Single-Leg Leg Extension
Working one leg at a time on the extension machine lets you give each quad full attention and expose any strength imbalance between sides. The single-joint action makes it a clean finisher for driving blood into the quads with little systemic fatigue. It is beginner-friendly and easy to progress by adding reps or slowing the tempo.
- Equipment
- Machine
- Body part
- Quads
- Type
- Strength
- Browse by muscle
- Rectus Femoris, Vastus Lateralis
- Browse by movement
- Knee Extension
- Target
- Rectus Femoris, Vastus Lateralis
How to do it
- 1
Sit in the leg extension machine and adjust the pad to rest on the front of one shin.
- 2
Set the back pad so your knee lines up with the machine pivot.
- 3
Hold the handles and keep your hips planted in the seat.
- 4
Extend the working leg until the knee is nearly straight.
- 5
Squeeze the quad briefly at the top, then lower under control.
- 6
Finish all reps on one leg before switching.
Tips
- Match the rep count and effort between legs.
- Avoid swinging or using momentum to throw the pad up.
- Control the lowering phase rather than letting the weight drop.
Variations
Common mistakes
- Starting with your stronger leg sets a rep target the weaker one cannot meet, which widens the gap you came here to close. Lead with the weaker side and copy its number.
- Twisting your hips toward the working side to squeeze out the last reps turns an isolation exercise into a trunk movement. Keep both hips in contact with the seat.
- Bracing the resting foot on the floor or the frame and pushing lets the whole body help. Let it hang loose or rest it flat on the machine without driving into anything.
- Cutting the load to well under half of your two-leg weight out of caution; most people find one leg can handle a little more than half, so start at about half and build from there.
- Letting the pad sit across the middle of one shin lets it roll sideways as you extend. Center it just above the foot so the line of pull stays straight down the leg.
Frequently asked
- How many sets and reps of the single-leg leg extension should a beginner do?
- Two or three sets of 10 to 12 per leg. Work the weaker leg first and let it decide the reps for both sides. Since you are doing double the sets for the same total volume, keep the load modest and treat the second leg's set as a repeat, not a contest. When both legs reach 12 with a clean squeeze at the top, add a plate. Twice a week is realistic, because it costs very little systemic fatigue.
- What can I do instead of the single-leg leg extension with no machine?
- Sit on a high bench or table and extend one leg against a band anchored behind you, or hang a light dumbbell or an ankle weight from your foot. Single-leg step-ups, heel-elevated split squats and a one-knee reverse Nordic all load one quad at a time, though the hip helps in a way the machine does not allow. A slow single-leg sit-to-stand from a chair is the simplest home option and exposes an imbalance just as quickly.
- Who is the single-leg leg extension for, and when is it a waste of time?
- It is for anyone who suspects one quad is doing more than the other: after an injury, after a long lay-off, or when the bar drifts to one side in a squat. It also lets you give each leg an unhurried squeeze, which makes it a good low-fatigue finisher. It is a waste of time when both legs already perform alike and your session is short, since it takes twice as long as the two-leg version for the same quad volume, and it builds nothing for the hips or hamstrings.
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