Which should be training duration to build muscles?

It is depended on which exactly is your goal when building your muscles.It is of great importance to have at least 1 exercise for  all major muscle groups. This means that you must do at least 8 different exercises and mix multi and single - joint exercises.Follow the guidelines presenting on the next table which are best for strenght/power resistance traininig phase:

	Hypertophy	Strenght	Power	Peaking
Sets	3-5	3-5	3-5	1-3
Repetition/test	8-12	2-6	2-3	1-3
Intensity	Low	Moderate	High	Very high
Volume	High	High	Moderate	Low

Tip: Prefer single joint exercises if you are untrained or at an injury rehabilation stage.