The whole point of muscle building is to increase the size of muscle. These tips are designed to maximize training sessions and make lifting weights pay off faster and more effectively. Never lift weights that are too light. Muscles need to be overworked during training. Overworking the muscles increases their mass. Light weights may tone the muscles and burn some calories, but no additional mass will be added. Heavy weights stimulate the muscles to grow.
When trying to pack on mass, even lifting heavy weights is not enough during reps. To measure weights and make sure they are heavy enough to stimulate muscle growth, do some reps. If muscles tire and need a break half way through the reps, these are heavy enough. When failure occurs, building muscle the right weight load has been selected. On average, most muscle builders can make it through eight reps then experience failure around reps 10 or 11. If failure occurs before rep 8, the weights are too heavy and need to be taken down a notch.