Fluids, Fuels & Electrolytes Required For Beating The Heat
THE MARATHON de SABLES, AN ULTIMATE TEST,THE TRANS-SAHARA DESERT FOOTRACE
By Dr. Bill Misner Ph.D.
Marathon des Sables (”Marathon of the Sands”), is known as the “Toughest Footrace on Earth”. Over 500 ultramarathon runners from 30 countries on six continents are entered in the 15th annual event. Men and women will traverse nearly 150 miles across the Sahara Desert of Morocco over seven days while carrying all of their food and gear. Most will carry back packs
weighing over 13 pounds! A ration of nine liters of water and an open-sided Berber tent are provided daily to competitors.
The Sahara’s climate is very hot and dry. Although it is very hot during the day, it does become cold at night. Day-time temperatures of 40°C (110°F) are common and 50°C (125°F) sometimes occurs. Night-time temperatures may drop as low as 5°C (40°F).
The terrain varies from year to year, but generally covers rocky plains, lake beds, sand dunes, or traverses through small villages.
This footrace is a competitor’s ultimate physical stress test. Many will not finish or drop out after nearly a full year’s training.
Over half of those that fail to complete the event, fail due to improper hydration, lack of a balanced intake of electrolytes with a supportive levels fluid and fuel.
ULTRAMARATHONERS IN MOTION ARE BIG HAIRY “WATER BAGS” WITH MANY POROUS LEAKS
The average 154 lb. person has 2 compartments filled with 85 lbs.(total) fluids that must be kept in constant osmotic balance. Inside our cells where potassium ions are 15 times higher than outside, 25 liters of water[53 lbs.] is stored in homeostatic balance with the more water is stored outside cell walls.
Outside the cells, sodium ions are 10 times higher than inside, an additional 15 liters or 32 more lbs. of water are stored.
What happens when the heat goes up is a runner can lose up to 2.2 pounds of water per hour. which is 2% of a tiny 110 lb. person or 1% of the larger athlete!
Symptoms that have been observed when a percentage body water weight is lost is as follows
0% — normal heat regulation and performance
1% — thirst is stimulated, heat regulation during exercise is altered, performance decline
2% — further decrease in heat regulation, increased thirst, hinders performance
3% — more of the same(worsening performance)
4% — exercise performance cut by 20 - 30%
5% — headache, irritability, “spaced-out” feeling, fatigue
6% — weakness, severe loss of thermoregulation
7% — collapse is likely unless exercise is stopped
10% — comatose
11% — death likely
When an athlete loses up to -3% body water weight of these valuable life-giving fluids from evaporative sweat cooling, performance begins to suffer dramatically. After a 5% water-weight loss, mental concentration is impossible, following a 10% body weight loss of fluids the athlete loses consciousness, lose only -1% more[11% fluid loss] and death is likely.
Exercise in thermic conditions dramatically effects our normal tissue-fluids state of being[2, 5]:
NON-EXERCISE EXERCISE IN THE HEAT INTAKE
URINE -1400 ml. -500 ml. FLUIDS+1500 ml.
SKIN -350 ml. -350 ml. FOOD + 800 ML.
BREATHING -350 ml. -650 ml.
SWEAT -100 ml. -5000 ml.
FECES -100 ml. -100 ml.
__________ __________ ______________
TOTAL -2300 ml. -6600 ml. +2300 ml.(Normal)
= -4300 ml.(Exercise)
Normal activity shows a daily balance, but add exercise to the model, resulting in a -9 lbs. water weight deficit or nearly 6% of the original 154 lb. athlete’s total body weight ! Dr. David C. Nieman, Ph.D. describes a 6% loss as very serious, causing impairment in temperature regulation and rapidly increasing heart rate.
Water is most efficiently replaced by distilled water or water that has been precisely modified with a low-sodium electrolyte profile. High sodium or high electrolyte fluids are held longer in the vascular compartments than the lower non-electrolyte
composite. One reason salt tablets were eliminated from professional athletic training kits is that shortly after a sodium depleted athlete would slug a few salt tablets, stomach cramps would bend them over double. One report suggests however, that total correction or overcorrection of sodium solution may result in irreversible damage to the brain. Why is this and what causes these pressure gradients to occur?
BODY FLUID OSMOLAR PRESSURES ARE ABSOLUTE FOR OPTIMAL PERFORMANCE
Equilibrium of solutes in concentrations of Osmotic pressures occurs at 300 milliosmoles per liter(mOsm/l.) When a change in the pressure of the solutes or electrolytes vary, correction of the pressure deviance will occur in a single cell in less than 60 seconds! When the whole body is “Whacked” out of equilibrium as little as a 3% fluid loss, it takes up to 30 minutes of NO activity, using a perfect fluid-electrolyte replenishment drink to restore osmolarity to 300 mOsm/l. to the 40-liter intra- and extra-cellular fluid content inside a typical 154 lb. athlete exercising in thermic conditions.
The kidneys filter 180 liters of the body vascular fluids per day, but returns 99% of its filtrates, while eliminating only 1-1.5 liters as waste water. These magnificent filters help us maintain a constant 300 mOsm/l. Osmolarity. When the body senses a
+ or -3% solute change, the following mechanisms may be called upon to assist the kidneys in osmolarity balance:
(1) The Pituitary secretes ADH(Anti-Diuretic Hormone) enabling water to be reabsorbed, sensing it is too concentrated.
(2) The Adrenal Glands secrete Aldosterone when sodium concentration in plasma is low, causing sodium to be reabsorbed producing a more diluted urine.
(3) An osmolarity rise of 1% may cause a thirst craving for drinking fluids, and diluting blood serum-urine concentrates.
All of these control mechanisms are sensitive to a + or -3% deviations in sodium and a + or -7% deviation in potassium, while calcium levels are also monitored in the extracellular fluids within a few percents by secretes of the parathyroid.
It is also interesting to note that normal healthy body fluids in saliva, gastric juices, and small intestine produce a 7:3 ratio** of potassium to sodium, similar to the number deviation which triggers control mechanism restoring normal electrolyte-fluid osmotic balance.
Under normal conditions(during non-exercise) intake of a liter of water will cause 8 times the normal urine output within 45 minutes lasting up to 120 minutes after intake. Want to know if you are properly prerace hydrated? To measure how hydration before an exercise or after, consume a liter of water, then measure urine output from 45-120 minutes.
OTHER BODY FLUID ELECTROLYTE PROFILES (8 fluid ounces=240 ml.)
(1) SALIVA=800-1500 ml./day: 877 mg.Sodium Chloride, 1170 mg. Potassium, 3000-4000 mg. Bicarbonate
(2) GASTRIC JUICES=1500 ml/day: 1120 mg. Potassium Chloride, 175 mg. Sodium Chloride, 5600 mg.HCL
(3) SMALL INTESTINE=1800 ml/day: Pure Water from Extracellular fluids
PRERACE-RAISING EXTRACELLULAR FLUID STORES BY GLYCEROL HYPERHYDRATION
Hyperhydration-The use of glycerol in a 3-day hyperhydration loading schedule will maximize body fluid uptake-storage before an event by diverting some of the kidney filtration back into extra cellular stores. When doing the loading technique, daily weighing should confirm a fluid weight gain of up to no more than +3% of original weight. Should the athlete gain more, it is wise to stop loading at the +3% gain juncture.
Each glycerol product has different instructions, however 2-3 tablespoons of glycerol sipped with 24 ounces fluid in 3 hours sessions 4 times each day for 3 days should enhance water hyperhydration stores. What about the weight gain? You will lose
the excess in the first 90 minutes of running in the heat.
FLUID-FUEL-ELECTROLYTES MECHANICS FOR REFINING BALANCE DURING THE RACE
During an extreme hyperthermic ultra event, Noakes suggests 16-24 ounces FLUID intake per hour for endurance athletes performing at 75-85% VO2 Max in which he documents his treatise on fluid volume of observed in endurance events [1985-1993] lasting from 3-12 hours.
Selected fuel need to be diluted at 1 ounce (28.3 grams)of long chain carbohydrates to 5 liquid ounces of water, or roughly a 20% solution(fluids:fuel, 5:1 by weight), to provide mOsm at body fluid osmolality of 280-300 mOsm/l. for optimal fuel and fluid gastric emptying. Many athletes using simple sugared products such as sucrose, fructose, or glucose do not realize
that simple sugars may double the osmolality rate, significantly delaying gastric absorption. When absorption of fuel is delayed due to a high osmolar sugared solutions, fluids and electrolytes must be drawn[out of the body] across gastric linings in order to lower the osmolar pressures to allow transition of much needed fluids and fuels for working muscles. If a sugared solution is chosen it should be no higher than 5-6%, while long chain maltodextrins may be readily absorbed at between 15-20% solution!
Better to avoid all the simple sugar solutions! Why? Take a look…
TYPE OF FUEL CALORIES PROVIDED AT 280-300 mOsm
Glucose 0.2 cal/ml
Fructose 0.2 cal/ml
Sucrose 0.4 cal/ml
Maltodextrins 1.0+ cal/ml
The suggested use for “Electrolytes” during a hot-humid event (70 degrees-70% humidity) or very hot dry[102 degrees 0-20% humidity] will vary between individuals.
The electrolyte lost most is Sodium, which may be lost at a faster rate than the total volume of perspiration fluids are lost.
The average American[Western Diet] eats and stores 7000-8000 mg. of Sodium. With that much in excess the body likes to throw it off in sweat at the rate of 2000 mg. per hour. As the body begins to biochemically detect sodium depletion, it tells the kidneys to recirculate blood serum sodium and stops throwing it off in the urine. Unfortunately, it does not communicate this message to the body’s largest organ, the skin, which is stressing in survival instinct to cool the brain due to its sensitivity to overheating. What sodium gets caught up in the perspiration flow is lost in spite of the kidneys recycling all the blood serum sodium that comes through its filtering passages. Most individuals under most circumstances are satiated by 200 mg. to 600 mg. sodium per hour with few exceptions.
Sodium is the electrolyte lost most, followed by Chloride, Potassium, and Magnesium. Some have argued that a well-balanced electrolyte formulae should include substantial amounts of Calcium, Vitamin B-6, and L-Tyrosine.
SEVEN HINTS FOR BEATING THE HEAT
Each person’s biochemistry responds in a unique individual manner. Long training efforts in race-like hyperthermic conditions should be regularly attempted at distances of at least 75% of the total daily stage race-distance at race or sub-race pace with a weighted pack, fluids, fuels, and electrolytes in tow. Each runner is responsible for acclimatization of their biochemistry to each factor similar-to-race conditions as possible.
Time in training is necessary to physiologically adapt to the ideal mixture of fluids, to fuels, to electrolyte profiles. Of the DNF’s and/or “Failures” who report to me each year, “What did I do wrong?”, 90% of them did not acclimatize their body to hyperthermic conditions similar to those they encountered during race conditions, were inadequately trained, e.g. not fit, or they did one of the following:
(1) Drank too much, average intake exceeded +30 oz/hour, causing dilutional hyponatremia:
The symptoms of Hyponatremia are as follows:
(a) Strong thirst and loss of appetite.
(b) Increasing hemoconcentration, dry mouth, low urine or high clear urine output depending on individual biochemistry and volume of water loss or water dilution.
(c) Increased effort to exercise even at lower exercise rates.
(d) Difficulty concentrating, dizziness, increased HR, flushed or white skin.
(e) Muscle-spasms and muscle-twitching, swollen tongue, inability to balance with eyes closed.
(f) Low plasma serum sodium below 130 mEq/L or mmol/d. Normal plasma serum sodium if highly diluted will be below 130
mmol/d or mEq/L.
(g) Severe Heat Cramps with excessive salt-stain residue on clothing in an athlete who claims to have hydrated at least +30 ounces of fluids per hour or more each hour of exercise.
(h) Circulatory insufficiency, decreased blood volume, labored breathing.
(2) Ate a sucrose, glucose, or fructose based product raising gastric osmolality to high above normal body fluid osmolar pressure.
(3) Took no electrolytes, too little, or too much[salt tablets].
(4) Took a product containing caffeine, ginseng or ephedra.
(5) Failed to acclimatize their body to hyperthermic conditions Heat-adapted athletes were shown to be cooler at the end of hot humid exercise largely because they start cooler. The lower terminal temperature is not due to a reduction in heat storage. Implication? Slight drops in resting core temperature could be used as an index of the heat adaptation response when training in the heat. Heat acclimatization takes 7-10 days of exercising for 2-4 hours daily in the heat wearing heavier, heat-retentive clothing. Once heat acclimatization is accomplished by such daily grueling practices, the body will maintain this adaptability to
“handle the heat” for up to 2 weeks. Is acclimatization, heat training, fluids, fuels, electrolytes intake, and gastric compatibility important? Absolutely “Yes!” Just look at the adaptive electrolyte profile from the sweat-measured differences in fit-acclimatized vs. fit-unacclimatized, and just imagine which one had the better performance:
ELECTROLYTE(g/L.) FIT-ACCLIMATIZED FIT-UNACCLIMATIZED
SODIUM 1.8 g/l 2.6 g/l
CHLORIDE 0.9 g/l 1.1 g/l
POTASSIUM 0.1 g/l 0.15 g/l
MAGNESIUM 0.1 g/l 0.1 g/l
(6) Self-destructed by “Pushing” individual body core temperatures too high without practicing occasional cooling: Sponging face, neck, chest, stomach and shoulders with either a wet towel or sponge has been demonstrated to lower body temperature effectively during a 1-minute walk break, during a run, or a “Slow Down” like taking a 1-minute coasting break on the bike. Some athletes rehydrate during this 1 minute cooling phase, sponge off, lowering their body temperature 3-5 degrees. During extreme temperature readings practice by taking 1 minute walking breaks for every 5 minutes run. Pace and intensity of effort build up inordinate amounts of heat from metabolizing fuels in the energy cycle.
As intensity or rate of exercise increases, the body must decide on whether to pump more blood to meet the energy demands in the muscles or to assist heat dissipation by increasing skin blood flow. Faced with this conflict demand, the body always favors blood flow to the muscles, resulting in increased heat build up within, less heat dissipation without, from blood diversion to the muscle demand. By slowing down the rate of pace or walking 1 minute in every 5, evaporative heat dissipation may be managed even during 3-digit temperature readings and high humidity(+60%).
This is very effective in resolving momentary heat stress relief in a survive mode while all those around you are wasting away, wilted in the heat.
(7) Clothing chosen. “Fish Net” clothing provides the best heat loss evaporative mechanics. Light colored clothing dissipates heat and is superior to dark clothing in hot climatic conditions. Shading the head with a double brim ventilated cap lowers brain temperature which saves both fluids and electrolyte losses from overheating the head alone. Shade permits up to 10 degrees less than direct sunlight exposure. Direct or high-angle sunlight heat is hottest during the hours of 10 A.M. to 4:00 P.M. and should be avoided, except when Heat acclimatization is being attempted.
There are dozens of electrolyte drinks, powdered mixes, pills, and potions, and even more fuels to utilize in liquid, powder, gel, bar, and tablets that fizz.
Chose a fuel, a fluid amount, and an electrolyte formulae mix that enables you to train through the hotest 105 miles in one weeks time[75% of 140 miles] plausible at least 6 weeks prior to the “Toughest Footrace On Earth”, and your biggest worry will be how to pass the competitor climbing the Sahara sand dune on the horizon!
-Grandjean & Ruud, Clinics in Sports Med. Vol 13(1);235-246. Jan 1994.(Nutrition for Cyclists)
Rozelle LT, “All in the Body’s Balance”, WATER TECHNOLOGY, March 1997:126-132.
-Nieman DC, SPORTS MEDICINE FITNESS COURSE, Bull Publishing, Palo Alto Calif., 1986.
-Knochel, JP, Hypoxia Is the Cause of Brain Damage in Hyponatremia, JOURNAL OF AMERICAN MEDICAL ASSOCIATION, 1999;281:2342-2343.
-TEXTBOOK OF MEDICAL PHYSIOLOGY, AL Guyton, WB Saunders, 1991.
-Noakes TD, [a listing 25+ key research studies], THE LORE OF RUNNING, Leisure Press, Champaign, Illinois, 1991: 115-117.
-Misner WD, NUTRITION FOR ENDURANCE: FINDING ANOTHER GEAR, Dolezal & Associates, Livermore, Calif.,1998: 264-274.
-Buono MJ, Heaney JH, Leichliter SG, Vurbeff GK., Acclimation to humid heat reduces resting core temperature but not heat storage. Medicine and Science in Sports and Exercise, 1997; 29(5), Supplement abstract 560.
-Verde, T., et al., Sweat Compostion in Exercise and Heat, JOURNAL OF APPLIED PHYSIOLOGY, 1982 ;53(6):1541-1543.
Dr. Bill Misner, Ph.D. is the full time Nutritionist for E-CAPS INC. & HAMMER NUTRITION.
He is a former 2-time U.S.A. 50-Mile National Masters Champion. In 1998-1999, he established two “World Records” completing the first-ever 10,000 miles and 20,000 kilometers ever run in an organized footrace.
The above article is reprinted by permission of the Endurance Marketing Group, E-CAPS INC. & HAMMER NUTRITION LTD.
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Dr. Bill Misner, Ph.D.
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