I don't understand what your Garmin has to do with it.

I see the same using the 910xt, so I stopped pacing by looking at the avg pace on the watch, instead I pace based on time.

It may seem different, but I'm pretty sure that your Garmin has nothing to do with it. I'll sometimes vary up directions on the track (helps alleviate some injuries), and have never noticed any perceived change in effort compared with pace in one direction or the other.

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Yeah I don't see how the Garmin is involved. Are you talking about using a footpod and looking at pace, rather than simply lap-times?

If so, then it could absolutely have an effect because your stride is going to be very different on the bends, so regardless of which shoe you have the footpod on it's going to be screwy.

Every Sunday, weather permitting, I run to the local high school track (as a warm up), 8 to 12 "400's", and run home. I've been doing that for probably 5 or 6 years. I always wear my Garmin - originally a Forerunner 305, now a 910xt. I run in lane 2 CCW (normal direction around the track)

My 305 used to be all over the place for each lap, even though distance was obviously the same. That made the pace vary. Last Sunday my 910xt recorded 12 laps and each one was .27 miles long, except for 1, which was .26 miles long. Because the distance is so short a .01 difference in distance can have a 10 or 15 second difference in calculated pace. Understand that at sub 6 minute pace, with the accuracy of the GPS system to start with, you can easily vary that much just in when you start and stop the watch. Add in going the other direction where you might run a different or more loose path around the curves and what you are seeing seems normal.

This has come up before for accuracy on the track (Garmins used to suck really bad on the track) and the consensus was that since the lap distance was known all you should really be evaluating is the lap time. I have my Garmin screen for track work set to only show me lap time and rest time and I know what I should hit at the markers. I'm using at $350 device as a $15 stopwatch. I don't use the pace or distance screens except for the run there and home.

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"...the street finds its own uses for things"

Are you saying you're running the same pace both directions but your Garmin is giving you a different pace each way? Or are you saying you're literally running faster in one direction than the other? Or are you saying you don't know if you're running faster in one direction over the other?

Since you're on a track with a measured distance, go by time, not the pace Garmin is calculating. They're not as accurate on the track because of the tight turns. I use mine at the track to record the workout, but I check my splits by time, not the pace the watch is calculating.

why even bother with a Garmin when running on a track? A stop watch, or a clock, would suffice, no?

Yeah. I just use mine to record the workout and then it auto uploads to trainingpeaks, but I only watch the time so I'm using it like a stopwatch...a very expensive stopwatch.

Garmins are not accurate enough to measure a track. Stop using a Garmin to pace on a track and learn your efforts and how to monitor every 200.

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^^^^^This.

Just look at your watch each 200, and it's pretty easy to know what pace you're at. With some experience, you'll just know by feel how fast you are going, since you get feedback/correction every 200.

The only reasons I have a Garmin when I go to the track are: it's my stopwatch, and it's recording the workout for Strava.

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I like to analyze data on strava later. I just want to ensure if it's bio mechanical issue of mine or the watch (is wear on left arm). Next work out I will just hit lap button at marked points to compare both directions later

You shouldn't analyze incorrect data.

Again, the GPS is not accurate enough to measure correctly on a track. Get out of your data obsessed trathlete mode and just accept that.

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https://markmcdermott.substack.com

Or buy a Stryd Fodpod! It claims to be 99% accurate, even on track or on trails, with those edge-case leg movements. Stryd will handle both of these situations far better.

Disclaimer, I work for Garmin but not fitness. Always wear your Garmin on the inner wrist on the track. If you switch direction, switch the wrist. Don't ask me why. If you want to know, I can get an answer. You will get decently accurate and consistent results with 920 that way. Accuracy of GPS is reduced on any curved trajectory with short radius, ie your track curves will tend to throw it off.

aha! i had a feeling it is something to do with this... perhaps the accelerometer is also used with gps in the algorithms

I wear my 920 on the inner wrist and pace is still crap on a track. Always at least 5s/km faster than I really am. GPS is just useless on the track, no matter what wrist you put it on.

Actually on the road pace is a just a little bit more accurate, but not by much. It's still puts me ~3s/k faster than I really am on a certified course. It's just that it's much more noticeable on a track.

Sure, hitting the lap button is the way to go for future efforts, but you can still validate your findings with old data where you didn't.

You saw a 20sec/mile difference between the two directions? That is 5sec/lap (ish...yeah, yeah 1609 and all that). You can look at the map of your run and see where you crossed the start/finish line for each lap. As long as you were using every second recording*, you can see when you crossed the line within a second. To data points (start and finish of lap) = 2 seconds of error. Since 2 seconds of error is less than the 5 second delta...you'll be able to validate! Simply list all the CW laps and all the CCW laps and compare.

*If you are using smart recording, change it right now.

AutomaticJack wrote:

...Last Sunday my 910xt recorded 12 laps and each one was .27 miles long, except for 1, which was .26 miles long. Because the distance is so short a .01 difference in distance can have a 10 or 15 second difference in calculated pace...

Just because your watch only displays .01 miles of resolution, that does NOT mean that it is calculating pace with such rough data. Your .26 mile laps were probably more like:

• .2598
• .2643
• .2610
• .2624
• .2648
• .2576

...and the .27 lap could've been: .2652.


So of course, if you ran perfect pacing and tagged the lap button right on the line, the lap pace for each interval will vary simply because distance from GPS isn't perfect. But, it isn't because your watch only displays hundredths of a mile.

Do you happen to know anyone that has the Stryd footpod?

Genuinely interested.

I am confirming that switching wrists did correct the problem. So the watch must be on the wrist facing inside of the track

Great! Keep it up. Now, off ST and more training. :)

Heaps of people saying this, but i run at a track every week and mine comes up very damn close to 400m, no more or less accurate than running on the street.

well that's simpler than the quantum adjustment formula for the greater sidereal motion effect. !!

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