Single set to failure or multiple sets for isolations?
I'm a 25 year old male, and I started weight training about 6 months ago. I work with an older man in his late 50's who used to be a bodybuilding/fitness coach back in the late 80's early 90's. I told him I wanted to start working out but I'm not out to become a bodybuilder. I've always been heavy-set & big boned so, I said "I just want to get big and strong, and lose some belly fat". He told me that for isolation exercises, "there is no point in doing a lot of multiples, just do one set & push it to failure, but try to use a heavy enough weight that you're gonna hit failure somewhere in between 8 to 15 reps".
And that's what I've been doing. I'll use my biceps for example, I do 5 different exercises for my biceps each week and I alternate the days so I don't get bored. So far, I've gotten stronger & my arms have gotten bigger.
So i am seeing results. But the reason I'm asking is, I have so many people telling me I need to do multiple this and multiple that or if i don't do multiples I'm gonna have "wimpy" arms! But I am getting results and my arms are bigger than theirs!
So, I would like your opinion, are multiple sets necessary for isolation's or is a one set to failure good enough?