All the models, THRESHOLDs, numbers and so on are just guides! They ALL have weaknesses and limitations, and if you don’t KNOW them, you will run into problems sooner or later with your athletes!

Teun van Erp wants you to understand that ALL these models are just mathematical models; that even the best HRV and recovery gadgets are JUST using heart rate. That does NOT mean they are bad, but that you have to use them specifically and precisely rather than generalistically.