Should You Keep a Vertical Shin for Glutes? The Science of Glute Bias
You have probably heard it in a gym or a reel: keep your shins straight up and down, push your knees back, and your glutes will grow. It sounds smart, and there is real science under it. But the popular version of this cue is half right and half wrong. The wrong half can quietly load your lower back while doing less for your glutes than you think. Let us break down what your shins really change, and how to actually send the work to your glutes.
| THE MYTH “Keep your shins vertical and your glutes will grow.” |
START HERE
Meet the players
Two muscle groups run this show. The hip muscles (your glutes, with help from the hamstrings) straighten your hip. The knee muscle (your quads) straightens your knee. Every squat, lunge, and hinge shares the load between the hip and the knee. So the whole shins question is really one question: where does the load go, the hip or the knee?
| READ THIS FIRST · WHAT “TORQUE” MEANSTorque is just how hard a joint has to work to hold or move a load. More torque at the hip means more demand on your glutes. More torque at the knee means more demand on your quads. |
| ONE HONEST CAVEATMore demand is not the same as more growth. These cues point the work at your glutes. You still have to train hard and add weight over time. A bigger number on a chart is not a promise of a bigger muscle. |
PART 1
What a vertical shin actually does
Here is the part the cue gets right. When you pull your knees back and keep your shins vertical, you move load off your knees and onto your hips.
Researchers tested this directly. They had lifters squat two ways: once letting the knees drift forward naturally, and once with a board blocking the knees so the shins stayed vertical. Then they measured the torque at each joint. With the shins held vertical, knee torque dropped by about 22 percent. But hip torque jumped from about 28 to 303, more than ten times higher. So yes, a vertical shin really does hand the job to your hips.
A vertical shin puts your hips far behind the load (a long hip lever) and keeps your knees close to it (a short knee lever). Knees forward flips it.
Fry et al. 2003. Holding the shins vertical cut knee torque by about 22% and multiplied hip torque roughly ten-fold.
| WHY IT HAPPENS · A LEVER Torque = force × distance from the joint. A vertical shin puts your hips far behind the bar, giving the hip a long lever. That long lever is where the big hip number comes from, not the shin by itself. |
PART 2
It’s the trunk, not just the shin
Now the part the cue gets wrong. Your shins are not the real switch. Your trunk is. A vertical shin only sends load to your hips because it usually comes with a forward lean. Lean the trunk and the hips take over. Stay upright and the knees take over. Shin angle just tags along.
When scientists compared them head to head, trunk angle predicted the load on the knee far better than shin angle did. According to a comprehensive biomechanical review of the squat exercise, the rule they found is simple: if your trunk leans more than your shin, the hips lead. If your shin leans more than your trunk by about 8 degrees or more, the knees lead.
Trunk versus shin decides it. Lean the trunk past the shin and the glutes take over (Straub 2021; Barrack 2021).
| Stop staring at your shins. Watch your torso. To feel your glutes, hinge your hips back and let your chest come down, then drive your hips forward to stand tall. If you ever feel your form breaking down into lower back pain instead of a glute pump, it’s a sign that your mechanics are slightly off knowing why you have lower back pain after hip thrusts or squats can help you troubleshoot your trunk position. |
PART 3
The catch, and the smarter way
So should you freeze your shins vertical on every squat? No. Here is the catch. In that same study, forcing the shins vertical did not only load the hips. It also forced the lifters to lean much further forward, dumping a big load on the lower back. Chasing glutes by locking your shins can quietly punish your spine, and it caps how deep you can go, which your glutes actually want.
There is a smarter way to get the same hip bias:
1) Hinge and lean. In a lunge, leaning the trunk forward raised glute and hamstring activity, with no extra load on the quads. Same idea in a squat: let your chest come down over hips that sit back.
2) Go deep, and go wide. Deeper squats give the glutes a bigger share of the work, and choosing a wider stance secretly decides which glutes grow by letting you reach a hip bias with less forward lean, which is much easier on your back.
3) Use the Bulgarian split squat. This is the quiet winner. Because one leg does the work, your hips can produce about twice the force per leg of a back squat, at the same load on your lower back. A big glute stimulus without frying your spine.
The Bulgarian split squat: about double the hip work per leg, at the same low-back cost (Arakawa et al. 2025).
| THE PROOF · FARROKHI 2008 In a lunge, a forward trunk lean raised glute and hamstring activity while the quads stayed the same. It is the lean, not the frozen shin, that feeds the glutes. |
| THE VERDICT: HALF TRUEA vertical shin does move load onto your hips. But the shin is not the real lever, your trunk is. And forcing a bolt-upright shin in a squat mostly just loads your lower back. To build glutes: hinge and lean, go deep, go wide, and use single-leg hinges like the Bulgarian split squat. |
THE DATA
By the numbers
| Move | Glute bias | Why |
|---|---|---|
| Bulgarian split squatchest forward | ● ● ● ● ● | ~2× hip work per leg, low back cost |
| Romanian deadlift / hip hinge | ● ● ● ● ● | Vertical shin is correct here; big hip load |
| Hip thrust | ● ● ● ● ● | Pure hip extension, easy on the knees |
| Deep squat, wider stance | ● ● ● ● ● | Hip bias with less forward lean |
| Bolt-upright narrow squat | ● ● ● ● ● | More quads; forcing vertical shins taxes the back |
Dots show glute bias, not overall value. Every move here can build muscle when trained hard.
QUICK REFERENCE
At a glance
| Your goal | Do this | Why |
|---|---|---|
| More glutes | Hinge and lean, go deep, go wide. RDL, hip thrust, Bulgarian split squat. | Sends the load to the hips |
| More quads | Let the knees travel, stay upright, heels elevated, narrower stance. | Long knee lever = more quad |
| Balanced legs | Full-depth back squat with natural knee travel. | Shares hip and knee |
| Save your back | Widen your stance or go single-leg instead of forcing a vertical shin. | Same hip work, less spinal load |
| BOTTOM LINE It is not your shins. It is your hips versus your knees. Lean, hinge, and go deep to send the work to your glutes. Let your knees travel when you want quads. And never freeze your shins vertical in a squat just to chase glutes, that mostly just taxes your lower back. Want the glute work without the back tax? Hinge, or go single-leg. |
 | Want more myth-busting, science-backed glute training? bootycenter.com |
References
1. Fry AC, Smith JC, Schilling BK. Effect of knee position on hip and knee torques during the barbell squat. J Strength Cond Res. 2003;17(4):629-633.
2. Straub RK, Powers CM. A Biomechanical Review of the Squat Exercise: Implications for Clinical Practice. Int J Sports Phys Ther. 2024;19(4):490-501. doi:10.26603/001c.94600.
3. Straub RK, Barrack AJ, Cannon J, Powers CM. Trunk Inclination During Squatting is a Better Predictor of the Knee-Extensor Moment Than Shank Inclination. J Sport Rehabil. 2021;30(6):899-904. doi:10.1123/jsr.2020-0397.
4. Barrack AJ, Straub RK, Cannon J, Powers CM. The relative orientation of the trunk and tibia can be used to estimate the demands on the hip and knee extensors during the barbell back squat. Int J Sports Sci Coach. 2021;16(4):1004-1010. doi:10.1177/1747954121997957.
5. Farrokhi S, Pollard CD, Souza RB, Chen YJ, Reischl S, Powers CM. Trunk position influences the kinematics, kinetics, and muscle activity of the lead lower extremity during the forward lunge exercise. J Orthop Sports Phys Ther. 2008;38(7):403-409. doi:10.2519/jospt.2008.2634.
6. Arakawa H, Nakashima H, Li X, Tanimoto M. Rear leg-derived moment contributes to resistance against hip extension in Bulgarian split squats. Int J Exerc Sci. 2025;18(7):881-894.
7. Caterisano A, Moss RF, Pellinger TK, et al. The effect of back squat depth on the EMG activity of 4 superficial hip and thigh muscles. J Strength Cond Res. 2002;16(3):428-432.
