This is going to be a bit of a long post and is kind of complicated, but here goes.
So I recently read 80/20 Running by Matt Fitzgerald and have been trying to incorporate the 80/20 rule into my training.
I bought myself a Polar watch with a heart rate strap and started by doing a 30 minute time trial which gave me an average of 169bpm for the last 20 minutes, which I put down as my lactate threshold. I then used this number to work out my 5 heart rate training zones.
Today I attempted another test in order to convert my various heart rates into corresponding paces. Unfortunately I found this to be very tricky and ended up giving up on it.
It's a little difficult to explain but basically I got my heart rate to the minimum number it had to be for zone 1, then tried recording the pace I was at before going on to do the same for the minimum/maximum of all 5 zones. The problem was that I just found everything a bit too inconsistent to be reliable.
I'm new to heart rate training so first I'll mention something that seems to be happen with every run. When I start out I feel like I have to run relatively fast just to get my heart rate into Zone 1. Then after a few minutes I feel like I have to force myself to slow down to avoid overshooting into the heart rate next zone.
In the 80/20 Running book Zone 1 is recommended for warmups and recovery runs. But it just seems really weird that I have to go faster at the very start of the run just to reach Zone 1 only to slow down significantly a few minutes later to avoid going into Zone 2. I know that fatigue over time is a factor but surely it shouldn't be making that much of a difference over the course of a few minutes.
Now because of this I wasn't sure whether to start my Heart Rate-Pace test feeling fresh or to run for awhile first to make it more reliable. I ended up jogging gently for about 5 minutes before attempting to get my heart rate to settle on the minimum for Zone 1, which is 127bpm by the way. Due to the lag that comes with measuring heart rate I found it tough to get it to stay on that exact number. I initially recorded my Zone 1 minimum pace as roughly 7:58 minutes per km. The problem was that I found that my pace had to be constantly up and down just to get my heart rate to stay on 127, which obviously makes the whole thing unreliable. I tried to continue onto the other zones and had the same problem. My minimum Zone 3 pace was even faster than my maximum Zone 3 pace, which makes no sense at all.
By this point I felt like I was having to run almost all out just to get to my maximum of Zone 3, and even then I think I only got to it running for a while rather than by going faster, which makes pace irrelevant and defeats the purpose of the whole test. After this I gave up as I didn't think I could even get into Zone 4 or 5 without running for ages. I believe the whole point of those last 2 zones is to use them for High Intensity Intervals, in which case you wouldn't be running at a fast pace for long.
Now I've begun to doubt how reliable my 30 minute time trial was in finding my lactate threshold. I say this because I should be able to get my heart rate into those higher zones without the need to run for ages if my lactate threshold is really 169.
Anyway sorry if this was overlong or sounded confusing. I'd really appreciate any advice anyone could offer. Also if anyone else uses the 80/20 method it would be great to know how you went about this.
Thanks in advance.