Myth #3: The reason one should rotate the body along the long axis in freestyle is to reduce drag.
Please don't tell me this is not a myth. I hear this from beginner coaches all the way to some of America's top swimming coaches. Rotating the body is very important....so is reducing drag. I just don't think we do it for that reason. If we did, kicking on our side would be faster, whether underwater or on the surface, than kicking on our stomach...and there is not much difference in speed either way. Besides that, we really spend very little time on our sides in freestyle. Most of it is in transition from one side to the other and closer to horizontal than vertical. Finishing a freestyle race in a pool on our side is also important...because we can extend our reach further..not reduce drag.
So if body rotation is not about drag reduction, why do we do it? Two reasons. The first is to gain more power. By rotating, we put our arm into a mechanically better position of strength, engaging much bigger muscles in our back and core to help with the pulling. The second reason has to do with the counter-rotation. When we enter our right hand in the water, for example, our body is rotating to the left. At the very moment we begin our catch, the body has stopped rotating left and initiates the counter-rotation back to the right. We call this point the connection (between arm and core/hips). This counter rotation creates a stabilizing force that gives us something to pull against. Remember, it is you and the water molecules out there...no walls, starting blocks or pitching mounds to push off or pull against. So we create our own stabilizing force out of the rotational motion of our own body. The faster and longer the counter-rotational turn, the greater the stabilizing force and the better distance per stroke (dps) we can achieve. This is one advantage the hip/leg driven swimmers have over the high stroke rate swimmers...holding in front longer gives them more time to rotate/counter-rotate the hips. But before you all go rushing back to that technique, if you don't have the legs driving you, even that extra dps cannot overcome the inertia problem. You are still swimming 'stop-and-go' freestyle..not as efficient as the high stroke rate.
Most swimmers I teach swim very flat...like a surfboard that grew arms and legs. That would be ok if we had the buoyancy and drag coefficient of a surfboard, but we don't. We are bricks and to move a brick through the water, we need the added power that the body rotation gives us. BTW, this is why wetsuits enable one to get away with swimming flatter.
Can you use good body rotation with a high stroke rate? Yes...but it takes work. The body rotation doesn't just happen. You make it happen...but because there is less time, it becomes more oriented from the shoulder and less from the hip which takes longer to turn (although hip motion is still important). Thus the name shoulder-driven freestyle.