Physiology, Podcast, Technology, Training

Physiology, Training, and INSCYD with Sebastian Weber (part 1) | EP#237

 June 8, 2020

By  Mikael Eriksson


In this Episode you'll learn about:

  • INSCYD's Power Performance Decoder (PPD) - a tool that can take any combination of data (lactate, VO2, or power only) and calculate VO2max, VLaMax and anaerobic threshold with a high degree of accuracy
  • The accuracy of the PPD, and how it compares to traditional lactate or ventilatory testing
  • The mechanism of calculating VO2max and VLaMax using power data only
  • The original VLaMax testing protocol, and why it's near impossible to "DIY" it
  • Best practices for executing the testing protocol
  • FatMax: confusions around the metric and what it depends on
  • Benchmark values (and realistic expectations) for VO2max and VLaMax for males and females
  • How physiological testing on the bike relates (or doesn't) to running and swimming

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What is the power performance decoder?

06:20 - 

  • The power performance decoder is basically a way to connect the mechanical power that is produced and measured by your power meter to the physiological and metabolic background of that power production.

    One can say that it is a refined version of the power-duration curve, which also provides us with the metabolic profile/fingerprint of the athlete.
  • The reason for why one should consider getting a power profile by the power performance decoder is to get an understanding of how the power is produced and in the next step, be able to direct the training towards what physiological/metabolic areas that requires the most improvement.
  • The power performance decoder has three pilers, which are anaerobic threshold (FTP), VO2max (maximum aerobic capacity) and VlaMax (maximum glycolytic capacity).

    All these tests can either be manually entered or be calculated by doing a few all out efforts of different durations.

    We have developed a specific protocol that contains a 20s, 3 min, 6 mins and 10-12 min all out efforts, and from this the Inscyd software can calculate all of these three pilers.

    The 20s test is mainly there to calculate VlaMax while the VO2max is calculated from the 3 min test.

    From the longer 6 min and 10-12 min tests are the anaerobic threshold calculated by doing a power-duration curve.

    In regards to the 20s test, it has become clear over the years that it is essential that this test is carried out in a very strict and specific manner in order to really be able to measure the maximal rate of the glycolytic system (VlaMax), and this power performance decoder make sure of just that.
  • One can improve the accuracy of the power performance decoder by adding lactate to the testing, however, the degree of additional accuracy is quite small, and for the VlaMax parameter it is not even greater with lactate compared to without.

    The margin of error for the VlaMax value obtained is around 0.5 mmol lactate per liter and second, this can be compared with the typical range of VlaMax of 0.3-0.55 where most triathletes are, hence, a value of 0.45 could then actually be between 0.4 and 0.5.

    For VO2max on the other hand, there is a margin of error of about 1 % when it is combined with lactate compared to around 2.5 % when only using power.

Getting a VO2max value from a power only test

34:50 -

  • When someone does a 3 min all out effort, we can be rather certain of that the average power produced is not entirely being produced from aerobic metabolic pathways, how big of an anaerobic contribution to the power vary tremendously between athletes.

    In order to determine how much of this power from the 3 min all out test that is coming from aerobic pathways, we enter the VlaMax value from the 20s test, and as we know this parameter the software can calculate how much power that is coming from the aerobic system, i.e. VO2max.

Spreading the all out efforts out or doing them all on the same day?

38:45 -

  • From a result perspective it doesn’t matter that much if one does all the efforts on the same day or if they are spread out over 2-3 days, maybe the 6 min and 10-12 min test can be suffer a little bit and one may not be able to squeeze out the best numbers one have on these two tests, but that won’t influence the results too much.
  • Despite this, I use to argue for spreading the tests out over multiple days as that would simulate a training situation more.

    We all know that we feel slightly different on different days and this also affects performance, by spreading the tests out, the test result will reflect your ”average physiological status” in training more accurately.

Parameters obtained from the INSCYD test and the interactions between these

43:10 -

  • After completing the INSCYD test one does not only obtain VO2max, lactate threshold and VlaMax values but also information about fat (FatMax) and carbohydrate (CarbMax) combustion.

    These ”sub categories” of parameters are highly dependent on the three pillers and cannot change much on their own without VO2max, anaerobic threshold and VlaMax changes too.

    For example, one can increase your FatMax either by increasing VO2max or decreasing VlaMax, an increase and decrease respectively in these two categories will come with an increase in FatMax as a mandatory consequence.

    An exception from this could be anaerobic threshold in running and swimming, which are two sports that are highly dependent on work economy, then an increase in threshold can be seen without obtaining changes in VO2max and VlaMax and would then hence be to an improved working economy.

Typical INSCYD values for amateur athletes

50:15 -

  • For recreational and beginner athletes, a VO2max of 40 ml/min/kg would be a rather common value.
  • For more experienced age group athletes such as Kona qualifier, their VO2max values start typically at around 60 and can in some cases reach 70.

    An athlete training around 10 hours per week in general has a VO2max of around 60.
  • For professional athletes competing on Kona, 75 would be a typical value.
  • For females, the values are about 5-10 units less compared to the males.
  • In regards to how you should interpret your test results, for long distance triathlon, VlaMax and FatMax (closely linked to each other) is far more important than VO2max.

    Often one does not need to target VO2max specifically in training as this parameter tend to go up over time as training volume increases and/or accumulates.

    What also needs to be stated out is that a higher VO2max enables a greater improvement potential by affecting VlaMax.

    For instance, an endurance athlete with a VO2max of 40 and a VlaMax of 0.7 should focus his or hers training solely on improving VO2max as even though the athlete manage to decrease VlaMax to desirable 0.3-0.4, VO2max is too low to take advantage of an optimal VlaMax.

    An athlete with a VO2max of 60 and the same VlaMax of 0.7 should therefore direct his or hers training on improving VlaMax as the relatively high VO2max in combination with a better VlaMax would ”open up” for great improvement in lactate threshold as well as longer endurance performance.
  • It is really difficult to translate the parameter values from one sport to the other, for instance biking to running or vice versa, it will be somewhat in the same ballpark but it could still vary greatly.

    In general, one can say that your VO2max on the run will be the same or higher compared to the VlaMax on the bike (not lower).


Mikael Eriksson

I am a full-time triathlon coach, founder of Scientific Triathlon, and host of the top-rated podcast That Triathlon Show. I am from Finland but live in Lisbon, Portugal.

Please contact me if you have feedback on the podcast or want to make suggestions for improvement or send in a question for a Q&A episode.

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