After a while I am having problems with heartbelts. All ready my third belt gave up because the readings were way off. Heart on the wrist with optical heart rate is unreliable. Runalyze uses heartrate for recovery etc and trimp. I run about 2,5 years with a Stryd and love the way power is already integrated in Runalyze. Can’t power be used as an alternative for the parameters ? For example the use of % off critical power wich is about VO2 max? They’re closely related according to the book running with power from Hans van Dijk and Ron van Megen.