Do we use body protein for energy during endurance exercise?

Depending on the duration of exercise, amino acids may be counted on to generate as much as 6 to 10 percent of the fuel with the remainder split between fat and carbohydrate. The use of amino acids for energy is mostly a consideration for higher-level endurance athletes. This would include people who would train seriously several times a week for extended periods such as a couple of hours. This is one reason why marathoners often look very lean but not as muscular as sprinters or milers, for example.

 

One of the most significant reasons that more and more amino acids are used for energy is because cortisol levels in the blood are increased as the higher intensity activity is endured. Cortisol can cause the breakdown of muscle protein and the freed amino acids can be used for energy. Some amino acids will be used directly by muscle to make ATP, while others will circulate to the liver and be converted to glucose.

 

What are protein recommendations for endurance athletes?

Bodybuilders, power lifters, and football players recognize high protein intakes as an avenue to achieve and maintain enhanced muscle mass. Contrarily, endurance athletes recognize a relatively higher protein (total grams) intake as a means of replacing the body protein used for fuel during training, competition, and recovery and adaptation. Although individual protein requirements will vary with the level of intensity and duration of the activity, some sport nutritionists recognize that 1.5 to 2.0 g of protein per kilogram body weight will provide adequate protein along with a little margin of safety. This is pretty much the same recommendation discussed previously for weight trainers however because of differences in body weight the resulting protein quantity is lower for endurance athletes.

 

Do endurance athletes need a protein supplement?

Before traveling to the local nutritional supplement supplier for a protein supplement, first estimate current protein intake. Since many people, especially males, already eat 100 to 130 g of protein daily (about two times the RDA) only small if any dietary adjustments may be needed. Furthermore, endurance athletes tend to eat more energy than more sedentary people, so more protein is probably, but not definitely included. Endurance athletes should assess their diet prior to spending their money.

 

Can fat loading improve aerobic performance?

Fat loading is a dietary attempt to enhance fat utilization during exercise, thereby decreasing carbohydrate usage and thus slowing glycogen breakdown. The most important considerations with this protocol are timing and practicality as it will take about a week or so for this adaptation to occur and a high fat diet may not be tolerable for many athletes.

 

Eating more fat and less carbohydrate may not build the same glycogen depth prior to competition. So even though they may use less carbohydrate during competition they might have less available to spend during exercise anyway. This may be okay for a marathoner running a slower pace (e.g., 8 minute/mile pace), however for a runner competing at a higher intensity (e.g., 5 or 6 minute/mile pace) this could be disastrous. This is something that an athlete would have to experiment with and become comfortable with prior to competition.