Hamstrings: Learn Your Muscles

Three separate muscles make up the hamstrings. They are semimembranosus, semitendinosus, and biceps femoris. Together, they work to bend your knee, bring your femur (thigh bone) behind your body, and balance the pull of the quadriceps (the muscles on the front of your thigh).


hamstringsAll three of the hamstrings originate on the ischial tuberosity. This is the IT part of the SITs bones, which I mention frequently. The biceps femoris has two heads, so it has two origins. The other origin for the biceps femoris is on the bottom, back of the femur (thigh bone).

Semimembranosus inserts on the back of the medial condyle of the tibia (upper inside part of the tibia). Semitendinosus inserts on the upper medial surface of the shaft of the tibia. Biceps femoris inserts on the head of the fibula and on the lateral condyle of the tibia (upper outside part of the tibia). The tibia and fibula are the two bones in your calf.


The hamstrings flex (bend) the knee and extend the hip joint. This means they bring your leg behind you. Semimembranosus and semitendinosus also medially rotate (turn in) the lower leg when the knee is flexed. Biceps femoris laterally rotates (turns out) the lower leg when the knee is flexed. If the hamstring muscles are balanced in strength, your leg should be in a neutral position meaning that it is neither rotated in nor out.

Common Dysfunction

Hamstring dysfunction can cause several different issues. Since the muscles impact the hip and knee joints, it stands to reason that hip pain or knee pain could be from tight hamstrings. This tightness and tugging on the pelvis could lead to low back pain also.

You may also notice you have a tight hamstring if you feel your walking stride is restricted. Perhaps one leg hurts when it is behind you or maybe your knee doesn’t bend as well. In these ways, it can be very easy to observe if you have tight hamstrings.

Tendonitis can also occur in hamstrings. This is frequently caused by overuse of the hamstrings, but it can also be caused by an imbalance in strength between the quadriceps and hamstrings, improper warming-up before activity, or not allowing a previous hamstring injury to heal.

Hamstrings can also be strained. Here is some information on hamstring strains from David Keil’s article “Hamstrings.”

“When any one of the three hamstring muscles is stretched beyond its limit, hamstring strain can occur. Hamstring strains tend to be either the result of sudden stopping and starting during a sport, sprinting for example or extreme stretching as might occur in gymnastics, dance, or yoga.”

“Risk factors that increase the chances of straining one or more of the hamstring muscles include:

  • Activities that require extreme stretching or a lot of sudden stopping and starting
  • Previous hamstring injury
  • Tight hamstrings
  • Inadequately warmed up before exercise
  • Returning to sports or other activities that are demanding of the hamstrings before a hamstring injury has fully healed

There are three grades of hamstring strain. Grade 1 strains include milder strains that can be treated at home. Grade 2 strains are more severe and include more loss of range of motion. Severe grade 3 strains may include avulsion, where some part of the muscle actually detaches from its connection to bone.”

Restoring or Maintaining Health

Hamstring injuries are no joke. If you feel like you have injured your hamstrings, please consult your physician. Since some injuries do require surgery, it is always best to check with your medical professional as soon as possible. If it is determined that you have a mild strain that can be treated at home, here are some suggestions.

All forward folds in yoga will stretch your hamstrings. Particularly, I recommend Uttanasana and other standing forward folds because you can put a slight bend in your knees to reduce the stress and strain on your hamstrings. Do poses like Downward facing dog so that you can feel your SITs bones rotate toward the ceiling. As the SITs bones rotate, the hamstrings will open. Poses like Chair pose challenge and strengthen the hamstrings.

More Information

For more information, I recommend “The Hamstrings” by David Keil. Also, he has a wonderful yoga anatomy book that I enjoy called [easyazon_link identifier=”1905367465″ locale=”US” tag=”custpilandyog-20″]Functional Anatomy of Yoga[/easyazon_link]. When you buy this book through this link, I earn a small commission.

Another book that I find helpful is [easyazon_link identifier=”1623170206″ locale=”US” tag=”custpilandyog-20″]The Concise Book of Muscles[/easyazon_link] by Chris Jarmey. I used lots of information from his book while writing this post. The link I have provided is to an updated version of the book I have. It appears to be a very thorough update, although I have not personally looked through the whole book.

How do you keep your hamstrings healthy? Let us know in the comments below.

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About Sarah Stockett

Hi, I'm Sarah! I'm a certified Pilates and yoga instructor with a passion for pain relief. I believe you can use simple exercises to relieve your aches + pains. AND, I believe I can teach you how.