SPORTS ANATOMY LESSON #1
The Knee Flexor (Hamstring) Muscles
The knee flexor muscles are a group of three muscles located in the posterior thigh region on both sides of the body. Their names are: 1) Semitendonosus, 2) Biceps Femoris and 3) Semimembranosus. These muscles are also known as the hamstrings and are shown in Figure 1 below:
Figure 1. The Knee Flexors or Hamstring Muscles.
INNERVATION (NERVE SUPPLY)
The nerve supply to the hamstring muscles is supplied by the great sciatic nerve. It is the largest nerve cord in the body and is as thick around as your thumb. It is formed by the fourth and fifth lumbar nerves and the first three sacral nerves. See Figure 2 below.
Figure 2. The Great Sciatic Nerve.(Posterior View)
"LifeART (and/or) MediClip image copyright (2005) Lippincott Williams & Wilkins. All rights reserved."
The hamstrings function is to flex the leg behind the thigh. This occurs during activities such as running and riding a bicycle. This is illustrated in Figure 3 below.
Figure 3. Flexion of the right leg behind the right thigh.
Muscles involved: R-Semitendonosus, R-Biceps Femoris and R-Semimembranosus as shown.
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