My instructor has me doing a stroke whereby my hands are both fully outstretched between each stroke. So it's like

Both arms outstretched - right arm stroke - both arms outstretched - left arm stroke, both arms outstretched

It's starting to hurt my shoulder and I think it's because I actually lose momentum at the "both arms outstretched" part. It's like pedaling a bike and pausing between each revolution.

I'm going to ask him about this but doubt that I'll get any decent answer because he's pretty rabid about this - even has people hold a dowel on the outstretched part.

What is the point of this? Why not move both arms like pedaling a bike?

Apologies for the terminology. I'm still learning!