It’s true what they say about young coaches: that they learn on the dead bodies of the first athletes they get to work with. I just didn’t want my kid to be sacrificed :eek: on the alter his his further education.

Last game my kid was awarded the “game ball” as best and fairest (or something like that), but they still lost their game. So it seems no hard feelings.

The coach is now on a development tour to Texas and LA etc where he is looking after the junior team and we have a much more experienced (but sometimes equally crazy - in a good way) coach taking care of the older, aspiring elite team as they play in those “Big Time” tournaments. One of the elite group attracted boys attracted some interest last year from scouts who wrote on their website favourably mentioning him (Ater Majok, a 6ft 10ins Sudanese refugee) as a NBA three-man prospect.

8

I only wish I was as sensible when I started coaching.

In regards to regaining proper hydration, I read somewhere that it takes 36 hours. I will try to dig up where I read that.

9

Water Intake
By John M Berardi
First published at www.skifaster.net, 2001.

Adequate water is an important part of any athletic regimen but it is often neglected. How much water is needed is a controversial topic in the popular literature. Let’s look to the science.

When looking at the research, there is a recent paper in the Journal of the American Dietetics Association (Volume 99, number 2, pages 200-206, 1999) that discusses water needs. In this paper, the author states that:

" To be well hydrated, the average sedentary adult man must consume at least 2,900 mL (12 c) fluid per day, and the average sedentary adult woman at least 2,200 mL (9 c) fluid per day, in the form of noncaffeinated, nonalcoholic beverages, soups, and foods. Solid foods contribute approximately 1,000 mL (4 c) water, with an additional 250 mL (1 c) coming from the water of oxidation."

The authors also state that “Dehydration of as little as 2% loss of body weight results in impaired physiological and performance responses.”

So it appears that in sedentary individuals the equivalent of about 12 cups of water per day are necessary (4 cups come from food, 1 cup from metabolism, and 7 cups from fluid intake). In fact, a few correlational studies have shown that individuals consuming this amount of water per day are less likely to suffer from:

* urinary stone disease
* breast cancer
* colon cancer
* urinary tract cancer
* childhood and adolescent obesity
* mitral valve prolapse
* salivary gland disorders

So for sedentary individuals, you should shoot for about 7 cups of water per day if consuming near your calorie needs.

As far as athletes, there is good research showing that dehydration seriously impairs mood, intensity, strength, and endurance. Although there is very little research looking at how much fluid is needed to prevent dehydration in athletes, the Guyton Textbook of Medical Physiology the following table showing the amount of water lost in the average 70kg athlete (154lb) in different exercise and non-exercise conditions:

Normal Weather -
No exercise
(68° F)

Warm Weather -
No exercise
(85° F)

Exercise in Warm
Weather (85° F)
Insensible Sweat Loss

  • Skin
    350 mL

350 mL

350 mL

  • Respiratory Tract
    250 mL

350 mL

650 mL
Urine
1400 mL

1200 mL

500 mL
Feces
100 mL

100 mL

100 mL
Sweat
100 mL

1400 mL

5000 mL
Total
2,300 mL (2.3L)

3,300 mL (3.3L)

6,600 mL (6.6L)

From this table it appears that although athletes will be getting more water from foods and will be making more “metabolic water” due to cellular metabolism, this probably is not enough water to support the higher levels of muscle mass, metabolic activity, and the higher sweating rates of more active people. Especially in warm weather climates. So more water may be necessary.

Since the first study I mentioned study proposed the idea that about 3L (12 cups) of water per day might be necessary for adequate hydration in sedentary individuals and that about 1.25L (5 cups) come from food and as a byproduct of metabolism, that means that 1.75L (7 cups) should be consumed per day.

Assuming that athletes are eating more food than the average person eats and that they have a higher metabolic rate, they might be getting about 2L (8 cups) per day from food and metabolism. Their water needs on training days, however are probably higher so drinking 2 additional liters (8 cups) of water per day might get the job done if they don’t live in warm weather climates. If living in warm weather climates, drinking an additional 4 liters (16 cups) might be necessary on training days. Base your water intake on your climate, sweat rates, and your activity levels. Remember the above examples are based on a 70kg athlete. If you’re bigger, you may need more.

Bottom line: on non-training days, it appears that ½ gallon of additional water is adequate in both warm and “normal” climates. On training days, however, you may require a gallon or more water per day to stay adequately hydrated.

© 2002 - 2005 Science Link, Inc. All Rights Reserved.

10

Thanks Herb,

Your article certainly addresses a deficiency of information on the topic. Now the forum search engine should be able to dig this out for future reference. Thanks, personally, from me also. I’ll be sending this to our young hoops coach… :slight_smile:

11

I would strongly suggest Noakes’ book “Lore of Running” for further information on the topic (pp 197-231). It’s very difficult to match the fluids you lose, not always possible (when they exceed 600 ml per hour), since fluids are also lost from nutrients used, too (e.g., carbs) and perhaps not necessary. In fact, too much (plain) water before and during exercise could lead to water intoxication (hyponatremia) and impaired performance. Ad libitum or at best encouragement of drinking may be enough (anywhere between 300-500 ml per hour), as the author has found no scientific support for current scientific guidelines suggesting ~1.5 L per hour (e.g, from ACSM).

Prevention of hypoglycemia is of paramount importance, however, as the liver will not release more than 1 g per minute during exercise (limited stores of 120 g maximum); hence, carb ingestion should be much higher than that (e.g., 60-80 g per hour), so its oxidation is not prevented (avoid fructose, of course).

The above are for endurance runners.

Hope it helps!

PS sorry, but I haven’t got time to read Herb’s post at the moment. I thought it would be good to just post these for now…

12

Thanks Nik,

It is new info and all of it adds to the knowledge we should hve at this forum on a topic basic but essential to performance.

Can you shed a little more light on your thoughts about the following item in your post:

“Prevention of hypoglycemia is of paramount importance, however, as the liver will not release more than 1 g per minute during exercise (limited stores of 120 g maximum); hence, carb ingestion should be much higher than that (e.g., 60-80 g per hour), so its oxidation is not prevented (avoid fructose, of course).”

kk

13

Good stuff Nik, I had been looking for the same info on the web.

Hypoglycemia refers to a below normal glucose content in the blood; and I think Nik refers to the inability of the liver to restore this while exercise is taking place. Another implication of this is the increased viscosity of the blood.

The effects of hypo/hypernatremia is probably the most important issue with regards to hydration - I think Noakes goes on to state that the body performs better in a slightly dehydrated state, as apposed to being over hydrated (hyponatremia).

14

Sorry for the delay.

On Dehydration
Carbohydrate ingestion generally enhances performance. However, the addition of glucose to the ingested solution increased fluid absorption. Hence, the beneficial effect of carbohydrate ingestion during exercise could theoretically be due to an influence of the added carbohydrate on fluid balance.
…
The closer the rate of fluid ingestion approaches the sweat rate, the less the degree of physiological disturbance that develops during exercise. If the degree of physiological disturbance resulting from dehydration determines the degree to which exercise performance will be impaired, then, logically, atheletes should drink at rates that equal their rates of fluid loss, if they wish to optimise performance. … (But,) there is at present no scientific support for the belief that performance will be optimised, if fluid is drink at the same rate that it is lost during exercise. This guideline, entrenched by the Position Stand of the ACSM (1996), is not supported by any scientific evidence.

On Preventing Heat-Impaired Performance
Cooling the blood in the large arteries in the neck, the carotid arteries, which carry blood to the brain, would be a more effective cooling strategy.
…
Humans, like camels, live in a state of perpetual dehydration except for a short period at night after the evening meal. Humans cannot store either fluid or salt to any great extent to reduce the degree of dehydration that occurs before the next opportunity to drink. Rather all mammals drink until they are no longer dehydrated. Humans are no able to exercise if they are dehydrated by more than 10%. Death in humans occurs at dehydration levels of 20% or greater.
…
In humans, the aim of ingesting fluid before exercise is to ensure that we are appropriately hydrated at the start of exercise. Overdrinking will simply result in more frequent trips to the toilet, effecting an increased loss of sodium and potassium in the urine. Only if drinks with an unpalatably high sodium content are ingested is there a small (~7%) expansion of the plasma volume, equivalent to an increased in whole body water storage of perhaps 500 ml.
…
Optimum hydration can be assessed easily by monitoring urine colour. A very lightly coloured urine is the best measure of the optimum hydration state. Accordingly, before competition, athletes should drink sufficiently to ensure that their urine is lightly coloured. As it takes between 1 - 2 hours for ingested fluid to be fully absorbed and the obligatory urine response to have occurred, athletes should probably take their last drink about 2 hours before exercise. The should carry 400 - 500 ml of fluid just before their event (e.g., longer than 1 10K race) and ingest that fluid in the last minute of two before the event begins.

During Exercise
The intensity of exercise, rather than the level of dehydration, is the most important factor determining the body temperature during exercise.
…
Competitive Ironman thriathletes can develop the hyponatremia of exercise, if they drink excessively during the bicycle leg and continue that practice during the running leg. Current guidelines for runners suggest they should aim to drink between 600 - 2000 ml per hour during competition (e.g., ACSM, 1996). Yet the only proven effect of such high rates of fluid ingestion (greater than 1 litre per hour) is the development of water intoxication (hyponatremia) and impaired exercise performance.
…
A figure closer to 200 - 400 ml per hour might be more likely (author’s view).

On Ingestion Equal to Sweat Rate
Ad libitum rates of fluid ingestion of ~500 ml per hour are so common in athletes during competition. Up to 3 kg of the weight lost during prolonged exercise may not represent a true fluid loss that needs to be replaced during prolonged exercise, if dehydration is to be prevented. Perhaps because their muscle glycogen stores (500 - 800 g) and the associated water content (1500 - 2000 ml) have not yet been restored. It is simply not possible to replace fluid at rates equal to the sweat rate, when the sweat rate exceeds about 600 ml per hour.
…
An number of studies have shown that there is no benefit in performance between drinking ad libitum and drinking fixed amounts suggested by ACSM, for example, apart from intestinal discomfort.

On Calculating the Sweat Rate
Weigh yourself naked on a scale calibrated in kilograms, immediately before (WB) and after (WA) exercise in conditions and at a pace to which you are accustomed. During the exercise period you need to measure carefully the total amount of fluid in litres that you ingest while exercising (F). Your sweat rate can be calculated fairly accurately:

Sweat Rate (litres per hour) = (WB - WA) / exercise time (hours)

Your fluid replacement will have been adequate, if after long exercise (e.g., >1.5 - 2 h), you lost less than 2 - 3 kg and are not dehydrated by more than 3%, calculated by the following equation:

Dehydration (percentage) = (WB - WA) x 100 / WB

(the above refers to runners)

Heavier people have a reduced capacity for losing heat by convection, yet they produce large amounts of heat even when running quite slowly. In contrast, when exposed to cold, heavier people are better able to maintain body temperature, as they lost less heat by convection.

On Rate of Fluid Ingestion and Absorption
The fastest runners require the highest rates of fluid intake during exercise, but it is precisely those who also have the greatest difficulty replacing their fluid losses during exercise. Slower runners have less difficulty in drinking adequately, since they travel slowly and some even have too much of a good thing, i.e., drink too much. The latter may develop the potentially fatal condition known as over hydration, water intoxication (low blood sodium concentration). The author is unaware of a single case report in the medical literature that clearly establishes that an athlete became critically ill during exercise as a result of dehydration only. When sodium loses are not replaced though and only water was drunk, hyponatremia results.
…
What is ignored is the weight of fat and carbohydrate that is burned irreversibly during exercise and that may amount to 800 g of carbohydrate and 200 g of fat in an Ironman Triathlon. The water lost from glycogen may constitute up to 2 kg. None of these eight losses contributes to dehydration.
…
Unabsorbed fluid from excess water-drinking will cause hyponatremia within a few hours, due to the lack of sodium in that water (sodium always moves towards fresh water to help in absorption). As a result osmotic pressure in the bloodstream falls, water moves from bloodstream into all cells making them soggy, the brain swells in the skull with no room for it, death results as the rising pressure causes the brain centres controlling breathing to stop functioning.

To be continued.

Source: T. Noakes (2001) Lore of Running. Human Kinetics.

15

On Electrolyte Content of Fluid
Electrolytes are chemical substances that, when dissolved or melted, dissociate into electrically charged particles (or ions such as sodium and potassium).
…
During prolonged exercise, the body is forced to deplete its fluid stores as a consequence of the sodium chloride losses in sweat. This is because the amount of sodium and potassium in the body determined the amount of water, not the other way around. If this did not occur and fluid stores were allowed to remain normal in response to drinking during exercise, a dilutional hyponatremia would develop.
…
It follows that the only way to prevent dehydration during exercise is to replace both the sodium and the water losses in sweat, as these losses develop by drinking an appropriate fluid that contains the optimum amount of sodium.
…
Yet, if the sweat rate exceeds about 750 ml per hour, it is impossible to replace all that fluid, probably because the fluid cannot be ingested and absorbed by the intestine at such high rates, at least during exercise. Thus, even if fluid is ingested at sufficiently high rates to replace all the water lost, that fluid must also contain sodium in the same concentrations found in sweat, which is between 40 and 80 mmol per litre, or from two to four times higher than the sodium concentrations currently found in athletic drinks.
…
Although it has been argued that both carbohydrate and sodium replacement during exercise cannot occur at the same time, when a solution containing both a high carbohydrate (6 - 8%) and a high sodium (50 mmol per litre) content was evaluated so that the osmolality* was also high (330 mosmol per litre), the rates of water and carbohydrate absorption were satisfactory.
…
It is important to maintain the ability of urine production, thereby preventing fluid retention, rather than the small extra amount of sodium ingested, that reduces the fall in blood sodium concentrations in all athletes, regardless of how much sodium they ingest. It is this ability that prevents the development of hyponatremia in those who ingest fluid at excessive rates. As athletes are not at risk of developing deficiencies of either magnesium or potassium during exercise, neither needs to be replaced until after exercise.

On Carbohydrate and Fat Content of Fluid
Carbohydrate ingestion prevents hypoglycemia, which profoundly affects performance. The most important factor determining the rate of gastric emptying is the volume of the solution in the stomach, not its carbohydrate content. The greater the degree of gastric distension an athlete maintains during exercise, the more carbohydrate and water will be delivered to the intestine, irrespective of the carbohydrate content of the ingested solution. How, then, do you make sure that you aren’t drinking too much? The answer is that vast majority of athletes do not drink enough to match their sweat rates and hence are not at risk of developing hyponatremia. Only those drinking more than 1.0 - 1.5 L per hour for many hours are ever likely to get into trouble -athletes who drink less than this should be within safe limits, unless they are very light (less than 45 kg) and exercise very slowly.
…
On Muscle Uptake of Carbohydrate
The factor limiting the oxidation of ingested carbohydrate is the rate of glucose released by the liver. As this is set at about 1 g per minute, it follows that ingesting carbohydrate at rates much faster than 1 g per minute during exercise will not be beneficial, as the carbohydrate will be stored in the liver and not used during exercise.
…
It is now known that the fate of the ingested carbohydrate is the same whether it is taken 3 hours before or 15 or 120 min after the start of exercise. It is believed that ingested carbohydrate is oxidised at a maximum rate of about 1 g per minute during exercise, provided the rate of ingestions is at least 70 to 100 g per hour. The optimum fuels for ingestion are glucose, maltose and fructose polymers, or soluble, branched-chain starches with high glycemic indexes, as present in spaghetti, bread and potatoes. In contrast, fructose, the sugar present in fruits, galactose, lactate and alcohol are all oxidised to a lesser extent than is glucose ingested during exercise. The ingestion of even quite modest amounts (about 50 g) of fructose, like that of lactate, produces gastrointestinal discomfort, becuase there is a limited capacity to absorb fructose from the intestine.

*Osmolality is determined by the concentration of all the particles -electrolytes, proteins, etc.- dissolved in the solution. Osmolality is, therefore, proportional to the total number of all the molecules dissolved in the solution.
…
There is a maximum rate at which carbohydrate ingested during exercise can be used by the muscles. The rate-limiting step appears to be the rate of release of glucose by the liver. Only when a “second liver” is introduced -by infusing glucose directly into the bloodstream at much faster rates (up to 3 g per minute) than the normal liver chooses to release glucose (1 g per minute)- can muscle glucose oxidation rates be increased to what may be a maximal capacity of about 2.5 g per minute. However, this procedure produces very high blood glucose concentrations (approximately 10 mmol per litre), which are twice the normal values.
…
The human was designed to maintain a blood glucose concentration of about 5 mmol per litre. During prolonged exercise (longer than 90 min), this balance is reached at a rate of glucose release by the liver and its use by muscles, both equal to 1 g per minute. when carbohydrate is ingested at sufficiently rapid rates (approximately 80 g per hour), the ingested carbohydrate completely suppresses liver glucose production, so that all the glucose oxidised by the muscles (1 g per minute) comes from the ingested carbohydrate. One reason for the limiting rate of glucose release might be the relatively small amount of carbohydrate (approximately 120 g) stored in the liver. Were very high rates of glucose release possible, the liver’s glycogen stores would be rapidly depleted, causing hypoglycemia and exercise would be terminated.

During Recovery
Increasing the sodium content of the fluid ingested during recovery reduces the urine losses and increases the rate of rehydration in proportion to the sodium concentration of the ingested fluid. As fluid ingestion will initiate some urine loss, the ingested volume needs to exceed the total fluid deficit by 25% to 50%.

The Ideal Sports Drink
The maximum rates of fluid loss for the faster athletes competing in moderate environmental condition is about 1000 ml per hour. However, no one has yet shown that, in competition, these athletes can ever drink more than 700 ml per hour without developing symptoms of fullness and bloating.
…
The key to developing the optimum replacement fluid for ingestion during exercise would seem to be to develop a drinking pattern that provides optimum fluid, electrolyte and carbohydrate replacement at an ingested rate of 500 to 800 ml per hour without causing gastric distress by forcing the athlete to maintain a large gastric volume or abdominal fullness as a result of a failure of fluid absorption.
…
A 7% carbohydrate solution ingested in 100 ml every 10 min and maintaining a gastric volume of only 200 ml is probably the more usual drinking pattern chosen by most athletes during competition.
…
Different carbohydrate concentrations would provide quite different rates of carbohydrate delivery. The latter, rather than the rate of water delivery, may really be the more important factor to consider, at least during more prolonged exercise lasting more than 3 hours.
…
To optimise intestinal absorption of carbohydrate and water and to replace the sodium lost in sweat, the ingested solution should have a sodium chloride content of about 60 mmol per litre.
…
The intake must be sufficient to provide the muscles with 1 g per minute of glucose. This is probably achieved with an intake of 60 to 90 g per hour. Higher rates do not appear to aid performance any further.
…
At a practical level, what should the average athlete do? An ideal solution (assuming a drinking rate of 500 to 800 ml per hour) that is also palatable could go along the following lines:

Carbohydrate Content: 7.5% to 12% (depending on the rate of drinking)
Carbohydrate Type: anything but fructose
Osmolality: 200 to 400 mosmol per litre (osmolality will depend on the type of carbohydrate used -glucose polymers will have lower osmolalities at any carbohydrate concentration)
Sodium Content: 60 mmol per litre

At present, there is still no solution conforming to the above criteria. Here are some guidelines, however, on what to look for when buying currently available sports drinks:

Palatability -the most scientifically formulated drink is of no value, if it is so unpalatable that it cannot be drunk.
Carbohydrate Concentration of 5% to 10% -higher carbohydrate concentrations only become important near the end of prolonged, competitive exercise, when the desire to drink falls, but the need for carbohydrate replacement is greatest.
Carbohydrate from a Variety of Source -a mixture of carbohydrate sources (glucose and maltodextrins) is necessary to maximise palatability and to maintain a low to moderate osmolality.
Sodium Concentration of 20 to 60 mmol per litre -the higher sodium concentrations aid fluid balance, when athletes are able to ingest fluid at high rates.

Source: T. Noakes (2001) Lore of Running. Human Kinetics.

16

Yeah, I think water intake is overated.

17

Yes and no. If you know enough to drink enough, then you’re probably fine. But there are still a few dinosaurs that don’t think to drink.

18

I think track and field has among the most enlightened coaches of any sport. Basketball, old school style USA, still has coaches aged in their thirties who associate water denial with guts.