Running Tips From iRun’s John Ruibal


Why does my GPS read 3.35 miles after my last 5K?

As more and more runners use GPS technology, this is becoming a common question. Race courses are measured by following the “tangents” of the course. Tangent is measured in straight-line distance. In a nutshell, this means that if you tend to run the curves, moving quickly to the left or right after a turn, you are probably running farther than the course distance. 

To understand this, think of running on a track. The track distance is calculated by the first (inside) lane, so every lane you run out from the first lane adds another 10 meters on to each lap. If you run in the middle of the track, every lap will cost you an extra forty meters – that adds about 500 meters to a 5K.

Here are a couple of tangent tips to finish your race closest to the measured distance:

  • Preview the course you are about to run. Take the time to look up the course prior to getting to the race. The bigger wellknown races will have their course and elevation posted online. The smaller races should have a course map when you get to the race. You can also preview the race by running the course easy for a warm up. Review all of the turns on the course and draw straight lines from turn to turn. These are your tangents.
  • Visualize the tangent when you are running the course. Be prepared for turns on the course. Remember that the shortest distance between two points is a straight line, so visualize your line from one corner to the next. If you have just made a righthand turn and your next turn is to the left, start to slide to the middle of the course.

If you run in major marathons like New York, a blue line is painted where the course is measured. All you have to do at these races is follow the blue line and you will be running the shortest distance.

iRunJohn Ruibal, MS, RD, CSSD, LD, is a registered dietitian and is board-certified in sports nutrition from the Academy of Nutrition and Dietetics. He coordinates the distance running classes available at both iRun Texas locations in San Antonio. He has been running for more than 40 years and coaching for 25. To connect with John or learn more about his classes, visit

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