Was doing some research on sumo vs. conventional DL and found the below equation. I was a conventional DL until Sara recommended I try sumo. Made a huge difference for me. I don't go full width sumo. About halfway between conventional and flu width. Works great and now the math shows why. My ratios are .85 and .68 which puts me solidly in the sumo category.

Tom

http://forum.bodybuilding.com/showthread.php?t=108595111&p=181075901#post181075901

It depends on what you're training for. If you're training for a sport, such as football, you should really be deadlifting conventional. Strongman contests don't allow sumo style, so you're forced to lift conventional.

If you're training for powerlifting, it's not quite as simple. Ultimately, you have to go with which style is more comfortable, but you can determine which method will allow you to lift the most weight biomechanically. To do so, follow this method.

1. Secure a tape measure to the wall with the zero end at the floor. Make sure the metric side (centimeters) is what you are using.

2. Stand with your back against the wall. Measure from the top of your shoulder to the floor. This will give you your total body measurement.

3. With a straight arm and your hand in a fist, measure from the top of your shoulder to the middle of your fist. This is your total arm length.

4. Raise your thigh to determine where your thigh rotates into your pelvis. Once located, lower your leg to the floor and measure from the top of the shoulder to this point. This is your trunk length. Also, subtract this measurement from your total body measurement to give you your lower body length.

Record these measurements and perform the following calculations:

1. Divide "trunk length" by "arm length".
2. Divide "trunk length" by "lower body length".

The resultant numbers will tell you the following:

1. Arm to trunk length ratio. Example: If your truk is 50 cm and your armi is 65 cm, divide 65 into 50=0.77. This indicates that your trunk is 77% of your arm length or that your arm is 23% longer than your trunk.

2. Trunk to lower body length ratio.

These numbers will help you determine which method, conventional or sumo, will allow you to lift the most weight by biomechanical standards.

CONVENTIONAL
If your trunk to arm ratio is less than 0.82 and your trunk to lower body length is less than 0.55, you should consider the conventional style. With your arms longer than your trunk, you'll finish the pull with the bar below your hip joint. This finishing position indicates that the initial starting position of your trunk (trunk angle) will be larger (more upright). This would indicate more activity from the quads as well as the hamstrings and glutes. A more upright trunk angle will also create a larger knee angle at the starting position, making the shift of the shoulders, knee, and hip more uniform-that is, they rotate in a biomechanically correct sequence.

SUMO
If your ratios are larger than 0.82 and 0.55, the initial starting angle of your trunk would be smaller (more inclined) and will therefore position you in a biomechanically ineffecient position. With your trunk more inclined, the activity of your trunk and hip extension muscles will have to follow a different, more inefficient pattern. This will basically result in increased activity from your hamstrings and glutes and decreased activity from the quads. This will also increase stress on your erectors and particularly the lower back and could cause rounding of your upper back. The solution would be sumo.

Hope this helps.