GPS Depression

GPS devices have become increasingly common among runners over the past couple of years, and we train with many people who use them on a regular basis.

The devices are supposed to take the guesswork out of gathering information from each day’s run – but many times, they can create just as many questions as answers.

Here’s a typical conversation after the group completes our usual Friday morning route – and keep in mind that we’ve all run the EXACT same course:

While we’re stretching in the parking lot, Dave will start by asking, "Just how long was that run?"

Andrew will look at his GPS device and say, "I’ve got 6.78 miles with 1,142 feet of elevation change."

Jim will look at his GPS and say, "Mine says 6.62 miles with 988 feet of elevation change, with an average pace of 6.33 minutes per mile."

Jon, our resident scientist, will say, "Mine calculates it to 6.8417834290876 miles with 1,045 feet of elevation, an average pace of 6:45 per mile, average temperature of 38.6 degrees, and our correlation coefficient speed of inertia had a Beta factor of 1.23.”

(Or, at least, he says something like that – sometimes we don’t catch all the details.)

That’s when Dave yells, "HEY - I just wanted to know if we’ve been gone more than an hour! I have to get to work!"

It’s easy to see how the advanced technology can cause us to lose the forest for the trees. It’s also been known to cause cases of GPS-related paranoia and/or depression among long-time runners.

Think of it this way: what if somebody from your college called to tell you that after reviewing your transcript, they realized that you were actually 2 units short of graduation. You didn’t really complete the work you thought you had, and they were revoking your diploma as a consequence. You’d freak out, right?

That’s sort of what runners feel like when using GPS devices for the first time. Suddenly, all of our runs become shorter than we always assumed, and our mileage totals don’t add up to the same numbers we’re accustomed to.

For example, the distance of our regular Friday run was historically agreed to be 7.5 miles. We have years of training logs attesting to the fact that we ran 7.5 miles every Friday. So you can imagine our horror when the first GPS readings from this run registered 6.7 miles.

The situation becomes even more nightmarish, as the GPS almost NEVER says a run is longer than we thought – only shorter. Our 13-mile Tuesday run is actually 12.7. Our 7-mile Wednesday run is merely 6.3. Worst of all, our crucial 20-mile marathon training workout may not even be 19 miles.

After all these years of running, we suddenly found out that we owe a lot of mileage to make our training logs accurate. When we thought we were 50 mile-per-week runners, we were actually only hitting the mid-40s. When we were proud to log 80 miles per week, it might have only been 74. It’s enough to drive runners towards antidepressants.

Some of the discrepancy can be chalked up to innocent confusion over certain distances. Before GPS, we’d drive road routes in our car to measure the mileage, or guess at trail distances based on our pace, and come out with close estimates. Then we’d do some rounding. 6.84 would round up to 7, and 5.06 rounded down to 5. We figured that over a long period of time, the occasional overestimates and underestimates would cancel each other out – and it made the math much simpler that way.

However, the short GPS readings can also be attributed to real live, honest-to-goodness scientific inaccuracy. GPS devices come with some inherent technical limitations based on their mode of operation. They can intermittently lose their satellite signal - particularly on routes through canyons or with a lot of tree cover - and need some lag time to recover. The distance you run while the antenna is searching is “uncredited”, and doesn’t count toward your overall mileage.

(While training routes seem to always be short by GPS, it’s interesting to hear GPS users claim, “the course was long” after doing a race. Over any course with lots of turns or curves, it’s very easy to measure a few tenths of a mile long if you’re not taking all of the tangents. Sometimes you just can’t please a GPS’r.)

Thankfully, we’ve also become familiar with the Beta factor, which seems to be just the anti-depressant we’ve been looking for. After one morning run measured remarkably short and caused much consternation among the group, Jon – remember, he’s our scientist - plugged his GPS into a computer running analysis program and calculated a Beta factor of 1.23 for on our 6.8 mile run.

What the heck does this mean? Well, taking in to account all the hills along with our speed, those 6.8 miles could be multiplied by 1.23 to arrive at an actual “training value” of 8.4 miles. As you can imagine, we absolutely love the Beta factor!

Of course, we still face the same training log dilemma. Do we record 6.8 miles, or 7.5 miles, or 8.4 miles with an asterisk? It all seemed a lot easier when we just wrote “one hour run.”

Actually, there’s nothing that prevents us from going back to the way things used to be. Some people will swear by GPS and never go without it – but the real joy of running is in the experience, not in the numbers. It’s something that all of us - whether we embrace the new technology or not – should always keep in mind.


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