The hamstring group of muscles is part of the posterior chain of the hip/ leg.  They are not as large as the quadriceps on the anterior side of the body; they have more length to them and are more tubular than broad.  However they are equally important, as they are responsible for hip extension and knee flexion.  Hence they are used a lot for every day walking and running.  The hamstrings are antagonists to the quadriceps muscles.  The muscles that work in synergy with the hamstrings are gluteus maximus, sartorius, gracilis and the gastrocnemius.

Three muscles make up the hamstrings group.

All three hamstrings originate at the ischial tuberosity; they broaden out and then become slimmer as they get closer to the knee, ultimately ending in long thin tendons posterior to the knee.  All three insert at different points.  The biceps femoris long head inserts at the head of the fibula, and the biceps femoris short head at the lateral lip of the linea aspera.  The semitendinosus inserts on the proximal medial shaft of the tibia.  The semimembranosus inserts on the posterior aspect of medial condyle of the tibia.  The latter two insertions along with the sartorius and gracilis form a duck foot like insertion called the pes anserinus.

Because the hamstrings are biarticular, they will affect the health of the knee, hip and even back.  Most athletes who are tight in their hamstrings can suffer a host of problems.  For example, when squatting with a heavy weight, they will not be able to lower their hips past 90 degrees.  This keeps them working in a ‘safe’ mid range zone, but exasperates the issue as the hamstring will not be fully lengthened. Then when it comes time to explode out of the squat, the full length of the hamstring muscles are not utilized.  This can get into a vicious circle, ending in weak and tight hamstrings.

Tight hamstrings also shed light on knee pain.  Again, let’s take the bottom of a heavy squat example.  If the hamstrings are too tight and do not allow full hip extension, the quadriceps will take over from the inefficient hamstrings, putting a tremendous load and strain on the knee.  Remember, all four quadriceps converge to form a single tendon above the knee that attaches to the top and sides of the patella, before attaching via the patellar ligament to the tibial tuberosity.  So if the quadriceps group works needlessly overtime, it’s going to affect the knee.

And there’s more!  Back pain also can be attributed to tight hamstrings.  Since the hamstrings are attached to the ischial tuberosity, tightness can tilt the pelvis back.  When this happens the lumbar vertebrae flex forward, adding compression to the vertebral discs.  It gets worse if we bend forward as the flexion is then coming from the lumbar spine.

Strengthening your hamstrings or keeping them strong is just as important.  Most dominance in sports comes from hip extension/explosion.  Take a runner as an example.  If a runner continually loads his anterior chain while running, he will weaken his hamstrings.  This pertains to proper running technique, whereby the hamstrings are asked to fire every time the leg is picked up off the ground. The inability to fire the hamstrings, can cause the hamstrings to tear, as they will not be able to take the constant load developed by the contracting quadriceps and the momentum that the hip extension generates.  There will be a drop in running speed as the hip flexors jam up, and the hamstrings contract earlier in the stride.

If you’re looking for a great hamstring stretch (among other things), check back for  a clip on Friday!

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Dear Hamstrings, Why Must You Be So Tight?

Yasmen Mehta

Yasmen, a native of India came to the United States to train as a ballet and modern dancer. Yasmen was the Artistic Director and choreographer for the California Contemporary Dancers for 16 years, touring nationally and internationally. She became a competitive short track speedskater after that and is the current gold medalist in the State of California. Speedskating brought her to CrossFit in 2009, and she is Endurance, Mobility, and Level 1 certified for CrossFit as well as YTU Certified. She wants to make a difference through her work with people from different walks of life.

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Alyson Wish

A very clear explanation of how agonist and antagonist muscles need to work in concert in order to perform tasks from the most mundane to high performance. Simply put, our hamstrings need attention, strength building, and stretch inducing techniques to alleviate pain, release tension, and perform like the rockstars that they are.


“Not as large as the quads” ! with the skin all over everything it’s hard to tell but that picture helps a lot. I guess it makes sense with our movement being forward mainly; we don’t practice as much extension at the hips, as we do flexion at the hips. Also the flexion at the knee (closing the joint of the knee) would take a smaller muscle compared to the muscle needed to flex the whole leg. (If I’ve got that all correct :S ).

Elizabeth Pezzello

This is very important for all athletes to know and understand. Our knees seem fragile and are often the first joints to suffer an injury but with these tips hopefully, we can lessen that risk!

Daniel Zachrisson

Great anatomy lesson here, I used to have pretty bad knee pain and the moment I started dedicating more time to my hamstrings it all changed. Getting my hamstrings firing up has brought so much more power into my movements as well, in both weightlifting and in yoga.

Jacqueline Matthews

This is a great anatomy lesson regarding hamstrings and knees. When I started with patellofemoral osteoarthritis, my PT focused on my hamstrings and gluts. However I had great range of motion in hamstrings and spent most of my time strengthening my gluts. Now I spend significant time training my posterior chain and have significantly reduced my knee pain.


Yes, lots of people forget about these super-important muscles on the back of our bodies. It’s easy to sit a lot in our workplace or at home and this weakens hamstrings and causes the back problems you write about.

Shelly Lutz

What a detailed description of the hamstrings! I enjoyed learning about how much tight and weak hamstrings can affect the low back, hips, and knees. So many of my clients have tight hamstrings, and knowing how much this affects their range of motion (like in a squat), or how they can get injured running, is quite useful! The daily position for most people of sitting on a chair all day does not help this issue. Thank you for the informative article!


I had never thought of my hamstring muscles affecting my functional movement so much – a student in one of my classes complains of knee pain when squatting – I will have her read this blog

Nick Shrewsbury

Wow, crazy that the hamstrings can affect so many areas of the body. I had considered the way that tight hamstrings affect a forward bend, but not the way they can chronically tilt the pelvis to the posterior and placing greater pressure on parts of the lumbar vertebrae as they are forced into flexion. It is also interesting to learn the way that people with weak hamstrings will overly rely on their quadriceps.. causing issues down the road.

Katie Rutterer

A great reminder to keep the hamstrings healthy and strong to not only prevent pain but to power up locomotion!


my knee issues are mostly probably related to tight hamstrings too!! I shall get working on it!! 😉

Isabelle P

Great article, so much injury in sports are due to thight harmstring. Let’s start taking care of them.

Melissa Sohn

My hamstrings are tight (from too much sitting for work and driving), and it makes it challenging for me to keep my pelvis position neutral in some yoga poses and exercises. I think it’s also likely responsible for the pain I get behind my knee from time to time. Thanks for highlighting the many consequences of tight hamstrings. I’m going to renew my focus on stretching and strengthening my hamstrings!