The average trainee is quite quad-dominant in my experience. I have a lot of other content that discusses why being quad-dominant isn’t necessarily ideal like this article here.
So let’s address that by learning how to attack the hamstrings.
The proximal (upper) fibers of the hamstrings are more responsible for hip extension, while the distal (lower) fibers are more responsible for knee flexion and eccentrically controlling knee extension.
The Biceps Femoris has leverage to extend the hip and externally rotate the femur, while the “semi-brothers” have more leverage to internally rotate the femur because they attach on the inner (medial) aspect of the tibia.
Research suggests (Beardsley, 2018), that each of the hamstrings displays an internal moment arm length (optimal recruitment) that peaks at a different knee joint angles:
- Biceps femoris (long head) = 50–60 degrees of knee flexion
- Biceps femoris (short head) = 70–80 degrees of knee flexion
- Semitendinosus = 90–100 degrees of knee flexion
- Semimembranosus = full knee extension
Therefore, spending time in these positions will help bias the recruitment of those given hamstring muscle fibers. Research also suggests that (in leg curl variations at least) turning the toes inward biases the medial hamstrings and turning them outward biases lateral hamstrings.
If we’re going to train the hamstrings, a neutral ribcage over pelvis (stack) is especially going to be important here. Being excessively extended (arched forward in the low back) is going to eccentrically orient the hamstrings and then we will have to overcome the disadvantageous starting position in order to recruit the muscle (length-tension relationships 101).
A poor position will also bias the hip flexors and quads to do more work than we want them to. Also, if hamstring recruitment is the goal, we are probably going to be better off doing RDLs than a deadlift from the floor.
We are mechanically recruiting the hamstrings more with less risk in the low back. Going from the floor allows for us to use more weight, but at the cost of potentially kicking in other muscles such as the quads and low back to help get the job done. Not bad, just not the context of this article.
Here is an example of how to target the Biceps Femoris. The lateral hamstrings are also more external rotators, and this position opens up the working-side pelvis/femur towards more external rotation:
Here is an example of how to target the medial hamstrings. You can optionally turn in the toes and/or hold a ball between the knees to bias the internal rotation aspect of the medial hamstrings. Hands on ribs to ensure no excessive back extension/rib flare: