Was the gym instructor right about women and weights?

There are NO hard and fast rules, including 3 sets of 12. I've been doing strength training for 13 years. I've worked with a few trainers and I've worked alone. When I start a new exercise, I tend to do a little lighter weight the first set or even the first few days until my form is good. CONTROL your motion; don't go too quickly. Doing an exercise with too light a weight is a waste of time. Doing with heavier weight but with bad form will likely get you injured. Let's start with basic bicep curls as an example: if you can do 12 without feeling likely the last couple are a serious strain, the weight is too light. If you're struggling and losing good form by 8 reps, the weight is too heavy. Having said that, sometimes I do super-sets, which means I'm doing a lot more than 12. The key for my body is to mix it up; sometimes I do a smaller number of heavier weights, other days I'll super-set. Sometimes I use free weights rather than equipment, which is nice because you can sort of create a gym in your basement without having to pay to go to a gym. An excellent workout video that uses supersets is Jari Love's "Ripped and Chiseled." I started with that but now just do it on my own, although I do it periodically jsut to make sure I'm still doing it correctly. She's not all in-your-face and eternally peppy, which drives me crazy. Amy Dixon's "Breathless Body" uses only body weight, so you don't need any equipment at all.

And don't worry about getting bulky; women just don't, unless they're doing something illegal (steroids). Your gym instructor sounds like she's working from a manual. 3 sets of 12 isn't a bad place to start, but you'll want something that's right for YOU in the long run. Have you lifted before? It's my favorite form of exercise, probably because it appeals to my left-brained nature.

LOL, loved this quote from the linked article:

"If you’re a bodybuilder and your primary goal is muscle mass, then the majority of your training should be done in the 6-12 rep range, but you should also do a little bit of training in the 3-5 rep range for power and strength, which will later facilitate hypertrophy (and prevent the powerlifters from making fun of you)"

I like that one too.

The key for my body is to mix it up; sometimes I do a smaller number of heavier weights, other days I'll super-set.

And don't worry about getting bulky; women just don't, unless they're doing something illegal (steroids). Your gym instructor sounds like she's working from a manual. 3 sets of 12 isn't a bad place to start, but you'll want something that's right for YOU in the long run. Have you lifted before? It's my favorite form of exercise, probably because it appeals to my left-brained nature.

What exercises do you super-set?

It's not just the testosterone issue that leads to getting massive, a person also needs to substantially overeat in order to get "big".