Legs · Leg extension machine
Leg extension: form, muscles and sets
The leg extension is the only common movement that loads the rectus femoris hard with the hip straight — which is exactly what squats cannot do.
Muscles worked: Rectus femoris, Vastus lateralis, Vastus medialis
How to do it
- Set the back pad so the knee joint lines up with the machine's pivot.
- Position the shin pad just above the ankle, not on the foot.
- Hold the handles, press the lower back into the pad and brace.
- Extend until the legs are straight, squeezing the quads for a full second.
- Lower over three seconds and stop just before the weight touches down.
Mistakes to avoid
- Pivot misaligned with the knee, which puts shear through the joint.
- Swinging the torso to fling the pad up.
- Dropping the weight fast and losing the whole lowering phase.
Sets and reps
| Goal | Prescription |
|---|---|
| Size | 3–4 sets of 12–20 reps, 60s rest |
| Knee health | 3 sets of 15 light with a slow lower and pause |
| Pre-fatigue | 2 sets of 15 before squats on a quad-focused day |
Swaps and alternatives
- Sissy squat — Same straight-hip quad load without a machine.
- Bulgarian split squat — Loads the quads with a balance demand.
- Reverse Nordic curl — Bodyweight stretch for the rectus femoris.
Common questions
Keep training
- Hip thrust
Barbell, bench, pad
- Romanian deadlift
Barbell or dumbbells
- Bulgarian split squat
Dumbbells, bench
- Hammer curls
Dumbbells
- Dumbbell shoulder press
Dumbbells, bench
- Incline dumbbell press
Dumbbells, adjustable bench