James: The CII is pretty much the sport standard among competitive rowers. The resistence is variable to best simulate a boat on the water. At the heaviest resistence you still won't be weight lifting but you will bog down the flywheel pretty quickly. Most people row with the resistence around the 4-6 setting on the model C and something similar on the D model. It's a little lighter but allows a quick fluid movement.
FWIW, the performance monitor on the rower calibrates the rate of deceleration and gonkulates drag to work to watts to pace or calories. Or at least the last time I knew much about these machines that's the way they worked. So you can set the resistence at 10 or 1 and the machine is still going to give you a pretty accurate work measurement. Hope this helps.