Swimmers are a challenging exercise that targets the back muscles, especially the erector spinae. Begin by lying face down on the floor with arms extended overhead and legs straight. Lift your arms and legs off the ground simultaneously, then bring your arms down to your hips and legs up the side then back to starting position in a swimming motion while keeping your torso stable and engaging your back muscles to maintain the lifted position, aiming for controlled movements and continuous engagement for an effective posterior chain workout.