Quick background - the damper controls how quickly the flywheel comes to a stop. A typical rowing stroke is mostly a leg exercise. You build up momentum by driv

Quick background - the damper controls how quickly the flywheel comes to a stop. A typical rowing stroke is mostly a leg exercise. You build up momentum by driving with your legs, and then finish off the stroke with your back and then (at the very, very end) your arms. By the point that you're using your back and arms, however, there is enough momentum in the flywheel that you don't put much load on them. During the recovery, (when you're bending your legs and preparing for the next stroke) the damper slows the flywheel back down. Wash, rinse, repeat. The load is repeatedly taken by the legs, with the back and arms adding a little extra at the end of each stroke. Putting the damper at 10 knocks this all to hell. The damper removes enough of the momentum during the stroke that you're putting a significant load on your back at the end of each stroke. At best, this will tire you out early. At worst, it can injure you. You want the damper to be between 4 and 6. I usually row with it halfway between 4 and 5. If you want a more intense workout, drive harder and pick up the stroke rate.