Leg Extension
Move · Resistance Training · Movement, Typed Supps
It is hardest at the very top, because that is where the pad on your shin has the most leverage against your knee.
Stage by stage
- Set-up (Knee aligned with the pivot): Seat and pad position determine where in the range the resistance actually peaks.
- During the set (Torque peaks near lockout): With the shin approaching horizontal, the pad's leverage on the knee is greatest, so the top is hardest.
- Hip angle (Hip angle changes the quads): Reclining lengthens rectus femoris, which crosses the hip; sitting upright shifts demand onto the vasti.
- Weeks later (Isolated quadriceps volume): It adds quadriceps work with almost no systemic fatigue, which is why it sits alongside compound lifts rather than replacing them.
Muscles trained
- Primary: quads, rectus femoris
Intensity
3.5 METs (Resistance (weight) training, multiple exercises, 8-15 repetitions at varied resistance).
Time to effect
- Weeks: Quad strength and control on the machine improve quickly as the movement pattern becomes familiar.
- Months: Visible quad development, especially through the lower and outer sweep, becomes noticeable with consistent progressive loading.
Related supplements
Common myth
"Leg extensions are bad for your knees." In reality: Open-chain knee extension does place more anterior shear force on the knee than a squat, but healthy knees tolerate this well, and the machine is routinely used in rehab to rebuild quad strength precisely because it loads the muscle without needing to load the spine or hips. Sensible loading and rep ranges, not the exercise itself, are what protect the joint.
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