If you want to make the front part of your thigh (rectus femoris) bigger, leg extensions work better than leg presses — after 12 weeks, leg extensions made it grow 12% more than leg presses did.

For people who don't usually work out, using a knee extension machine grows the front thigh muscle much more than using a leg press machine.

Doing leg presses and leg extensions for 12 weeks both make your main thigh muscles bigger about the same amount, but leg presses also make your butt and inner thigh muscles grow more, while leg extensions make the front part of your thigh (rectus femoris) grow much more.

Doing leg presses and leg extensions for 12 weeks both make your main thigh muscles bigger in about the same way, but only leg extensions make the front part of your thigh (rectus femoris) grow significantly.

Doing leg extensions makes the front thigh muscle bigger along its whole length more than doing squats, especially near the knee.

Doing certain leg exercises that only use the last part of the movement doesn’t seem to help untrained women build muscle in specific parts of their thighs — it’s about the same as not exercising at all.