Shock the muscles. 10 sets of 10 using a light weight. It should be around your normal weight. It might be because of a mental block. But if your legs are still sore from the last leg work out, take at least another day off.
Rest is when the muscle grows.
If you're training for maximum muscle mass, aerobics will slow down muscle growth. Normal Olympic barbells are 45 pounds. EZ-Curl bars are around 20. It's for your own purposes, so you don't have to, but when you start talking weights you should know that most people include the weight of the bar. In some cases, such as, Leg Press or various other machines, just record the weight you add.