The thigh, located between the hip (pelvis) and the knee, contains a single bone, the femur, the largest bone in the body. The femur articulates (forms a joint) with the tibia (main lower leg bone), the fibula (supporting lower leg bone), and the patella (knee cap) to form a hinge joint. The head of the femur articulates with the pelvis to form a ball and socket joint.
The main muscle groups of the thigh are adductors (inner thigh), quadriceps (front of thigh), and hamstrings (back of thigh). The muscles of the thigh can have their origin and insertion on the femur, their origin on the femur and their insertion on the tibia or fibula, or their origin on the pelvis and their insertion on the femur. (For a definition of origin and insertion see blog #3.) Thus, the action of the thigh muscles affect the pelvis above and the knee or lower leg bones below.
All of the adductors (five muscles on the inner thigh) are phasic and all of the hamstrings (three muscles on the back of the thigh) are postural. The quadiceps (four muscles on the front of the thigh) are composed of three phasic and one postural muscle. For a discussion of phasic and postural muscles see blog #2.
To bring balanced muscular action to the thigh it is necessary to isolate the engagements of the adductors, quadriceps, and hamstrings.
Example #1, Isolating the Adductors: Standing with your feet parallel and hip width apart, isometrically draw your feet towards one another.
Example #2, Isolating the Hamstrings: Continuing from example #1, engage the hamstrings and lengthen from the sit bone to the top of the lower leg bones.
Example #3, Isolating a Quadricep: Other than the vastus medialis (just above the knee on the inner thigh,) it is difficult to isolate the actions of the other three quadriceps because one is postural and the others phasic. To engage the vastus medialis, slightly bend your knees.
To balance the muscular action of any area of the body, concentrically engage a phasic muscle and then eccentrically lengthen an opposing postural muscle. For the thigh, concentrically engage both the vastus medialis (just above the knee on the inner thigh) and the adductors (inner thigh) and then eccentrically lengthen the hamstrings. As an added benefit, engaging the vastus medialis stabilizes the patella (knee cap.)
To balance the muscular action of the thigh while doing a forward bend (Uttanasana):
1. Stand with feet parallel and hip width apart.
2. Slightly bend the knees to make it easier to isolate the vastus medialis.
3. Engage the vastus medialis.
4. Concentrically engage the adductors from just above the knee to the top of the thigh (from insertion to origin)
5. Straighten your knees and eccentrically lengthen the hamstrings from the sit bones to the top of the lower leg bones (origin to insertion).
6. Maintaining these actions and keeping the upper body anatomically neutral, fold forward from the ball and socket joint at the hip. As you fold forward continue to engage the adductors concentrically and to lengthen the hamstrings eccentrically.
These thigh actions can be applied to any yoga pose. At first, putting your mind in the muscle may be all that is accomplished. Over time the body will learn to isolate these actions and balance the strength and flexibility of the thigh muscles. As the body becomes more balanced, ligaments and tendons will also become stronger and more supple.
Stay Tuned! Next Blog: Pelvis, Midsection and Core