Try different reps for different muscle fibres

When you are training your legs, you should choose a rep range to suit the muscle fibre composition. Most standard rep ranges for beginners will be between 8 and 12 reps for the majority of body parts. This is fine to start with with. Once you move beyond the early stages of training, you need to start altering your reps per set to create the required stimulus depending on the muscle you are hitting.

A prime example would be the leg muscles:

• The quadriceps in the front of the thigh are slightly more slow twitch. By slow twitch, we mean they are made of more slow twitch muscle fibres that are designed for more endurance based training. Don't go and run a marathon, but instead try lifting heavy for sets of 15-20 reps on your squats.
• The hamstrings in the back of the leg are predominantly fast twitch. You should be doing deadlifts with reps of 8 and below. The same applies for cleans and snatches, which 5 reps or less work well for. Jo Defranco, a world renownded strength coach, says to build big hamstrings you should do more sprints. Sprinting is explosive and this proves the point i'm trying to make.
• The calves are similar to the quads. The calves take a beating most of the day when we walk, run, play sport. So when training the calves, use a high rep range and a large volume. Most people's calves don't grow, simply because they don't do enough sets or reps, or simply don't concentrate on them as much as their biceps!! Hit 5 sets of 20 reps with a heavy weight. Lately, I have been doing sets of 15-20 calf raises between every other sets of leg exercises.

Try this:

1. Squats 2-3 sets of 15 reps
2. Stiff leg deadlifts 4 sets of 8 reps
3. Calf raises 5 sets of 20 reps