A total of 1 review of this product on Reddit.
>Do any of you know of guidelines backed by (statistically significant) research?
I mean there is a lot about this recently. You can look up, for example, Hear Rate Variability training (for example this write up by Alex Hutchinson https://www.outsideonline.com/health/training-performance/how-heart-rate-variability-tells-you-when-hammer/ ).
This Twitter thread is interesting in this context:
Also velocity based training is another thing you might look into if you are talking about resistance training. I haven’t tried it but you are supposed to be able to do it using just an iPhone with Carlos Balsalobre’s app:
A lot of the sports science people I follow on twitter having been talking about this book recently and if you look at the table of contents there is a chapter on recovery (I’ve ordered the book but don’t have it yet):