An Anatomical Secret to Effective Leg Curls!

Leg curls (see Figure 1) are the most commonly used isolation exercise to work the hamstrings (the group of muscles that make up the underside of your thigh – see Figure 2). However, most people are leaving significant gains on the table with them!! To get the most out of leg curls, you need to know that the hamstrings don’t only flex (bend) the knee… they also ROTATE the knee!!*

THE ANATOMY: The semimembranosus and semitendinosus, which make up the medial(inner) side of the hamstrings, do internal rotation of knee. While the short and long heads of biceps femoris, which make up the lateral (outer) side of the hamstrings, do external rotation of knee (see Figure 2 for diagrams of each).

THE APPLICATION: While bending your knees during leg curls, alternate between INTERNALLY rotating your knees (toes pointing in) and EXTERNALLY rotating your knees (toes pointing out) in order to achieve max contraction in the inner and outer hamstrings! 🔥🔥🔥 

*Note: The hamstrings also extend the hip… but we’ll leave that discussion for another time!

Relevant Research Articles:     
       1) Synergy of medial and lateral hamstrings at three positions of tibial rotation during maximum isometric knee flexion
       2) The Effect of Tibial Rotation on the Contribution of Medial and Lateral Hamstrings During Isometric Knee Flexion