What if I dont really fall exactly into either category?
Indeed, the majority of people may not see themselves as a perfect fit in either category, but the tool can still be useful. You should choose the study group that most closely resembles your own level of training. If you have been rowing regularly for several years, training at least 4 days per week, doing a variety of workout types and improving your rowing scores, then you are probably a better fit with the elite estimator. If you consider yourself a fitness rower and dont push yourself very hard or do any hard pieces, then the novice estimate may be better for you.
