10/31/2019
Muscle of the Day: Hamstrings
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Members:
Lateral Hamstrings: Biceps Femoris (Short Head & Long Head)
Medial Hamstrings: Semitendinous & Semimembranous
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The Hamstrings are a very interesting muscle group. They are a two joint muscle which means just that, they cross two joints lol. The Illiofemoral (hip) & Tibiofemoral (knee). Which means to truly isolate you must produce knee flexion + hip extension. Overall they make up 35% of the involved size and strength of the lower extremity. In addition, they also accumulate almost 49% of the force production of the lower extremity. In regards of functional anatomy the hamstrings have one job, to de-load the axial spine and the Tibiofemoral joint (knee) during heel contact phase of the gait cycle. In other words, every step you take the heel hits sending a force from the Calcaneus (heel) up the chain of the extremity into the glute & hamstring. Like all muscles the Hamstrings help absorb the shock of body weight and gravity to decrease joint stress.
Now onto the health of the spine. Due to the Hamstrings Origin on the Ischial Tuberosity they will contribute to Pelvic alignment. Let’s break this down further. As previously stated with other muscle of the day; the muscle will pull from Origin (where it begins) to Insertion (where it ends). So when the Hamstrings tighten they will pull Posteriorly (downwards) on the Pelvis. As a result of, the Mid thoracic must go backwards to maintain the body upright against gravity. This results in “Flat Back” and will cause significant low back pain, tightness, and potential for a Posterior Disc bulges. With this being said, keeping the Hamstrings pliable, supple, and mobile is a must. Likewise, a balance between the Psoas Major and Hamstrings will result in a neutral Pelvis. Side note: hypertonic hamstrings will also increase ACL injuries tenfold due to the posterior pull on the Tibia (bottom leg bone) (1). Reason why women are 69% percent more susceptible to ACL tears.
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