Before I got a GPS watch, I imagined they were all about the summary – how long was a run, what was the total time. Now that I’ve had one for a while though, I’ve realized sometimes it’s the interim information that makes them really worthwhile.

This past Saturday, for instance, I did a long event that was well laid-out (a surface-measured course is plenty-accurate to know your overall distance) and very well managed (chip timing is definitely more accurate than punching buttons on a watch as you navigate the start crowd, or trying to remember to do the same at the moment you cross the finish). There was no need at all for a GPS to tell me how I did overall, but boy did it help me make my goal – especially after my water-bottle kept popping out of my belt until it’s drinking lid shattered on the pavement and the thing got tossed in the gutter, from which point I stopped in at nearly every aid station to hydrate.

Thanks to GPS, I could see in the middle miles that I was running about fifteen seconds faster than my overall goal pace, so that should allow for slowing down and drinking – but I could have figured that out with a stopwatch and mile markers.

What I could not have figured out that way though, is that my perception of my pace got totally skewed after every aid station. I’d get my drink and toss the cup, and a hundred yards or so down the course I’d feel like, ‘OK, I’m back up to pace’. Looking at my GPS though, I’d see that what felt like the right level of effort and difficulty, was actually one or two (or more) minutes slower than I had been doing just before the aid station. And with every passing mile, that false sense of pace seemed to get more drastic (nothing surprising there – it’s called fatigue…).

Once the GPS gave me that news, it also helped my do better. Each time I looked down and saw a number that put the lie to how I felt, I’d focus on cadence – visualize my feet moving back and forth as fast as possible below an upright and stable torso. After I’d done that for a ways, I’d visualize my heels coming up higher and my strides stretching out a bit, but still snapping just as quickly. Time and again, I was able to get back up to pace within a fraction of a mile, and as I got used to ‘The Aid Station Effect’ I made that recovery more and more quickly, knowing what was happening and what I wanted to do about it.

Without GPS, I’m pretty sure I would have relied on that (false) perception of effort, and my pace would have gotten slower and slower thru those late miles. With it, I had the data to push through discomfort and momentary sensation, and ask of my body what training told me it was capable of. I was able to finish strong and make my goal, thanks in large part to the nearly-instantaneous feedback from that little electronic marvel on my wrist.

Now, if I can only do something about that water bottle-belt….