The glute bridge and hip thrust are support exercises often used to strengthen the glutes for the squat. They are also used in the world of "underactive" gluteal muscle rehabilitation.
The aim of this article is to break down the functional mechanics of the bridge compared to the squat, and explain how it is possible to train the bridge but still not be able to recruit the glutes during the squat.
(From now on, I'll be using "bridge" to cover both the gluteal bridge and the hip thrust).
How the muscles work
Before analyzing the squat and the bridge, we need to start with principles that will enable us to understand how the muscles work in an isolated exercise like the bridge compared to the compound movement of the squat.
“The bridge has a high level of EMG activity; Hence, it should teach our glutes to work when we do the more functional compound squats. Why doesn't that happen? "
Many training sciences deal in isolation with strengthening the muscles. This isolated method relies on a concentric muscle contraction that shortens and creates movement. At the bridge, the gluteus contracts concentrically to create a hip extension.
In an article titled Hip Thrust and Glute Science, Bret Contreras discussed the science of maximal buttock recruitment, including a study of the optimal amount of hip and knee flexion required for the highest EMG readings. The purpose of this article is not to question its methods as they are correct for the function and goal for which they are used – maximum gluteal contraction for maximum hypertrophic gains. Instead, this article will show that the bridge is inadequate to improve gluteus function in our goal, the squat.
The gluteal bridge allegedly evolved through the use of ligaments around the knees to push them off (hip abduction) and rotate the toes (external rotation). The theory states that performing all three concentric gluteus muscle actions (extension, abduction, external rotation) at the same time will ensure maximum EMG activity of the buttocks.
"Conscious muscle contractions come from isolated movements, but during functional (multi-joint) movement it is impossible to tell every muscle to work."
A high EMG level is considered very important when it comes to how well an exercise can recruit a muscle. The bridge has high EMG activity; Hence, it should teach our glutes to work when we do the more functional compound squats.
So why doesn't this happen?
How the body works
In the bridge, you are not teaching the buttocks to squat, just straightening the hips. The bridge works face up when lying down, with a nervous system that is as good as it is when you sleep. Couple this with prolonged bed rest, where muscles atrophy and people weaken because we lost our battle against gravity, which stimulates constant, low-level muscle activation.
When we lie down, we no longer fight gravity. This means that the nervous system experiences little to no activation throughout the body. So when the hips are propelled up, the only neurological drive goes to the buttocks, hence the high EMG level for the bridge.
When we are under load to crouch, the pressure experienced by the entire nervous system is greater than that of the bridge. When we begin the descent and move our hips toward the floor, every muscle in the body is exposed to neurological activity. As we squat, all of the muscles in the hip shorten and lengthen at different times and learn how to work as a team to overcome both gravity and the load traveling with the swing.
This is one of the key factors in why the gluteal bridge is not transferred to squats. The body works as a complete system, with huge neurological talk between the muscles to get the job done. When we perform a gluteus bridge, the glutes learn to work in isolation and there is little conversation with neighboring muscular friends. As a result, when we stand up and do a squat, the glutes no longer know when to contract relative to the other muscles that are working during the compound squat movement.
"When we do a gluteal bridge, the glutes learn to work in isolation and there is little conversation with neighboring muscular friends."
The nervous system works subconsciously to control all human movements. Conscious muscle contractions come from isolated movements, but during functional (multi-joint) movement it is impossible to tell each muscle to work. You cannot choose the order of the muscle firing patterns because more than one muscle is working. It is impossible to consciously control the complexity of this sequencing. Even if you could control the sequencing, you'd be so distracted from the task at hand that you'd likely fail the lift anyway.
How the mechanics work
Not only are the muscles arranged in opposite directions, the mechanics are also different. In the bridge, the buttocks start at a point of no activity and then shorten. The glutes have stored energy, but there is no stretch-shortening cycle like there is in the squat.
During the downward phase of the squat, the gluteus muscle moves through hip flexion, adduction (it starts in a relatively abducted position but continues inward as you crouch), and internal rotation. These are the natural mechanisms of squat descent.
The coupled mechanisms of the knee are flexion and internal rotation, so that an internally rotating femur occurs in the eccentric phase of the knee bend. Please note, I am not saying that the knees kiss. If the knee goes over the foot, it is an internal rotation of the hip.
The downward phase creates an elongation of the buttocks in all three planes of movement (hip flexion in the sagittal plane, hip adduction in the frontal plane and internal rotation in the transverse plane). This stretching process creates an elastic load that allows the buttocks to explode and concentrically expand, reduce, and rotate the hips outward so that we can stand.
"(L) restricted range of motion means that the glutes in the hole at the bottom of the squat aren't learning what to do, and then we really need the glutes to help us."
The above joint movements are not replicated during a bridge because there is no stretch shortening due to the limited range of motion in which the bridge is performed. One effect of the bridge is the tension in the buttocks, which means that the gluteal muscles can only contract in a shortened range of motion, not over a large range of motion like the squat. This restricted range of motion means the glutes in the hole at the bottom of the squat won't learn what to do, and then we really need the glutes to help us.
Take the lunge
To really aid in activating the glutes, the exercise that is closest to the squat is the lunge. The hip joint movements are almost identical – hip flexion, internal rotation, and adduction as the movement descends so that the glutes can go through its stretch-shortening cycle. There is a slight difference between the squat and the lunge, however. In the lunge, we have a floor reaction force when the foot hits the floor, so the mechanics are not completely identical as the squat has a top-down loading pattern.
During the lunge, however, the buttocks learn to work with all the other muscles of the hip in a coordinated and synchronized sequence of movements. The joint angles are similar to the squat (on the front leg) and, above all, the ankles, knees and spine also learn to move with the hips through this movement. In the bridge, only the hip moves and extends, with the ankles and spine in a completely different position and under a different load than in the squat, so that the correct movement pattern and the correct muscle sequence are not learned.
"Only the hips move and stretch in the bridge, with the ankles and spine in a completely different position and under a different load than in the knee bend."
The lunge also allows each leg to work independently and become strong on its own. I have yet to assess a squat that is 100% balanced. We all have a stronger leg that we prefer when doing squats. We have to try to balance the system.
So go ahead and pounce! But doing thirty lunges is not enough to make the desired changes in motor pattern recruitment. Part two of this article looks at the programming required to make significant changes to your motor patterns.
You will also find these articles interesting:
1. Contreras, B. "Hip Thrust and Buttock Science". The glute type. Last changed on 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 gluteal muscles." J Orthop Sports Phys Ther. 2001 Dec; 31 (12): 730-40.
Photo 1 courtesy of Shutterstock.
Photo 2, 3, and 4 courtesy of CrossFit Empirical.