[152] The curse of the GPS watch

Well, this hasn’t quite worked out like I had planned.

Last Wednesday I received my new GPS watch – I decided on the Timex Global Trainer due to mostly positive reviews and a price that fit my budget. So far it has let me down on both of the runs I’ve used it on – an easy 5.5-miler in the neighborhood on Friday and my 22-mile long run on Saturday. On the shorter run it measured my course a half-mile short. I gave it the benefit of the doubt because it was very cloudy and rainy that day. But the fact that it came up almost a mile short on my long run was frustrating because the weather Saturday was picture-perfect – clear and sunny.

Aside from the shortage on the length of the course, the pacing was all over the place, too. Now, let me say right here that I am fully aware of how inaccurate GPS can be when taking spot measurements of pace. (Read this article to find out why GPS can be so inaccurate – and thanks to David H. for sharing it with me!) But on Saturday’s run it was even throwing me off with the mile splits, ringing up 7:50s and even 8:00 when I knew I was running faster. Obviously, when the course measures short and the same time has elapsed, the watch is going to tell you that your mile splits are slower than they actually are.

Even though I rationally know how reliably unreliable a GPS watch can be, I still let the numbers start to get to me. My effort started to increase as I saw the mile splits pop up slower than I anticipated. My easy long run was becoming more of a challenging workout as I started pushing the pace. As the miles ticked by I found myself losing hope in my ability to actually achieve my marathon goal – if I was finding it so hard to produce 7:30-7:40 miles during this run, how was I ever going to run twenty six 7:15s in a row on race day? I questioned my race strategy and was ready to publicly throw in the towel on my goal of sub-3:10.

When I was done I was frighteningly disappointed and discouraged. I grew frustrated and even yelled at other drivers on the way back home – the complete opposite of the usual post-long run, endorphin-fueled bliss I experience every week. But when I got home and checked my GPS data against a more reliable map I discovered I’d actually had an awesome workout – I covered 22 miles at a 7:22 pace, only 7 seconds per mile off race pace. Suddenly it made sense – this pace was right in line with the effort I felt like I had been giving. My mood shifted instantly and I was almost trembling with happiness – the endorphins were back and I was riding high on a new wave of confidence about meeting my goal.

But here’s the thing – I always knew I could produce a run like this. If I had just run like my body had wanted to run I would have achieved the same result. Having the numbers staring back at me from the watch messed with my entire mental focus. Suddenly I wasn’t thinking about matching my effort to the terrain or running with a fluid motion. Instead, I was merely trying to make certain numbers appear on the display. And when they didn’t appear, I let the watch convince me that I wasn’t living up to my potential and would perhaps have to rethink my goal.

That’s a scary thought – that a simple watch with a known likelihood of error could make me question myself and a goal that I’m serious about. So I’m considering divorcing myself from the watch after our short-lived fling. I’ll probably hang on to it and use it for a few more runs as I try to figure out its idiosyncracies. But I won’t be investing myself in the real-time numbers it displays during a run, and I don’t know if I’ll be using it on race day. If it’s wrong during the race it could cause me to push harder than necessary early on, ruining my chances for a strong finish.

I bought the watch to help me zero in on my race pace, because with a goal this big I want to be sure I’m doing things right. But, happily, it turns out that my body already seems to know what it’s doing. It looks like I just need to have a little more faith in myself and realize that the technology is not what’s going to get me to my goal.

Bike: 19/166.2 miles
Run: 29.8/182 miles
This entry was posted in biking, marathon, progress, running. Bookmark the permalink.

5 Responses to [152] The curse of the GPS watch

  1. steena says:

    It’s too bad the GPS caused you all that commotion. The watch can be handy, but I agree it can really mess with your head too. To this day I still wish I would have turned my Garmin off before the start of Chicago Marathon last fall.
    You’re lucky that you have a good feel for pace and effort, you’ll be more than ready without the GPS on race day.

  2. David H. says:

    You should read Matt Fitzgerald’s book about the mind-body method of running – http://www.amazon.com/RUN-Mind-Body-Method-Running-Feel/dp/1934030570. It’s a great book. While I’m not going to ditch my watch, that book helped reassure me that training plans are flexible and it’s best to run whatever you feel like doing.

    Most GPS watches really lack in the real-time pace, but the overall mileage pace is more accurate.

  3. jnkmiles.org says:

    The things mess with your mind like a bad drug. It’s horrible….My Garmin has gone wacky and had me running 11 min/miles when I knew I wasn’t. I’ve tried really hard this year to run more off RPE and then guess my pace based on my effort when the miles ding…I’m getting better, but I really don’t like racing with the watch because it messes with my head so much. I figure I’m doing the best I can so it doesn’t really matter what the watch says…

  4. Mark Bare says:

    Jeremy, I’m not sure if your watch has a way to calibrate the distance or not. With the Garmin, you go to a track, go through some calibration settings, walk a mile, hit stop, and it more accurately dials in the distance. I’ve gotten pretty accurate numbers with mine on known distance runs. Shamrock Half was 13.2, on the money for the first half with the mile markers, then it slowly started measuring the miles a little early. Easy enough to understand the pace from the watch was slightly faster than my real pace. A whole bunch of people wearing Garmins had the same exact experience, accurate for the first half with a 13.2 overall distance.

    My overall watch pace was 7:35, official pace was 7:37.

    At the Richmond Marathon, my Garmin measured 26.4 with a watch pace of 8:29 and an official pace of 8:33.

    I had no confidence in the numbers at the Bear Creek 10-Miler. Zig-zaggy, up-and-down course in the woods.

    See if you can calibrate your watch, and if not, return it. Nothing more expensive than tech gear that doesn’t work.

  5. Rebecca says:

    I can relate to that sense of panic when your effort doesn’t match your splits. I use my Garmin was a guide, but I often leave it at home when I don’t want the mental burden. I always wear it in races, though, because I zone out and forget where I am distance-wise.

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