What is progressive overload and how you can build muscles with verity of rep ranges
What build muscles?
Every one knows Mechanical tension is the primary driver of muscle growth. However not every one have a good undressing what progressive overload actually means. What is it exactly, adding plates to the bar? It isn’t adding plates to the bar per se. Mechanical tension means exposing muscle tissues to a stressor sufficient enough to disrupt homeostasis, adopt to it, then apply progressively higher stressor and continue to adopt to them.
You probably heard people say you have to train between 6-12 rep range “hypertrophy zone” in order to build muscles. This isn’t based on evidence other than most most body builders usually train in that rep range. This has debunked in the recent past. Hypertrophy zone does exist but it’s between 3-30 reps 
We need to understand 2 key principals in order to understand how we can achieve muscle growth in a wide rep range of 3-30 reps contrary to popular belief of 6-12 reps.
1. Henneman's size principle
According to Henneman's size principle motor units are recruited according to their force production potential smallest to largest. For example low threshold motor units are recruited when performing day to day activities like walking and High Threshold motor units are recruited when you try to sprint as fast as you can. Fatigue during a set in strength training exercise leads to increased motor unit recruitment. Motor unit recruitment increases as fatigue accumulate throughout a set. A high rep set doesn’t induce enough mechanical tension at the start of the set. However as fatigue accumulate throughout the set you start recruit more and more high threshold motor units
2. Force velocity relationship
When performing a heavy set (1-5 reps) bar speed will drop through the set. As force increases, velocity must decrease. Motor unit recruitment will be maximized throughout the set. In a set of 30 reps weight feels light at the begging of the set and the bar will move fast. However last 5 reps of 30 reps will look & feel exactly the same as 5 reps max. (CONTINUE IN COMMENTS SECTION)