I must tell you, I am confused as heck.

As a runner that is unfortunately tied to the treadmill due to two hip surgeries, two knee surgeries and currently a torn right meniscus (insert the sound of the world’s smallest violin), I have been relying on the data of my iPod, iPhone and Fitbit.

I love running, but I am not supposed to run more than a 5K or 3.11 miles. Therefore, I need to know how far I run on the treadmill and at what pace, but I’ve always struggled with how do I best measure distance on a treadmill?

Since 2007, I have been using the Nike sensors and measuring and comparing the recorded distance to my treadmill. I was able to get sensors to attach to my various iPods and use it for the Nike+ app.

Eventually I graduated up to a fancy pair of Nike running shoes with the Nike+ sensor that was inserted into the inside sole of my shoe beneath the cushioned insert.

After calibration of the Nike+ sensor, I was able to get a much better estimation of my distance and pace than relying on the treadmill.

Why? Because treadmills are wrong.

Now I know what you’re thinking? How can they be wrong? Well, they are wrong because treadmills run at a constant pace yet our bodies can run slower or faster that what we have the treadmill set.

For example, I always set my treadmill to a speed of 6.0, which equates to a 10’00” or a ten minute per mile pace. Yet at speed of 6.0, I can sprint or gallop like a horse. But if I run for 30 minutes at a speed of 6.0, the treadmill will show a distance of 3.0 miles. And in reality, I might be running a lot more or a lot less than 3.0 miles. Therefore, I never pay attention to the distance on the treadmill. Never ever ever.

Alas, after many years of using the Nike+ sensors, two years ago I upgraded to the iPhone 6+ and I was a bit shocked with I could no longer find the Nike+ app for my phone.

Puzzled, I said to myself, “Off to The Google.”

Shortly thereafter, I discovered Apple, due to the built in accelerometers within the iPhone, was no longer supporting the Nike+ sensors starting with the iPhone 6. All of my Nike+ sensors were no longer needed.

Awesome! No longer did I have to pay $20 to replace the sensor that I lost or left in my other shoes, I could simply use my iPhone measure my distance.

I then installed the Nike+ RunClub app on to my new iPhone 6+ and was ready for a run. As I switched over to an indoor run, I received a very important popup window that said something to this affect: “Apple recommends holding the phone in your hand to best capture running motion.” Nike also recommends you hold the phone in your hand as well.

Great. Now I have to hold this massive phone in my hand and hope that my profuse sweating doesn’t cause my phone to sling shot out of my hand and hit someone in the gym. On the plus side, I was able to run without the need for any additional Nike+ sensors.

Which Brings Me To My Fitbit

I first bought a Fitbit Flex about four years ago. At first, I thought it was great for counting steps. That was all I really used it for, which is reality seems a bit silly.

I then migrated to the Fitbit Charge HR and now I am currently wearing a Fitbit Charge 2. I really like the Charge HR and Charge 2 for some of the additional functions beyond just step counting, such as sleep measurement, weight tracking (I have an Aria Fitbit scale), water consumption and exercise tracking.

Truth be told, I have never been a big believer that the steps being measured by Fitbit are accurate. The reason being is that once I input my height and gender, Fitbit then calculates my stride distance and the Fitbit’s accelerometer picks up motion and steps are counted. I also use a lot of hand gestures during the day and guess what, those are also counted as steps. Whoopsies.

Now I could actually measure my stride and input the correct walking and running strides, but that just seems like a whole lot of extra work. But if you are really trying to measure the accuracy of your steps, I would highly recommend you do so this extra calibration.

My Fitbit Charge 2 also has the ability to track specific exercises similar to how I might track a run on my iPhone using the Nike+ RunClub app. As long as I start the runs at the same time, I could measure the two devices compared to the treadmill, which runs at a constant rate.

Apple vs. Fitbit

For all of my testing purposes, I set the speed of my treadmill to 6.0 or a 10’00” or ten minute per mile pace. At the same time the treadmill started, I immediately pressed start on my Nike+ RunClub app and the Fitbit Charge 2 Run.

My iPhone 6+ was being held by my left hand per Apple and Nike’s recommendations and my Fitbit Charge 2 was on my right wrist.

According to the Nike+ RunClub app and utilizing the accelerometer within the iPhone, I finished by 5K run, or 3.11 miles, in 23’08” or a pace of 7’40” or seven minutes 40 seconds per mile.

Apple vs. Fitbit

According to the Fitbit Charge 2, I finished the same run, in 23’08”, but I ran 13.2% less distance and only completed 2.7 miles. This resulted in a pace of 8’50” or eight minutes 50 seconds per mile.

Apple vs. Fitbit

And the treadmill set to a constant speed is even worse, saying that in the same 23’08” I ran 25.7% less distance or 2.31 miles at 10’00” or ten minute per mile pace. Yikes!

Apple vs. Fitbit

What the heck? Which distance is right? The treadmill, the Fitbit or the iPhone?

Well, I’m never going to believe the distance on the treadmill. Second, I don’t have a lot of faith in the distance measured by my Fitbit, which leads to holding my iPhone as the best alternative for measuring distance while run on the treadmill.

So what leads me to this conclusion? Over the past 12 months, I have completed over 100 runs testing my iPhone with the Nike+ RunClub app and comparing the data to Fitbit and treadmill data. I then compared GPS data while running outside, with my Nike+ RunClub set to indoor mode as though running on my treadmill, as well as my Fitbit.

In each of these outdoor running sessions, the distance recorded by the accelerometer on the iPhone and Nike+ RunClub app was always significantly closer to the GPS distance than the calculated distance on my Fitbit.

Therefore without a doubt, the iPhone and the Nike+ RunClub for me is the best way to measure distance while running on a treadmill.

Now don’t get me started on which device measures calories and heart rate better.

I’ll save that for another post. But I’ll give you a hint. It is neither.


 As published on Medium.