The rate of muscle building can be described as the balance between catabolism (muscle protein breakdown) and anabolism (muscle protein synthesis). When anabolism is greater than catabolism, your body builds muscle mass, otherwise you lose muscle.
Working out and especially lifting weights is a highly catabolic process. That’s actually contrary to mainstream belief that muscles grow when you lift weights. Muscle protein breaks down during your workout – the more intense or longer the workout, a bigger catabolic process occurs.
But before you get all paranoid let me tell you that this catabolic process is actually normal and even needed in order to build muscle.
Your muscles rebuild themselves after this catabolic process. That’s why it’s safe to say that muscles grow out of the gym, not in it. After an intense workout the protein synthesis increases rapidly so the body can rebuild the broken muscle fibers and grow them a bit bigger to ensure they can withstand the same stress next time.
It’s not entirely clear how muscle building process happens, but it is believed that muscle breakdown and muscle synthesis trigger the release of enzymes that are responsible for starting a chain reaction in the organism, resulting in increased protein synthesis or protein breakdown.
Mainly, there are three ways to stimulate the muscle building process: muscle micro tears, tension and metabolic stress:
Micro tears in the muscle.
If you work out, chances are you have experienced the muscle soreness a day or two after the workout. The soreness is known as DOMS – delayed-onset muscle soreness and it happens as a result of micro tears in the contractile proteins as well as the muscle cell membrane. Once your workout ends, the body produces a special kind of molecules, cytokines which trigger the release of growth factors, which then lead to increased muscle size and increased ability of the muscle to cope with physical stress. Read – “can you gain 10 lbs of muscle in a month?”
A certain tension applied on muscles will lead to an anabolic response. A greater tension will lead to a greater anabolic response. The problem is that this happens to a certain extent; there is an upper limit to which tension has an effect on muscle growth. After that limit is passed some other factors become important for further muscle development.
Metabolic stress occurs from metabolites buildup, such as lactate, hydrogen ions, inorganic phosphate, creatinine, etc. Perhaps the most interesting factor associated with muscle growth is exercise-induced metabolic stress.
Several researchers have proposed that exercise-induced metabolic stress may in fact confer such an anabolic effect and some have even suggested that metabolite accumulation may be more important than high force development in optimizing muscle growth. (1)
Some studies have found that pressure-cuff exercise performed with light weights, far less than what is normally considered sufficient for promoting muscular adaptations, can promote significant muscle growth as a result of generating a substantial amount of metabolic stress.
When you think about it , it’s actually impossible to apply each one of these factors alone to increase muscle size. Every one of them is connected to the other two. To increase your muscle mass, you should apply these factors as a balanced mix in your workout.