Machine Leg Extension
A machine-based isolation exercise that targets the quadriceps through knee extension to build strength, hypertrophy, and knee stability; ideal for isolating the front thighs without other muscle involvement.
About Exercise
Equipment
Leg Extension Machine
Difficulty
1/5 • Beginner
Primary Muscle Groups
Quads
Secondary Muscles
Hamstrings
Accessory Muscles
Hip Flexors, Abs
Popularity Score
9
Goals
Training Style
Setup Requirements
Requires Rack
No
Requires Bench
No
Requires Spotter
No
Space Needed
Small
Noise Level
Low
Muscle Breakdown
View Muscle MapQuads
10/10Rectus Femoris, Vastus Lateralis, Vastus Medialis
Hamstrings
3/10Biceps Femoris
Hip Flexors
2/10Iliopsoas
Abs
2/10Rectus Abdominis
Programming
Typical Rep Range
8-15 reps
Rest Between Sets
60-90 seconds
How to Perform
Sit on the leg extension machine with your back against the pad. Adjust the seat so your knees align with the machine's pivot point and position the padded lever above your ankles.
- Exhale and extend your legs by contracting your quadriceps.
- Straighten your legs until nearly fully extended without locking your knees.
- Pause briefly at the top and squeeze your quads.
- Inhale and lower the lever slowly in a controlled manner.
- Repeat for the desired repetitions while maintaining form.
Coaching Tips
Form Cues
- Squeeze quads at top
- Keep back flat against pad
- Control the lowering phase
- Align knees with pivot point
Breathing
Inhale as you lower the weight, exhale as you extend your legs. Brace your core throughout.
Tempo
2-1-2
Range of Motion
Start from a 90-degree knee bend and extend to near full leg straightening with a slight bend at the knee to avoid joint stress.
Safety
Safety Notes
- Avoid full knee lockout to prevent joint stress
- Ensure proper machine adjustment for knee alignment
- Use moderate weights to minimize shear forces on knees
- Consult a professional if you have knee injuries
Spotting
Spotting not typically required; use the machine's weight stack pin or safeties for controlled drops if needed.
Common Mistakes
- Locking knees at the top
- Using momentum to lift
- Allowing back to arch off the seat
- Incorrect pad placement on shins
When to Avoid
- Acute knee pain
- Patellar tendonitis
- Recent knee surgery
Flexibility Needed
- Knee flexion to 90 degrees
- Hip flexibility for seated position
Build Up First
- Familiarity with machine adjustments
- Basic understanding of knee extension movement
Also known as
Seated Leg Extension, Quad Extension
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