If you’ve read any of the posts here at the Strength and Conditioning Research blog, you’d be forgiven for thinking that all that ever crosses my mind is squatting. However, that’s not true because I also think about deadlifts.
With deadlifting, one of the interesting questions is how the sumo and conventional stances are different from a biomechanical perspective. This is the first step to understanding how they can best be used and trained. It could also help explain why some lifters naturally gravitate to one style rather than the other.
Fortunately, one of the very best studies on deadlifts gives us a lot of help towards answering that question.
The study: A three-dimensional biomechanical analysis of sumo and conventional style deadlifts, by Escamilla, Francisco, Fleisig, Barrentine, Welch, Kayes, Speer and Andrews, in Medicine and Science in Sports and Exercise, 2000
What does the literature say about deadlifting biomechanics?
The researchers put a lot of work into their literature review at the start of their study and discuss in detail the various studies that have previously investigated the barbell deadlift from a biomechanical perspective.
They report that, at the time of their review in 2000, three studies had examined lumbar spinal loads, two studies had investigated the effects of intra-abdominal and intra-thoracic pressures, but only one study had quantified joint and segmental angles, and similarly only one study had calculated joint angles and joint moments.
Given the prominence of the deadlift in strength and conditioning, that’s not really a lot of studies. And what’s more, only two of these studies compared sumo and conventional deadlifts, as follows:
- McGuigan (1996) performed an analysis of the joint angles during the deadlift using competitive powerlifters as subjects. They noted that the during the sumo deadlift, the powerlifters had a more upright trunk. They also noted that during the sumo deadlift, the powerlifters displayed a greater range-of-motion (ROM) of the shank, which implies that the ankle must have moved by a greater amount.
- Cholewicki (1991) investigated the lumbar loads and hip and knee moments for both the sumo and conventional deadlifts, again using competitive powerlifters as subjects. These researchers found that there were significantly greater shear (i.e. perpendicular) forces at the lumbar spine (specifically at L4-L5) among the powerlifters who were performing the conventional deadlift.
The researchers explain that these studies were limited in that they employed a two-dimensional (2D) analysis and only recorded a sagittal view of the lifter. While this is probably an acceptable assumption for analyzing the conventional deadlift, it could easily lead to error in the sumo deadlift, because the feet are often turned out considerably.
What did the researchers do?
The researchers wanted to investigate and compare the joint angles, moments and moment arms of the hip, knee and ankle during both sumo and conventional deadlifts in 3D.
Before we go any further, let’s recap quickly what moments and moment arms are because some of the most interesting results of this study involve differences in both of these.
Moments (also called torques) are used to describe forces about a fixed point, like a joint. The moment about a joint is equal to the product of the force acting perpendicularly to the pivot and the distance between the pivot and the point where the force acts. This distance is also called the moment arm. The following picture shows a very basic model of a moment and how to calculate it.
OK, so let’s come back to the study now. To compare these joint angles, moments and moment arms, the researchers recruited 24 male, masters powerlifters (12 powerlifters who used the sumo deadlift in competition and 12 powerlifters who used the conventional deadlift in competition). The researchers then recorded the deadlifts of all the subjects using a 3D motion capture system.
Grip and stance differences
The researchers found that the powerlifters using the sumo stance used a foot stance that was 2 – 3 times wider (c. 70cm) than those using the conventional stance. In contrast, those using the conventional stance used a 17% greater grip width on the bar.
The researchers also noted that the powerlifters using the sumo stance turned their feet out 40 – 45 degrees while those using the conventional stance only turned their feet out by 10 – 15 degrees.
Bar speed differences
The researchers observed that the powerlifters using the conventional stance reached peak bar velocity significantly faster than the sumo group. This meant that they spent significantly less time accelerating than the powerlifters using the sumo stance. This is a fascinating result and we can only speculate why this might be the case.
Mechanical work differences
The researchers noted that those powerlifters using the conventional stance moved the bar through 20-25% more ROM than the those using the sumo stance and therefore performed c. 25–30% more work.
Again, this is fascinating, as it would suggest that the conventional deadlift is much harder work than the sumo deadlift. So why do some of the best heavyweight powerlifters use the conventional stance? There must be other very meaningful factors involved.
The researchers found that there were significant differences between the two deadlift variants in terms of joint angles at lift-off, knee passing and at the sticking point. You can see the differences if you look at the following two diagrams, which show the sumo and conventional styles in sequence:
In brief, we can see that from the beginning the sumo deadlifters have a much more upright trunk and a more horizontal thigh and that these two features are both carried through to the sticking point. This makes the sumo deadlift look a bit more like a squat than the conventional deadlift does.
We can also see that to finish the lift from the sticking point, the conventional deadlifter mainly has to perform trunk/hip extension, while the sumo deadlifter has to perform both trunk/hip and knee extension. This may translate to greater hip moment impulses at the sticking point through to completion for the conventional deadlift but it’s hard to say from this study.
Here’s a stage-by-stage discussion…
At lift-off, the powerlifters using the sumo stance retained a significantly more upright trunk, placed the thigh closer to the horizontal, and positioned the shank more vertically. Oddly, however, the actual hip and knee angles were not significantly different.
At knee-passing, the powerlifters using the sumo stance displayed significantly greater hip flexion and knee flexion than the conventional deadlifters. Additionally, the researchers found that between lift-off and the knee point, the powerlifters using the conventional stance extended the hip, knee and shank through a greater ROM than those using the sumo stance.
At the sticking point
At the sticking point, the powerlifters using the sumo stance displayed a significantly more upright trunk, placed the thigh closer to the horizontal, and positioned the shank less vertically. Oddly, however, while the knee angle was also significantly different between the two variations, with the conventional deadlifters being significantly more extended, the hip angle was not (although there was a strong trend for the hip angle also to be more extended in the case of the conventional deadlift).
Finally, we can see that from the diagram above, in order to complete the lift from the sticking point, the sumo deadlifter must complete around 28 degrees of knee extension ROM and 69 degrees of hip extension ROM (a ratio of 2.46 times as much hip extension as knee extension ROM).
On the other hand, the conventional deadlifter must complete only 16 degrees of knee extension and 57 degrees of knee extension ROM (a ratio of 3.56 times as much hip extension as knee extension ROM). This might mean that the conventional deadlift requires a greater hip joint impulse than a knee joint impulse in order to complete the lift from the sticking point. However, it is hard to tell from this study as not even joint moments were reported at the sticking point.
The researchers found that the ankle and knee moments were much larger during performance of the sumo deadlift than during the conventional deadlift. However, hip extensor moments were found to be similar in both groups. The following chart shows the various moments at the point of lift-off for both lifts.
Although the chart doesn’t show the moments at the knee-point or at lock-out, and the moments are different at those points, the differences between the moments in the sumo and conventional stances follow a similar pattern at all the points, so this chart is representative for our purposes.
The important thing to note is how very different the ankle and knee moments are and how similar the hip moments are. The hip moment is only 14% greater in the conventional stance than in the sumo stance, while the ankle and knee moments are 130% and 74% greater in the sumo stance than in the conventional stance. Additionally, it is to be expected that the moments in the conventional deadlift should be higher, as the acceleration observed is greater.
Joint moment arms
The researchers also noted that the moment arm lengths changed in a very similar manner to the moments, suggesting that the main reasons for the differences in moments is the moment arm lengths and not the production of force by the various muscles. The following chart shows the various moment arm lengths at the point of lift-off for both lifts.
Again, the difference in hip moment arm lengths is small, only 9%, while differences in the ankle and knee moment arm lengths are considerable, at 130% and 78%. You can see that the percentages are similar to the differences between the moments. So this suggests that lifters who have anthropometry that causes a large hip moment arm length will favor the conventional deadlift.
Very simply speaking, the main factor that would cause a large hip moment arm length is femur length. So lifters with long legs will most likely find the conventional deadlift more to their liking than the sumo deadlift. And given that the conventional deadlift is favored by the heavyweights and the sumo attracts the shorter lifters, this makes sense.
What did the researchers conclude?
From their analysis of moments, the researchers suggest that the primary lower body muscles used during a conventional deadlift are the hamstrings, gluteus maximus, gastrocnemius and soleus. On the other hand, they concluded that the primary lower body muscles used during a sumo deadlift are the gluteus maximus, hamstrings, quadriceps and tibialis anterior.
The main differences between groups are therefore the involvement of the quadriceps and tibialis anterior in the sumo deadlift and the involvement of the gastrocnemius and soleus in the conventional deadlift. This corresponds with the commonly held view that the sumo deadlift is more like a squat, because of the much higher quadriceps involvement.
What were the limitations?
The study was limited by the specific population used as subjects. Non-powerlifters may display slightly different biomechanics because of different form.
Moreover, the study did not measure the electromyographical (EMG) activity of the various muscles during the lifts at the various points (lift-off, knee point and lock-out), so it is difficult to confirm whether the muscular force at those points was similar.
What were the key points?
The key points were as follows:
- Sumo deadlifting generates much larger ankle and knee moments than conventional deadlifting at lift-off, knee level and lockout. However, hip extension moments are similar in sumo and conventional deadlifts, although the hip extension moment is slightly higher in the conventional deadlift.
- The hip moment arm length is responsible for the slightly greater moment in the conventional deadlift, which may therefore favor the taller lifter.
- The primary lower body muscles used for sumo deadlifting are the gluteus maximus, hamstrings, quadriceps and tibialis anterior while the primary lower body muscles used for conventional deadlifting are the hamstrings, gluteus maximus, gastrocnemius, and soleus.
- During the conventional deadlift, the bar is moved through 20-25% more ROM than in the sumo deadlift and 25-30% more work is performed.
What are the practical implications?
Training to improve both deadlift variants should of course involve significant amounts of gluteus maximus and hamstrings work. However, the sumo deadlift should also include a greater emphasis on quadriceps and tibialis anterior strength, while the conventional deadlift will require greater calf muscle strength.
Shorter lifters may find the sumo deadlift a better choice, while taller lifters may find they are able to deadlift more in a conventional style.
Powerlifters who make use of the sumo deadlift will likely find greater carryover from their squat to their deadlift performance than powerlifters who deadlift conventionally. This is because of the greater quadriceps involvement in the squat and sumo deadlift.
For bodybuilders and physique athletes
The sumo deadlift may be superior to the conventional deadlift when training for increasing muscular size because of the greater amount of time spent accelerating. It is also helpful for that similar hip extension moments are produced for less lower back loading.
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