Podcast, Science and Physiology

Training talk with Sebastian Zeller | EP#259

 November 9, 2020

By  Mikael Eriksson


Sebastian Zeller

Sebastian Zeller, PhD, is a full-time triathlon coach with a strong background in sports science. In this training talk we cover a number of key topics on endurance training, and Sebastian goes into detail on his approach and methodology.

In this Episode you'll learn about:

  • Sebastian's coaching approach
  • Using lab testing to individualise training
  • Training structure and appropriate use of different intensity levels
  • Key markers of performance: VO2max, VLaMax, FatmMax, Anaerobic Threshold, Lactate Minimum
  • The impact of muscle fiber type (fast twitch and slow twitch) on training
  • Using Heart Rate Variability to analyse training
  • Projects on carbohydrate combustion and ketones with Bora Hansgrohe cycling team

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03:00 -

  • My name is Sebastian Zeller and I am a 35 years old sports physiologist and coach from Cologne, Germany.

    During the years I have both taught sports science at the University, done some research as well as been working as a coach.

    Nowadays, however, I am a full-time triathlon coach, who coach both professional athletes and age groupers.

Coaching philosophy

04:55 -

  • As a sport scientist, I am a little bit ”against” the term philosophy, I see it more like different kinds of coaching approaches or strategies.

    First, I always put the athlete first and the final decision is always up to the athlete, which I think is an important part of the education process of the athlete since in the end, it is the athlete that takes all the decisions during racing and hence, he or she needs to really know his or hers body extremely well.

    Second, in the world we live in today with plenty of information circling around everywhere, you’re almost also like a performance or sports scientist consultant as a coach today, which requires you to be able to filter all the information out there and explain to the athlete why we need to take a certain approach.

    Third, education is another central aspect of my coaching approach, I want my athlete to know why we are doing certain workouts, the purpose with them etc.

    Fourth, I try to convey to my athletes that most success comes by doing the basics right, so I try and focus on making sure that all my athletes are really doing the most simple things 100 % correctly before moving on to more ”fine tweaking”.


15:05 -

  • For me, having accurate and reliable tests are massively important if one wants to use tests in one’s practice, therefore we are still doing most of our testing in the lab.

    In the lab we do a combination of three tests, a step test for measuring FatMax, a ramp test for establishing VO2max and a lactate minimum test.

    In general we test our athletes every 8-12 weeks (professionals slightly more frequently), and every test is preceded and followed up by a specific training intervention, for instance increase VO2max, improve FatMax etc.

    So after a test, a ”weakness” or improvement opportunity is identified, which we target in our next training block (8-12 weeks), and after that period of training we retest to make sure that the training intervention was successful and at the same time we can identified a new training intervention for the next upcoming training block.

    We also do tests prior to Ironman races in order to find the right pacing and nutritional strategy for the athlete.
  • In my opinion, VO2max is one of the most important parameter for endurance performance, and hence we are highly focused on this parameter.

    For Ironman racing, we also know that FatMax is very important as well.
  • Strategies that we implement for improving VO2max does not only include volume, instead we look a lot at the intensity distribution and in particular accumulated time over 90 % of VO2max, which we have found to be really crucial in order to develop an athlete’s VO2max.

    In my opinion, how difficult it is for an athlete to hit 90 % of VO2max seems to be mostly related to how high of a VO2max the athlete has.

    Different athletes reach 90 % of VO2max variously quickly or easily, and we use our tests to determine at which power every athlete hit 90 % of VO2max.
  • We also monitor VlaMax really carefully, especially leading up to an Ironman race, since we know that this parameter is really important to have in the right place before and Ironman.
  • In regards to FatMax, on average, our athletes have their FatMax at 68 % of FTP, but this can also vary quite much from athlete to athlete, but most people have their FatMax right in the middle of the endurance training zone.
  • For athletes not having access to laboratory tests, I think that doing a 20mins test on the bike could be a good way to assess if one has progressed, and the same applies for running.

    To evaluate progress in VO2max, power over 4-5mins can be used, as that is a good proxy for VO2max.

Implications of different muscle fibre distributions 

34:30 -

  • One good way to find out if an athlete has a large or low percentage of fast twitch muscle fibers is to have a look at the VlaMax.
  • If the VlaMax is high (a high anaerobic capacity), then it is likely that the athlete has a large proportion of fast twitch muscle fibrers.

    Leading up to an Ironman, these muscle fibrers’ oxidative capacity needs to be improved (i.e. lowering the VlaMax), which we mainly do by medium intensity work (sweet spot training) in combination with high torque (in form of low cadence on the bike).

    When we are focusing on lowering the VlaMax, then maybe 3-4 sessions per week are dedicated to this purpose and we are not only trying to maximize the response by training intensity and specific torque targets but also by nutritional means (going into the sessions fairly glycogen depleted).
  • For athletes with a low VlaMax, this can become an issue when it comes to trying to increase the VO2max during certain periods.

    Then we are trying to increase the VlaMax, mainly by weight training, in order for the athletes to be able to easier hit 90 % of their VO2max during intervals and hence be able to provide a sufficient stimulus to the VO2max system.

    Having a too low of a VlaMax can also pose an issue when it comes to the stress high intensity training puts to the body, if the VlaMax is low, then the aerobic system gets very overloaded during high intensity workouts, which takes plenty of time to recover from and can hence not be done too much of.

    By increasing the VlaMax, one can then raise the ability for the body to tolerate more high intensity training, which in turn may be necessary to provide a big enough stimulus in order to raise the VO2max.


47:25 -

  • There aren’t much research conducted on periodization, which I personally would like to see more of, and this makes this subject a bit tricky to relate to.

    I think age groupers can benefit from periodizing their high intensity training, and this approach I therefore implement for many of my amateur athletes that I coach (generally I prescribe 5 high intensity workouts per week during these periods, since the total volume of training during these weeks are quite low, they are also rather easy to combine with a family-work life).

    For professional athletes, I think the total volume of training is more important and therefore I don’t tend to use a periodization approach towards pro athletes.

Medium intensity training

52:45 -

  • Even though I am a fan of polarized training, I do think that medium intensity training does play a role (in addition to a means for lowering VlaMax) in triathlon training in some situations.

    In the weeks leading up to a race (primarily Olympic and 70.3 distance races) I think tempo and/or sweet spot training is very important as this is highly specific to race intensity.

    I also think these workouts can be really good from a mental aspect, you need to concentrate during long intervals (preferably in the aero position) and ”getting comfortable being uncomfortable”.

    In the phases leading up to a full distance triathlon, I wouldn’t, however, focus too much on medium intensity as that would not be race specific, instead I use to focus more on the fat and carbohydrate metabolism.

Tracking training

55:00 -

  • The two most important aspects that I keep track on is training volume and intensity distribution.

    Overall volume is probably the most important factor, but how this volume is distributed intensity wise is also very crucial.

    Moreover, I have recently also started to track heart rate variability (HRV) as a tool to monitor the athletes’s state of recovery.

Working together with Bohra Hansgrohe cycling team

01:00:00 -

  • In the first project with the Bohra Hansgrohe cycling team we focused on carbohydrate combustion in the cyclists, trying to calculate how much carbohydrates the cyclists burned during easy aerobic rides as well as during high intensity sessions.

    This expenditure could then be used as a guideline for nutritional choices in the athletes.
  • In the other project we investigated in what capacity the use of ketones could have for potential place in endurance sports, in our small ”study” we saw no such indications (instead the opposite).

Final advice

1:06:15 -

  • For people living all year around at altitude, I think it is important for these athletes to do training camp at sea level in order to execute some really high quality training.

    I don’t think it is desirable to stay on altitude all year around, but it is probably extremely beneficial to stay most of the year at altitude and during some periods of times come down to sea level for training and/or racing, much like the African runners do.

    The same recommendations on when to go back to sea level for a race (at sea level) applies for people living at altitude as the athletes being on altitude training camps.

Altitude tents and chambers

1:10:00 -

  • First, make sure to get the basics right!

    The basics include consistency, have a certain degree of volume with a certain intensity distribution and don’t burn too many matches too early in a big training block leading up to a race.
  • Have a concept, which you adapt from time to time (bring new stuff into the process as this creates a bit of excitement, new stimulus and increases motivation).
  • Be humble, it’s just sport!

Upcoming project

01:07:50 - 

  • Currently I am just about to start getting really into how to manage heat adaptation, in order to be able to give my athletes the best advice going into the Ironman World Championship in Kona.

Rapid fire questions

1:08:40 -

  • What is your favorite book, blog or resource related to endurance sport? ”The Science of Winning” by Jan Olbrecht.
  • What is a personal habit that has helped you achieve success? Not giving up and finding my way.
  • Who is somebody that you look up to or have inspired you? Dan Lorang, who is a very honorable man and a very nice human being as well.


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.

If you are a long-time listener and appreciate the value the podcast brings, please consider taking a couple of minutes for leaving a rating and review on iTunes/Apple Podcasts, or wherever else you can think of leaving a rating and review.

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