joxguy saidFrom years of coaching:
Heavy weights and fewer reps builds bulk: Heavy weight and use 15 reps then 12 reps and last 8 reps for three sets
lighter weights and more reps tones: 15 reps repeated by 15 reps two sets.
This is what my college rowing coach said, and my ballet teachers have said. Oddly, in ballet, they stress muscle confusion (hence all the various combinations and moves), and light (as opposed to heavy) weight training. You have to have 'toned' classic lines with long-firing muscle fibers so you can dance intensely for an hour. Not bulky muscles of short-firing muscles that, while allowing you to lift a small car, will only allow you to do that once or twice.
There are 3 different types of "twitch" fibers. Slow, Fast, and Fast 2. Ballet dancers (and runners) focus on having a lot of slow muscle fibers that can essentially suspend and move our limbs for hours. We then want some Fast fibers to allow us to jump, leap and do the extraordinary moves photographers love to photograph. Weight lifters or those who want to "look" big, should likely focus on type 2 and 3 fibers.
Here's a re-direct to get you started. http://www.bodybuilding.com/fun/sclark20.htm