Where are my Hamstrings?

Your hamstrings are a group of muscles in the posterior compartment of your thigh. In anatomy, they consist of 3 muscle bellies, but practically speaking there are 3 muscles, including 4 total muscle bellies.

1) Biceps femoris - that's right, there is a biceps in the leg too! it has 2 muscle bellies aka 2 heads; a short head and a long head. Technically, the short head isn't considered part of the hamstrings in anatomy because it doesn't attach in the same place as the other hamstrings muscles, but for working out purposes, it provides the same functionality during lifts.

2) Semitendinosus 

3) Semimembranosus


Posterior Thigh

Name Breakdown: 

Biceps femoris ("bi"= meaning 2 "cep"= meaning head (this muscles has 2 heads/bellies); "femoris"=meaning on the femur (the thigh bone)) 

Semitendinosus ("semi"= half; "tendinosus"= tendon-like; so named because it has a long tendon-like appearance halfway down its length) 

Semimembranosus ("semi"= half; "membranosus"= membrane-like; so named because it has a long membrane-like appearance halfway down its length)

Hamstrings: The Reason for the name "Hamstrings" is because all three muscles have the same proximal attachment (the one under the glutes) and butchers utilize this common tendon (aka strings) to hang a ham from after they have removed the hind leg from the carcass. That's right, when you eat ham, you are typically eating the quadriceps, hamstrings, and adductor muscles of the pig! 

Why This Matters

Application for Workouts

The Hamstrings are a powerful group of muscles and one of the primary movers in the "posterior chain" so many people talk about. Similar to how the Biceps brachii flexes the elbow and draws the forearm closer to the arm, the Hamstrings flex the knee and bring the leg closer to the thigh. These muscles also have the dual function of Extending the Hip (backwards).

Because of this dual functionality, it is possible to recruit your hamstrings in many different leg exercises. Presses (such as deadlifts) as well as Pulls (such as stiff-leg dead lifts, leg curls, or reverse squats) all have the potential to utilize the hamstrings. As a result, any leg day can be suited to include hamstrings, and on the other side having a hamstring focused day may see you performing a wide range of exercises.

On a Hamstring day:

  • Hamstrings+Short Head: any type of leg curl would be well suited to targeting all 4 muscle bellies of the hamstrings. These can be seated, standing, or laying hamstring curls.

  • Hamstrings 3 Only: In order to remove the effort of the Short Head of the Biceps femoris, you would have to contract the Hamstrings without bending the knee. This means doing hip extension exercises such as: glute kickbacks, reverse hyper extensions, stiff leg deadlifts

  • Biceps femoris: while you cannot isolate only the short-head, you could utilize the outside or inside portion of the hamstrings more or less than the other. The Biceps femoris is the outside muscle (including both short and long heads). to focus more on these, perform various exercises with the toes pointed slightly outward (laterally rotate your thigh/leg).

  • Semimembranosus/Semitendinosus: these two muscles are on the part of your hamstrings closer to the center of your body (medial). To place higher emphasis on this group, have your toes pointed inward while performing various exercises.

Emphasis on Bodybuilding

Hamstrings are an important muscle for bodybuilding because having toned posterior thighs contribute to creating the "tie-in" that so many competitors crave. The tie-in is located at the insertion point of the Gluteus maximus, but having toned hamstrings will help pull the whole area together. This area is similar to the Deltoid/Biceps brachii tie-in in the arm, and like this area the two muscle groups help compliment one another.

If you are in a higher level than bikini, or a male competitor, it becomes even more important to have lean and strong hamstrings. These muscles can be difficult for some to isolate, and for others they may find it difficult to keep their hips still and not cheat the reps. focus early in your career on developing proper mind muscle connection before placing too high of a load. Keep good form and go until true failure at a weight you can manage to increase blood flow. The more you do this, the more you may feel the muscle under tension.

It is important to maintain strong, healthy hamstrings because, like mentioned earlier, they are recruited in almost every lower body compound movement, whether as a primary mover or a stabilizer muscle. Be sure to stretch and train these muscles regularly.


1) Biceps Femoris Short-Head: linea aspera and lateral supracondylar line of the femur

The short head is much smaller than the other three muscles, and is of less aesthetic importance. Because you cannot isolate it, it is best to focus on the big 3 Hamstring muscles. 

2) Biceps Femoris Long-Head, Semimembranosus, Semimembranosus: Ischial tuberosity

The 3 Hamstrings muscles make up the majority of the posterior thigh. on those with enough development and leanness, the semitendinosus is the one you see in the middle. All three are important for a variety of back and side poses.


1) Biceps Femoris Short-Head & Long Head: Lateral aspect of Gibular head

The 2 Biceps femoris heads come together laterally to insert together on the Fibula bone (outside of leg, just behind the knee). 

2) Semimembranosus, Semimembranosus: Medial condyle of Tibia

The Semimembranosus & Semimembranosus heads come together medially to insert together on the Tibia bone (inside of leg, just behind the knee). 


1) Biceps Femoris Short-Head: linea aspera and lateral supracondylar line of the femur

The primary action of the Short head of the Biceps femoris is to bend the knee. The anatomical term for this is Flexion of the knee, or Flexion of the leg AT the knee. This movement is somewhat similar to when you lift your forearm up during an arm curl. An example of this would be to try to kick your own butt with one leg. A good example of this movement is the Seated Leg Curls or the Laying Leg Curls.

2) Biceps Femoris Long-Head, Semimembranosus, Semimembranosus: Ischial tuberosity

The primary action of the Main 3 Hamstring muscles is the same as the Biceps Short head, which is Flexion of the knee. f

The Secondary action of these 3 muscles is to bring the thigh backwards, as one does when standing from a seated position. The anatomical term for this is Extension of the hip, or Extension of the thigh AT the hip. This movement is somewhat similar to when you kick a door closed behind you as you leave a room but your hands are full. A good example of this movement is the Glute Kick back, the Stiff-Leg Deadlift, and the Hip Thrust.


When a muscle acts as antagonist, it is trying to resist the action of a different muscle. Since the Hamstring has 4 different heads and 2 different motions, it has 2 different opposing directions as well. The major antagonists are the Quadriceps femoris and Hip Flexors (Iliopsoas).

  1. The Quadriceps does both hip flexion and knee extension, therefore it opposes both of the actions of the Hamstrings.

  2. The Iliopsoas is the main hip flexor, therefore it opposes the hip extension action of the main 3 Hamstrings.

Nerve Supply:

The Hamstrings are innervated by the Sciatic nerve. This nerve also innervates splits into the common fibular nerve and tibial nerve, which innervate the leg and foot. The Sciactic nerve leaves the pelvis and enters the back of the leg by passing underneath the Gluteus maximus and Piriformis muscles.

This nerve comes from the Lumbosacral Plexus. The Lumbosacral Plexus is the main set of nerves that innervate the pelvis and legs. Occasionally, the Sciatic nerve may become pinched by tight "Glutes;" which is why it is important to maintain proper flexibility and mobility in the hips. 

Blood Supply:

The Hamstrings are primarily supplied by the Deep Femoral Artery. This is is a branch of the Femoral Artery which supplies the Quadriceps femoris in the front of the leg. the main artery travels with the axillary nerve through the armpit from front to back. 

Blood Flow: Heart -> Aorta -> Common Iliac -> External Iliac -> Femoral (Common Femoral) -> Deep Femoral -> Perforating branches that directly supply Hamstrings.

Example Exercise Videos to Isolate this Muscle

Hamstrings as a Secondary/Stabilizer Muscle