To some, the term ‘comfort zone’ sounds like it should involve only minimal activity, perhaps with snacks or hors d’ouevres and a glass of wine. Consider in the context of moderate exercise that the term is used for a range of exertion you would want to repeat the next day rather than fear or avoid. The ‘comfort zone’ can mean many things:
I am rowing as hard or as easily as I want to at the time;
I am comfortable according to whatever measure I am using, whether that is my breath or wind, my pulse, my feeling of fatigue, how readily I recover, whether I am enjoying myself, my ability to continue indefinitely, etc.;
I do not feel a need, a physical pressure to stop;
I can speak comfortably (or sing along with the music?) while rowing;
It feels like taking a walk or riding a bike to relax;
And so on.
The comfort zone can accommodate a wide range of effort. It will not include rowing all out and trying to keep going at that pace (except for the very few and very fit whose goal is to do just that on the day in question). But your comfort zone may include rowing harder than normal for a relatively short period – i.e., doing short intervals with adequate rest between the hard intervals. It may include rowing much harder today than you rowed or could have rowed six months or a year before. It could involve developing so much better wind that it is pleasurable to row out of breath because you know you can keep it up without pain or discomfort. Perhaps most importantly is that the comfort zone for moderate rowing can include rowing hard for those who wish to do so. And that can lead to a dilemma for us as we age: Can we continue to row as hard as we used to? Can we maintain the same intensity? Or will we necessarily ratchet back as our bodies age or weaken?
Certainly pay attention to your health and your doctor's advice. And let's compare notes on what works to keep a comfortable level of effort going and what we may need to add to our training regimens to maintain strength and speed.