One leg, one box, zero hiding.
Push through the top leg, don't bounce off the bottom foot to cheat the rep.
Driving your whole bodyweight up through one heel makes the quads of the top leg extend the knee against real load, with the glutes finishing hip extension as you stand tall on the box. Because each leg works alone, there is nowhere for a lazy side to hide, which is exactly why coaches love it for fixing left-right gaps. It earns its spot as a foundational single-leg builder that scales from rehab to brutal simply by changing box height and tempo.
Around knee height is the standard, your thigh roughly parallel when your foot is on top. Lower for beginners or higher-rep work, higher for more glute and range, but never so high that you have to lean and heave.
Slow down and think of the bottom foot as dead weight. Some people hover the back toes or point that foot down so it cannot spring. If you cannot rise without the push, the box is too high for now.
They cover similar ground, single-leg quad and glute work. Step-ups are usually kinder on the knees and easier to keep strict, lunges add a bigger stretch at the bottom. Strong legs generally do both across a programme.
