Semi-Sumo / Modified Sumo Deadlift Biomechanics

Depending on how you view such things, Ed Coan is perhaps the best deadlifter of all-time. His deadlift success is so outstanding that the “Ed Coan Deadlift Program”, which he didn’t even write, is one of the most popular routines of all-time. That said, the thing about Ed’s deadlifts that perhaps sparks more interest than any other is his deadlift stance: he used a very close, “semi-sumo” stance.

The great Ed Coan. He once pull 901lbs at 220lbs body weight.

The great Ed Coan. He once pull 901lbs at 220lbs body weight.

Of course, this invites the question, why do some people use a “modified” sumo stance in powerlifting? The answer is simple; they pull the most weight with that particular technique. The more interesting question to try and answer is why some people pull more with that particular technique in the first place.
If you’d rather watch than read:

Basic Biomechanics of Deadlifting

As a powerlifter, you have to think about how you’re affecting leverages with the technical choices you make. While it is true that a sumo deadlift shortens the range of motion and reduces the moment arm between the bar and the hips in the starting position, it also significantly closes the knee angle and opens the hip angle. In other words, knee extension is rendered more difficult by a less mechanically efficient position while hip extension is rendered less difficult for the same reason. This is why the sumo deadlift is traditionally known to be “hard off the floor” and “easy at lockout”. And this is the basic trade you make when you decide to pull sumo: shorter RoM, better leverages, but you also get worsened mechanical efficiency in terms of knee extension compared to the relatively stronger starting position afforded by the conventional deadlift stance (ex: half -squat vs. quarter-squat).

Compare the knee angle and hip angles of the conventional deadlift (left) to the sumo deadlift (right).

Compare the knee angle and hip angles of the conventional deadlift (left) to the sumo deadlift (right).

The Biomechanics of Rounding Your Back

Now, “semi-sumo” or “modified” sumo enters the picture, in my opinion, because of one factor: back rounding. While back rounding is a technical flaw for a general strength trainee, and dangerous for even powerlifters, it is also a tool that can be used to manipulate leverages. When you round your back, any part of it, you effectively shorten your torso segment which opens both the knee and hip angle in the starting position AND brings your hips closer to the bar. In other words, safety aside, rounding your back greatly improves both mechanical efficiency and leverage… in the starting position.

Again, compare the hip angles and knee angles of the round back deadlift (left) and the flat back deadlift (right).

Again, compare the hip angles and knee angles of the round back deadlift (left) and the flat back deadlift (right).

The problem occurs, in terms of lifting the most weight possible, when the hips/legs have ceased contributing to the movement but the bar is still not locked out. At this point, the lifter has to finish the lift using raw lumbar strength which is inefficient. After all, you can extend your hips with much more weight than you can uncurl with your erectors. In reality, this is the reason, by my analysis, that the conventional deadlift has a reputation for being harder at lockout: people simply round their backs to start the movement. The most open knee angle you can have in the starting position of a deadlift will come from a conventional stance with a round back.

The Deadlift Spectrum

So, when you’re comparing the sumo deadlift to the conventional deadlift, you have to keep in mind that, for powerlifters, more often than not, what you’re really comparing is the sumo deadlift to the round back conventional deadlift; what you’re really comparing is an interplay between starting position efficiency and lockout efficiency. Range of motion really isn’t the only, or even the primary, consideration here. A flat back sumo deadlift with a maximum width stance is going to give you the best possible leverages at lockout while the round back conventional deadlift is going to give you the possible leverages in the starting position. Everything else falls somewhere in the middle of this spectrum.
Now with all of this in mind, let’s consider the “semi-sumo” stance popularized by Ed Coan. What in the hell could Ed possibly be doing here? Well, like most “semi-sumo” pullers, what Coan is really doing is a round back conventional deadlift with a wider stance. To make things plain, due to his individual leverages and personal muscular strengths and weaknesses, he has traded a bit of starting position efficiency for a somewhat more difficult starting position and a somewhat less difficult lockout. Because of the back rounding, breaking the bar from the floor isn’t the hardest part of the movement for him. In fact, given a conventional stance, it would likely be the part of the range of motion where he was strongest. So, again, he sacrifices some of that starting position efficiency in exchange for a lockout position where it will be easier to overcome his rounding.

Coan was a round back sumo puller.

Coan was a round back sumo puller.

He’s merely picking a technique that falls in-between the two extreme ends of the spectrum. Ed had freakishly long arms, but he was also a tremendous wide(ish) stance squatter. I suspect that the slightly wider deadlift stance allowed him to take better advantage of his particular muscular strengths while still performing a variant of the conventional deadlift and thus retaining the advantages of that style of pulling.

Is Semi-Sumo Right For You?

Now, the question that I’m sure most of you really want answered is: how do I know if pulling “modified” sumo is for me? As always, the best thing you can do is just try it out. That said, if you’re a poor bencher, a strong deadlifter, and you prefer to squat with a wide(ish) stance, there is a pretty good shot this technique will work very well for you. People with long arms and long legs tend to gravitate towards semi-sumo.
Remember, for most people, the semi-sumo stance is really more similar to a conventional deadlift with a wide stance than it is to a true sumo pull. You’re not trying to be completely vertical and you’re not trying to drop your hips super low. You’re trying to pull it just like a conventional deadlift with a wide stance.
In any case, I hope that cleared up a lot of the questions people frequently have about the semi-sumo stance.

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