If you are cycling any distance, I would have thought it was fairly difficult to keep your heart rate at less than 60% max for over an hour. However, I don't really know. My theoretical maximum heart rate is 168 (220-age); 60% of that is 92. Whenever I get on the treadmill, strider or gym cycle my heart rate goes way above that. I reckon my heart rate would exceed 93 just walking.
Being fat is a risk factor for coronavirus and exercise is one way of losing it, although more from suppression of appetite than calories burnt, so I've read. I've seen people lose tons of weight through exercise.
Another effect of exercise is increasing the body's ability to take up oxygen, which might help if you get a disease of the lungs.
I really want to get a little fitter and reduce some of the flab I've put on the last several years, particularly as I have entered the danger zone of being over 50. My preferred method of exercise is running, but I can't do very much before my knee starts to break down. I really should be getting out on the bike a bit more.