I think you have to go back to how C2 came up with the mythical 300(k)Cal/h number.
Jon Williams of Concept2 (12 Aug 04) wrote:
The 300 kC/hour has always been our best approximation for keeping alive and awake and going through the rowing motion at a reasonable stroke rate on an erg with the flywheel removed. This was arrived at from internal experiments and observations, data from Fritz Hagerman and studies done at Ball State.
Fritz Hagerman - the one whose data the V02 calculator is based on. My beginning 2000m times gave me a NEGATIVE V02 using his calculator.
Now that I (re?) discovered the calorie adjustment calculator -
I went back to a couple of my rows and the c2 monitor isn't that far off:
I rowed 10, 000 m in 55:58.9 minutes (2:47.9) - the Suunto estimated a calorie consumption of 563 kcals (included 7 extra minutes surrounding the workout.) I don't have the exact c2 data but using the various equations - I calculated that the c2 would have given 599 kcals and with weight adjustment (I used 60kg) 526.
I tested again with a 30minute row (performed 2 days later) (5600m, 2:40.7 split). I had the monitor on for 47 minutes - total kcal 372. Actually calculating the concept2 calories with weight adjustment gave me 372.
But the real issue is this - for the 30 minute row my HR was > than 180 for 6.5 minutes and between 160-180 for 23.5 minutes. And with the 10,000 meter row my heart rate was between 160 and 180 52:40 minutes. These workouts were considered in the "overreaching" range by the H.R. monitor.
From the standpoint of aerobic fitness - it's a easier for me to judge appropriate effort using the HR monitor (and its fancy training effect and EPOC calculations) than it is using power output. It becomes obvious why, if I did care about calories - long slow rows are necessary to accumulate them. A long row with a split of 3:45 still had my heart rate between 140-160 for over 55 minutes and over 160 for a couple minutes. (140-160 is actually within 75-85% of my maximum heart rate.) That was encouraging for me because faster rows can really exacerbate some musculoskeletal issues that I have. So even if a world champion rower and I burn similar amounts of calories at the same power which clearly has to be set to the low level that I can actually obtain and sustain (although I still think they might burn fewer) - I can clearly obtain aerobic benefit from rows which would have minimal to no aerobic benefit for them.
Much of the information and discussion of power/pace on these forums or for training - are aimed at people with much faster splits. And I think it can be difficult for the deconditioned newbie, particularly a lightweight female, to know how to appropriately aim their rows from the power ratings/pace given that there is little good information for comparison. That is the main reason I think the HR monitor is useful not because if its potential greater calorie estimation accuracy. I certainly felt a lot less discouraged about rowing so slowly and about the times where I have to slow down from the musculoskeletal standpoint.
Connecting workouts with their effect on my CV system, helps me remember that even though I rowed for over 7 minutes longer than the other 14 rowers in the 6k during my first race (it's so lonely rowing alone) my split of 2:34.6 was still a real accomplishment for me (especially given that it was after a P.B. 2K 4.5 hours earlier)
(Don't actually know what my HR was - but this was only 4 weeks after the 30 minute row above.)