Section 4 - Muscles and Movements

Knee/Leg Flexors (Hamstrings)

Figure 1. Knee/Leg Flexors

The knee/leg flexors are a group of three muscles located in the posterior thigh region on both sides of the body. Their names are:

1) Semitendinosus
2) Biceps Femoris
3) Semimembranosus

They are commonly known as the hamstrings.

These muscles are shown in figure 1 above.

The hamstrings have two functions:

1) Flexion of the leg behind the thigh, and 2) Extension of the thigh behind the hip.

For the purposes of Exercise #10, we will be exercising the hamstrings to flex the leg behind the thigh (function 1 above). For Exercises #4 and #5 we will be exercising the hamstrings for both functions 1 and 2 above. This is illustrated in Figures 2a and 2b.

Figure 2a.

Figure 2a.

Flexion of Leg
Behind Thigh

Figure 2b.

Extension of Thigh Behind Hip


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