Kicking the weight up
Lift smoothly and pause at the top so the quads, not momentum, move the pad.
Isolation · Machine
Leg Extension
The leg extension is a seated machine exercise where you straighten your knees against a padded lever. It isolates the quads, including the rectus femoris that squats under-train, and suits anyone adding direct quad work.
- Primary
- Quads
- Starting rep range
- 10–15 reps
- Target effort
- 1 reps in reserve
- Progression
- 5 kg / one stack step
Muscles worked
All four quad muscles extend the knee, and because the hip stays flexed, the rectus femoris gets more work here than in squats. No other muscle meaningfully contributes.
How to set up
- Adjust the back pad so your knees line up with the machine's pivot point.
- Set the shin pad just above your ankles.
- Sit back firmly and hold the side handles.
- Start with knees bent about 90 degrees or a bit more.
How to do each rep
- Extend your knees until your legs are straight.
- Squeeze your quads hard for a second at the top.
- Lower under control over 2-3 seconds.
- Keep your hips down on the seat throughout.
Common leg extension mistakes
Knee not aligned with pivot
Adjust the back pad until your knee joint sits in line with the machine's axis.
Hips lifting off the seat
Hold the handles and reduce weight so your butt stays down.
Sets, reps, and progression
Surpass starts the leg extension at 10–15 reps with about 1 reps in reserve. As an isolation exercise it fits well after your main compound lifts.
Use 10-20 reps and add a pin once all sets hit the top of the range with a pause. Slower negatives are a good way to progress when stack jumps are too big.
Know what to lift next time
Surpass shows what you lifted last time beside a target for this set, and adjusts it from your reps and RIR. Free on iPhone, no account needed.
Leg Extension alternatives
These train the same main muscles. Swap when the equipment is busy, something hurts, or progress has stalled for several weeks.
Programs that use it
12-Week Physique Plan4 days a week · intermediatePush Pull Legs (6-Day PPL)6 days a week · intermediateUpper/Lower Split (4 Days)4 days a week · beginnerArnold Split (6 Days)6 days a week · advanced5-Day Bro Split5 days a week · intermediatePPL + Upper/Lower Hybrid (5 Days)5 days a week · intermediate
Questions
Are leg extensions bad for your knees?
For most people, no, when the machine is set up correctly and the weight is controlled. If you have knee pain, use a lighter weight and a range that feels comfortable.
Do leg extensions replace squats?
No. They isolate the quads well but don't train hips, balance, or strength in a compound pattern. They work best alongside squats or leg presses.