"Hyperextensions" is a video demonstrating an exercise that primarily targets the lower back muscles (erector spinae). This exercise is typically performed on a hyperextension bench or Roman chair. To execute hyperextensions, you position yourself face down on the bench with your hips resting on the pad and your upper body hanging off the edge. You then lower your torso towards the floor while maintaining a neutral spine, and then raise your upper body back up until it is in line with your legs, squeezing your lower back muscles at the top of the movement. The video emphasizes proper form, technique, variations, and the benefits of incorporating hyperextensions into a workout routine to strengthen the lower back, improve posture, and prevent lower back pain.