Well what's it going to be a conventional stance or a sumo stance? Is there a difference? Here are some interesting studies done on the deadlift. Cholewicki et al. (1991) reported in a recent study comparing the sumo and conventional styles that there were no significant differences in compressive disc forces at the L4 or L5 vertebrae. However the conventional deadlift showed significantly more movement and load shear forces in the L4/L5 that the sumo. So as we all pretty much are already aware, the sumo deadlift takes much of the strain and movement from the low back. To further back this statement, Horn (1988) found through an EMG study that the erectors were twice as active in the conventional stance as the sumo.
There are many anecdotal reports as well that claim the sumo deadlift is much more technical and requires more skill. Many also say this technique is more biomechanically sound and more efficient because the bar does not have to travel as far. How true are these anecdotal reports?
To investigate some of these claims McGuinan and Wilson (1996) recently did some extensive biomechanical analysis of the sumo and conventional style deadlift. The following is a summary of what they found:
The lift-off
The sumo has a trunk angle that is significantly closer to vertical that conventional lifters. Sumo lifters were also found to have much larger hip and knee angles at the start of the lift. This style shifts the bulk of the load on the hips and knees. While the conventional lifter with a more stooped-over trunk position at liftoff utilizes more low back muscles to get the weight moving off the floor.
The distance the bar must travel
As reported in other studies, this study also found that the average total distance the bar must travel to complete the lift was reduced by 19%. As we all know work is defined by taking the amount of force or weight and multiplying it by the distance the bar must travel. So by reducing the distance by 19%, the sumo lifter has automatically reduced the amount of work necessary to lift a given amount of weight.
Bar path
Grabiner and Garhammer (1989) noted that the most of the most important factors to be considered in lifting weights is to keep the weight as close to the body as possible. This reduces the lever arm distance, thus significantly reducing the resistive torque. Cholewicki et al. (1991) found that using the sumo stance not only kept the bar closer to the body than the conventional stance but it also reduced the lever arm distance by shortening the movement of the lumbar. McGuinan and Wilson (1996) similarily found that the sumo lift kept the bar path significantly closer to the body that of the conventional stance.
Lift time
Power is defined as total work divided by time. So the actual amount of power it takes to lift the weight is highly dependent on the amount of time it takes to lift the weight. However, McGuinan and Wilson (1996) determined that both the sumo and conventional stance required an average of 2.0 seconds to complete. Thus, there is no difference in the amount of power produced by either lift.
Sticking points
It was found half of the sumo lifters had a sticking point somewhere in the second half of the lift where only 15% of the conventional style lifters got stuck here. However, there seemed to be no exact point in common between the lifters. McLaughlin et al. (1977) claims that these sticking points are actually caused at the point where the most effective muscles in the deadlift are in a disadvantaged position. Because we are all built slightly different, this point could vary from lifter to lifter. This exact position can be determined with a Peak motion analysis. Horn (1988) determined that a kinetic analysis using an EMG study of the ankle, hip, and low back in conjunction with strength testing could also accurately determine which muscle group would limit performance during the deadlift. Then proper assistance work could be used to lessen these sticking points.
The available literature does seem to indicate that there were several biomechanical advantages in using the sumo over the conventional style of deadlift.
1. Greater range of knee extension at the bottom of the lift.
2. A more upright posture.
3. The distance the weight must be moved is greatly reduced.
4. The bar path is kept closer to the body, thus making the levers more efficient.