Why you should be measuring seat movement at the catch when rowing

In this video, Ken Davey demonstrates how to measure seat movement at the catch. Measuring seat movement with the naked eye can be difficult; using this method, any coach can easily measure it. If the seat moves before the blades are connected, that portion of the rowing stroke is wasted. 

​A tiny seat movement is necessary to place the blade in the water, but any more will rapidly decrease the effectiveness of that stroke.