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Hamstrings: Video #14 of Introduction to Functional Anatomy

Hamstrings are a group of three muscles found in the back of the thigh. These muscles are responsible for knee flexion and hip extension, and work together to maintain posture by helping to keep the pelvis stable. This video will provide an introduction to the anatomy of the hamstrings and how these muscles are used in functional movement. We will discuss the origin, insertion, and action of each muscle, and will provide examples of how these muscles are used in everyday activities.

Transcript

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You have more than one hamstring. Your hamstring is not a single
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muscle. It's hamstrings as in there are several muscles. We can kind of split
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them into medial and lateral. Your medial hamstring
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is your semitendinosis and semimembranosus.
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What joint do these muscles cross?
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The hip and the knee. They cross the back of the hip, so what are they going to do
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at the back of the hip? Extension. They cross the back of the knee, so what
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are they going to do with the knee? Flexion. That seems easy enough.
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Why did I separate them into medial and lateral? They both attach to the tibia.
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One attaches to the medial side of the tibia though and one to the lateral side
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of the tibia. One's on the inside of the hip, one's on the outside of the hip.
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My medial hamstrings being on the inside of the hip and attaching to the
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inside of the knee, what other joint action do you think they might help out
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with at the hip?
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Internal rotation, good. What about the knee? Tibial internal rotation.
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You want to feel that? I just got a face, it's not gross, this is something your
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knee naturally does. If you grab the inside back of your knee,
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you'll feel to guitar strings. I want you to take this hand, I want you
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to run your hand underneath your patella and right along the crest of your shin,
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the crest of your tibia, you'll find a bump. That bump is your tibial tuberosity,
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it's the insertion of your quadriceps. It's just a good bony landmark. I'm
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going to have you feel tibial internal rotation and feel your semi's
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contract, you ready? If you try to turn your foot in until you feel your tibial
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tuberosity turn in with you, you'll feel your semi's contract. Can you feel that?
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Cool, huh?
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Now do 15 more. Then we have the lateral hamstring, what's the lateral
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hamstring called? Biceps femoris, as in what is 'bi" mean. "Two." What is "ceps?" "Heads."
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"Femoris" as in femur. So this is the two-headed muscle of the femur. This is
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on the lateral side, what joints does this cross? Hip and the knee.
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What is it going to do at the hip? It runs up and down and back of the hip.
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It's going to be more extension. All of our hamstrings contribute to hip
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extension right, is that we just figured out? Which means our hamstrings help who?
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Who's the big extender? The gluteus maximus. Hip extension- all of my
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hamstrings help my glute max. What does my biceps femoris do at the knee? Flexes
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the knee. You kind of already know where I'm going with this
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conversation because we just did the semi's. Since the biceps femoris is on
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the lateral side, what do you think it's going to do? External rotation of the hip
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and tibial external rotation. You want to do that same experiment?
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Grab the guitar strings underneath the back outside of your knee,
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the lateral side of your knee, you can find your tibial tuberosity again,
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the bump along your tibial crest that's that line that you feel. Grab this,
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turnout. You can feel your biceps femoris contract right away. This is probably a
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little easier actually because you have more external rotation at the tibia than
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you do internal rotation. Feel that one?
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So all of the hamstrings once again do what two joint actions? Hip extension and
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knee flexion. The semi's, the medial hamstrings do what? Internal rotation of
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the hip and tibial internal rotation. My biceps femoris, the lateral hamstrings do
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external rotation and tibial external rotation.
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Difference between the -tendinosis and -membranosus, joint action wise they're the same.
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One thing for you to consider is do we see more people walk with feet turned
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out or feet turned in? Feet turned out, so do you think these muscles are created
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equal as far as tightness goes? Who do you think has a propensity to get
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tighter? The biceps femoris, the one who turns out is usually the tight
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hamstrings. Semitendinosus and semimembranosus usually not tight. You
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don't need to stretch your semitendinosus. It's not necessary. Biceps