Ah! Hypermobile EDS. That explains everything, except that I don't think any of us here know enough to be of much help. Basically autonomic dysfunction, so your HR is going to be weird. Once you get over 160, the breathing thing for VT1 and VT2 should still work? It's weird to have only a 20 HR useful band. None of the usual formulas will work for you to define zones. Try using the 3 zone model:
1) Anything below the onset of more rapid breathing, i.e. being able to recite the alphabet.
2) In between 1 and 3
3) Anything above where one starts panting.
In the 3 zone model the 5 zone model's zones distribute as follows:
1) 5 zone model:1 and 2
2) 5 zone model: 3 and 4
3) 5 zone model: 5 and up
That's fairly simple and you don't need a power meter or HR to know what zone you're in.
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