On all fours, drive a straight leg back for a deep glute squeeze.
Keep the leg straight and stop at hip height, don't hyperextend the lower back.
Lifting a straight leg behind you from all fours puts the glutes in charge of pure hip extension, with the hamstrings assisting since the straight knee keeps them under tension through the lift. The long lever of a straight leg makes bodyweight feel like more than it is, and stopping at hip height keeps the work in the glute instead of the lower back. It suits activation before squats and deadlifts, higher-rep glute volume, and training each side on its own to expose imbalances.
A bent knee shortens the hamstring and puts more emphasis on the glute alone, a straight leg lengthens the lever so the hamstrings join in and every rep feels heavier. Both are worth doing, the straight-leg version just buys more total posterior work from the same position.
You are lifting past hip height and arching to get there. The glute finishes its job when your leg lines up with your torso, anything higher is your spine hyperextending. Stop at that line and squeeze harder instead of higher.
Slow the lowering to three seconds, pause and squeeze for two at the top, or loop a band around your ankles. Long levers plus strict tempo make bodyweight go a surprisingly long way.
