Indoor rowing using a tool like the Concept2 Rower is just as well-studied and documented - it's easy to compare performance between rows because of the consistency between machines.
How about some rowing badges? The usual suspects would include:
- 100 meter
- 500 meter
- 2k (painful measure of VO2Max)
- 5k for time
- 6k for time (measure of Anaerobic threshold)
- 30'R20 (that's 30 minutes at "rate 20" or 20-strokes per minute) - measures aerobic base at a category 5/6 intensity, and if you can build your Aerobic base up, it also pushes up your Anaerobic, and consequently your VO2max which benefits your ability to race over 2km
- 60 minutes
- HM - Half-Marathon
- FM - Full-Marathon
- 50k ultra
- 75k ultra
- 100k ultra
- 12-hour