Rowing is considered an aerobic/endurance form of cardio but it can also be an anaerobic exercise if you incorporate sprints into your training routine.

If you watched the sprints at the Olympics you would have noticed the muscle mass of the sprint rowers. Doing sprints will build muscle if the intensity is high enough.

Do you include sprints in your routine?
Well, to be quite honest, ever since of days of playing sports as a kid I hated sprints. Not really my fault though, because they were always the punishment, so how is a kid supposed to like them. Every time you messed up, it was go do sprints. I think that is a little unfortunate, and it kind of sours a lot of people on them, even though they are a great way to train. Interesting stuff, though, and thanks for sharing.