I have to say, the Body Battery is my favourite feature on the 945. That is, in the absence of any training!
Not surprisingly we have First Beat to thank for this, rather than Garmin. I find it really accurate in-terms of reflecting the impact of physical and mental stressors.
When I’ve had a mentally exhausting day and feel frazzled, I can immediately see the impact of this which also reflects how I’m feeling. Equally when I’m focused, relaxed and in the flow, it reflects positively.
Interestingly I can also see this with certain foods I eat, when I’ve eaten a lot of refined carbs and gluten it immediately spikes my stress and reduces my body battery in contrast with fat and proteins which are fine.
IMO this tech goes beyond just monitoring pulse rate, and must also take into account HRV, which for a WHR monitor is pretty impressive.
Hopefully Garmin acquiring Firstbeat doesn’t impact the stability or improvement of these features!