The bench press is a foundational strength exercise. A common technical debate exists, particularly for those new to lifting, concerning the position of the spine. Many beginners are taught that the back must be pressed completely flat against the bench for safety and effectiveness. This advice often overlooks the specific biomechanics required to maximize power and protect the shoulder joint during the movement. The correct spinal position is important for both lifting heavy weights and maintaining long-term joint health.
The Recommended Bench Press Technique
The spine should not be entirely flat against the bench. Instead, the recommended technique involves establishing a controlled, moderate arch, often referred to as thoracic extension. This means the upper back is slightly extended to create a stable, elevated platform for the lift, rather than forcing an extreme curve in the lower back.
This technique ensures that only the upper back (around the shoulder blades) and the glutes remain in firm contact with the bench surface. A slight gap forms between the lower back, or lumbar spine, and the bench. This moderate extension is distinct from excessive, uncontrolled hyperextension, which can strain the lower back. The correct position is achieved by actively pulling the shoulder blades back and down before the lift begins.
Biomechanical Reasons for Spinal Curvature
A slight spinal curvature serves several biomechanical functions that improve stability, power, and joint protection. This positioning locks the shoulder joint into a safer, more stable socket. This greatly reduces the risk of anterior shoulder impingement or strain on the rotator cuff muscles.
The arch also significantly reduces the distance the barbell must travel, known as the range of motion. By elevating the chest toward the bar, the path of the press becomes shorter. This allows the lifter to handle a heavier load due to the decreased mechanical work required. Furthermore, a moderate arch can increase the recruitment of the pectoral major muscles compared to a completely flat-back press, as it places the chest fibers in a more advantageous line of pull. This mechanical efficiency allows lifters using a moderate arch to handle significantly heavier loads compared to those pressing flat.
This stable position allows the lifter to effectively utilize the entire body. By driving the feet into the floor, a force known as leg drive is generated, which travels up the body and is anchored by the rigid arch. This full-body tension improves overall stability and contributes to the upward force applied to the barbell.
Risks Associated with Forcing a Flat Back
Attempting to press the entire spine flat against the bench, especially under a heavy load, introduces specific risks to the shoulder and spine. When the back is forced flat, it prevents the necessary retraction and depression of the shoulder blades. Without this stabilization, the shoulder joint is placed in a compromised, internally rotated position at the bottom of the movement.
This lack of scapular support increases the risk of shoulder impingement, where the rotator cuff tendons are compressed against the bony structures of the shoulder. The absence of an arch also means the upper back cannot be effectively wedged into the bench, leading to a less stable base and potential energy leaks during the press. Forcing the lower back flat can improperly shift tension and may cause the lumbar spine to bear an undue load, increasing the potential for lower back strain as the weight increases.
Practical Steps for Establishing the Arch
To establish a correct and stable arch, the setup process must be deliberate, beginning with foot placement. The feet should be planted firmly on the floor, positioned slightly behind the knees if possible, to prepare for effective leg drive.
The next step involves getting the shoulder blades into the right position. This is done by reaching overhead and then actively pulling the shoulder blades down and back toward the hips. This action creates the thoracic extension and locks the upper back into the bench, forming a solid, stable base.
Lifters can use the barbell or the uprights of the rack to help pull themselves into this position, ensuring the chest is elevated and the shoulders are depressed. The final check is to ensure that the glutes remain in contact with the bench and the core is braced. This bracing prevents the arch from becoming excessive or uncontrolled during the lift itself.