Follows is an articles written by Dr. L. Lee Coyne, Ph.D. relating to sports drinks for athletic activities:
Sport Drinks in Review
Written by Dr. L. Lee Coyne, Ph.D.
Sport drinks through extensive marketing, have become very popular, over-used, mis-understood and mis-represented. There are also many food items or drinks promoted as substitutes for sport drinks and there is flurry of “home-made” sport drinks options promoted by those opposed to the commercial versions. The following review is designed to clarify and explain the role, the rationale and the research behind sport drinks.
The first commercial sport drink was Lucozade, developed by GlaxoSmithKline Pharmaceuticals in 1953 in England. The first North American product was based on research in 1965 by a group of researchers at the University of Florida headed by Dr. Robert Cade and tested by the Florida Gators Football team – hence the name “Gatorade”.
Sport Drinks have become the most researched sport nutrition product in the marketplace. Some of the most thorough research on this topic was reported by Dr. Ethan Nadel of Yale University in American Scientist in 1988 when he was lead physiologist for the Daedalus Project (man powered flight from the Greek Island of Crete to the island of Santorini across the South Aegean Sea). This work was followed by Dr. John Greenleaf at the NASA Ames Research Centre in California and reported in several Technical Bulletins from NASA in 1992.
A sport drink is specifically designed to provide water, calories and electrolytes during exercise. The criteria for a good sport drink involves optimum osmolality to ensure rapid absorption, significant energy (100 calories / cup) and a good balance of electrolytes to maintain hydration and many metabolic processes. Such criteria are particularly important for endurance sport activities that last for 50 minutes or more. The longer the event and the hotter the environment, the more significant the effect.
Re-hydration products used in hospital environments, recovering from non-competitive exercise or relaxing on the patio do not need to meet the criteria above.
It’s All About Osmolality
The effectiveness of pre-mixed commercial sport drinks, powdered ingredients that must be mixed in water, the convenience packed Gel products and “home-made sport drinks” is dependent on the OSMOLALITY of the product. Here is where the most of the mistakes are made. Imbalances will inhibit gastric emptying, intestinal fluid absorption, blood flow, and induce side effects such as fever, and cramping.
Osmosis, to review your high school science, is described as the movement of a solvent (water) through a semi-permeable membrane (gut wall and blood vessel wall) from a less concentrated solution to a more concentrated one. If only water existed on both sides of the membrane there would be no net flow and the two solutions would be considered isotonic. You cannot calculate osmolality from a formula, it has to be measured.
Similarly, if the concentration of particles (number of particles, not the size) in the gastric fluids was the same as it is in the blood, there would be no net flow of water in either direction. However if the gastric fluids are primarily water (meaning very few particles and a very low osmolality) there would be a net flow of water into the blood in an attempt to equalize the osmolality.
This low osmolality of the gastric fluids would be defined as hypotonic (less concentrated than the blood). On the other hand, if the gastric fluid were more concentrated (meaning more particles and a high osmolality) than the blood, there would be net flow of water from the blood to the gut and this would be known as a hypertonic solution.
The osmolality of blood hovers around 280-290 mmoles/kg (that’s how they measure osmolality) so the best sport drinks have osmolality measures near or below these values. Maugghan, reported in the Canadian Journal of Applied Physiology in 1999, after a thorough review of the science that the optimal osmolality for sports drink to be defined as in “the slightly hypotonic range between 200 and 260 mmoles/kg”.
The carbohydrate content of the drink seems to exercise the greatest influence on osmolality (electrolyte content also contribute) and that is why you see most Physiologists recommending 6 – 8% carbohydrate solutions (see the most popular grocery store sport drinks). This usually results in a solution of 12 to 16 grams of carbohydrate (50 to 60 Calories).
However there are a few drinks that are 10 -12% carbohydrate and containing up to 25 grams of carbohydrate (100 Calories). This can make a big difference in the glycogen sparing action during an Ironman or Ultra-marathon race. These are the products that use maltodextrin which is a chain of 3-17 loosely connected glucose molecules that in terms of osmotic effect is the same as one molecule of sucrose which is one molecule of glucose and one molecule of fructose.
Even mild dehydration – 1% of body weight – which would represent approximately .75 to 1 litre of water (1% of 75 Kg = 750 ml.) can create a reduction in muscle performance and start to show dehydration symptoms. If the dehydration is 2 – 3 %, serious performance inhibition occurs. Dr. David Costill (of Ball State University) demonstrated that at these low levels of dehydration 1 – 3% even the time for 1500 meters was inhibited. The time for a competitive 10 K was reduced by 2.5 minutes which is serious in a 30 min 10 K.
1. Sugar Sources: So how can there be such a variation in carbohydrate content if osmolality is to be maintained? The answer is – not all sugars are created equal. The best sugars are maltodextrin, for reasons stated above.
2. Electrolytes: most drinks have 2 electrolytes, sodium and potassium but there are other significant electrolytes like Calcium, Magnesium, phosphorous and Chloride that all play a role in optimum muscular performance. The ratio of sodium to potassium should be approximately 2:1.
3. There is no place for protein and fat in a sport drink, they would require digestion and negatively affect the osmolality.
4. Commercial gels require the athlete to “play biochemist” while running in order to be sure there is enough water to effect a hypotonic reaction for absorption.
5. Energy Drinks are not sport drinks!! They usually contain caffeine, other stimulants, few electrolytes and inadequate water hence are hypertonic.
6. Recovery drinks are not sport drinks. Recovery drinks should contain a carbohydrate to protein ratio of 3 or 4:1.
7. Coconut water, although a healthy refreshing drink and does have some supportive research in hospital electrolyte recovery situations, it does not meet the criteria for a sport drink. The electrolyte and carbohydrate content varies widely, depending on the age of the young coconut. The osmolality is hypertonic and the carbohydrate / energy content is too low. Although it is high in potassium it is far too low in sodium and other electrolytes in small amounts.
8. Home made sports drinks or alternative food items have been advocated by several writers who suggest you can do better than commercial products. They seem to think they can compete with some of the best biochemists and exercise physiologists in the country. Dr. Sam Mettler of Zurich published in the Swiss Journal of Physiology in 2006 evidence that most home made drinks, although hypotonic but poor in electrolytes and low in carbohydrates. Watermelon and bananas are two of the home version suggestions I recently read. Besides both being somewhat cumbersome while running, both are low in sodium, carbohydrates and several electrolytes.
9. Coca Cola (“de-fizzed”) has been referred to by some to be the first sport drink but the osmolaity is very hypertonic, (493 mOsm/kg), the sugar is high fructose corn syrup and the electolytes are barely evident.
10. Fruit juices are all very hypertonic and inconsistent with electrolytes.
The Table shows the charateristics of several commercial sport drinks and they are in rank order (my preferences) based on osmolality, Carbohydrate / energy content and electrolyte profile. Several alternative items discussed are also shown.
See Attached Table.
So for optimal performance and optimal protection from dehydration I recommend you use a reputable scientifically based product (mix according to directions) and avoid playing biochemist on the run. Long endurance challenges require more than just water. The delivery of energy and electrolytes is also critical to avoid fatigue and health problems.
L. Lee Coyne
Just for my friends: $25.00 off your first home cleaning! Use my code james1864 or use this link: homejoy.com/james1864?utm_…
Saturday May 23, 2015 — 6:12 PM
Saturday May 23, 2015 — 11:41 AM
Thursday May 21, 2015 — 9:31 PM
Wednesday May 20, 2015 — 7:31 PM