There are many different ways to do deadlifts, and the most popular are conventional and sumo. More and more, sumo is becoming the deadlift of choice among powerlifters. McGuinan and Wilson (1996) did biomechanical analysis of the sumo and conventional style deadlift. The following is a summary of what they found:
1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
So, it appears from points 1-3 that sumo deadlifting has biomechanical advantages over conventional deadlifts.
My coach, Dan Green, deadlifts easily 800 pounds, sumo style. 800+ pounds. No big deal.
So why am I deadlifting conventional style? For now, my legs are weak compared to my back. The fact that conventional deadlifting uses the back more than sumo is actually to my benefit. At the beginning of my training however many weeks ago that was, I tried a few sumos and they felt very awkward. Ultimately, I will probably have to change to sumo style but with less than 2 weeks til my meet, there is no way I am switching now