Band on the ankle, drive the knee like a piston.
Stay tall on the standing leg and drive the knee high without leaning back.
Driving your knee up against a band anchored behind you loads the front of the thigh through the exact knee-drive pattern you use when sprinting. The glutes assist on both sides of the movement, extending the hip as the foot returns and stabilising the standing leg so you stay tall. Because it is one leg at a time, it doubles as balance work and shows you instantly which side drives weaker.
It trains the knee-drive action of running against resistance, so the thigh muscles that lift the leg get direct work instead of only ever pushing into the ground. Sprinters and field-sport athletes use it to sharpen turnover.
Leaning back is your torso cheating the rep. Brace your core, keep ribs stacked over hips, and only drive the knee as high as you can without tipping. Height means nothing if your posture folds.
Low, around ankle height, and looped on the ankle of the working leg. Step far enough from the anchor that there is tension at the bottom of every rep, not just at the top.
