We decided not to include the HR drift test in the new book because it requires one to have a Training Peaks account. While we are big believers in the value of TP we are not affiliated with them in anyway and in fact pay them quite a lot of money each month for the use of their platform (which shows how valuable we think it is). To make Training Peaks a requirement for the use of any part of the book seemed too much of a commercial endorsement to all three of Kilian, Steve and me. We were afraid there might be backlash and we wanted anyone to be able to use this book to create a plan for themselves. So we left what could be construed as a commercial endorsement of TP out.
We use this HR drift (HR decoupling as TP terms it) with all of our coached clients. We have seen very strong correlation with gas AeT tests (probably approaching 95%). So, I would rank it second or 3rd behind the Gas test and a lactate test. Definitely more accurate for more people than the others. MAF works great for most people but I have seen it be way off in both directions on several occasions. Same for the nose breathing test. For those with a good aerobic training history I’d say it is corresponds perfectly with a lactate test. But when if one does not have that aerobic background I have seen it off by a mile.
Not everything made it onto the first or the second book which is why we provide so much free information on this site.
I hope this helps.