Essentials of Nutrition for Sports

No Improved Performance with Amino Acids Burke et al, MSSE, 2003

16

Louise Burke studied amino acids in a carbohydrate sports drink

supplement.

The question was whether time trial performance after 2.5 hours

of exercise was changed depending upon whether or not protein was added to a carbohydrate drink.

Recovery drinks of 8% carbohydr

ate and 2% amino acids were

compared with 8% carbohydrate alone, and 10% carbohydrate. The 10% carbohydrate solution was calorically equivalent to the 8% / 2% solution.

After 2.5 hours of cycling at 70% of VO

2 max, cyclists

performed a 7 kilojoule per kilogram time trial. Eight cyclists received one of the three supplements on each of three different occasions.

In a preliminary abstract report, Burke reported insulin

concentrations were the same between trials. There was no difference in fat or carbohydrate oxidation. Time trial performance was the same regardless of treatment.

Summary

Muscles, composed of protein, c

ontain carbohydrate and fat that

are used to fuel their action. Some protein may also be broken down during muscle use.

It makes intuitive sense to replace carbohydrate, fat, and protein

used during exercise.

16 Burke, L.M., et al. (2003). Addition of amino acids to sports drink does not enhance endurance

performance.

Medicine and Science in Sports and Exercise, 35(5), Su

pplement abstract 1164.

http://www.ms-se.com/pt/re/msse/fulltext.00005768-200305001-01164.htm;jsessionid=Blq3jqYpUDhL1EHLQ1M3JjKsLfp1jT2cPtC1zLU8FBTOYmzXVOb2!-914190194!-949856032!9001!-1?index=11&resu

lts=1&count=10&searchid=10&nav=search

. Accessed

11-24-2004.

The critical questions are how and when. Stored carbohydrate, glycogen, has been studied for more than

half a century.

Restoring glycogen promptly, in

the so-called glycogen window,

has been shown to improve subsequent performance in those who exercise daily.

Whether protein and fat replacement needs to be as prompt as

carbohydrate replacement has not been convincingly shown.

Protein may eventually be shown to help restore or improve

muscle structure, but it has not been convincingly shown to help glycogen replacement when carbohyd

rate intake was adequate or

calories consumed were the same for each group.

Fat replacement after exercise may help restore intramuscular

lipid.

Even if prompt protein consumption is eventually shown to

improve recovery, it is doubtful that this replacement best comes from relatively expensive, advertised, incomplete, and formulated artificial products. Although sports

products will be convenient and

palatable for some, “real food” is probably better—more complete, balanced, tastier, and less expensive.

During high-intensity exercise, athletes cannot tolerate solid

foods. They use sports drinks to replace fluids, electrolytes, and calories. Such sports drinks are convenient and formulated in concentrations generally well-tolerated by the gastrointestinal tract.

After exercise, specialty sports nutritional products are rarely

required.

Consider traditional snacks such

as sandwiches, fruits, cookies,

juices and milk for your immediate after-ride glycogen replacement.

Consider for meals what your parents may have recommended:

lots of carbohydrate with moderate

amounts of protein and fat. And

of course, lots of vegetables.

Nutrition for Sports, Essentials of 73