  In each rowing sport, the oars have their very own characteristics most of
the time selected through a long time experience. Here we address
experimentally and theoretically the problem of rowing efficiency as function
of row lengths and blades sizes. In contrast with previous studies which
consider imposed kinematics, we set an imposed force framework which is closer
to human constraints. We find that optimal row lengths and blades sizes depend
on sports and athletes strength, and provide an optimisation scheme.
