Single Leg Leg Extension (Machine)
The Single Leg Leg Extension is a machine-based isolation exercise that targets the quadriceps muscles one leg at a time. This unilateral movement helps correct strength imbalances between the left and right legs while improving muscular definition in the front of the thigh.
Iridium uses this isolation movement to accumulate specific quadriceps volume when your 7-day workout history shows high systemic fatigue from heavy spinal loading. The AI tracks your per-muscle recovery to ensure you stay within your Maximum Recoverable Volume targets while sparing your lower back. Additionally, Iridium adjusts the session's time calculations to account for the extended duration required to train each leg independently.
Form Cues
- Align your knee joint directly with the machine's pivot point
- Press your hips and lower back firmly against the seat pad
- Squeeze your quadriceps hard at the top of the extension
- Lower the weight slowly with a controlled 2-3 second tempo
- Don't let your hips lift off the seat during the lift
- Don't kick the weight up explosively using momentum
- Don't lock your knee aggressively at the top of the movement
- Don't let the weight stack slam down between repetitions
Common Mistakes
- Misalignment of knee and pivot point
- Lifting hips off the seat
- Using momentum to swing weight
- Dropping the weight without control
- Setting the ankle pad too high
Muscles Worked
This exercise is a pure isolation movement for the quadriceps group, specifically targeting the rectus femoris, vastus lateralis, vastus medialis, and vastus intermedius. By eliminating hip extension, it focuses entirely on knee extension, making it highly effective for strengthening the 'teardrop' muscle (VMO) and fixing left-to-right strength imbalances.
Primary
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