Electrolytes, Hydration and Long Distance Running

With all due respect to this expert exercise physiologist's opinion, her advice on the importance of taking in electolytes during marathons and long runs is not accepted by everyone.

Currently there is no evidence to suggest that humans incur any meaningful sodium deficits during exercise, even when the humidity is high and the individual is sweating profusely. -The Science of Sport

Summarizing another article in The Science of Sport about electolytes during a 2 hour run:

1. If you don't drink at all, your blood sodium level doesn't fall, it RISES!

2. If you replace 50% of your sweat losses with plain water in the same run, your blood sodium concentration remains in the normal range.

3. If you replace 100% of your sweat losses with plain water (2 liters in 2 hours- 1 liter is approx. 1 quart), your sodium concentration falls dangerously low, leading to hyponatremia.

4. If you replace 50% of your sweat losses with Gatorade, the result is comparable to the water trial.

5. If you replace 100% of your sweat losses with Gatorade, again the result is not much different- a 4 hour marathoner will likely end up in the hospital with hyponatremia.

Interesting that Hall believes adding salt to his drink helps him retain more fluid in hot weather. I wonder why he thinks that's not as important on a cool day?

While you certainly need fluid replacement during a long hot run, be careful not to over drink. Practice by weighing yourself before and after, and note that while losing a few pounds is normal, any gain is not! As for Gatorade during a long run, the calories are what you need, not necessarily the electrolytes.

I love the Science of Sport blog!

Rehydrate With Food!

...five male and three female cyclists cycled in a steamy environment (34 degrees Centigrade, 55 per cent humidity) until they had dehydrated them-selves by about 2 per cent of body weight. After the exercise, the athletes ingested either a carbo-hydrate-electrolyte sports drink or else a standard meal comprised of 53 per cent carbohydrate, 28 percent fat, and 19 percent protein, along with water (at a volume 1.5-times greater than the amount actually lost during exercise).

Total urine output was significantly lower after the meal, compared with the sports drink, probably because of all the electrolytes (especially sodium and potassium) naturally found in the food, which helped hold water in the body. When only the sports drink was ingested, the subjects' body-water levels were still down by about 10 to 11 ounces six hours after the exercise had concluded, while the meal-and-water combination restored fluid balance to normal ('Restoration of Fluid Balance after Exercise-Induced Dehydration: Effects of Food and Fluid Intake,' European Journal of Applied Physiology, vol. 73, pp. 317-325, 1996). Obviously, combining good water intakes with consumption of electrolyte-rich foods can be a great way to rehydrate. -pponline.uk

MY COMMENT: Eating after a long workout does much more than restock muscle glycogen!

If You Think You Need Electrolytes- READ THIS!

1.Sweating causes some sodium loss, but because the sodium content of sweat is so low relative to body fluids, your sodium concentration will rise. And it is the concentration that is important, since this controls fluid shifts in the body. It is NOT possible, even for a "salty sweater" like Randy in these scenarios, to LOSE sodium through sweat.

2.Rather, we have demonstrated that the only possibly theoretical way that the sodium level can fall is if Randy drinks too much. If he drinks more than he sweats, then he will really be in a lot of troube. For example, if Randy took Gatorade's earlier advice and drank 40 Oz per hour (1.2 L), then his sodium levels would fall to 125mM

Anybody considering a marathon or beyond should read this interesting post on fluid and electrolyte replacement. Take the time to read through the facinating debate on this subject that follows. The Science of Sport

There are companies out there now (Enlyten, Ultima Replinisher) that market electrolyte replacement as essential for optimal performance, even more so than carbohydrate (which is absurd!)

Enlyten Sports Strips-Testimonials

Enlyten Strips are in the news! If you haven't heard, Enlyten now offer electrolytes, appetite suppressant, calorie burners, antioxidants, energy, and melatonin. Just stick one of the strips on the inside of your mouth and the product absorbs directly into the blood stream.

Check out the list of testimonials I will remain a skeptic until a lab somewhere can demonstrate benefit (what a great project for an exercise physiology masters thesis!)

Enlyten Sports Strips

Enlyten is a product that delivers electrolytes through strips placed on the tongue. Does is work? I guess somebody needs to produce some research to convince me that electrolyte replacement during exercise enhances performance. I have my doubts.

Are Electrolytes Overrated?

However, there is little direct evidence of a beneficial effect of electrolyte replacement for any but a small proportion of endurance athletes. The fact that electrolyte concentrations in plasma usually rise during exercise without fluid replacement (Costill et al., 1970, 1974, 1976, 1981) indicates that electrolyte supplements are not needed. Furthermore, during repeated exposures to prolonged physical exertion, the kidneys very effectively conserve sodium and potassium so that the electrolyte balance is usually maintained when an athlete consumes a normal diet or a diet low in potassium (Costill et al., 1976), or a diet high or low in sodium (Armstrong et al., 1985). However, recent case studies have been reported in which athletes who participated in very prolonged exercise experienced severe hyponatremia, i.e., low plasma sodium concentrations during exercise (Hiller et al., 1985; Noakes et al., 1985) or up to 7 days after competition (Noakes et al., 1985). These athletes usually consumed large quantities of water or beverages low in electrolytes. -Fluid Replacement and Heat Stress, Institute of Medicine

The effects of consumption of the individual components of a sports beverage (electrolytes, water, or carbohydrate) and of the combination of all components have also been assessed. Compared with the electrolyte-only trial, performance during the water-only and carbohydrate-only trials was approximately 6 percent faster. However, the combination of carbohydrate and water caused a performance enhancement that was approximately 12 percent faster than the electrolyte trial and 5 to 6 percent faster than when water only or carbohydrate only were consumed. -healthline.com

If no fluid is ingested during prolonged exercise, serum Na+ concentration, osmolality and anti diuretic hormone activity all increase (9). The rise in serum Na+ concentration and osmolality correlate with the increase in (body) esophageal temperature and may be a stimulus for the reduction in skin blood flow and sweating that develops at advanced levels of dehydration (10). An important goal of fluid ingestion during exercise may therefore be to prevent rises in serum osmolality and thereby maintain sufficient skin blood flow for maximum evaporative and convective heat losses. -ultrunr.com

MY COMMENT: I still am a bit perplexed by the hype surrounding the need for electrolytes and the perception that supplementation will somehow enhance marathon performance. Americans are overloaded with sodium to begin with, and dehydration increases concentration in the blood. So why would the typical marathoner need to take additional electrolytes? Unless you are sweating heavily and drinking more water than you are losing, marathoners do not need to replace electrolytes until they cross the finish line.

Why Salt Tablets Are Not a Good Idea

Sodium (Na) is the predominant cation (positively charged element) found in extracellular fluid. It is important in maintaining the proper acid-base balance and in the transmission of nerve impulses. Sodium teams with potassium, the chief cation of intracellular fluid, to maintain proper body fluid and acid-base balance in the cells and tissue and maintain blood pressure. Potassium and other electrolytes—such as magnesium and chloride—perform numerous, multifaceted roles in the body. They work in concert with sodium to regulate acid-base, electrolyte, and water balance; conduct nerve impulses; promote normal muscle contraction (including the heartbeat); regulate the transfer of nutrients to cells; and maintain the normal function of the kidneys, heart, and nerve cells. An imbalance of any electrolyte can have far-reaching, serious effects within the body. -elitewater.com

Salt tablets present problems for athletes if taken orally to correct sodium deficiencies. In their raw form, salt tablets are often difficult to digest, causing gastric irritation, with accompanying nausea and diarrhea a common side effect. The stomach has difficulty in the immediate digestion of salt tablets, meaning that the benefit of the sodium is delayed; sports drinks, and their nutrients, are far easier for the body to absorb. Swallowed alone, without significant fluid to accompany the salt tablet, the sodium will act to further accelerate the dehydration of the body. -World of Sports Science

Post Exercise Rehydration
Inclusion of sodium (0.5-0.7 g ? l-1 of water) in the rehydration solution ingested during exercise lasting longer than 1 h is recommended since it may be advantageous in enhancing palatability, promoting fluid retention, and possibly preventing hyponatremia in certain individuals who drink excessive quantities of fluid. There is little physiological basis for the presence of sodium in an oral rehydration solution for enhancing intestinal water absorption as long as sodium is sufficiently available from the previous meal. ACSM Position Stand on Exercise and Fluid Replacement (note: it says "rehydration"- sodium would be appropriate for individuals that drank "excessive" volumes of fluid

Guidelines for Preventing Hyponatremia

I was very irritated at the Bellingham Marathon organizers when I discovered they were serving Ultima Replenisher on race day. Ultra Replenisher is a sports drink containing electrolytes but only 10 calories per 8 ounces, virtually worthless. When I asked a race official about it, the answer I got was "What about hyponatremia?"

Hyponatremia is a potentially life threatening condition characterized by low sodium levels in the blood. How does it occur? Overdrinking to the point that you actually gain weight during a long race. According to one study conducted on 488 Boston Marathon finishers, 63 were classified as hyponatremic. Primary risk factors identified were weight gain, a finishing time > 4 hours, and low or high body weight. Most drank more than 3 liters (a liter is about a quart). Others have identified the possibility that genetics, anti-inflammatories, stress, and nausea are contributing factors. Another important factor is sweat rate- the more you lose the greater the risk.

Symptoms of hyponatremia include feeling bloated, nausea, vomiting, swelling in extremities, headache. Lethargy, confusion can also appear. In advanced stages, seizure, trouble breathing, and unconsiousess may occur.

Back to Bellingham- can you prevent hyponatremia by using an electrolyte drink instead of water. The answer to that question is clearly no. While sports drinks are recommended over water "Hyponatremia is caused by excess fluid from any source, not by lack of salt or calories." (Sports Drinks Won't Prevent Dehydration or Hyponatremia).

Recommendations for preventing hypotatremia include:

1. Don't drink obessively in the days leading up to a marathon.

2. Avoid taking anti-inflammatories such as aspirin or ibuprofen before, during, and immediately after a marathon. Wait until you are fully rehydrated.

3. Weigh yourself before the start and write it on your number- this will help any medical staff should you need attention.

4. Drink when you are thirsty during the race but don't overdo it.

5. In workouts, weigh yourself before and after without drinking to estimate your fluid loss (remember 16 oz = 1 lb). This gives you a guide (assuming the same environmental conditions) on how much you need to be drinking to just maintain losses.

6. Acclimatize by wearing extra layers during your workouts for 7-10 days prior to your race.

7. After your race nibble on salty snacks and be careful not to drink too much.

references

How much should you drink during a marathon?


HYPONATREMIA - TOO MUCH FLUID; TOO MUCH SWEAT

(c) Dave Elger 2009

Sports Nutrition: Fluids, Electrolytes, and Minerals

SODUIM: Alternatively, humans may dehydrate during exercise because they lose up to 60 mEq of Na+ for each litre of sweat (7). As a result, the equivalent of ~ 10 g of replace sweat and energy losses during exercise remain to be established. The NaCl is lost over three hours of exercise and the complete restoration of the fluid and electrolyte losses in three hours of exercise can only be achieved by the consumption of ~10 g of NaCl in food over a 24 hr period.

Drinking isotonic (280 mOsm) CHO + NaCl solutions will not adequately replace sweat Na+ losses. For the maintenance of plasma and interstitial Na+ ion concentrations and hence volumes, an athlete would have to ingest one litre of a CHO solution containing 60 mmol/l of NaCl every hour. But such a solution is unpalatable. NaCl is only palatable up to concentrations of 20 mmol/l and most athletes can only drink ~ 0.5 l/hr. Hence, whether the replacement of 10 of the ~ 60 mEq of Na+ lost in sweat per hr significantly helps to maintain plasma volume during prolonged exercise is open to debate.

POTASSIUM:Potassium is the major intracellular ion and is lost from the body in sweat and urine during exercise. However these losses are small (<1 gm even during very prolonged exercise) and are replaced by the normal daily dietary intake of 2-4 g. There is no evidence that potassium supplementation is required by the physically active

Magnesium: Magnesium is another intracellular ion that, like potassium, is lost in sweat and urine during exercise. But the losses are trivial. There is no published evidence showing that magnesium deficiency is either common amongst the physically active, or that magnesium supplementation can either increase the intracellular magnesium stores, or enhance performance.

source: ultarunr.com

MY COMMENT: Dr. Noakes is recognized as a pioneer in the science of dehydration and fluid replacement for endurance athletes.

Bellingham Bay Marathon

Here I go again- another marathon with no long runs under my belt other than the Skagit Flats Marathon 3 weeks ago. I am doing the Bellingham Bay Marathon Sunday.

I actually feel optimistic

- I've done more road than trail running recently, so my pace has been quicker.

- I've done a couple of decent interval workouts since Skagit Flats.

- I've felt ok on a couple of tempo runs- something that I've been neglecting recently.

- I have that marathon under my belt 3 weeks ago that I am convinced will help and not hurt.

- Temperatures should be ok.

One negative that I see is race organizers are serving something called Ultra Replenisher- a drink loaded with electrolytes but only 10 calories per 8 ounces. BIG MISTAKE! Since when do electrolytes enhance endurance performance?? As far as I know electrolytes become more concentrated in the body as you dehydrate/

This study published in the J of Applied Physiology measured "a significant rise in serum sodium and potassium immediately after the marathon run."

"Electrolyte deficiency probably does not occur during marathon running"
-Run The Planet

There is little physiological basis for the presence of sodium in an oral rehydration solution for enhancing intestinal water absorption as long as sodium is sufficiently available in the gut from the previous meal or in the pancreatic secretions (84). Inclusion of sodium (<50 mmol ? l-1) in fluid replacement drinks during exercise has not shown consistent improvements in retention of ingested fluid in the vascular compartment (20,23,44,45). A primary rationale for electrolyte supplementation with fluid replacement drinks is, therefore, to replace electrolytes lost from sweating during exercise greater than 4-5 h in duration (3). Normal plasma sodium concentration is 140 mmol ? l-1, making sweat (~50 mmol ? l-1) hypotonic relative to plasma. At a sweat rate of 1.5 l ? h-1, a total sodium deficit of 75 mmol ? h-1 could occur during exercise. Drinking water can lower elevated plasma electrolyte concentrations back toward normal and restore sweating (85,86), but complete restoration of the extracellular fluid compartment cannot be sustained without replacement of lost sodium (39,70,89). In most cases, this can be accomplished by normal dietary intake (63). If sodium enhances palatability, then its presence in a replacement solution may be justified because drinking can be maximized by improving taste qualities of the ingested fluid (9,25).
-ACSM Position Statement on Exercise and Fluid Replacement

26 Tips for Marathon Training and Racing: #1- Post Marathon Recovery

"You’re not ready to run another marathon until you’ve forgotten the last one."- Frank Shorter

Once you've completed your marathon, consider yourself injured. More than likely you are dehydrated, depleted, and inflamed. Your sodium levels are probably low, and your immune system is suppressed. Core body temperature is elevated and your legs are sore- usually very sore. Soreness is a sign that those muscle fibers have been severely traumatized and are damaged.

In order to repair properly, you need to eat, drink, and rest. Replace your electrolytes and start snacking as soon as possible. Dr. Tim Noakes cautions that a small number of slower runners who drank large quantities during the race might actually be over hydrated and should be careful not to drink too much in the period afterward.

If you sit for too long, you'll become very stiff, so I like to walk as much as possible in the first hour. Once fully re hydrated, over the counter anti- inflammatory should help reduce inflammation and speed recovery.

This article from sportsinjurybulletin.com discusses how antioxidant supplements like vitamins C and E can speed recovery of traumatized muscle tissue. Antioxidants may also protect you from post race illness.

Many marathons mistakenly believe that jogging the day following a marathon speeds recovery. You are better off resting until the soreness is gone before resuming light jogging. For most people, that takes 3-4 days. A very light massage may also help heal tissues, but basically you just need rest. If you must exercise, head to the nearest pool.

After 26.2 miles you are entitled to eat just about anything you want at that first meal. You certainly deserve it, and one incidence of over indulgence following that kind of effort means nothing. Ideally you should begin replacing healthy portions of carbohydrates and protein as soon as you can. Surprisingly, you may not have much of an appetite at first, but there is no doubt that you will be hungry within 2-3 hours.

The general rule of thumb for complete recovery is 1 day for every mile raced, so figure it takes a month to get everything back to normal after a marathon.

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