High heartbeat on concept2 compared to e.g. spinning

[M. Podolsky]

I was going to say that it usually takes at least 30 minutes of hard rowing on the erg for my HR to approach max, and it would be easier for me to perceive 30 minutes on the bike as only "a while" compared to 30 minutes on the erg. Looking at my logbook, I see that there's a lot of variability.
In general, when I stick to the planned pacing my ending HR is a lot more likely to be under max, but if I get stupid and try to test my limits too soon, I'm liable to hit max HR before the end of the piece. And for things like 60 minutes or a half marathon, even with a properly executed pace plan, it's possible to finish at or close to max HR by timing the start of the final sprint. So maybe you just haven't done anything stupid on the erg yet.

[gkucera]

I think you are correct. I also think my muscle conditionin for rowing will help. I will try a 10k TT this week and we will see what I can do.

[hjs]

I'm really not so knowledgeable on this subject, so please enlightenment if I've got it all wrong.

But I don't think it is entirely just about how hard you push yourself. I find it easier to get near my max heart rate on the rower and when running then I do when I bike, swim, or cycle, or especially when I am in my seakayak--even when I am pushing myself very hard. Ironically it seems more difficult for me to reach max heart rate in the aerobic activities that I am the least trained in (the exception might be the rower, which I'm still pretty new to.) I think for some sports you need to develop the sports-specific muscles before you can max out. Bigger, well-developed muscles draw on more oxygenated blood than weak tiny ones, right? So if I've achieved a pretty high level of aerobic capacity from years of running, but then take up something like kayaking, which draws on different, less developed muscles, it is harder for me to get to max heart rate even when I'm pushing myself.

Does this make sense, or is this nonsense?

No , this is very true, if you do an exercise which you body is not used to, the muscles will be tired before your heart is at it's max.
So a well trained biker will be able to reach his max on his bike, but a well trained runner won't be able to do so. He needs to run, his body is trained to run not to bike.