Why Is My Running Watch Wrong on the Treadmill?
The treadmill says 8 miles but your watch says 7.42.
You have now spent an hour running without going anywhere, and your two machines cannot even agree on how far you went.
I do a lot of treadmill running. Living in the Mojave Desert, we have 3 brutal summer months and a heck of a lot of wind. Sometimes, it’s just better and more fun for me to run indoors.
Looking for the best treadmill for runners? I wrote a post titled that exact thing: Best Treadmills for Runners.
Why is your Garmin, COROS, Apple Watch, or other running watch wrong on the treadmill?
Indoor running forces the watch to calculate distance differently from an outdoor GPS run.
Why Does My GPS Watch Get Treadmill Distance Wrong?
When you run outdoors, your watch can use GPS to follow your movement across a route. On a treadmill, you stay in the same location. A watch therefore has to use other information to estimate indoor distance.
COROS says Indoor Run mode turns off GPS and uses internal sensors, calibration, user input, and a cadence-to-pace model to estimate treadmill pace and distance.
Apple says Indoor Run uses the watch’s accelerometer, and outdoor calibration helps Apple Watch learn stride length at different speeds.
Your watch is doing the math based on the way you move indoors. It does not know exactly how much treadmill belt passed under your feet.
Why Is My Watch Farther Off During Treadmill Intervals?
Your stride at 6:00 pace is different from your stride at 9:00 pace or 12:00 or 15:00 or 20:00…and your cadence can change too. Your watch is trying to keep up with repeated changes while estimating indoor distance from your movement.
COROS allows runners to enter treadmill speed and grade manually in Indoor Run mode, which can be useful when the treadmill pace is known. Its indoor calibration system can also update the cadence-to-pace model after eligible treadmill runs. I’ve found the COROS indoor calibration to be good, not great. You can get your overall mileage and average pace but say you ran a workout with both 6 minute and 10 minute miles. COROS is going to smooth everything to say each mile was around 8 minutes.
How Do I Calibrate a COROS Watch for the Treadmill?
If your running watch is wrong on the treadmill…COROS can prompt you after the run to confirm the distance after eligible Indoor Run activities.
For that calibration option, COROS currently requires a recorded distance of at least 1 kilometer, no manually selected speed, and no structured workout or training plan during the activity. Entering the corrected distance updates its cadence-to-pace model for future indoor runs. You can also edit the distance of an Indoor Run later in the COROS app.
One catch: COROS says its indoor distance calibration does not automatically carry over to third-party apps, because those platforms may process the data differently. I actually haven’t had this issue before with the thousands of mikes I’ve put on my COROS.
How Do I Calibrate a Garmin Watch for the Treadmill?
Compatible Garmin watches offer Calibrate & Save after a qualifying treadmill activity. Garmin says newer devices generally require the watch to record at least 1.5 miles before treadmill calibration becomes available, while some older models use a 1-mile minimum. If your running watch is wrong on the treadmill, than you enter the treadmill distance before saving.
If your Garmin is consistently off indoors, use the treadmill activity profile and calibration feature rather than correcting the math in your head after every run.
How Do I Improve Apple Watch Treadmill Distance?
Full disclosure: Apple Watches have always been off for me on the treadmill. I would rather use no watch than an Apple Watch.
Use Indoor Run for treadmill running.
Apple also recommends outdoor calibration. Run or walk for about 20 minutes in an open area with good GPS reception. If you train across different speeds, Apple recommends calibration time at those different speeds too.
If nearly all of your outdoor running happens at an easy pace, then you jump on the treadmill and start running much faster, the watch has less information about what your stride looks like at those faster speeds.
Does Holding the Treadmill Rail Affect My Watch?
It can interfere with the motion information a wrist watch is using indoors.
Apple says Indoor Run uses the accelerometer, and its accuracy guidance notes that arm movement contributes to activity tracking. If you spend a large chunk of the run holding on, I would trust the wrist-based distance less. You shouldn’t hold onto the treadmill rail anyway because you’re hindering your own workout.
Is the Treadmill or My Running Watch More Accurate?
For training, I use the treadmill speed and time for the workout I programmed, then calibrate the watch afterward when the option is available.
Why Is My COROS Distance Different Once It Uploads to Strava?
COROS specifically says its indoor distance calibration does not apply to third-party apps. Platforms such as Strava may parse or recalculate uploaded data using their own methods.
Why Is My Running Watch Wrong on the Treadmill?
Because treadmill running takes GPS out of the equation and forces the watch to estimate indoor movement through sensors, stride information, cadence models, calibration, or manually entered speed.
Use the correct indoor activity mode. Calibrate when you can. A foot pod or compatible treadmill connection can also improve indoor data on supported devices. COROS, for example, supports direct pace and distance data from compatible accessories and some connected treadmills.
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Questions for you:
Do you use the treadmill?
Have you had your running watch wrong on the treadmill?