Exactly How Far Did You Run?
Some people are better judges of distance than others. This assumption was put to the test in a study published in the Journal of Strength and Conditioning Research where 100 subjects completed the run of their choosing and then reported the distance against GPS tracking.
Although there weren’t large differences between reported and actual run distance, the variation did exceed 10% which was outside the range of error. If you’re just running for exercise, this is no big deal, but if you’re deep into very specific training wearing a GPS device might help keep you on track.