Polar FT4 and heart rate zone

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Hi there,

I just purchased the Polar FT4, and I have a few questions about how to use it to make the most of my exercise.

* Do I have to find my own heart rate zone, or can I trust the numbers that are in it from typing my personal details?

* Is it easier to have it set on where it shows the % of max pulse, or beats per minute?

* How do I know if I am exercising effective enough? The whole point of getting the monitor was to get an indication of my training, but that doesn´t much when I don´t know what to aim for.. lol

Any tips regarding this topic is much appreciated :)

My goal is to lose weight, at least 20 kg (44 lbs), and of course get in better shape.

I am female, 80 kg (176 lbs), 157 cm tall (5"2) and 26 years old if that information is useful for any information you can give me