Today’s guest post comes from Bret Contreras, author of the recently released 2×4: Maximum_Strength.

Many strength coaches, personal trainers, and strength athletes claim that the squat is the best exercise for promoting gluteal muscle development. Recently, the hip thrust has stumbled onto the scene, and its reputation for building impressive backsides has gained traction.

There is currently no published research examining the gluteal hypertrophic effects of squatting or hip thrusting, yet anecdotally we’re aware of their glute-building potential. While nobody can say for sure right now which is best for gluteal growth between the squat and the hip thrust, I hope that by the end of this article, you’ll be convinced that both exercises should be employed for optimal glute development.

Hypertrophy Science

According to hypertrophy researcher, Brad Schoenfeld, there are three primary mechanisms to muscle growth. The most important mechanism appears to be mechanical tension. A close second in terms of importance appears to be metabolic stress. Finally, we have muscle damage, which appears to be of slightly lesser importance. As it currently stands, we don’t know for certain how to optimize these three stimuli in our programming in order to maximize muscle growth. The way I see it, until more is known, we should do our best to hit every base in our training. Therefore, we want to perform exercises that create the most tension in the glutes, produce the most metabolic stress in the glutes, and create reasonable amounts of damage in the glutes. How do squats and hip thrusts fare in regards to the three mechanisms of muscle growth?

Let’s take a deep look at what happens biomechanically and physiologically in the glutes when we squat and hip thrust.

Gluteal Biomechanics During the Squat

Let’s say you have the bar loaded up to around 80% of your one-rep maximum (1RM). You set up and take the bar off out of the rack. The upper glutes help stabilize your pelvis as you walk the bar backward. Once you get set, the glutes calm down. Now you start descending. Glute activation during the eccentric phase is very low – around 20-30% of maximum voluntary contraction (MVC). At the bottom position, the point where everyone thinks is so amazing for glute activation, is where the glutes actually reach their lowest activation during the rep – around 10-20% of MVC. I realize that this hasn’t been mentioned in any journal. It’s something I’ve noticed over the past year with the last fifteen or so individuals I’ve tested in EMG. These are highly experienced squatters, including several Arizona state record holders in the squat.

Now, before you call me crazy, please not that a similar phenomenon is seen in the erector spinae as they’re stretched under load; this has been deemed the lumbar flexion relaxation phenomenon. As the glutes are stretched out, their activation diminishes. This could be related to the passive-elastic force that they produce in this position, or some other reason, possibly related to the changing sarcomere length or the changing muscle moment arm length.

At this point, you explode out of the hole. This is where the glutes do their thang – during concentric actions. Glute activation will reach around 80-120% of MVC as you rise upward, peaking around halfway up, and gradually diminishing before you reach the top. You pause for a brief moment, and then resume the next repetition.

Mean activation is fairly low – around 50-70% of MVC – since the top portion of the squat is rather unloaded for the glutes, and since there is usually a considerable pause in between reps as the lifter takes a deep breath, resets, and gets tight, and since the glutes don’t fire very hard eccentrically during the lift. Because of this, you won’t feel a pump or a burn in the glutes when you squat, since blood in the gluteal region has plenty of time to escape during the set. However, you will develop glute soreness in the days following the workout, due to the fact that the glute fibers are stretched eccentrically to long muscle lengths while being activated, albeit at low levels. But this is only true for the lower gluteal fibers; the upper fibers of the glutes will generally fire at around 30-40% of MVC during a heavy squat.

Gluteal Biomechanics During the Hip Thrust

Now let’s discuss the hip thrust. Just as in the case of the squat, let’s say you’re using around 80% of 1RM. The bar is placed onto the hips. The body is wedged into place. Before the lift begins, the glutes are silent. The lifter then thrusts the hips upward until full hip extension is reached. During this concentric shortening, peak activation will typically reach around 120-200% of MVC, and this level of activation will be elicited in both the upper and lower gluteal fibers. The peak is reached at full hip extension, as the glutes reach their shortest muscle length. This could be due to the changing sarcomere length or the changing muscle moment arm length.

On the way down, the eccentric EMG activity mirrors the concentric activity, gradually diminishing until the bottom of the range of motion is reached. The movement is quickly reversed. Due to the rapid movements and consistent tension on the glutes, mean activation during the hip thrust is extremely high – around 100% of MVC. Due to the high levels of activation and constant pumping of repetitions, levels of metabolic stress are very high as well. Incredible “glute pumps” and burning will typically set in from multiple sets of hip thrusts. However, since the glutes are not fully stretched at the bottom of the hip thrust, muscle damage will not be very severe.

Theoretical Imposed Adaptations

As you can see, the squat and the hip thrust are actually quite different in biomechanics. Let’s examine some commonalities and differences.

Both exercises make for excellent glute exercises due to the bent knee position, which shortens the hamstrings and places more burden on the glutes for hip extension (when the hamstrings are shortened, they cannot produce maximum force due to active insufficiency).

Both exercises require dual actions out of the glutes. In a squat, the glutes must fire to create hip extension torque, but they must also fire in order to create hip external rotation torque to prevent knee valgus (caving in of the knees). In a hip thrust, the glutes fire to create hip extension torque, but they must also fire in order to create posterior pelvic tilt torque to prevent anterior tilting of the pelvis and lumbar hyperextension.

Squats can be limited by back strength, which is not the case for hip thrusts. Squats require more balance and coordination, whereas the hip thrust is very stable and simple to perform. The hip thrust is generally limited by glute strength, meaning that the set reaches failure when the glutes can no longer raise the hips. Squats move the hips into deeper hip flexion.

Let’s see which exercise outperforms the other in various biomechanical and physiological categories in the chart below.

As you can see in the hypothetical chart, the squat outperforms the hip thrust in 2 of the 7 categories, whereas the hip thrust outperforms the squat in 5 of the 7 categories.

The Verdict

Now, it doesn’t take a genius to imagine how combining the squat and the hip thrust would elicit greater adaptations than performing either exercise alone. In terms of imposed neural adaptations, the hip thrust requires more neural drive to the glutes, but there may be neural benefits to including squats due to the myotatic “stretch” reflex. In terms of mechanical adaptations, the two movements target different ranges of motion and therefore different gluteal muscle lengths, which likely lead to different mechanical adaptations as far as fascicle length and pennation angle are concerned. For full range gluteal strength, a more complete neurological stimulis, and full development of the upper and lower gluteal fibers, you’ll want to perform both the squat and the hip thrust. Either exercise alone won’t suffice. The good news is that we don’t have to choose between squats or hip thrusts for maximal glute development; we should perform both movements.

Squats elicit moderate levels of activation while promoting tolerable levels of gluteal muscle damage. Hip thrusts maximize tension and metabolic stress on the glutes and do a better job of hitting the upper fibers. The two exercises combine to produce one heck of a glute hypertrophy stimulus.

If you’re looking for a great resource to take your strength training program to the next level, I’d highly recommend Bret’s 2×4: Maximum_Strength. It’s on sale this week at a great introductory price.