Leg extension

Leg extension machine

Also called leg extensions, quad extension

Leg extension, start position — Images: Free Exercise DB (public domain)

Leg extension, end position — Images: Free Exercise DB (public domain)

Sit in the machine with the pad on the lower shin. Extend the knees to straighten the legs, then lower slowly to a full stretch.

Pad on the lower shin
Pause briefly at the top
Lower slowly to a full stretch

Movement

Pattern: Knee extension
Type: Isolation, one joint moves
Sides: Both sides together
Equipment: Leg extension machine

Muscles worked

Main movers get full credit for a set, helpers half.

Lower body

QuadsMain

Ratings

Scores 1-5 averaged over sources. Tap a rating for the claims behind it. Claims are our summaries of the linked sources, fact-checked by AI.

Muscle growth higher is better3.3
Solid; a reasonable default. 3 sources.
- 2/5 Average machine is C/D: limited bottom range and tension is highest at the top; a cammed long-range one is B. Renaissance Periodization, Every Gym Machine Ranked by Exercise Scientists @ 32:25videoExpert opinion2025checked by AI
- 4/5 All four heads work, a new study found more quad growth with seat back; lower overload than squats; A tier. Jeff Nippard, The Best & Worst QUAD Exercises (Ranked Using Science) @ 7:39videoExpert opinion2024checked by AI
- 4/5 A well-done leg extension is about as good as quad isolation gets. Jeff Nippard, How To Do Leg Extensions With Perfect Technique (Grow Every Quad Head) @ 6:10videoExpert opinion2019checked by AI
Stimulus to fatigue higher is better4.5
Large stimulus with little fatigue. 2 sources.
- 4/5 Gives a decent quad stimulus with little systemic carryover, so bodybuilders lean on it. Renaissance Periodization, Four Index Approach to Exercise Selection | Advanced Hypertrophy Concepts and Tools | Lecture 11 @ 27:00videoExpert opinion2021checked by AI
- 5/5 Main purpose is adding quad volume without creating much recovery demand for other muscles or joints. Jeff Nippard, How To Do Leg Extensions With Perfect Technique (Grow Every Quad Head) @ 2:08videoExpert opinion2019checked by AI
Injury risk lower is better2.0
Low risk with basic technique. 1 source.
- 2/5 Not inherently dangerous; no evidence of added injury risk for people with healthy knees. Jeff Nippard, How To Do Leg Extensions With Perfect Technique (Grow Every Quad Head) @ 2:38videoExpert opinion2019checked by AI
Progression higher is better2.0
Coarse jumps or a low ceiling. 1 source.
- 2/5 Single-joint, so limited ability to overload with weight; use reps 12 to 20 and chase extra reps, technique and pump instead. Jeff Nippard, How To Do Leg Extensions With Perfect Technique (Grow Every Quad Head) @ 1:36videoExpert opinion2019checked by AI
Knee stress lower is better3.0
Moderate; fine for healthy knees with sensible load and range. 1 source.
- 3/5 Shearing and ACL fears are overstated per Schoenfeld for healthy joints; skip it or shorten the range if it hurts, and balance with hamstring work. Jeff Nippard, How To Do Leg Extensions With Perfect Technique (Grow Every Quad Head) @ 2:38videoExpert opinion2019checked by AI