I recently got a Fitbit Surge. It's a pretty cool little toy. It has a continuous HR monitor, monitors sleep very well, keeps track of steps taken during the day, and it has GPS for running or hiking. The GPS function does place quite a strain on the battery, limiting you to about 5 hours of continuous use.
With GPS turned off, the unit goes about 5 days between charges.
There is an iPhone app for the FitBit, but the online user dashboard is much more impressive and useful.
I've had a few minor complaints with the unit, mostly similar to what I'd read online about HR measurements. In particular, it seems that my resting HR, which is measured overnight, is simply too high. There are times when my instantaneous HR will be 20 beats lower than my alleged resting HR, so I think there are some algorithm or sensor issues. But, the HR data does seem to be consistent, and as such, it's useful, even if the magnitude might be incorrect.
So, I'd written previously about feeling somewhat ill and taking it easy and trying to let my body recover. While I was doing that, my resting HR dropped consistently from 5/22 through 6/9. In those 18 or so days, my RHR dropped by 13 bpm. I took that as a good sign that I was doing the right thing and my body was recovering.
Then, on 6/10, my RHR went up, by a single beat compared to the day before. I didn't pay much attention to that one blip. Over the course of last week, I did CrossFit on Monday and Tuesday. I felt good on Monday and squatted heavier than I'd squatted recently. Tuesday wasn't too hard, but by Wednesday, I was sore. On Wednesday, I did a hilly hour-long walk, but skipped CrossFit. Thursday and Friday, I was back at CrossFit and I worked hard on Thursday. Saturday, my wife and I went for a run. Sunday, I did a hilly hike at Sugarbush, spending a lot of time bushwhacking, looking for a ski one of my students lost off-trail last winter. I was out for 2+ hours. Sunday night, I was exhausted. My appetite was gone again. I felt terrible.
I wasn't really paying attention to my FitBit dashboard. Monday, I noticed that my resting HR had increased by 1 or 2 bpm every day for six straight days. I had this data and I simply ignored it. And, I trained harder than my body was ready for me to train. A clear data line showed that my body was getting tired and I was pushing the training anyway.
Monday, I took a rest day. My resting HR dropped that night. Tuesday, I did CF, but with light weights and fairly easy overall. My resting HR dropped again that night. Wednesday, I did CF again, but again, I took it easy. My wife and I were the last 2 people to finish the workout on Wednesday. My resting HR dropped again overnight.
I have spent so much time since I got the FitBit, looking at the dashboard, and focusing on how many steps I took each day, and how much sleep I got each night. I completely forgot to pay attention to another important piece of data. By doing that, I basically set back my recovery from my recent fatigue by a couple weeks. I feel like an idiot - having good data and ignoring it.
My resting HR last night was the same as it was 14 days ago. It was 5 beats higher than the lowest number the FitBit has recorded. I'm not going to consider a single hard workout until I've gotten down to that lower number. And, if the RHR increases, I'm going to take a rest day.
What's the use of having the information if I'm not going to use it?