Protein isn't considered a great energy source for the human body, however our body does use small amounts of protein for energy. The amount increases in certain cases:
The amino acids available to the body come from the digestion of dietary proteins and from the breakdown of body proteins. These amino acids can be used to synthesize new body proteins or other nitrogen-containing molecules.
If the nitrogen-containing amino group is removed from an amino acid, the remaining carbon compound can be broken down to produce ATP. In some cases, it can be used to make glucose via gluconeogenesis.
Protein metabolism is affected by exercise intensity. Highintensity exercise increases the rate of protein usage. Low-intensity exercise does not. Because amino acids can be used to make glucose via gluconeogenesis, protein becomes a more important energy source as carbohydrate stores are depleted. During exercise, muscles can use amino acids to generate ATP and to produce molecules needed for aerobic metabolism. After exercise, amino acids are used to build and repair muscle proteins.
The body's need for protein is increased by strength training and endurance exercise. Strength training stimulates muscle growth; additional protein is needed to supply amino acids to build muscles. Endurance exercise increases protein needs because amino acids become an important source of energy when exercise continues for many hours.
Also, amino acids are used to synthesize glucose by gluconeogenesis. The glucose produced by gluconeogenesis helps maintain blood glucose levels during endurance activities. Additional protein also may be needed to repair muscle damage caused by intense training.
Exercise FatigueExercise fatigue is due to a combination of psychological, environmental, and physiological factors. Psychological factors, such as mood, can affect exercise performance. A depressed athlete may feel fatigued even before an athletic event. Environmental factors, such as temperature and humidity, also can affect how quickly an athlete becomes fatigued.
Physiological factors that affect fatigue include changes caused by the production of heat, the buildup of metabolites from energy metabolism, and the depletion of liver and muscle glycogen. When athletes run out of glycogen, they feel overwhelming fatigue, called "hitting the wall" or "bonking." Glycogen stores are depleted faster when oxygen is not available and anaerobic metabolism predominates.
Sooner or later, all exercise causes fatigue and exhaustion. When this occurs will depend on the type and duration of exercise, the exercise intensity, and the fitness of the person exercising. During high-intensity exercise, oxygen cannot get to the muscles fast enough, so the body must rely heavily on the anaerobic metabolism of glucose.
This causes glycogen stores to be used up rapidly, leading to fatigue. At a lower intensity, aerobic metabolism predominates, and exercise can continue for longer periods before fatigue sets in. Aerobic metabolism is more efficient and uses mainly fatty acids for energy, sparing glycogen. However, even aerobic metabolism uses some glucose, so glycogen stores will eventually be depleted.
Our website is not responsible for the information contained by this article. Webworldarticles.com is a free articles resource thus practically any visitor can submit an article. However if you notice any copyrighted material, please contact us and we will remove the article(s) in discussion right away.
This article was sent to us by:
Janine Frouber at
01112011
1. Have fun exercising and get fit in no time
All articles in this directory are property of their respective authors. Additionally, read our Privacy Policy
© 2010 WebWorldarticles.com - All Rights Reserved. Partners: Gunblade Saga