Understanding the basics of growing muscle is essential to know if the program you are doing will grow your muscles, or leave you spinning your wheels. Most people working out want to grow muscle, even if they say they just want to “tone up”, but if you asked them how they are going to grow that muscle, they may leave you with a blank stare. The more we know about what we are trying to accomplish, the more successful we will be. The 3 variables that we will be covering do not have to be practiced at the same time to see results, you could train 1 variable at a time and periodize which stimulus you want your body to respond to. At least 1 of these variables need to be present to build muscle.
The first variable in building muscle is Mechanical Tension. This one could be simply summed up as using a challenging weight. When you train with challenging weights, your body will understand that it needs to respond by building stronger muscles. Muscle size and strength go hand in hand as one of the ways the body increases strength is by increasing the size of the muscle (cross sectional area).
When muscles are damaged, the body wants to protect itself from damage in the future, so it rebuilds the muscle bigger and more resistant to damage. This does not mean that you should go to the gym and just demolish your muscles every day, you must recover to see results. Since most muscle damage is done on the eccentric portion of the rep (lowering or lengthening), you can use this method by adding in negatives, or focusing of the lowering portion of the rep. Muscle damage is also what causes muscle soreness.
Metabolic stress is that burn you feel inside the muscle. Inside skeletal muscle you have 2 main groups of muscle fibers, type 1, and type 2. Type 1 fibers are used mostly for endurance and get tired slowly, type 2 is made for strength and power and get tired quickly. Type 2 fibers are also larger. As you do more reps and more type 1 fibers get tired, the more you rely on type 2 fibers. Type 2 fibers also produce lactic acid, and the main ingredient to the burning feeling which is hydrogen. When you train for the burn, the body uses hormones to signal the muscle to grow.
If you are using one of these 3 principles in your training, you are on the path to building muscle.
B.S. Exercise Science