I think yo have hit on a good point. There aren’t many American coaches who are very familiar with HRM training and therefore most of the basic stuff you read out there is lacking in knowledge.
Here is a case in point. My workout for Sunday was to be 1 hour and 45 minutes whereby 60 minutes in the middle were to be run at 155-160 HR. This is just below my LT. I took off running and as I warmed up I hit the 3rd mile in 6:34 and my HR was 133. I felt great but I knew from experience that this is a tell-tale sign of one of two things. I proceeded into the hour part and was cranking along at 6:05-10 pace. Like I said, I felt good but could not get my HR up to what is usually a very easy range for me to hit (my maxHR is 183).
I finished the run and wrote an email to my coach. He immediately confirmed for me exactly what I had thought. I was suffering from low glycogen levels. I had put in quite a few hard days over the past week.
Here is where the runner who lacks knowledge like this gets it wrong. Even though I felt great for the workout, the HRM told me something was wrong. Typically, another runner would see this as a good sign and hammer again over the next few days thinking they had just made a break through. This would actually take them in the opposite direction of where they wanted to go. I saw it as a warning sign that my body needed a few days of easy jogging and my coach, who has over 20 years of LT coaching and HRM use confirmed this.
There is nothing that can give you better feedback than this. Had I gone “by feel” I would have been wondering why the next few workouts or even races would have FELT flat.
Now I’ll be ready to rock and roll come Sunday’s race.