Exercise guide
Seated Single Leg Knee Extension
- Beginner
- Isolation
- Rep-based
- Lower legs
- Upper legs
- Waist
This isolation exercise targets the quadriceps to improve knee stability and muscle definition, making it ideal for correcting unilateral imbalances. By performing it seated, you maximize focus on the knee extensors while maintaining a stable torso.
Reviewed by the Crucible Fit team · Updated June 2026
Muscles worked
Setup
- Sit upright on the edge of a flat bench or step with your feet flat on the floor and knees bent at 90 degrees.
- Grip the sides of the bench firmly to stabilize your torso and keep your chest lifted.
- Shift your weight slightly to one side and lift the target foot an inch off the ground to the starting position.
How to do it
- Exhale as you extend your knee, lifting your lower leg until it is fully straight and parallel to the floor.
- Squeeze your quadriceps hard at the top of the movement for a one-second peak contraction.
- Inhale as you lower your leg back to the starting position using a controlled 3-second tempo.
Form checklist
- Keep your hips glued to the bench; do not let them lift as you extend the leg.
- Maintain a neutral spine and avoid leaning back to compensate for the weight of the leg.
- Ensure the movement is fluid and driven entirely by the knee joint.
- Keep your ankle flexed with your toes pointing toward the ceiling throughout the set.
Pro tips
- To maximize VMO (inner quad) activation, slightly rotate your foot outward as you reach full extension.
- Focus on the mind-muscle connection by imagining you are pushing the back of your knee down into the bench.
Make it harder
- Apply manual resistance by using your hand to push down on your ankle during the extension phase.
- Perform the movement with a 5-second isometric hold at the top of every repetition.
Frequently asked
- What muscles does the seated single leg knee extension work?
- The seated single leg knee extension primarily targets the quadriceps, and also works the abs and hip flexors as secondary muscles.
- What equipment do you need for the seated single leg knee extension?
- The seated single leg knee extension requires no equipment — just your body weight.
- Is the seated single leg knee extension good for beginners?
- Yes. The seated single leg knee extension is a beginner-friendly movement and a strong foundation to build on.