Theoretical debates are a waste of time and energy. How about you just try stuff and reach your own conclusions? I'm an informal researcher myself. Instead of a science lab, I do my experimenting in the gym. I conduct my research using dumbbells, power racks, barbells, and real athletes.
Here's what my real-world experience has taught be about the controversial Bulgarian split squat vs. bilateral squat debate.
Some argue that the Bulgarian split squat isn't a good strength exercise because it doesn't lend itself to long-term progression like bilateral squatting does. This sentiment doesn't jibe with my personal experiences as a coach and a lifter though, so I have to respectfully disagree.
Last summer I made a deal with my athletes that I'd buy lunch at Chipotle for anyone who hit 225 pounds for 5 on Bulgarian split squats. Thankfully for my wallet, only a couple kids cashed in.
I had to take that offer off the table this summer because otherwise I'd have gone broke. I had a group of 21 boys ranging from 15-21 years old and by the end of the summer, every kid in the group had maxed out the 100-pound dumbbells, meaning they were doing at least 200 pounds for 5 reps. Three guys hit 315 for 5!
So based on that, I think there's tremendous potential for long-term progress, and the ceiling for unilateral leg strength is a lot higher than people think.
If you take this as an attack on heavy bilateral leg training, you're missing the point entirely and need to work on your reading comprehension skills. For the record, I'm pro-unilateral training, and I'm also pro-bilateral training. Unilateral and bilateral training aren't binaries, and it's best to do both and be proficient at both. I want my athletes to be strong all across the board. More than anything, I'm pro-strength.
The case studies I'll present below show the relationship between various exercises – how the numbers compare, how they carry over to one another, etc. With that in mind, here are my thoughts:
- If you want to improve a specific lift, you must practice that lift a lot for best results. However, if you're not tied to any one exercise and just generally want to get stronger, you have more leeway in terms of exercise selection.
- No exercise is irreplaceable. If you can't do an exercise for whatever reason, don't force it. Try something else. But whatever you chose, make sure to get damn good at it.
- Not everyone should be doing heavy Bulgarian split squats, just like not everyone should be doing heavy bilateral squats. It really depends on your goals, injury history, and the logistics of your setting.
- After lifters become proficient with Bulgarian split squats, they tend to be able to handle approximately the same weight that they can front squat – some slightly more, others slightly less – and approximately 75-85% of what they can back squat.
Based on the numbers, as well as my own experiences lifting, I'd argue that the Bulgarian split squat has the potential to be a better leg exercise than bilateral squats.
I know the front leg doesn't do all the work and the back leg definitely helps, but it's not even close to 50/50. You'd need a force plate to figure out just what percentage of the weight is on the front leg, but I'd suspect for most people it's around 85/15 or 80/20 between the front leg and the rear leg.
You could also argue that the depth of a Bulgarian split squat is less than a full squat, and again I'd agree with you. But I'd still say the numbers are skewed so much towards Bulgarian split squats that they win out from a pure leg overload standpoint – provided you're good at them.
Now you could certainly make a great argument for squats being a better total body exercise, which is why I think both have value.
- Unilateral leg work definitely has carryover to bilateral squatting, and the carryover is even greater when you're also doing light squatting to help groove the pattern.
- Conversely, bilateral squatting definitely has good carryover to unilateral leg work. People who've built up a strong bilateral base first progress much faster on unilateral exercises than people who just start doing unilateral exercises from the get-go with no strength base.
- Unilateral leg training can help increase vertical jump. Now I can't say if it does so any better or worse than bilateral training because I have no control group to compare results, but my gut feeling is that optimal results would come from a mixed approach rather than an either/or.
- Anyone who thinks single-leg work is "foo foo" probably isn't very good at it.
Here are some "studies" I conducted that make a huge case for the effectiveness of the Bulgarian squat.
Subject A is a recently graduated college football player who has trained with me for about four months. When he started he was already a proficient squatter. His best back squat was 425 pounds and he'd also done 405 for 3. His best front squat was 335 pounds and he could do 315 for 3.
He did quite a bit of single-leg training so he was proficient with the exercises, but he'd mainly treated it as accessory work, so he didn't really push the loading.
For most of the summer his heavy lower body training consisted of single-leg work – Bulgarian split squats, landmine sliding reverse lunges, single-leg squats, and skater squats. On the last training day of the week, we usually did complexes that involved squatting, which allowed him to continue practicing his technique. These were never done with more than 225 pounds, though, so nowhere near his max.
Over the course of the summer he worked up to 315 for 5 on each leg with the bar on his back.
I then found that using the Dead-Squat™ Bar made it easier and safer for him to perform Bulgarian split squats with heavy weights and he was able to hit 335 for 5 on each leg. Here he is crushing 315 for 5 like it's nothing, not even taking a break between legs:
He also worked up to doing landmine sliding reverse lunges with 150 pounds on the bar for 8 reps per leg, single-leg squats with 110 pounds of additional load for 6 reps each leg, and 120 pounds of additional load for 6 reps each leg on skater squats.
Towards the end of the summer I had him do low handle trap-bar deadlifts with the Dead-Squat Bar and he hit 515 for 3 his first time before losing his grip. The next week I let him use straps and he hit 515 for 9. At the end of the summer, I tested his front squat and his back squat. He front squatted 315 for 5 – a two-rep increase from his previous best – and then hit a single with 365, up 30 pounds from his previous best.
He then back squatted 445 for a single, up 20 pounds.
Subject B is a 17 year-old high school hockey player who's going into his senior year. He's been training with me for over three years and started as a high school freshman with no weightlifting experience whatsoever. For the last three years his two primary heavy lower body exercises have been the low handle trap-bar deadlift and the Bulgarian split squat.
His best trap bar deadlift is 500 for 7 (using the Dead-Squat bar), up from 405 for 12 nine months earlier.
And this summer he worked up to hitting 315 for 5 for Bulgarian split squats with the bar on his back, up from 210 for 11 ten months prior.
He hasn't done much heavy squatting, but he's worked a lot on his squat technique with goblet squats and light front squats in complexes, but never with more than 150 pounds.
Right at the end of the summer he decided to join a new hockey team that front squats as part of their workouts, so I had him practice. He already had good form from the work we'd done in the complexes, so I just gave him a few quick pointers and showed him how to use straps so it would be more comfortable to hold the bar.
I had him squat to a 12-inch box, which put him at parallel at the bottom. The box is just to serve as a depth gauge to ensure consistent depth on each rep. His first time working up to heavier weight, he easily hit 275 for 6 and could've definitely kept going if I hadn't told him beforehand to stop at 6.
He then hit 315 for 2, again with great form and without too much of a struggle. Not too shabby for anyone, let alone a 17 year-old kid doing it for the first time. In the past six months, his vertical jump went from 29.2 inches to 31.4 inches.
Subject C is a Division 1 college hockey player going into his junior year. He's trained with me for the past three summers but lifts with his school program during the school year.
He back squats at school, but during the summer I've had him do almost exclusively single-leg work because back squats and trap-bar deadlifts tend to bother his lower back. He does do some light front squatting in complexes.
At the end of last summer he built up to doing 235 for 5 on each leg for Bulgarian split squats, but he wasn't doing them as heavy during the school year, so when he came back at the start of this summer he started at 185 for 5. By the end of the summer he worked his way up to 275 for 5 on each leg with the bar on his back.
He also did lots of heavy skater squats and single-leg squats, working up to using over 100 pounds of additional load on both exercises. Here he's crushing some deficit skater squats:
Here he's doing some weighted single-leg squats:
At the end of the summer he tested his back squat to reacquaint himself with the exercise before going back to school and he hit 315 for 6 to a 12-inch box, up from a previous best of 295 for 5. When he went back to school for preseason testing, he hit 320 for 5.
Over the course of the summer his vertical jump went from 30.6 to 32.0.
Subject D is a 17 year-old high school football player heading into his senior year. He's trained with me for about six months, but has lifted on his own for several years.
When he first started with me, he back squatted 315 for 5. His depth wasn't very deep, but far from the worst I've seen. He'd never done the trap-bar deadlift and had virtually no experience with single-leg work.
Over time he worked up to 425 for 5 on low-handle trap bar deadlifts and 245 for 5 on Bulgarian split squats with the bar on his back. That may seem like extremely fast progress for Bulgarian split squats given that he'd never done them before, but remember that he already had strong legs from squatting, so it was more a matter of learning to apply that strength to a new exercise.
At the end of the summer, he retested his back squat and hit 335 for 8 to a 12-inch box to ensure consistent depth.
His vertical jump improved from 27.4 to 31.2.
This isn't meant to be taken as formal research, but rather to provide food for thought and future discussion or, better yet, future action. There's enough bickering and theorizing about this stuff already. Rather than spend your energy arguing on the computer, put it towards getting stronger.