Anatomy of the Thighs:
The front portion of the legs consist of 4 powerful quadriceps muscles: the rectos femoris, vastus intermedius, vastus medialis and vastus laterals. The main function of the quadriceps muscles is to extend and straighten the legs. The back portion of the legs is known as the hamstrings, or leg biceps. The main function of the hamstrings is to curl the leg back.
There are three basic types of thigh exercises:
Presses: In which the legs are pushed and straightened in a straight line
Extensions: In which the legs are extended in an arc away from the body
Curls: In which the legs are drawn in an arc towards the back. Presses and extensions primarily stress the quadriceps and curls stress the hamstrings.
Complete Thigh Development:
In order to achieve well balanced thighs, you must perform all of the exercises explained above to make sure the legs are hit from all necessary angles. Here are some of the best mass building exercises for the thighs:
I recommend performing at the least 15 sets for the legs since they are the most powerful muscles on the body, and can certainly handle the stress because they are designed to support your body to walk all day. You will find that the legs have a better muscular endurance than your upper body muscle groups, this is why I find it necessary to stress complete development. My personal thigh routine looks like this:
Leg extensions - 4x6-12
Squats - 4x6-12
Leg presses - 4x6-12
Leg curls - 4x6-12
Anatomy of the Calves:
The 2 headed muscle of the lower leg is known as the calve. It consists of the soleus muscle and gastrocnemius muscle. The main function of the calve is to flex the foot. Think of it is standing on the tips of your toes.
The basic exercises for the calves are known as:
Raises - In which the foot is flexed onto the tips of the toes.
Raises completely isolate the calves.
Complete Calf Development:
In order to completely develop the calves, you must perform 2 or more raise type exercises, I recommend standing and sitting raises. Some of the best mass builders for the calves are:
Seated calf raises
Standing calf raises w/ hack squat machine
My personal calf routine looks like this:
Seated calf raises - 4x6-12
Standing calf raises - 4x6-12
Combine all of that with some intensity principles and you have yourself a killer leg workout.