Why do OwnZone limits vary?
OwnZone can be determined for every exercise session separately. We recommend that you always redetermine it when changing exercise environment, exercise mode, or if you are uncertain about your physiological state when starting the exercise.
Your OwnZone can vary even daily because maximum (HRmax) and submaximum heart rate responses vary. The heart rate responses are affected even by small changes in one’s physiological condition. Also factors such as exercise intensity and mode, environmental temperature, body position, mood, eating and drinking habits, as well as recovery from earlier exercise affect the heart rate response and therefore your OwnZone.
It is common that OwnZone limits vary between 5 to 10 beats per minute, but variations up to 30 bpm can also occur. In fact, this type of variation shows how sensitive to the state of your body the OwnZone feature is. OwnZone is a good tool for learning about your body and how it reacts.
As training tends to decrease the HRmax and because the OwnZone Basic (65-85% HRmax) is determined as percentage of your HRmax, the OwnZone beats per minute (bpm) can decrease over time when training.