Hi! I'm wondering if my vivvomove HR is still ok as, these last days, on speed walks (6.5 to 7.5 km/h), I don't get higher that Zone 3 when, just few weeks ago, I was up to 160 for quite a time. Or is it my body adjusting to the effort. To be more specific, I'm a 62 years woman, and started this activity one and half year ago. Also, my heart rate at rest was around 80 bpm, it's now between 55- 62. Thank you for answers as I have nobody around to help me about all this.