Strength Training · Bodybuilding
Single-Leg Extension
The single-leg extension is a seated machine exercise that trains the front of one thigh at a time by straightening your knee against resistance.
- Beginner
- Isolation
- Low injury risk
- Rest 1 min
How to do it
- Adjust the seat so your working knee lines up with the machine’s pivot.
- Set the roller height to contact your lower shin just above your ankle.
- Place your working shin behind the roller.
- Grip the handles with your back against the backrest.
- Raise the roller by straightening your working knee.
- Lower the roller to the starting position.
Form cues
- Keep your thighs parallel.
- Exhale as you lift.
- Keep your shoulders relaxed.
Common mistakes
- Swinging the weightUse a controlled lift with a two-second lowering phase instead of kicking the roller upward.
- Lifting or twisting your hipsReduce the load until your pelvis stays level against the seat throughout the rep.
- Snapping the knee straightSlow down near the top so you reach extension without forcing your knee backward.
Safety
Excessive resistance or jerky repetitions can irritate your knee. The moving lever can strike your unused leg if it rests in the mechanism’s path.
- Start substantially lighter than your two-leg extension load.
- Keep your unused leg clear of the moving lever.
- Let the lever settle fully before changing sides.
- Stop the set if you feel sharp or increasing knee pain.
If you have an existing knee injury or recent knee surgery, ask a physiotherapist or doctor about an appropriate load and range before doing this exercise.
Muscles worked
Primary muscles
Equipment
- Leg Extension Machine
Sets and reps
- Sets
- 2–3
- Target
- 10–15 reps per leg
- Rest
- 1 min
Start with your weaker leg and match its repetitions on the stronger side.