Lying leg curl
Bending the knee against a pad — and it trains only half of what the hamstrings actually do.
- Pattern
- Isolation
- Equipment
- Machine
- Space
- A bench or a seat
- Difficulty
- Foundational
- Load
- External load
What it is
Lie face down on the machine with the pad against the backs of your ankles and the pivot roughly level with your knees. Curl your heels towards your backside, pause, and lower under control.
Hips stay down on the pad throughout.
What it demands
Knee flexion, from the three hamstrings and the short head of biceps femoris.
And here is the thing worth understanding: that is only half their job. Two of the three hamstrings cross the hip as well as the knee, and hip extension is arguably their more important action. A leg curl trains none of it.
That is why a hamstring programme built only on curls is incomplete, and why the Romanian deadlift is the complement rather than an alternative — one trains knee flexion, the other trains hip extension, and the muscles do both.
The short head of biceps femoris is the exception: it crosses only the knee, so this is the only movement in the collection that reaches it directly.
What usually goes wrong
The hips lifting off the pad. As it gets hard the backside rises, which shortens the range and recruits the lower back.
Slamming the weight down. The lowering is where hamstrings are loaded while lengthening, which is the part worth having.
Pivot misaligned with the knee.
Cramping. Extremely common here, and usually means the load or the range is ahead of where you are.
Where it sits
The knee-flexion half of hamstring training, and the direct counterpart to the leg extension.
Its value is precisely that it is not a hinge — it reaches the one hamstring portion that hinging does not, and it needs no back position at all. Its limitation is the same fact stated the other way: it leaves out the job those muscles mostly do.