It all depends on the readings. So for example I had to feed in my HRV this morning to see if I recovered enough from a tough interval training last night. I hadn't even though I thought I had and I have do a zone 2 or rest today. Zone two for me is to keep under 140 BPM. If I go over I have to slow right up or walk. It's a totally different way of training but I have never been fitter.