It’s common for many people to question why dietary protein is so important when it comes to physical training. To begin, it’s important that they understand why dietary protein is so important for everyday living.



Proteins are essential parts of many bodily processes and constitute much of the stuff from which the body is made. Some proteins function as enzymes that catalyze biochemical reactions and are vital to metabolism. Other proteins are used also for structural or mechanical purposes in various types of tissue, including muscle. And still other proteins are important in cell signaling and as part of the body’s immune responses.

As part of the digestion process, proteins that are consumed are broken down into amino acids that can be used as the building materials for proteins in the body. Many proteins are “made on demand” through a process known as transcriptional regulation. Other proteins need to be bound by another molecule in order to be activated. This is known as receptor-mediated activation. Others require a sequence of events to occur before they can be activated. Some amino acids are termed “essential” because the body cannot synthesize them, so that there is need for a new supply (for synthesis) to compensate for the amount lost (through degradation). The essential amino acids are leucine, isoleucine, valine, lysine, threonine, tryptophan, methionine, phenylalanine and histidine. The first three are believed to account for over half of all muscle tissue.

In muscle tissue, amino acids taken up into muscle tissue perform two basic functions at the cellular level. In one, they become cellular catalysts. Without these catalysts, muscle fibers would not be able to function. The rate of depletion is related to the amount and duration of the work performed. In the scheme of things, the use of amino acids for catalyst replacement takes precedence over repairing damaged tissue.

In terms of muscle conditioning, the second function for amino acids is for use as building material for creating and repairing tissues throughout the body. If the intensity of exercise is sustained for too long, proteins used as catalysts are depleted and need to be replaced quickly in order for them to carry on survival functions. Those amino acids that have been absorbed for use in protein synthesis are the first to be converted into catalysts. If there are not enough amino acids present, tissue from the muscle will be used in the process of gluconeogenesis. This is part of overtraining and is obviously counterproductive for a program that seeks to increase or maintain lean muscle mass.

Because the body uses protein for many functional and structural purposes other than as a source of fuel, it is necessary to have some dietary intake of protein on a regular basis. And because the body needs a constant source of protein for survival purposes, if need be, it will tap into the primary storage areas–muscle.

So, in order to spare proteins for their primary uses as catalysts and for cellular repair following a workout, it is beneficial to provide the body with sufficient fuel sources. Perhaps the easiest way for someone to avoid this form of depletion from overtraining is to ingest an adequate amount of total calories, to include some protein, every 3-4 hours. Since the body’s preference is to use carbohydrates for energy, making sure to consume an adequate amount of carbohydrates spares protein for other uses, including, of course, as catalysts and as material for cellular repair and growth.

In terms of a workout routine, it is important to set up a program that does not lead to overexertion. This will allow sufficient post-workout recovery catalysts and provide enough energy to immediately initiate the process of growing new cells and maintaining tissues (anabolism).

While most people get enough protein through multiple sources for everyday living, it is important that clients are aware of the basic uses of amino acids in muscle and why adequate protein intake is so important for lean tissue mass increase and maintenance. Not everyone counts calories, and fewer still count grams, so providing clients with some examples of good quality protein sources can go a long way toward making sure they are stocking up on the right building materials.


1. The National Federation of Professional Trainers. Sports Nutrition Manual. 2nd Ed. Lafayette, IN: NFPT, 2006.

2. “Protein in diet”. Medline Plus Medical Encyclopedia. U.S. National Library of Medicine and National Institute of Health. September 2, 2003. Retrieved 2013-2-27.



These resources are for the purpose of personal trainer growth and development through Continuing Education which advances the knowledge of fitness professionals. This article is written for NFPT Certified Personal Trainers to receive Continuing Education Credit (CEC). Please contact NFPT at 800.729.6378 or with questions or for more information.