Originally Posted by ElementalVirago
Guys, correct me if I'm wrong but higher rep/lower weight doesn't necessarily make the muscle grow. Really you're just burning calories, which can burn fat, which can make the muscles you have more visible. To me, this is what most people mean when they say "I want to look toned." They don't necessarily want the muscles to be bigger, they just want to have more definition.
If you want to make muscles grow, you have to make them work hard, and that usually means lifting heavy. Lifting heavy creates microtears in the muscle fibers, which causes your body to rebuild those tears by adding more muscle.
When I first started with weights, I only had a max of 5kg dumbbells; I used to do 3 sets of 20 on most exercises...added 10 lbs of bodyweight and lost inches (even though I was already pretty slim). That to me indicates that muscle was built along with a bodyfat loss and the biceps certainly stood out...plus, the doctor commented about the muscles.
That info is probably better than any study or theorised info that may be out there.