How many sets per workout and how many times a week?
In the past 2 months i've been doing chin ups 3 times a week, 5 sets of 12-15 reps. I have gotten a little bit stronger even if I gained 5lbs in that period, but I still can't do 15 reps on every sets.
Should I start doing weighed chin-ups? I have a 25lbs vest, but i'm afraid for my door frame as you can see in this picture :