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.
2,000 meter Row 50 Thrusters (95/65 lb) 50 Bar Over Burpees 1,000 meter Row 30 Thrusters (95/65 lb) 30 Bar Over Burpees 500 meter Row 20 Thrusters (95/65 lb) 20 Bar Over Burpees