Breaking Down the Single Leg Squat

by Ben Bruno – 8/09/2011
Single-leg squats can be a valuable addition to virtually any lifter's program, whether the goal is strength or physique oriented.
That is, if the lifter can perform single-leg squats. Most simply can't.
Let me clarify that statement; most can't in the beginning. Unfortunately, the majority of lifters never make it past the beginning stage. They try it once or twice – if they even try it at all – fail miserably, and immediately write it off as a bogus circus exercise.
I was one of those people. I was introduced to single-leg squats when I started interning for Mike Boyle, at whose gym I now work. Before my internship, I remember reading Mike's writings praising one-legged movements and thinking "bullshit."
I considered myself to be a pretty strong guy (at the time, I had over a triple bodyweight deadlift and near double bodyweight front squat) and the first time I experimented with single-leg squats, I couldn't even do one rep with just my bodyweight. Had I not committed to my internship already, I probably would've quit doing them right there.
I quickly realized that trying to simply drop into a full single-leg squat right off the bat was going to be an embarrassing endeavor, so I took a step back and started through a methodical progression system to work my way up to it. It took about three sessions to get the hang of it and about six sessions to get to where I felt comfortable enough stability-wise to start adding additional load.
Keep in mind, I wasn't devoting entire workouts to just single-leg squats. I'd do a few sets of whatever progression I was on followed by my regular leg workout, so I didn't miss out on valuable training time while I learned the movement.
With some concerted practice, it soon became a staple in my program, and I've never looked back. My legs have gotten significantly stronger, and they've even grown despite not training specifically for hypertrophy. As an added bonus, my back has never felt better.
It's not just me though; I've also seen them work wonders for the hundreds of athletes that train with us.
To understand why I like them so much, let's take a closer look at the benefits single-leg squats have over their bilateral counterparts.

Balance

Balance takes on a dual meaning here. First is building balance between legs. Single-leg squats can both detect imbalances and asymmetries between legs and help to correct them once they've been brought to light. Symmetry is crucial for both aesthetics and injury prevention, so it's not something to take lightly.
The other part of balance comes from standing on one leg. Single-leg squats help to improve overall balance and proprioception by strengthening some of the smaller stabilizing muscles in the hips and pelvis, namely the adductor magnus, gluteus medius, quadrates lumborum, and the external hip rotators to prevent rotation of the femur and pelvis in a way that doesn't occur in a bilateral stance.

Less Spinal Loading

Single-leg squats allow you to target the legs with greatly reduced shearing forces on the spine. Moreover, the overall external loads used for single-leg squats are typically less than with bilateral lifts, so there are fewer compressive forces, making them much more low-back friendly than their bilateral counterparts.
This is obviously appealing for back-pain sufferers, but also healthy back populations, too. One study revealed that in a random sample of 98 "healthy" asymptomatic backs, 64% of the subjects had a disk abnormality of some sort.
Also worth noting is that while the overall prevalence of disc abnormalities didn't change much with physical activity, the prevalence of disc protrusions at L5-S1 was higher in people that exercised regularly as compared to more sedentary folks (16% to 4%). Remember, these were asymptomatic subjects, so just because you're not currently experiencing back pain doesn't mean that your spine is necessarily healthy. Chances are it's not.
Don't take your spine for granted. Remember, you only get one.

More Load on The Legs

While the total external loads used for single leg squats are typically less than in bilateral squats, the overall load on the legs is actually higher due to a phenomenon known as the bilateral deficit, which means that the sum of the forces produced by each leg is greater than the total bilateral force production. To understand this, it helps to use some calculations and real-world examples.
Once our athletes familiarize themselves with the exercise, it's not uncommon for females to use anywhere from 20-50 pounds of external load and male athletes to use upwards of 75-110 pounds, sometimes more.
For example, one of my high school freshman hockey players recently performed six reps on each leg with 80 pounds of external load at a bodyweight of 176 pounds.
To calculate the load being placed on the working leg, we must first calculate his "super incumbent bodyweight," which is the weight above the joint being used to lift the load, in this case, the knee.
If we estimate that the lower leg and foot weighs 12 pounds, then his superincumbent bodyweight during a single-leg squat would be 164 pounds. Add in the 80 pounds of external load and you get 244 pounds of load on the working leg.
Now let's compare how much weight would be needed in a bilateral squat to get the same amount of load on each leg. During a back squat, the superincumbent bodyweight for this kid would be 152 pounds, so he'd need to squat 336 pounds for six reps to achieve the same overload on his legs. There's no way in hell he could handle that weight for one rep, let alone six.
I recently used 184 pounds of external load for a set of six at a bodyweight of 183 pounds. Taking into account my superincumbent bodyweight (171 pounds), that's 355 pounds of load on the working leg.

To get the same overload on my legs during a back squat, I'd have to use 539 pounds. I doubt I could even get 539 pounds off the pins, much less squat it six times.
The message is, for the majority of people, there's more potential to overload the legs during a single-leg squat, and the balance swings even more in their favor with increased proficiency.

Now What?

All of this is irrelevant though if you can't single-leg squat right to begin with.
I want to share with you the progression system I used to reap the many benefits that single-leg squats have to offer.

• If it looks like a long, arduous road ahead, fear not. It won't take nearly as long as you might think. Individual times will vary from person to person, but most will become reasonably proficient in about 6-10 sessions.
• You have to be willing to check your ego at the door because if you try to bypass steps, it will only take longer, and you'll probably end up making a fool of yourself in the process.
• You also have to be open-minded. Many people (guys in particular) go into it with the mindset that they can't do it or simply aren't "built for it." That's a cop out. Sure, certain body types lend themselves better to certain exercises, but we use this exercise with people of all shapes and sizes; short and tall, thick and thin, from middle school girls to older adults to 300-pound NFL lineman, and everyone in between. The key is just to follow the progressions.
• There's no preset amount of time that you should spend on each step. Move through at your own pace, but make sure you've mastered each one before moving forward.
• If you have no prior background with unilateral leg training whatsoever, spend some time with more basic exercises like split squats, lunges, and rear foot elevated split squats (Bulgarian split squats) to build stability and get acquainted with the feeling of being on one leg. If you've already done some of these exercises, you should be good to go.

Breaking It Down

The progressions are largely related to the range of motion, but the main tenets of the exercise remain the same throughout.

• Hold small dumbbells in your hands to serve as a counterbalance. I can't stress this enough. It may seem counterintuitive that holding extra weight would make the exercise easier, but it does. I'd recommend 5-8 pound dumbbells for smaller individuals and 8-15 pounders for bigger guys.
• Begin each rep with the dumbbells at your sides and raise them to shoulder height as you squat down. This is important. It's easy to get lazy and only raise them to waist level, which causes you to lean forward, lose balance, and round at the lumbar spine. The higher you raise the arms, the easier it is to keep the torso upright. Similarly, keeping the arms straight as you extend them helps significantly with balance. For this reason, I rarely recommend that anyone use more than 20-pound dumbbells for a counterbalance because shoulder fatigue becomes an issue, which can negatively affect form.
• In the beginning you should squat to a bench, which for all but the tallest people will be a few inches above parallel. This could be considered the single leg equivalent to the high box squat.

• Start by sitting down on the bench with both legs and standing up on one. Once you've got that down, lower yourself down to the bench on one leg and use both legs to stand back up. From there, try to do the entire motion on one leg. Do not bounce off the bench. At first, it may help to pause on the bench, but try to work towards making it one continuous motion. When you can control the eccentric and come back up without the knee caving in, it's time to move on.
• The next step is to increase the range of motion. The best way to do this is to stand on a step placed in front of the bench so that the non-working leg can drop below the foot of the working leg. Work down gradually until you reach a depth where the femur is at least parallel to the floor.

Remember that you're not sitting on the bench here; it's merely functioning as a depth gauge. It's important to keep the weight on the heels as you descend to take stress off the knee. If you struggle to keep your heel planted, you may benefit from using a heel wedge (a small five-pound plate can also work) until you build up the required mobility to do it correctly.

• Once you can complete smooth and controlled reps to parallel, you have two choices: begin loading the exercise, or progress to a free standing squat without a box behind you. If you choose the latter, stand on the edge of a box or bench to allow the non-working leg to hang freely and descend until the femur of the working leg is at or slightly below parallel to the floor.

I prefer the free standing variation because people often end up bouncing off the box, so taking it away forces them to control the reps more. That said, the box can be useful for certain people to standardize depth, such as those with a history of knee pain who want to avoid going too low, or those that habitually do their reps high.
Taller athletes also tend to do better with a box, although I've seen guys as tall as 6'6" do the freestanding version just fine. Folks with knee pain may also benefit from pausing on the bench each rep.
Note: I'm not advocating a true "pistol" squat, which would be done standing on the floor, "ass to grass." I don't think the pistol is a bad exercise; it's just that in my experience, most are unable to do it correctly due to mobility restrictions or anthropomorphic considerations. Either they can't reach depth or if they can, they go into severe lumbar flexion, often resulting in back pain. This is especially true with taller individuals.
Standing on a box is much more user friendly, and you don't lose anything performing them that way. If you're one of the few who can do a full-range pistol while maintaining an upright body position and neutral spine, more power to you.

Advanced Variations

If you've gone through the entire progression and still aren't satisfied, here are a few ways to make them even harder. These are great for people that don't have access to things like weight vests and chains because they add difficulty through other ways than external loading.

Paused Reps

Pausing each rep at the bottom kills the stretch reflex and forces you to control the eccentric portion of the rep to avoid bouncing out of the bottom.

Slow Eccentrics

Slow on the way down, fast on the way up. These are brutal.

"1.5" Reps

Squat down, come halfway back up, squat down again, and come all the way back up. That's one rep. If you're looking for something to add size to your quads, look no further. I'll warn you right now, these burn.

Closing Thoughts

• How you choose to incorporate single-leg squats will largely depend on your goals. For people with back problems, I'd advise making them your primary form of squatting (along with other unilateral variations) to allow you to continue to train the legs hard without loading the spine.
• For strength athletes concerned with improving their squat, single-leg squats can be useful as an assistance exercise. I personally noticed tremendous carryover to my bilateral squatting after focusing almost solely on unilateral work for the better part of a year. I still front squat every couple of months (probably not the smartest idea given my back issues) and I'm always pleased to see my numbers climbing despite hardly ever doing them. It makes sense that if you strengthen your legs and build up the stabilizing muscles in the hips, your squat will improve.
• For lifters who are relatively healthy and just train to look and/or perform better, single-leg squats should absolutely be part of the equation, and not just as an afterthought. You must take them seriously to receive the maximum benefit. I'd recommend adding single-leg squats to the start of your leg workouts while you're fresh because they'll be much harder to learn in a fatigued state.<

The goal here is not to denounce bilateral squats but to show you that single-leg squats are another legitimate way to build bigger and stronger legs. Single-leg squats and bilateral squats are brothers of the same mother, just like barbell rows and one-arm dumbbell rows. They're all good choices under the right circumstances.
Check your ego, be patient, follow the progressions above, and most importantly, give the exercise a chance before forming your opinion. You might be pleasantly surprised.

References

Mike Boyle. Advances in Functional Training. On Target Publications. Aptos, California. 2010.

Mike Boyle. Functional Training for Sports. Human Kinetics. Champaign, Illinois. 2004.

Maureen C. Jensen et al. Magnetic Resonance Imaging of the Lumbar Spine in People without Back Pain. New England Journal of Medicine. July 14, 1994; 331:69-73.

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