We have around 650-700 muscles in our body (depending on how you do the math) which are playing different roles of our bodily functions. But what comes to actual serious bone-movers muscles that do the real work, like pecs, delts, lats, glutes, biceps, triceps etc., there are close to 200-300 of those.

And maybe another hundred muscles if you include the fiddly little muscles of the hands and feet and the major facial muscles.

So, you look for building them?

The way our hormones and the immune system responds to training and how they affect muscle growth depends a lot on our nutritional status (quality before quantity), overall stress management and of course, the way we train (intensity, loading parameters, frequency, tempo manipulation, structural balance etc.).

Muscle consist of about 20 % of proteins. Water, phosphates and minerals make up the other 80 %. Research often break  down hypertrophy into two classifications (note that these two are still on a lot of debate but either way).

1. Sarcoplasmic hypertrophy; increases muscle size by increasing the volume of fluid in the muscle cell.

2. Myofibrillar hypertrophy; increases muscle size by increasing the contractile proteins.

Growth can occur in all muscle fibre types (type I, II a and II b), but different types of muscle fibres have different potential for growth.

Fast twitch fibres (type II a & II b) are more likely to grow than slow twitch with intense and heavy training. Classic bodybuilding training with higher volume, moderate weight and short rest intervals stimulates one type of muscle growth (sarcoplasmic due to metabolic adaptations). Using very heavy weights and overloading mechanical tension stimulates the other (myofibrillar). When you combine both approaches together via carefully planned periodization you get the best of both. You need to train heavy, but you also need train lighter, faster and "for the pump". Even if you are doing an exercise for 15-20 reps/set with 30 sec rest intervals, you should still pay attention to how much load you're working and try to gradually increase that load.