Hamstring exercises

Hip hinge or knee flexion?

A muscle that crosses two joints can be loaded from either end. In the Romanian deadlift the knee stays nearly straight and the hip bends, so the hamstrings work hardest in the stretch, at the bottom of the rep. In a leg curl the hip stays put and the knee does all the moving, and the hardest point is at the top, with the leg bent tight.

The practical difference is that a hinge is an exercise for the whole back of the body. The glutes, the spinal erectors and your grip all take a share, and under a heavier bar they are often the ones that give out first. A leg curl has no such problem, because the rest of you is lying or sitting still, which makes it easier to fatigue the hamstrings themselves.

The list also has single-leg variations. The single-leg Romanian deadlift adds balance work to the hinge and exposes side-to-side differences that the two-leg version hides - the description suggests outright that you rehearse the movement unloaded before you reach for a dumbbell.

What if you have no leg curl machine?

Leg curls bring a machine to mind, but the catalog has several versions that do not need one: a stability ball rolled in with the heels, a TRX, a band hooked around the ankle, a bodyweight version lying down. They all do the same thing, which is bend the knee while the hip stays still.

The difficulty in those variations does not come from the load, it comes from the position. On the ball and on the TRX it is your hips held high that decide how much work reaches the hamstrings; let them drop and the movement turns into something much easier. That is why both descriptions start with the same thing: a straight line from your shoulders to your heels.

On the hinge side it looks worse. With no load at all you are left with the single-leg deadlift, where the resistance is the weight of your torso and your free leg. A pair of dumbbells or a band opens up the rest of the list, including the good morning, which loads the same pattern starting from an upright torso.