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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
