Last week was a great week for me running wise.  I was able to fit in 40 miles for the first time since Baby C was born 11 weeks ago.  I accomplished this with 5 days of running, ensuring that I had my 2 rest days for adaptation and recovery.  I had an awesome tempo early in the week and ran another timed mile. 

6:11 – 17 seconds off of my unofficial mile PR of 5:54 from 2009.

Unofficial?  I have never raced the mile, so my mile PR is unofficial.  I went to the track one summer day in 2009 and told myself I was going to race the mile.  I warmed up and then headed to the start line.  I gutted it out for 5 minutes and 54 seconds and was ecstatic to have broken a 6 minute mile for the first time ever.  A 5? Does this say 5?  I am capable of something in the 5’s?

I used my Garmin and vaguely recall my watch beeping I had hit a full mile before I had actually hit the white line marking 1 mile on the track.  At the time I thought nothing of it.  I don’t know how precisely this track is measured, I thought.  I don’t know if I ran the shortest route.  It seemed perfectly logical that the Garmin would be slightly off from the track, but that my dear Garmin was correct and not the track.

Was I wrong?  Maybe. 

It’s hard to admit that a mile time I have been over-the-moon about for 2 years now might not reflect what my mile PR at the time should have been.  Would it have been faster? Would it have been slower? It’s a distinct possibility it could have been the later.

Why do I bring all this up?

Have you ever had someone complain to you that their Garmin said they ran XX:XX:XX and that the race course they ran most certainly had to be long?  I have – way too many times to count.  I’ll admit that I am even guilty of saying that my Garmin had me faster than the time on the clock and that the distance I ran was longer than say 26.2.  I always just assumed that I had not run the tangents on the course and that I had indeed run more than 26.2 miles on the course even though the course was probably exact.

My point in all of this is to bring to light the fact that your Garmin is not GOD.  The numbers on the Garmin are not as exact as you or I would like to think.  Further that any course certified by the USATF is certainly more accurate than the precious indispensable Garmin.

Need proof? Read this eye opening article In GPS We Trust.

That being said I ran my 6:11 mile on the treadmill this week and do feel the time was accurate, yet still “unofficial.” 

For the first 3 miles of my 5 mile run I ran an easy pace slowly increasing the pace. Mile 4 I increased the pace so at the end of the mile I was running a 6:11 pace before mile 5 started.  I did this to ensure that mile 5 was indeed a 6:11 mile.  I can tell you that it was the hardest mile I have run in I-don’t-know-how-long.  My thighs were burning, my arms felt heavy and every second seemed to feel like an eternity.

It got me excited for what is to come this year! 

After my last post Jim asked me:
Great advice on the tempo run on the treadmill … it’s probably the only saving grace for treadmills this time of year. I would love to hear your thoughts on treadmill paces … in general, do you think they are accurate? thanks – great post!

I certainly do think the pace on treadmills are accurate!  I’d venture to say that if they weren’t you would have some sort of class action lawsuit again treadmill manufactures – wink – wink.

As all of us know running on a treadmill is supposed to be easier than running outside, but for many of us it is not.  I believe that when you talk about paces and times in relation to a treadmill you have to say it was a treadmill mile, or a treadmill 10K.  I can’t simply say I ran a 6:11 mile without including it was on the treadmill.  Whether it is faster than I could run outside or slower is a good question. I am not sure the answer.  I personally typically have slower times on a treadmill than those I run outside.

Wardian after the Woodrow Wilson 1/2 Marathon 2010

I think I’m in good company when it comes to slower treadmill paces.  Local stand-out runner Michael Wardian ran the fastest treadmill marathon on record in 2004, with a time of 2:23:58.  I was at Pacers Running Store in Arlington and watched him as he set this record [which has since been broken].  His marathon PR is 2:21:37.  Meaning that he should technically be able to run faster on the treadmill because there is no wind resistance or hills to contend with, but can’t.


  1. Chris Duckworth says:

    I read somewhere that most road races add a little more distance – several hundred yards, at least – to their courses, just to be safe. So the 13.19 miles that my Garmin recorded at the Richmond Half Marathon might be my zig-zagging along the course, but it might also be due in part to an intentional, but slight, lengthening of the course by the organizers.

  2. Chris, the organizers wouldn't lengthen the course. The SportsBackers can't afford to do that. That would jeopardize their standing with the USATF, among other things. After 13.1 miles — almost 13.11 technically — an extra 0.8 is not much. That's actually pretty good accuracy. The point is, your Garmin isn't 100 percent accurate no matter which route you take.

  3. I ran a 5k once and was clocked at 18:29. My Garmin said 3.20. I approached others with garmins and it ranged from 3.13 all the way to 3.22. So many different variations. From my understanding, you always go with longest route. GPS works from pings and if you miss a ping it will appear short. So, if any of us in the 5k missed a ping or two, we still came up with an overage on our mileage. GPS readings can never be long, but can always appear short.

    The frustrating part, if you take my time and convert it to average mile time to an actual 5k, I ran my first sub 18 minute 5k…or did I?

    GPS is not accurate, but its the most accurate tool we have for hands on instant feedback.

    Garmin Forerunner 305 user since 2007!

  4. The Gittelman family says:

    I have the same issues with my Garmin. It always measures races long. I also figured it was because I wasn't running the tangents. I have adjusted the smoothing feature but to little avail. I'm just used to it now but it can be frustrating when it beeps before you hit that important mile-marker! I'll bet RD's get fed up with people coming up to them and saying, "but my Garmin says…." :)

  5. Brian Johnson (TheRunningMan23) says:

    I used to work for Garmin. I hired a lot of engineers for that company. The thing on your wrist gets it's info from several satellites miles above the Earth's surface…. Yeah, safe to say that global positioning isn't an exact science, just a useful one.

  6. great post. i agree, our garmins aren't exactly accurate. Congrats on a super fast mile post-3 kids!! you rock.

  7. When I was in my RRCA course, our instructor talked about that and said basically what the article said. So, it's useful, but not terribly reliable.

    As far as treadmills, I have to wonder how well they stay calibrated over time…

    Nice job on the mile though!

  8. Jim ... 50after40 says:

    Thanks for another great post … I try not to look at my garmin mileage during a race – it never matches the course and it freaks me out when it's off. I just look at it like, even if the course was actually off – I still gotta run it! Great job on the workouts!

  9. Gracie (Complicated Day) says:

    It sort of drives me crazy when people say courses are "long" by their Garmin. Besides the inaccuracy satellite GPS factor, we can't forget that courses actually ARE measured "long" for USATF certified races.

  10. I often wonder how accurate my Garmin is. I am debating whether or not to wear it in my marathon this Sunday. Sometimes it hurts me more than it helps me.

    Awesome speed by the way!!!!

  11. I've ran races with and without my Garmin….and to be honest, I prefer with – regardless if it is off by a few seconds. I prefer to avoid doing math along the course – especially at miles 16 – 24 – to take into account the difference between the clock & chip time. I use it as a guide….a much better guide than my brain late in the race!

  12. I always add 10 seconds to my Garmin's projected pace in races, because that seems to be where it hooks up to the mile markers. That article was very interesting, me and one of my running friends were discussing it once before and he was going on about Garmin having the same technology used in missile guidance systems and how accurate it must be… Apparently, not so.

  13. The Samson Family says:

    I agree, Garmins are always off. That's why I wear two watches during the marathon :)it's a little type A but more things to play with during the loong 26.2. I heard somewhere that the Garmin satellite signal gets confused on the track (not too techincal sounding but thats what I heard) so I dont like to wear mine there. you can def run a real 5:54 or faster though…:)

  14. I think garmins are pretty accurate on the road, but on a track the corners are so tight that the accuracy can be off +/- 5%. I definitely trust the track rather than the watch on that one. As for races, I think its very difficult to run the exact distance measured due to crowds or more open turns. If this adds only 1-2% to your distance, thats still .26-.52 miles added to your marathon!

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