Human movement arises from the interaction of muscles, bones, and joints, organized into a highly efficient system for producing force and motion. Among resistance training exercises, the bench press is one of the most popular due to its relevance for strength development, hypertrophy, and its historical role as a benchmark of performance in strength sports. Despite its popularity (or maybe because of it), variations in technique can significantly alter the biomechanical demands of the movement, diminishing its benefits.

One of the most common mistakes is to lift the hips off the bench. Understanding why this is not recommended requires an analysis grounded in physics and biomechanics, particularly concepts such as levers, moment arms and mechanical work.

The musculoskeletal system as a lever system

The human musculoskeletal system functions as a complex network of levers. When a muscle contracts, it shortens and generates tension that is transmitted through its tendon to the bone at the attachment site. This force application produces either rotational movement around the corresponding joint or stabilizing isometric tension, depending on the task being performed.

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During the bench press, force production relies primarily on the pectoralis major, anterior deltoid, and triceps brachii. The pectoralis major originates on the clavicle, the sternum, and costal cartilages, and inserts onto the humerus. When it contracts, it drives horizontal adduction of the shoulder, moving the humerus toward the midline. The anterior deltoid, which originates from the lateral clavicle and also inserts onto the humerus, assists in shoulder flexion and stabilization throughout the lift. The triceps brachii, originating from the scapula and humerus and inserting onto the olecranon of the ulna, extends the elbow to push the bar away from the torso.

Together, these muscles act on the humerus and ulna across the glenohumeral and elbow joints, functioning as force generators within a system of levers that ultimately allows the barbell to be lifted vertically against gravity.

As the bench press becomes heavier, however, it is common for lifters to raise their hips off the bench during the final repetitions in order to complete the set. In some cases, this can occur even on every rep. If not screamed at immediately, this technical deviation may develop into a habitual movement pattern.

There are several factors that make the bench press with the hips lifted off the bench feel easier. To understand them, it is useful to separate the analysis into two scenarios:

1. Hips raised before completing the eccentric phase

When the lifter has his butt off the bench before the bar touches his chest, the range of motion is reduced, since the chest is positioned higher. In that sense, the movement is easier, because the bar has to travel a smaller distance.

In a physics analysis, we can identify that mechanical work to move the bar decreases, since we get to it using the equation:

W = F x d

Where W is mechanical work, F is the weight of the loaded bar, and d is the vertical displacement of the bar to finish the movement. When d decreases, mechanical work also decreases.

In that same scenario, there is one more consequence to the mechanics of the movement. With a smaller range of motion, the moment arm at the shoulder decreases, as the bar touches the chest closer to the shoulder joint.

The moment arm is defined as the perpendicular distance between the shoulder joint (the axis of rotation) and the line of action of the bar’s force. A shorter moment arm places the lifter in a more favorable mechanical position by bringing the line of force closer to the joint. Since torque is given by the product of force and moment arm (τ=F x r), reducing the moment arm decreases the torque required at the shoulder, making the lift easier to complete.

2. Hips raised after the bar touches the chest

In this case, the total mechanical work remains the same, because the same weight on the bar has to travel approximately the same vertical distance as in a properly performed bench press. But the lift may feel easier due to two factors:

a. Raising the hips elevates the chest, which can help accelerate the bar upward. In other words, the hip extension contributes mechanical energy to drive the bar upward during the initial phase of the concentric movement.

b. With the hips off the bench, there is a likely greater involvement of the lower fibers of the pectoralis major, which are more favorably aligned in this position. These fibers originate at the sternum and insert into the humerus at an oblique angle, making them more efficient when the torso is in a declined position.

Comparison with the Decline Bench Press and its Applicability

In this sense, lifting the hips after the bar touches the chest can be seen as a way to use the hip extensors to move the barbell up in precisely the most mechanically disadvantageous position (close to the chest) and effectively turning the movement into something closer to a decline bench press, where most lifters can press heavier loads than on a bench press due to the same biomechanical advantages described previously: a shorter range of motion, a reduced moment arm at the shoulder, and more favorable fiber orientation of the lower chest.

This raises an important question: if we can lift more weight and possibly use more muscle mass than in a regular bench press, why not use the bench with the hips up or even the decline bench press?

To begin addressing this question, we must consider the four criteria that we use to choose what movements we should do, especially the one regarding that it happens “over the longest effective range of motion.”

In the case of hips raised before completing the eccentric phase, as we demonstrated, the range of motion would be shortened, so the criterion regarding the movement happening over the longest effective range of motion is not satisfied. As an analogy, this is why partial movements such as pin presses or board presses are not typically used as primary strength exercises.

Raising the hips after touching the chest doesn’t decrease the range of motion, however, this modification introduces significant involvement of the hip extensors, reducing the relative contribution of pectoralis major, anterior deltoid, and triceps brachii. This is undesirable for two reasons: (1) interferes negatively with the strength development in the upper body; and (2) it’s an inefficient way to train the hip extensors, considering the limited range of motion when compared to the squat or deadlift. For the same reasons, the push press is not a main movement in the Starting Strength Method.

It’s worth noting that the most mechanically disadvantageous position in the bench press occurs near the bottom of the movement. In this region, the moment arm at the shoulder is maximal, increasing the mechanical demand on the primary movers. At the same time, the pectoralis major operates at a less favorable length, while the triceps brachii has not yet reached a position of optimal contribution. This combination results in a transient reduction in force production efficiency, often referred to as the "sticking point."

In that sense, training should emphasize strength development in the portion of the movement closest to the chest, and not use the hips to avoid the position or help accelerate the bar up. One day the bar will end up at your chest, either because one of your feet slips, a powerlifting competition, or your brother challenging you on the bench press. In any case, you need to be able to lift the bar if you want to continue alive and with your original pec attachments.

Lastly, touching the chest while maintaining contact between the glutes and the bench provides an objective marker to make sure the bench press isn’t just being shortened as the weight goes up. It results in reliable data, because if the lifter adds weight, touches the bar on the chest and finishes the rep, we know he got stronger because we controlled all the other variables.

As a side note, not raising the chest to increase the range of motion also wouldn’t be beneficial, because of the other criteria. We want a high chest position to have a steeper angle with which the pecs and the delts attach to the humerus, because a lever system is more efficient when the applied force gets closer to being perpendicular to the moment arm. 

Therefore, the goal is to maximize muscle involvement (isometrically or concentrically), to bring the shoulders back, raise the chest, be more stable, lift more weight and thus facilitate the process of getting stronger.

Hip Position Under Competition Rules

Hip position becomes especially relevant when the bench press is performed under powerlifting competition standards. In this context, the lifter is required to maintain contact between the hips and the bench throughout the lift.

However, even when the hips remain in contact with the bench, not all forms of force transfer from the lower body are acceptable. While proper leg drive is allowed as a means of creating stability and efficient force transmission, it must not result in visible displacement of the torso or loss of positional integrity. Sometimes referred to as an "upper body thrust," this movement can be understood as a biomechanical compensation strategy in which the lifter generates upward momentum by rapidly elevating the chest or jerking the torso immediately after the "Press" command.

Unlike proper leg drive, which provides static stability, this thrust represents a dynamic attempt to overcome the bar’s inertia by using torso movement to assist the ascent. Although the strictness of officiating may vary across federations, this type of “thrust” or “heave” is generally prohibited in order to preserve the bench press as a standardized test of upper-body strength.

Conclusion

There are several factors that explain why the bench press with the hips off the bench is easier, but there are no compelling reasons to include it as a regular part of your training. This is because it:

(1) uses an ineffective range of motion and thus reduces the moment arm at the shoulder joint, which in turn decreases the torque required to lift the bar;

(2) increases the contribution of the hip extensors at the expense of the upper-body musculature, interfering with strength development on the range of motion closer to the chest;

(3) makes the movement less reproducible, because lower body contribution and torso position may vary, making it difficult to reliably compare performance over time.

(4) compromises safety, because it doesn’t provide reliable data and because primary movers are less trained in the most mechanically disadvantageous position of the lift.

(5) is prohibited in bench press competitions according to powerlifting rules.

There are specific situations that could justify practicing a shorter range of motion on the bench press, like a way to train around an injury, improving the lock out of the lift, or an equipped bench press competition. But for all of that, there are better options than benching with the ass off the bench, like the pin press, the board press, the Spoto press, and the use of supportive equipment such as the Slingshot.

Finally, even if you want to develop maximum hypertrophy in your chest, benching with the hips up wouldn’t be the best choice for all the reasons above. Now if your bodybuilding coach insists on you focusing on your “lower pecs,” exercises such as the decline bench press or dips are more appropriate choices.

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