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Garmin 910xt - footpod or GPS for pacing?

jalesliejaleslie
in General Training Discussions

I moved from a 310xt to 910xt at Christmas.  With the 310xt, I always selected GPS for "calculation" of current pace, which I of course use to pace intervals and races.  It always seemed to be pretty accurate, and my 1 mile lap paces seemed to line up with what I had been seeing for each mile.

The 910xt is giving me wacky current paces when using GPS....I mean....REALLY wacky.  Like, 5:30, 5:50, 6:30, etc....when I'm in the middle of an interval I'm trying to run at 7:45 for example.  (The ONLY time I run 6:00 is when someone is chasing me with something sharp!)  My ultimate lap pace will be around 7:45....but during that lap, I will have been seeing Peter Noyes or Matt Aaronson paces!  I'm learning to sort of ignore the ones that are really wacky, but then....what's the point of having that info if I can't trust it?  If I switch to footpod, I get much more consistent current pace.  Is it OK to use that?  Is it as accurate (distance-wise)?  What do you do?  

I'll try to find something on Garmin.com, but thought maybe others have already researched this and could help?

Thanks in advance.  JL

 

Comments

  • ezellrhezellrh

    FWIW (and having never used a footpod), I have current pace and lap pace up on most of my 910xt screens. I get strange readings on current pace sometimes too; but then I know I'm not going at a 5 minute pace. The only time I really care is when I'm doing my Wednesday interval runs, and then I have current pace/lap pace/lap distance only. Between those readings and RPE, I find I get pretty close on most targets.


    My only concern with the use of a footpod (again, hypothetical and NOT based on using one) is that I believe that the calculation is based on stride length. I worry about the proper calibration of that data point because logically I think my stride length MIGHT change based on the intensity of what pace/RPE I was aiming for. We'll save the discussion for whether it (stride length) should change for a different thread, I'm not a big form guy



    Don't know if this helps, but good luck either way.
  • Chris DavisChris Davis
    I get similar types of numbers from time to time on my 910. I've noticed them being closer to the beginning of an interval, and then they tend to get back to what I'm expecting the further I get into the interval. I've always thought it had something to do with a sampling error. For instance, when my arm (and thus the watch) is all the way back, it takes a point, and then the next point it catches is when my arm is all the way forward. It would make it look like my distance between those two points is my actual distance, plus the distance my arm traveled out in front of me, and thus the pace seems faster.

    And like Roy said, the footpod calc is probably based on an average distance per stride, and could be off by quite a bit depending on hills, wind, or numerous other factors. I tend not to trust the footpod numbers myself, except in keeping track of my cadence.
  • Bill BejinBill Bejin

    I have paced many marathons and any GPS / footpod is going to an have error.  (How many races have you done where the Garmin is exact for the race distance?)  I don't look at the Garmin for the first 400 because it is going to be wrong in both directions - too fast and too slow.  I only rely on the lap pace and PE because it does smooth over a longer distance.  I always enjoy how "fast" I am during the 30 sec. strides during the warm-up of a Wednesday or Sunday run.

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