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How to Break Your Marathon PR Using an Individual Fuelling & Pacing Strategy

Updated: May 24, 2022

The Running Power-Performance Decoder revolutionizes running training. But this isn’t where it ends. A lab level accurate metabolic profile allows to create an individual fuelling & pacing strategy to break your PR. Here is how…

Bernat Xamena tried to run a sub-3 marathon in Barcelona, but he blew up after 30 km. His coach concluded: “Bernat had nutrition issues and also started too fast.”

After a lesson learned the hard way, they were ready to do things properly this year. They chose to do an INSCYD test three weeks before the race.


Xamena’s coach Jo Spindler (Trisutto) : “We did the test on a track, so the closest possible to a race scenario. For me, this is the beauty of INSCYD: you can test in real-world conditions, you don’t need to go to a lab and you don’t need a treadmill.”

Based on the test results, it was clear that Xamena should be able to run 4:08 per km, and have finish in 2 hours 54 min for the whole marathon.

“With the INSCYD tests I was able to calculate exactly the highest pace my athlete was able to run without running out of energy." JO SPINDLER Running Coach


After the race, Xamena sent a pretty eloquent picture of his pace breakdown to Jo: average pace: 4:08 per km. Total 2:54:19. Job done!

The screenshot Bernat sent to his coach Jo after the race.


But how did they really predicted the result so precisely using INSCYD?

“I looked at how many carbs Xamena would burn to sustain a certain speed, according to the fat and carbohydrate combustion chart. At the prescribed speed of 4:08min/km (= 4,04m/s) he burns 187g of carbs per hour, so 561 over the entire marathon.” (Read more about using fat and carbohydrate utilization in runners in this blog.)

Example fat and carbohydrate combustion chart

“We planned his race nutrition with a supplement of 60g of carbs per hour after the 1st hour. So that gives him 120g for the marathon (1st hour: 0g / 2nd: 60g / 3rd: 60g). Therefore, to sustain the effort, he needed about 440g of carbs stored in his body (561 minus 120). The INSCYD test report showed that this is realistic for his level and body composition.”

"When you need to predict the final outcome of a race (and understand how to get there), INSCYD is the number one tool you have to look at." JO SPINDLER Running Coach


Using INSCYD and getting the data Xamena’s coach used has never been so easy before with the Running Power-Performance Decoder.

It eliminates the barrier of access to a testing lab, by capturing all the data you would get in a lab – and more – in a simple field test. The only thing you need: a GPS watch.

Although only a GPS watch is needed for the testing, the PPD-R software is able to use and compare lab test data (e.g. VO2) and field tests (e.g. lactate measurements).

“With the help of the INSCYD software, I have been able to cater my training to my own unique energy systems." LIONEL SANDERS Pro Triathlete


  • VO2max (maximum aerobic capacity)

  • VLamax (maximum anaerobic capacity)

  • Anaerobic Threshold (FTP)

  • Lactate accumulation rate at high intensities

  • Lactate recovery rate at low intensities

  • FatMax (intensity at which the runner burns the most fat)

  • Fat and carbohydrate utilization at any intensity (kcal/h and g/h)

“I use VLamax as the main parameter to prepare the training.” DAN LORANG Coach of World Champion Triathlete Jan Frodeno, Anne Haug & Team BORA

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