how long does it take to build muscle?
Best Answer: About 3 months if you use gym weight machines (guys can gain 5 pounds of muscle mass a month). You need at least a day or two of rest between weight training sessions (in your 20s and younger), two or three days (in your 30s), three or four days (in your 40s), four or five days (in your 50s)â¦and so on.