Thursday, July 12, 2012

Marking 1 Year with the FitBit - 2 Million Steps!


How many steps do you take in a year?  I just found out I took about 2 million steps last year.
I've previously mentioned that I use a FitBit; that cool high tech pedometer.  Yesterday I passed a milestone.  I took my 2 millionth step since getting a FitBit back on July 14th of 2011. This milestone came in just a few days less than a year.  Sure there were a couple of weeks missing in there when I lost my first FitBit, and I suppose there are a few times I forgot it etc, but generally it appears that I took about 2,000,000 steps in the last year.  I thought this would be a good time to give you some impressions of the device after 2 million steps of use.


The FitBit is a pedometer, but with a bit of a modern twist.  It uses an accelerometer to measure your steps, and then it uploads this data to their servers where they give you all sorts of analysis of your activities.  In addition to the accelerometer, the latest version can measure barometric pressure, which allows it to track whether or not you are going up or down steps.   Seeing this data is quite fun.  It is compelling enough that I've worn mine almost everyday for a year now.  We've also gotten FitBits for the rest of the family.  I think its great when we get toward the end of the day and see that we haven't gotten enough steps yet, so we decide to go for a walk.


10,000 steps

There are several studies that show that people who take 10,000 steps per day are generally healthier.  It is correlated with everything from lowering the risk of diabetes, or maintaining bone density not to mention that too much sitting still can apparently cause cancer.  For the average person, a mile is about 2000 steps, so 10,000 steps means walking the equivalent of about 5 miles a day.  It appears that there is nothing magical about 10,000 steps, but that it is a good stretch goal for many people.  With my desk job, I get 2000-4000 steps a day unless I make an effort to go and get some extra steps.  My goal is still less than 10,000 steps per day, but I'm getting significantly more steps than I did before I had my FitBit.

How it works (& some technical details)


To use a FitBit, you clip it to your clothing and it uses the accelerometer to sense periodic motion consistent with walking.  Based on your height and weight it makes some estimates as to your stride length and other factors which allow it to figure out how many steps you took, how far you walked and how many calories you burned to do so.  Its pretty good at telling the difference between walking and driving on a bumpy road, so overall it does a pretty good job.  Generally, it seems to be detecting periodic motion that is in the range of about 1Hz to 4Hz.  I don't know their exact algorithm, but if I were designing this device, I might use data about the overall force on the accelerometer in addition to the pace to determine just how fast the person is walking/running.  In other words,  I suspect that the amount of time a pedometer spends in free fall and the intensity of the impact on landing, may be good clues about the nature of your movement just as the cadence is.
In our tests, we've found the FitBit to be surprisingly accurate.  At first I wondered how well it would do estimating things like distance based on steps, so we did a few experiments.  Whenever we've tested it in real situations, its always been easily within 10% of the measurements that we have gotten by other means (GPS, map measurements etc) or others with FitBits.  We got pretty good results in our experiment to find out the variability of FitBits.  Going up and down hills throws it off a bit because you take shorter steps going up than down, but these tend to even out if you end at the same altitude that you started from.  I haven't had a chance to test this with the newer FitBit with and altimeter.  It may be able to use this extra information to get more accurate results.
The battery life is pretty amazing for such a small device.  You need to charge it about every 10 days, by leaving it on the base station for a couple hours.  The long battery life and automatic syncing make the hassle factor very low on this device.  All you need to do is remember to clip it to your clothes and you are good to go.
Whenever you get within range (~15 feet) of a base station (A USB dongle) the FitBit automatically syncs itself to the FitBit cloud.    This system works quite well and the syncing seems to happen without me paying any attention to it at all.  The wireless component is based on ANT+, a very low power RF protocol heavily used in fitness equipment.  This is a major factor in keeping power consumption down.  It is much simpler and more low power than Bluetooth.  The new Bluetooth Low Energy (BTLE) standard may challenge this some day, but for now ANT+ is the wireless protocol of choice for low-power, short-range fitness devices.
The newer version has an altimeter that uses minute changes in barometric pressure to detect stair climbing.  My first FitBit did not have an altimeter, but I lost that one and the replacement was a newer one that did have it.  This means that for the last 6 months or so I've been able to track the number of flights of stairs I climb in a day.  Because the altimeter is detecting actual air pressure changes, this means that, because your altitude doesn't actually change, you can climb all day on a stair machine at the gym and not get any credit for it on your FitBit.

The Data

As you walk around wearing the FitBit, you are generating data.  All this data ends up on a private area of the FitBit website, where you can monitor your activities.  By pressing a button on the FitBit, you can identify special activities whose stats can be tracked separately so that you know just how you are doing with your workout at the gym.

To me, the most interesting thing about the FitBit is that it monitors you continuously, so your data can be divided up into 5 minute chunks that tell you a lot about how you spend your day.  This is the real secret of this device and provides a lesson that other sensors can learn from.   Taking my pulse or blood pressure is interesting, but if I could see a graph of it over the course of a day/week/month, it gets much more compelling.  In the case of FitBit, it measures every step I take (within a margin of error).  This is how I know that nearly 1000 miles last year.  Who knew?  For each day I can see how much time I spend sitting around and how much time I spend moving.  It puts this data together for me into weekly goals and badges that I earn as I reach certain milestones.


In addition to number of steps you get estimates of calories burned and if you are good about manually entering data, you can also put in information about how many calories you consume in order to see if you are balancing your input to your output.


What does this data tell you?  A few month ago I moved to a new office building.  It turns out that at this new building I get significantly fewer steps.  I might not have noticed this, but it makes sense since my parking spot is closer to my office, I don't have to walk as far to lunch and the bathroom and kitchen are nearby.  Because I have my FitBit I saw my total number of steps each day drop significantly and realized quickly that I needed to do a little more extra work to burn those calories that I used to burn without thinking about it. 


Here are some badges I have received.
This particular gadget is compelling enough that we've gotten them for the whole family.  I get a pretty good sense of just how active the kids are during the course of the day - which is really useful as they enter the occasionally slothful teenage years.  It works out pretty well.  


Another interesting thing you can do with the FitBit is monitor your sleep.  You wear the FItBit on an wrist band as you sleep and it tracks your movements over the course of the night.  I have been playing with other gadgets for monitoring sleep, but the FitBit actually does give you a basic idea of how restful your sleep was.  It can also help you to determine, for example, if there is a clock chime or other regular sound that affects your sleep.  If you move every hour on the hour, or every night at exactly the same time, maybe you should check to find out what external influence is that is affecting your sleep at that time.
Of course, this function is fairly limited.  Just because I'm lying still does not mean that I'm sleeping.  Conversely, motion does not always mean that I'm awake.  Overall, I do find that the FitBit is a reasonable indicator of how soundly I slept.  It is especially useful when I look at the trends over time.  I can see if I'm not getting behind on sleep and need to make an effort to catch up, before it affects my performance significantly.  I have another device that is able to correlate your sleep patterns with other data, like whether or not you crank caffeine the evening before.  With the FitBit, you have the data, but you must do the correlation manually.  A much better tool for monitoring sleep is the Zeo which I may talk about in another post some other time.

Issues


We really like our FitBits, for some reason, they keep getting lost or broken.  My original FitBit somehow jumped off my belt while I was at CES this year.  Both the kid's devices are being help together with tape because they have been damaged (granted kids aren't easy on these sorts of things) to the point where they are no longer working.  Monika's FitBit has been missing for two weeks now.  I think having a mode where you can make them beep would be great for finding them and figuring out a new style for the clip might make them a little less exposed and subject to damage.  These things are NOT cheap, so replacing broken/damaged ones for a family of four is a significant investment.  The people at FitBit are very helpful and have a decent replacement/discount policy, but this is an area that could use improvement.

Who owns the data?


One major annoyance with the FitBit is that you have to pay for a premium service ($50/yr) in order to be able to download your data.  You can look at the data on their website for free, but to download it you need a pro account.  With health data that I generate, I feel strongly that I own the data.  If they want  me to pay for some additional value that they add in convenience or in analytics, that is fine, but don't charge me for access to my own raw data!  In particular I want to be able to correlate this data with other data that I collect through other means, but with FitBit, that is impossible without using their service.  This is a significant failing of the FitBit business model from my perspective.

The FitBit also integrates with some other health devices.  We have a WiThings bathroom scale that logs our weight.  I have set that up to forward its data to the FitBit website so that I can see my weight changes on the FitBit website along with my step data.  This is useful, but there are other devices, such as the Zeo, that do a much better job of showing correlations.  Of course, while FitBit will import data from others, they wont export, so you can't get those other sites better analytical information about your step data.

Overall I really like these devices, but I do hope that they work on these issues.