When it comes to increasing muscle size or definition, you’ve probably been told that lifting weights breaks down a muscle, which then becomes stronger or bigger as a result of the repair process. But is this really true or simply another one of the common gym myths that is passed along from more seasoned veterans to newbies?
Well, unlike many common gym myths, this claim is actually based in fact because resistance training to the point of fatigue does indeed cause muscle damage. Specifically, that damage occurs to the proteins that comprise muscle fibers. Muscles are bundles of individual fibers wrapped in fascia and connective tissue.
The smallest components of muscle fibers are the actin and myosin protein microfilaments. The sliding filament theory suggests that actin and myosin overlap, and that when they receive the signal from the central nervous system to contract, they slide across one another to create a force-producing, muscle-shortening action.
There are two types of overload that can stimulate muscle growth: metabolic and mechanical. Metabolic overload refers to the amount of work that a muscle performs that depletes it of its available supply of energy. As a muscle is repeatedly exercised to the point of fatigue, the muscle cells adapt to hold more glycogen for fuel. Because 1 gram of glycogen can hold on to 3 grams of water, when a muscle stores more glycogen it can increase in size due to the extra glycogen and attached water.
Mechanical overload refers to the structural damage that occurs to the actin-myosin protein filaments as a result of strenuous exercise like weightlifting or explosive plyometrics. The muscle damage initiates a repair process in which certain hormones, along with the macronutrient protein, synthesize new satellite cells, which are used to repair the damaged muscle fibers. In other words, the role of protein is to help repair tissues damaged by exercise.
Read on to learn nine things about the role that protein plays to support the body during and after exercise.
In the human body, proteins are the primary structural components of cells and perform a few different duties. The primary function of the protein consumed in the diet is to build and repair cells, including the muscle cells damaged when exercising to the point of momentary fatigue. (Note: Failure is not completing a repetition; fatigue is not being able to perform another repetition.) Additional roles that dietary proteins play in the body include transporting cells, serving as enzymes to support various physiological functions and acting as hormones.
While the primary role of protein is to repair damaged tissues, it can also be used to produce energy for muscle contractions when other sources of adenosine triphosphate (ATP, the cellular form of energy), namely fats and carbohydrates, are not available. Gluconeogenesis is the term that describes how protein is converted to glycogen for ATP. However, this only occurs as the result of moderate-to-high intensity for an extended period of time.