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

Introduction

The glute bridge and hip thrust are frequently employed as assistance exercises to fortify the glutes for squats. Additionally, they find utility in the realm of rehabilitation for cases of “underactive” glutes. This article aims to dissect the functional mechanics of the bridge in comparison to the squat, elucidating why training the bridge may not necessarily translate to effective glute recruitment during the squat. Henceforth, “bridge” will encompass both the glute bridge and hip thrust.

How the Muscles Work

Prior to analyzing the squat and the bridge, it is essential to commence with fundamental principles that enable us to comprehend how muscles function 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 an isolated manner. 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.

Maximizing Glute Recruitment

In the article “Hip Thrust and Glute Science,” Bret Contreras delved into the science of maximizing glute recruitment, including a study on the optimal degrees of hip and knee flexion necessary for achieving the highest electromyography (EMG) readings. The intention here is not to challenge his methods, as they are appropriate for their intended function and goal of attaining maximum glute contraction for maximal hypertrophic gains. Instead, this article will demonstrate why the bridge may not be suitable for enhancing glute function in the context of our objective, which is the squat.

Enhancing the Glute Bridge

The glute bridge has purportedly been enhanced through the use of bands around the knees to facilitate 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 maximum EMG activity of the glutes.

The EMG Conundrum

A high EMG reading is often regarded as a crucial indicator of an exercise’s efficacy in recruiting a muscle. The bridge exhibits high EMG activity, suggesting that it should train our glutes to function during the more functional, compound squat. However, this is often not the case. The question remains: why doesn’t this transfer occur?

How the Body Works

The Bridge and Hip Extension

In the bridge exercise, one is not training the glutes to squat but rather only to hip extend. The bridge is performed in a supine position, where the nervous system is relatively dormant, akin to the state during prolonged bed rest. During bed rest, muscles atrophy and individuals become weaker due to the reduced stimulation from gravity, which is essential for maintaining low – grade, constant muscle activation.

Neurological Activation Disparity

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

Conversely, when standing under load preparing to squat, the entire nervous system is subjected to a greater amount of pressure compared to the bridge. As the descent of the squat commences and the hips move towards the floor, neurological activity is distributed to every muscle in the body. During the squat, the muscles within the hip undergo shortening and lengthening at different times, learning to work in unison to overcome both gravity and the load with momentum.

The Isolation Dilemma

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

Subconscious Neural Control

The nervous system operates subconsciously to regulate all human movement. Conscious muscle contractions typically arise from 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 chosen due to the involvement of multiple muscles. Even if one could control this sequencing, the distraction would likely lead to failure in executing the lift.

How the Mechanics Work

Muscle Sequencing and Mechanics

The sequencing of muscles is not the sole differentiating factor; the mechanics of the two exercises also vary significantly. In the bridge, the glute begins from a state of inactivity and then shortens. Although the glute has stored energy, there is no stretch – shortening cycle, as is present in 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.

The coupled mechanics of the knee involve flexion and internal rotation, resulting in internal rotation of the 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 leads to the lengthening of the glute 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 stand.

Bridge Mechanics

These joint motions are not replicated during a 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 required in the squat. This limited range of motion means that the glute does not learn how to function at the bottom of the squat, precisely when its assistance is most needed.

Enter the Lunge

Lunge as a Squat – Adjacent Exercise

To genuinely assist in glute activation, the exercise most closely resembling the squat is the lunge. 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 descent of the movement, allowing the glute to engage in its stretch – shortening cycle.

However, there is a subtle difference between the squat and the lunge. In the lunge, there is a ground reaction force as the foot contacts the floor, resulting in non – identical mechanics compared to the squat, which has a top – down loading pattern.

Muscle Coordination in the Lunge

In the lunge, the glute learns to work in a coordinated and synchronized sequence with all the other hip muscles. The joint angles are similar to those of the squat (specifically, on the front leg), and importantly, 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 a completely different position and under different stress compared to the squat, preventing the acquisition of the correct movement pattern and muscle sequence.

Balancing Leg Strength

The lunge also enables each leg to work independently and develop its own strength. Rarely does one encounter a perfectly balanced squat; most individuals have a stronger leg that they tend to favor during squats. The lunge can help in balancing this system.

While performing lunges is beneficial, simply doing thirty lunges is insufficient to induce the desired changes in motor pattern recruitment. The second part of this article will explore the programming required to effect significant alterations in motor patterns.

Related Articles and References

• Related Articles:
  • Squats and Hip Dysfunction: 2 Common Problems and How to Fix Them
  • What’s New on Breaking Muscle Today
• References:
  • Contreras, B. “Hip Thrust and Glute Science.” The Glute Guy. Last modified April 6, 2013.
  • 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.