In Reply To:
Rolling is almost entirely a biomechanical issue, not a hydrodynamics issue. You can bring more muscles into play and use them more effectively if roll your shoulders. Just try it on a lat machine with some one arm press downs. You can't help but rotate your working shoulder towards the machine. It makes the lift easier and/or allows you to lift more weight.
However, I believe there is a difference in drag depending on the depth of the object.
I agree.
I actually think we have less drag when closer to flat because we are higher up in the water and have less FRONTAL area that the water "sees." But some rotation is critical to be able to have a shoulder-friendly recovery and to set up a more powerful pull. You don't have to have a lot of rotation to have your shoulder up out of the water. More rotation isn't necessarily going to make it much less. Consider we (I) drop in the water when rotated on side (i.e., I can't kick on side and just swivel my head to air... I'm too low unless I wear fins to keep speed way up).
Another doubt I have about more than minimal rotation is that I do not think the hips have any role other than to provide a stable platform for the kick. Many many many more qualified people will strongly disagree w/ me on that one.
I swam five 200s last night using different amounts of rotation and hip action. Of course, I'm slow and it's impossible to put in exactly the same effort and the number of tests was small, so it may not be worth anything. The more hip action/rotation I used, the slower I was. Flattest = fastest. The diff was about 7 seconds. Interestingly enough, when I tried it with a snorkel, I was slowest of all, nearly 10 secs off the flattest.
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