Hello.
I've been always criticizing Garmin harshly about inaccurate HR readings for interval type of workouts including lots of arm flexions.
Because i could not accept it seeing a famous sports watch brand beaten by a smart watch in terms of HR accuracy as being a long time Garmin user.
I know that wrist hr readings vary from person to person and different conditions such as skin colour, hair density, blood flow, ambient temperature etc. But clearly Apple was better at this.
However, the latest review by Techy Agent shows that Garmin has improved the HR sensor. It performs quite well on weight training and it's reactions to HR variance even seems to be faster than AW 4 whom HR sensor is accepted as the most accurate one by all of the famous reviewers such as DCRainmaker, Desfit, Techy Agent etc.
Here it is;
https://www.youtube.com/watch?v=2KgTelvlxic
Congratulations Garmin !
