Fishermen have a long reputation for being stretchers of the truth. They’ve been known to exaggerate the size of the epic catch years ago, or – even better – the one that got away. But here’s something that hasn’t made it to mainstream common knowledge: Runners lie as badly or worse than any angler in history.

When a running buddy asks you to join him or her for five miles at a 10-minute pace, be prepared for six and a half at 9:30. This principle applies across all levels of the athletic spectrum, from the super fast to the casual run / walker. Scientifically speaking, I’ve noticed a fib factor of around 20%, though it can certainly go higher.

I confess that I’m an offender myself. A few days ago, a friend and I set out for what I said would be six by 800-meter repeats. Finishing the fifth one, I announced “only two more.” She wasn’t even surprised. And just this morning I told my wife I was going out for six or seven miles. The final tally? 8.2.

Unlike fishermen, whose tales exceed reality, runners misrepresent themselves in the opposite direction. I’d like to believe that’s because we’re people of such high integrity. More probable it has to do with the ease in which our exploits can be fact checked. Apps like Strava, Garmin Connect, and Nike Fit keep us honest, and race results are posted online for anyone to see. Saying you ran a four-hour marathon doesn’t hold up to scrutiny when the official event website shows 4:35:19. Internet-connected surveillance cameras on deep sea charter boats might have the same effect.

The big question is “Why do runners say they’ll do less and then do more?” Perhaps because actually running is way more fun than thinking about running – at least up to a point. Six miles might sound daunting when you’re pondering it, but when you get to four, and your breathing is rhythmic, your legs are moving like a fluid machine, and you’re enjoying the scenery … well, heck, it’s just a little farther.

So if you’re ever in a bar and a fisherman and a runner walk in, there will no doubt be interesting conversations all around. But don’t believe a word either of them say.