Q: for girls: how can we make sure we don't overdo the weights and become unwantingly, overly muscular?

A: The simple answer is to eat so you lose weight or just maintain your present weight and not to gain weight. It is hard enough for most men to gain muscle and it is literally ten times harder for women. The only way for anyone, and especially for a woman, to gain a significant amount of muscle is to combine weight training with a diet that will cause them to gain weight. Without the weight gain, the muscle gains will be quite limited even in men and much much more so in women. So watch what you eat and don't gain weight -- then no matter how hard you weight train you will not become overly muscular.

The popular notion that weight training automatically leads to bulky muscular physiques is quite misguided. It may be somewhat true for less than 10% of men who are genetically gifted in this respect. It is not true for vast majority of men, especially after mid 20s. And it is not true for pretty much all women. So as long as a woman watches her weight, she does not have to worry about becoming overly muscular no matter what training regimen she follows.

There are a couple caveats to this... If you are short in stature, then even a little bit of muscle may create the impression of muscularity. Also if you are a runner, it is possible that your calf muscles may grow to be quite muscular (for many people, both men and women, calf muscles grow from running much more than from weight training). So if you are a runner you may have to make a decision as to whether your running is more important than having non-muscular calves. In case you have short stature or just feel that any muscle tone is undesirable for a woman, you will probably want to limit your weight training to high reps and low weights -- for any given exercise pick a weight that you can do 20-25 reps with before exhaustion and actually do 15-20 reps. Such training will minimize muscle development, but will still give you some of the metabolic benefits of weight training.

But the main point I'd like to emphasize again is that becoming overly muscular sshould not be a concern for a woman as long as she is not gaining weight through overeating. She can and should follow the same weight training programs as men (obviously with lighter weights, according to her strength) and reap all the metabolic fat-burning benefits of weight training and not look muscular. If the thought of any muscle gain at all scares you, then stick to high reps as I described above. But if you want to have a well-toned body, then follow the standard weight training programs that are recommended for men and just watch your diet.