As much as rowing seems like an exercise in the arm, most of the strength for each stroke really comes from the leg push. It's also important to note that it's not just how many strokes a minute you can do, but about the quality of each stroke and how much space you can create for each stroke.
Complete the following movements every 10 minutes on the minute for 4 Rounds: 500 meter Row 400 meter Run 1 mile Assault Air Bike 20 Air Squats 15 Push-Ups 10 Pull-Ups