As someone that a year ago was wary of a heart attack, I did something about it. I was 378 and worried about being around much longer. I decided on weight loss surgery, specifically gastric sleeve. 113 pounds down from my heaviest, 91 since surgery. Followed my cardiologists guidelines. And for me, closely follow the 220-age. I'm 56 now. Was a runner and cyclist in the past. Knee replacement, back injury, another failing knee, Achilles tendon repair on one ankle and the other severely injured, I gained weight. Exercise was difficult and painful. And now, with weight coming off I feel better, can move better. My cardiologist doesn't want to see me for a year. Coronary calcium scan was a perfect zero... And she cleared me to any heart rate I am comfortable with.
Above effort was 30 minutes on my trainer, bike is a 86 KHS upgraded to mostly Shimano 105 5600 level. Compact crankset. I would say for myself, the effort was hard. But not into difficult range yet, the mag trainer was on the 3rd level. Even so, far better than I could imagine year ago. My RHR is about 60. A year ago it was 105...
For now, the 220-age is sufficient. But as I get stronger, I will re-evaluate. With my cardiologist's approval of course... Damn. How did I get old enough to need a cardiologist?