Find a stable surface about as tall as your knees, such as a bench, coffee table, couch, chair, stool, or low ledge.
Lie down on your back facing the surface. Place your feet on top of it, adjusting your position so that your hips are just about below your knees. Pull your core toward your spine and make sure your back is flat against the floor with no arch. Relax your arms by your sides.
Push into your feet to lift your hips a few inches off the floor. Make sure your hips are still under your knees and really drive your feet into the surface to activate your hamstrings. Continue squeezing your core and glutes and keep your hips square, facing the ceiling.
Push your feet down even more and squeeze your glutes to pulse your hips up one more inch.
Lower your hips one inch but keep them lifted off the ground, still holding your core firm.
Continue pulsing your hips up and down for one minute without touching the floor. If this causes discomfort in your back or knees, do the pulses with your feet on the floor in a glute bridge instead.