Essentials of Nutrition for Sports

Protein as an Aid in Recovery

We are not interested in debating the overall daily protein

requirement here. We are interested

in looking at whether the timing

of protein consumption is important.

What we will address here is whether protein is an important

component of recovery drinks or should be part of a specific recovery strategy after exercise.

At the heart of this issue is whether ingesting protein early in the

recovery process improves gl

ycogen replenishment.

Carbohydrate Fuels Muscles

As discussed on page

43

, muscles are fueled by carbohydrate

and fat.

Since about the 1960s, it has been known that the higher the

intensity of work, the more carbohydrate is burned.

Carbohydrate is supplied from stores in muscles as glycogen and

from the blood stream.

With prolonged moderate- or high-intensity exercise, glycogen

stores can be exhausted. Until these glycogen stores are replaced, the athlete’s ability to exercise repeatedly at moderate or high intensity is limited. Sparing Glycogen

Athletes can supply carbohydrate to working muscles by eating

or drinking carbohydrate while exercising. Ingested carbohydrate travels through the blood stream as simple sugar—for example, glucose—to muscles.

Studies have shown that fueling muscles by ingesting

carbohydrate can spare muscle glycogen.

There is a practical limit as to how much carbohydrate can be

ingested to fuel working muscles. This appears to be roughly 300 carbohydrate calories per hour, 1.2 grams of carbohydrate per

kilogram of body mass, 0.5 grams per pound of weight, or 2 calories per pound. Replacing Glycogen

It is widely accepted that athletes who consume carbohydrate

relatively promptly after exercise, during a

glycogen window

, replace

muscle glycogen more efficiently than those who delay eating.

Again, there is a limit as to how quickly carbohydrate can be

replaced. This also appears to be at the rate of roughly 300 carbohydrate calories per hour, or 1.2 grams of carbohydrate per kilogram of body mass, 0.5 grams per pound of weight, or 2 calories per pound.

Here are details about the science and about the hype:

Protein Replacement Half Truth Van Loon et al, AJCN, 2000

8

Luc JC van Loon et al published an often-quoted study in the

American Journal of Clinical Nutrition, July, 2000.

This research is quoted to prove that protein helps recovery. The

heading

Half Truth

refers not to researcher van Loon, but to how his

research has been manipulated in advertising.

The study was based on eight subjects. Van Loon compared (a) a carbohydrate recovery drink to (b) the

same carbohydrate drink plus one-half again as many protein calories.

8 Van Loon, L.J.C., et al. (2000). Maximizing postexercise muscle glycogen synthesis: carbohydrate

supplementation and the application of amino acid or protein hydrolysates mixtures. The American Journal of Clinical Nutrition. 72(106).

http://www.ajcn.org/cgi/reprint/72/1/106?maxtoshow=&HITS=

10&hits=10&RESULTFORMAT=1&author1=Loon&ando

rexacttitle=and&andore

xacttitleabs=and&and

orexactfulltext=and&searchid=1101346278391_18141&s

tored_search=&FIRSTINDEX=0&sortspec=rel

evance&journalcode=ajcn

. Accessed 11-25-2004.

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