Anaerobic Threshold Method, Not a Perfect Solution

Well, I'm sure many patients have successfully employed this method to get enough exercise done while avoiding the post-exertional sickness. In my case, however, my heart rate is so variable that I would end up getting half as much exercise as I could if I kept my heart rate at 60% of the maximum.

Yesterday was an example. I strapped on my new Polar H7 and ran the usual errands. My heart rate was elevated at above 110 even just sitting in a bus. It went up above 130 when I started walking and then 140 when going up a hill. If I were to stick to 60% of my max heart rate, I should've stayed home. I walked 2 mi instead, and I'm not sick today. (This could be attributed to my recent improvement. But walking faster, even for a short distance, still knocks me out, so I'm by no means out of the woods.)

Sticking to 60% of your maximum heart rate or doing 50% of what you think you can accomplish would be a good strategy if your goal is to avoid post-exertional sickness. But if the goal is to get as much exercise as you can, we need something better. And measuring the speed by counting steps, rather than heart beats, has been a more reliable way for me. (This has been the case even when I was sicker 7 years ago). The problem is that the intensity is different on a slope and your safe speed no longer applies. (This is particularly problematic in SF with lots of hills.) That is why I slow down as much as possible on uphills, just to be on the safe side, and then resume my speed when I get to a flat terrain.