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Unveiling the Truth: Why Your Treadmill Is More Accurate Than Your GPS Watch on Treadmill Runs

Today I want to talk a little bit about one of the most common questions that I get asked as a run coach and that is:

When I run on the treadmill, which do I trust–my GPS watch or the treadmill???

The answer is the treadmill.

You want to trust the treadmill. Sometimes, that might be really discouraging because it makes us feel totally awesome when we look down at our watch and it says that we're running paces that we didn't imagine we could ever run, but to be honest the treadmill is more accurate. Read on to find out why your treadmill is more accurate than your GPS watch.

The science behind how a GPS Watch works when we're on the treadmill

Your treadmill pretty much knows what pace, when you push the button, that it's supposed to be going. Occasionally you'll be on a really old treadmill or treadmill that's not calibrated correctly and that can cause differences or if it's not on a flat surface) like my treadmill is in my garage and so I have to have it on some wood in the back otherwise it's like a 2% incline even when the treadmill is flat because our garage is slanted a little bit). So, your treadmill knows how fast it's supposed to go right with small exceptions.

When you take your watch to the treadmill, it doesn't know. It doesn't know what it's doing and it's confused. Your watch is made to be used outsid–it's a GPS watch. It is connecting to GPS signals that are owned by the company or connected to ones that the company uses. When you take it and use it on a treadmill, what your watch is doing is saying, “when Jen runs a 6 minute mile outside, this is what her arm swing is like. So we're going to guess that because her arm swing is doing the same thing right now, she's running a 6 minute mile.”

The problem with that is a lot of us have slightly different form when we run on a treadmill than when we run outside. A lot of times when I'm running outside I'm holding a handheld water bottle or I'm messing with gu’s, different things like that I'm not doing on a treadmill. Also when I'm outside I'm not paying as close attention to what my arms and my shoulders are doing as I am on the treadmill. I know I'm not the only one that does that. On the treadmill, you have less to focus on–you're not worried about the terrain or stepping on things, so your watch is going to be not accurate at all.

What you can do when your watch is different from your treadmill?

My favorite trick when I'm running on the treadmill and I want it to match what the treadmill says is to calibrate it.

If you wait until the end of your workout on your watch you can actually end the workout and then instead of saving it right away, most GPS watches have a little section (if you put it in as a treadmill run) where you can calibrate the run. What that means is you just go in and it'll give you the option to change the distance that you ran so that it accurately reflects the work you did.

If you don't care you also can just not wear your watch on the treadmill when you're doing a run. I like to have it so that it syncs to my Garmin Connect app so that I have my total run miles for the year, steps for the day, that kind of thing, but if you don't care just don't wear your watch and trust the tread. But if you want that information, you can calibrate the run after the fact

Tracking intervals runs from your GPS watch to the treadmill

The last thing that I want to touch on is how to do speed work or how to do intervals on the treadmill when your watch doesn't match up. If you're like me, your watch is connected to your workout program or it'll tell you what your workout is supposed to be.

If you're running for distance on your watch it's not going to be accurate because your pace isn't accurate. It's going to be a whole mess. So I actually don't do the workouts on my watch. I just said it for a treadmill run and then I write the workout separate on a piece of paper and put it up next to me on the tread so that I can make notes as I go. If I need to I can put in the pace that I ran real quick with the pen that I have sitting there. If you're dialed into the pace, you can use an object to track intervals. I use seashells because my daughters have seashells everywhere but you can pick some object: Legos, pens, bobby pins, whatever you happen to have lying around and take that number of things, let's say you have 10 intervals, put it in one cup holder and then move it to the other side as you do it so that you're keeping track of how many intervals you've done and how many you have left to go. When you run out then you're done.

If you have any other questions about running with your Garmin on the treadmill or how to adapt things based on taking a workout to the treadmill please let me know you know I'm open and open book and I'm always happy to help.

Just remember – trust the tread!

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