The Disconnect Between Glute Bridge/Hip Thrust and Squat: Unveiling the Functional Mechanics

The glute bridge and hip thrust are commonly employed as assistance exercises with the intent of fortifying the glutes for squats. Additionally, they find application in rehabilitation scenarios for "underactive" glutes.

Article Objective

The primary objective of this article is to dissect the functional mechanics of the bridge in relation to the squat. It aims to elucidate why an individual can proficiently train the bridge yet struggle to engage the glutes during the squat. Henceforth, the term "bridge" will be used to encompass both the glute bridge and hip thrust.

How the Muscles Function

Prior to analyzing the squat and the bridge, it is imperative to commence with fundamental principles that enable us to comprehend how muscles operate in an isolated exercise such as the bridge, as opposed to the compound movement of the squat.

Isolated Muscle Strengthening

A significant portion of exercise science focuses on strengthening muscles in isolation. This approach is founded on concentric muscular contractions, which involve muscle shortening and the generation of motion. In the case of the bridge, the glutes contract concentrically to produce hip extension.

Glute Recruitment Science

In the article "Hip Thrust and Glute Science," Bret Contreras delved into the science of maximizing glute recruitment. This included research on the optimal degrees of hip and knee flexion necessary for attaining the highest EMG readings. The intention here is not to question his methods, as they are valid for their intended function and goal - achieving maximum glute contraction for substantial hypertrophic gains. Instead, this article will demonstrate why the bridge is ill - suited for enhancing glute function in the context of our objective, which is the squat.

Enhancing Glute Bridge

The glute bridge has been purportedly enhanced through the use of bands around the knees to promote hip abduction and by turning the toes for external rotation. The underlying theory posits that simultaneously performing all three concentric glute muscle actions - extension, abduction, and external rotation - will ensure maximal EMG activity of the glutes.

EMG and Muscle Recruitment

A high EMG reading is regarded as a crucial indicator of an exercise's efficacy in recruiting a muscle. The bridge exhibits high EMG activity, leading to the expectation that it should teach the glutes to function during the more functional, compound squat. However, this often does not materialize.

How the Body Works

Bridge vs Squat: Nervous System and Muscle Function

In the bridge, the focus is solely on teaching the glutes to hip extend, not to squat. The bridge is performed in a supine position, where the nervous system is relatively dormant. This can be likened to prolonged bed rest, where muscles atrophy due to the reduced gravitational stimulus, which is essential for maintaining low - grade constant muscle activation.

When lying down, the body is no longer combating gravity, resulting in minimal to no activation of the nervous system. Consequently, when the hips are elevated, the neurological drive is primarily directed towards the glutes, explaining the high EMG reading for the bridge.

Conversely, when preparing to squat under load, the entire nervous system is subjected to a significantly greater amount of pressure compared to the bridge. As the descent of the squat commences and the hips approach the floor, neurological activity is distributed to every muscle in the body. During the squat, the hip muscles alternate between shortening and lengthening at different intervals, learning to collaborate as a cohesive unit to counteract both gravity and the load in motion.

Isolated vs Integrated Muscle Function

This is a pivotal factor explaining why the glute bridge does not translate well to squatting. The body functions as an integrated system, with extensive neurological communication occurring between muscles to complete a task. During a glute bridge, the glutes learn to operate in isolation, with limited interaction with adjacent muscles. As a result, when transitioning to standing and performing a squat, the glutes struggle to determine when to contract in relation to the other muscles involved in the compound squatting movement.

Subconscious Nervous System Control

The nervous system operates subconsciously to regulate all human movement. Conscious muscle contractions are typically associated with isolated movements. However, during functional (multi - jointed) movements, it is impossible to consciously direct every muscle to work. The sequencing of muscle firing patterns cannot be consciously controlled due to the involvement of multiple muscles. Even if it were possible, the cognitive load would likely cause failure in the lift.

How the Mechanics Work

Muscle Sequencing and Mechanics

The sequencing of muscles is not the only differentiating factor; the mechanics of the bridge and squat also diverge significantly. In the bridge, the glute initiates from a state of inactivity and then shortens. Although the glute has stored energy, it lacks the stretch - shortening cycle characteristic of the squat.

Squat Mechanics

During the downward phase of the squat, the glute undergoes hip flexion, adduction (starting from a relatively abducted position and moving further inward as the squat progresses), and internal rotation. These are the natural mechanics of the squat descent.

Concurrently, the knee experiences flexion and internal rotation, resulting in an internally rotating femur during the eccentric phase of the squat. It is important to note that this does not imply the knees coming into contact; rather, if the knee tracks over the foot, it indicates internal rotation of the hip.

The downward phase causes the glute to lengthen in all three planes of motion: hip flexion in the sagittal plane, hip adduction in the frontal plane, and internal rotation in the transverse plane. This lengthening process generates an elastic load, enabling the glute to explosively and concentrically extend, abduct, and externally rotate the hip, facilitating the upward movement to a standing position.

Bridge Mechanics

The joint motions described above are not replicated in the bridge. Due to the limited range of motion in which the bridge is performed, there is no stretch - shortening cycle. One consequence of the bridge is glute tightness, restricting the glute to contracting within a shortened range of motion, unlike the extensive range of motion in the squat. This limited range means the glute fails to learn how to function at the bottom of the squat, precisely when its assistance is most crucial.

Enter the Lunge

Lunge as a Squat - like Exercise

To genuinely facilitate glute activation, the lunge is the exercise most closely resembling the squat. The joint motions of the hip in the lunge are nearly identical to those in the squat - hip flexion, internal rotation, and adduction during the downward movement, allowing the glute to engage in its stretch - shortening cycle. However, there is a minor distinction between the two exercises. In the lunge, the foot striking the floor generates ground reaction force, resulting in a slightly different mechanical loading pattern compared to the top - down loading of the squat.

Muscle Coordination in the Lunge

In the lunge, the glute learns to work in harmony with all the other hip muscles in a coordinated and synchronized movement sequence. The joint angles, particularly in the front leg, are similar to those in the squat. Significantly, the ankle, knee, and spine also learn to move in tandem with the hips during this motion. In contrast, in the bridge, only the hip moves and extends, with the ankle and spine in positions and under stresses vastly different from those in the squat, preventing the acquisition of the correct movement pattern and muscle sequence.

Balancing Strength with the Lunge

The lunge also enables each leg to develop strength independently. It is rare to encounter a perfectly balanced squat; most individuals have a stronger leg that they favor during squats. The lunge can help balance this system.

However, performing a mere thirty lunges is insufficient to induce the desired changes in motor pattern recruitment. The second part of this article will explore the programming necessary to effect substantial changes in motor patterns.

Recommended Reading

• Squats and Hip Dysfunction: 2 Common Problems and How to Fix Them

• What’s New on Breaking Muscle Today

References

1. Contreras, B. “Hip Thrust and Glute Science.” The Glute Guy. Last modified April 6, 2013.

2. Worrell TW., et al. “Influence of joint position on electromyographic and torque generation during maximal voluntary isometric contractions of the hamstrings and gluteus maximus muscles.” J Orthop Sports Phys Ther. 2001 Dec;31(12):730 - 40.

Photo Credits

• Photo 1 courtesy of Shutterstock.

• Photo 2, 3, & 4 courtesy of CrossFit Empirical.