Originally Posted by Carbonfiberboy

Don't know what "your stage" is. My stage is trying to get back into it after a heart attack and other heart issues. My technique is the same as it always was: plan a route with enough distance and climbing so that I'm exhausted at the end and damning myself for putting in those last 2 climbs. It doesn't take a super high HR to achieve that goal, just enough HR, held long enough, to do the job. I'm 6 weeks into my rehab and stronger every week. I went in for the usual heart attack rehab training, but the specialist said I was already beyond what's included in that program.

Yesterday's was only 30 miles and 1800', but that was enough to do the job. I did almost 2 hours of Z3, IOW not much else, short ride like that I'm working toward 60 miles and 3000' of hard. These hard rides are just once a week. That's all it takes. During the week I do mostly Z2, high and low cadence work and strength work in the gym. Strength work really helps endurance. When I was younger, that and those 60 mile rides were all I needed to ride a fast 400k. Lots of hard work builds endurance. The other thing is that "endurance" means enduring. I figured that out on my first 300k. 200k doesn't touch it. Ride long enough, hard enough, on a hilly course (that one had 9,000') and at some point it becomes a head thing.

The heart attack was because I couldn't take a statin. The stuff I take now to lower cholesterol was only invented recently. And all the above said, it's true that too much high end can result in stuff like Afib, but it takes a heckuva lot of it. I was always careful of that, no more than 45' of Z4/week.