It's an honest question.....
I'm of the theory that while the typical lunges, squats and leg extensions are all good options for beginners, they can't take a more "advanced" trainee to another level.
That's why I selected the REVERSE step-ups or step downs as my third favorite leg exercise. Here's why.
You see how you have to maintain your top foot position and drive back UP?
When a traditional step up your foot comes off the ground or you press up with your opposite leg.
Yet on steps downs, you drive your top foot into the box. That creates a whole lot of new leg growth.