I purchased my Charge 6 back in September mainly because it advertises as being 99% as accurate as a Polar S10 (I don't like chest straps).I have been very pleased with it and even got my wife one. About 2 days ago we got the firmware update and I wonder if they changed something with the heart rate monitor algorithm.
Yesterday my wife noticed that she only briefly (1 minute) got her heart rate above light during a rowing Tabata. Today I was doing a Norwegian 4x4 on an assault bike. I was surprised when despite going harder than normal during the warmup that my heart rate didn't get above moderate. About a minute and a half into my first interval I could feel my heart get to near maximum heart rate, but the Fitibit still only had me at the upper end of moderate (132). I, of course, backed off a bit. It felt like the Fitbit, eventually, caught back up but was still about 5 bpm low the whole workout.
I have been very pleased with the product to this point. However, today it was dangerously inaccurate. If I had kept on pushing when my heart was at maximum according to my knowledge of my body I assuredly would have given myself a heart attack. I realize that there may always be some lag but I never experienced anything like today before. Has anyone else had a similar experience? I will also be contacting customer support.
