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Sweat, Electrolytes and sports drinks

Interesting info regarding sweat

In order to avoid an increase in body temperature during longer physical effort, the body excretes liquid (sweat). The cooling effect of evaporation helps regulate body temperature. For every millilitre of sweat which evaporates, the body loses about 0.6 kcal of heat. There are strong individual differences in the production of sweat. The maximum amount of sweat evaporating from our skin can reach 30 ml per minute or 1.8 l per hour. The effective sweat volume is higher though, as not all sweat evaporates. A large part simply drops off our skin without little effect.

Sweating is essential for extreme physical exertion. Athletes can produce 2 - 3 l of sweat per hour. Leisure sports generally result in 1-2 l of sweat loss per hour. In the case of extreme exertion, the body not only loses water through sweat, but also from breathing - especially at high altitudes, such as mountain-climbing and skiing.

Air humidity - the level of water in the surrounding air - also influences sweat production.. High humidity prevents sweat production and heat transfer. At a humidity level of 90-100 %, for example, the transfer of body heat via evaporation (sweat effect) is virtually zero, as humidity is so high that sweat cannot evaporate. Sweat simply rolls off the soaked body without any cooling effect. In order to regulate the heat generated by exercise, however, the body continues to produce sweat - leading to increased liquid needs.

At a relative humidity of 50-60 % and more, you should be more careful - especially at high air temperature levels.

Well trained or extremely fit people can cope better with fluid loss than the untrained however, this should not lead them to believe they can drink less in order to reduce sweating. Why? The more you drink, the less you sweat. Well-supplied blood vessels can radiate more heat and less sweat is required to regulate body temperature.

The composition of sweat:

Sodium 1,200 mg/l Chloride 1,000 mg/l Potassium 300 mg/l Calcium 160 mg/l Magnesium 36 mg/l Sulphate 25 mg/l Phosphate 15 mg/l Zinc/iron 1.2 mg/l each

Source: (Konopka: Sporternährung 2001 p. 95)

The fitter you are, the more hypotonic your sweat is, i.e. the amount of most minerals in your sweat is lower than the amount in your blood. Well-trained sweat glands can retrieve sodium from sweat, but cannot remove potassium and magnesium. Fitter individuals who are sweating profusely often lacks these two minerals.

My Recommendations for Electrolytes in sports drinks

I would recommend the "Maximum Endurance Anti-Catabolic" drink as a base. With the electrolytes above so that the concentration of these electrolytes in the drink are as close as possible to the concentrations that they exist in your sweat. Because the amount you drink should be more or less equal to the amount that you sweat, this strategy generally works OK.

The article I wrote (http://www.custom-sports-drinks.com/sports-nutrition/The-Importance-of-Electrolytes.html) does a pretty good job explaining the need for electrolytes.

Salt

A prospective study was performed on 36 athletes during a three- to four-hour triathlon and 64 athletes at an ironman race, which lasts between nine and 15 hours. No athletes were hyponatremic (low sodium levels) after the shorter race, but 27 percent were hyponatremic following the Ironman(tm). An average of 17 percent of the Ironman(tm) participants required medical attention, most for hyponatremia.

I have a bias for limiting the amount of salt in sports drinks. This bias is because the majority of us eat far to much generally don't require extra sodium supplementation. In addition, if you're fairly fit, your sweat will have less salt than listed above. The sodium concentration in this proposed drink will replace 60% of the salt you lose through sweat if you are not too fit. If you're reasonably fit, it should replace 80-90% of the salt you lose. This should be enough.

Potassium:

Potassium is mainly lost through sweat and urine. In a study of athletes running 40 minutes at 70 degrees Fahrenheit, potassium loss was estimated at 435 mg/hour. Potassium is lost as cells release potassium into the bloodstream during exercise.

Based on this rate of potassium loss, supplementation after both short and long events is warranted. For post exercise replacement, athletes should take potassium supplements of about 435 mg/hour of exercise or 200 mg/kg of weight loss. As much as 150 mg/hour during activity can be tolerated by most athletes. The drink below has a potassium concentration of 150 mg/litre when mixed to 5%. This half as much potassium as you lose through sweat. If you'd like, I can up the concentration to 300mg/litre of sports drink later. But it's a good idea to see how your stomach handles this lower concentration first and then gradually up the concentration.

Anti-oxidants:

Aerobic athletes probably have an increased need for this vitamin because their cells undergo more oxidative damage than their sedimentary counterparts. Research shows athletes have less cellular damage when they ingest more vitamin E. Aerobic exercise places additional demands on the molecular free radical scavengers of the body, and vitamin E is a well-known scavenger.

In a study of 30 top-class cyclists, five months of supplementation with natural vitamin E (alpha-tocopherol) at an 800-IU daily dose significantly decreased markers of oxidative damage to muscle tissue. However, vitamin E did not benefit athletic performance.

It is not possible to add vitamin E to powdered sports drinks, but it is very important to include antioxidants in a sports drink. As a substitute, it is sufficient to consume 100mg of Vitamin C/hour.


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