Is leg extension as good as squats?
The bottom line is that squats don’t work your rectus femoris. They will work your vastus lateralis (the sweep) at the middle and towards your knee, but not up towards your hip. For optimal rectus femoris development, and vastus lateralis growth towards the hip, opt for leg extensions.
Is leg extension good for growth?
Leg extensions were found to provide superior muscle growth in the rectus femoris compared to squat training. Vastus lateralis tended to grow more in the distal parts (25% and 50% of femur length) from squat training but grew more proximally (75% of femur length) from leg extensions.