Many use a similar routine to get bigger legs:
4 sets of 8-12 Leg Extensions
4 sets of 8-12 Leg Curls
4 sets of 8-12 Partial Squats
4 sets of 8-12 Leg Presses
4 sets of 8-12 Stiff-Legged Deadlifts
They devote an entire day to it. It involves the same muscles over and over again, just with positions that only work them at different lengths. This just works them the same but in weaker or stronger positions. They add or subtract muscles depending on the exercise for no real reason than to supposedly blast the muscles from different angles. This hope remains despite the origin and insertion points staying the same. The lower body has large muscles with few attachments. Most of the major muscles will converge on a single tendon for the joint. For example, the quadriceps come together on a single tendon attached to the knee. This really calls into doubt the whole concept, and really most do these all just because everyone else does them.
They may rotate others such as hack squats, adductor/abductor machines, and other devices that allow for artificial movement. They may use unstable exercises such as lunges or other functional crap that limit the weight possible for size and strength gains. They really go for the burn by doing drop sets, partials, negatives, etc. You may even have to point your toes in various directions to address different heads of the muscle.
This routine is redundant and harmful to the average trainee. It involves too much volume and not enough effort. Isolation has no place in proper training. Most of these exercises are bad. For the average person, performing such a routine will overtrain you, destroy your joints, and make it all but impossible to progress in weight, which should serve as the goal of a good resistance training program. It has good intentions, but fail all but the most elite and drugged-up lifters.
Squats
If you don’t bend those legs and do those squats, you’ll never reach your potential.
– Paul Anderson
Study the anatomy closely, and you realize that squats hit all the muscles in the lower body. The squat works the entire hip, thigh, and leg regions. This means the hamstrings, adductors, glutes, quads, and calves. Joint motions include hip extension, knee extension, and plantarflexion. The core muscles and outer hips work to hold your position. The small stabilizers in the lower legs work since your feet interact with the ground.
Squats involve EVERYTHING from the waist on down. By including everything, you also allow for a safe exercise that leads to no imbalances. Imbalances harm the joints or fail to develop specific muscles. You must use proper form and positioning on the squat though to have this effect. Avoid any sort of fancy variations on squats as well.
The real key to addressing the muscles involves heavy weight and hard work. Remember, volume has nothing to do with results from strength training. Volume merely provides a way to generate tension. This tension comes from giving a great effort with great weights. This recruits the fast-twitch muscle fibers most responsible for growth. This means more work in the same or less time in the long-run. You must add weight to your squats over time. Use whatever reasonable rep range works for you, anywhere between 1-30. Use the least amount of volume possible.
Barbell deadlifts are unnecessary. While far better than most of the crap, it carries some risk. The hip and lower back muscles take over the movement, to the exclusion of the muscles attached to the knee. This can cause joint issues. Squats only exist as a quad-dominant movement if you assume the wrong position. Any sort of isolation, even within the context of a compound exercise by using a poor stance or selection, can harm your joints and generate less tension. If you do choose to deadlift, use a trap bar as your implement and make sure to practice it like a squat.
Stabilizers work to brace. These have a minuscule effect on size and have adapted for limited growth. Intervals can provide more work due to the unilateral nature if needed. You could also include some athletic intervals, such as sprinting, if you desire to give the stabilizers a bit more work. This will make little to no difference in your size though. Squats still involve significant bracing. This may serve as enough for these smaller muscles.
The legs represent the foundation of all great fitness and athletic feats and general function. Huge legs also have the indirect effect on the entire body.
Associate, do business, rely upon, or otherwise spend time with weaklings and hypocrites at your own peril. Remember that in a more sane and ancient society, they would not have lasted long on the field of battle or even in daily life.
Get Bigger Legs with Squats Alone
Squat with progressively heavier weight. Ignore all other lower body exercises for lifting. This will safely and effectively allow you to get bigger legs.