• Mark Turnbull

Dr. Seiler's Hierarchy of Endurance Training Needs

Updated: Jan 7, 2020

What is the hierarchy and priority order of the various elements in endurance and triathlon training? Distinguished sports scientist Stephen Seiler has summarised what we know about this from practical experience and research studies in a presentation called "Seiler's Hierarchy of Endurance Training Needs"


Introducing Stephen Seiler 



Stephen is an American sport scientist who lives in Norway. He is famous for his work in endurance sports science.  Among other things he is known for his great research on polarised training.  He was the dean on the faculty of Health and Sport Scientist at the University of Agder, in Norway. He now works mostly as a Senior Research Consultant for the Norwegian Olympic Federation.  He is on the Executive Board of Directors at the European College of Sports Science. 


Dr. Seiler's hierarchy is a pyramid of endurance training, which consists of 8 layers. The large bottom layer is the number 1 most important thing in endurance sports.  The further up the pyramid you go, the less important each layer gets.  You should focus on the bottom of the pyramid first to reach your endurance goals. 


1. Training volume


It's a well-established fact that volume of training is the most important layer in the hierarchy. There is a study on 2,500 recreational runners looking at how their weekly mileage correlated to their velocity.As volume increases on the X axis from 20, to 40 to 60 miles per week, the pace that the runners hold becomes increasingly faster. 


Source: Stephen Seiler. Original source: Vickers and Vertosick 2016


Another example is a case study on Bente Skari, who is one of the best female cross country skiers of all time.  She is a 5 time World Champion, Olympic gold medalist and has 46 World Cup victories.  Seiler presents a chart of her annual training hours and how it correlates with her VO2max test results each season.  At 18 years old she was training 350 hours per year, this increases until she is 26-28 where she reaches her peak training 800 hours per year.  Her best VO2max results per season were mostly around 73-76 and all cluster around this time, from age 26-31, when she was training at least 700 hours per year. Her best VO2 max outside of those seasons was 70 when she was training less than 700 hours.  Overall, her VO2 max scores seem to correlate with her volume of training.  Seiler further references a study that compares world class with national level cross country skiers.


It compares their:

  • Intensity distribution.

  • Percentage of low, moderate and high intensity training.

  • Their percentage of speed and strength training.

  • Their total training hours. 


They found that the big difference in training was training volume.30% bigger volume in hours per year in the world class athletes.  In the presentation there is a useful chart of annual training volume of champion athletes from different sports.It shows that distance runners may have peak annual training volumes of 550 hours per year. Whereas, cross country skiers are more than 800 hours per year.  Rowers are close to 1000 hours per year. Cyclists are close to 1200 hours per year.  Swimmers are close to 1400 hours per year.  This shows that the less impact there is, the more hours you can do to be successful in the sport.  Triathlon combines high volume sports of swimming and cycling, and adds running to it, which makes you realise that triathlon is a sport that really rewards high training volume. 


2. High intensity training


The second layer is high intensity training, which is again something that has been well established. It's not new, for example, world class distance runner Paavo Nurmi from the 1920's did high intensity training.  It has been researched since the 1970's since Swedish scientist Per Åstrand began researching it.  Stephen Seiler and colleagues are trying to answer the question regarding an optimal structure for high intensity training. Personally, I don't think we can say this for sure yet, but there are indications from these studies that there may be an ideal way.  Further research is needed. 


Seiler and his group ran a study which compared different versions of interval training with cyclists, accumulating either 64 minutes in zone 3, versus 32 minutes in zone 4, versus 16 minutes in zone 5. Participants were asked to rate their session RPE (rate of perceived exertion).  The sRPE was the same for all of these sessions. This study was designed with a control group that did only low intensity training of 4-6 training sessions per week.  They increased their training time by 15-20%.


The other groups has 2-3 low intensity sessions, and 2 of these interval sessions.

  • Either 4 x 16 minutes in zone 3

  • Or 4 x 8 minutes zone 4

  • Or 4 x 4 minutes in zone 5


They didn't prescribe zones, they asked participants to complete the sessions with the highest average intensity possible for the entire session.  Basically, go as hard as you can but be able to maintain it.





They compared the results of performance changes on VO2 max, power at 4mmol lactate (~lactate threshold) and time to exhaustion at 80% of VO2max. They found that the group who did 4 x 8 minutes around zone 4 (just above anaerobic threshold) improved the most in all of the parameters. These effects were statistically significant in most cases.  Time to exhaustion was not.  This group showed 8% change in VO2max compared to 3-4% in the 4 x 4 and 4 x 16 low intensity groups.  Similar differences in power at VO2max and power at 4mmol lactate. The variance of individual response in the 4 x 8 group was smaller than in the other groups. Each individual had at least a moderate effect.  In the other groups some participants had a trivial effect only.  This study indicates there may be a sweet spot in intensity training. 


Another study investigated 20 well-trained junior cross country skiers.  They did 8 weeks of high volume, low intensity training as a baseline.  They were then divided into three groups;Long intervals.2 interval sessions per week at 91% max heart rate. This translates to 5-10 minute intervals with 30-45 minutes total work.  Short intervals.2 interval sessions per week at 94% max heart rate.  This translates to 2-4 minute intervals with 15-20 minutes total work. Control group. Added 2 low intensity sessions per week. Both interval groups rated session RPE and it was the same across both groups. When they measured changes in performance using VO2max and changes in lactate threshold they found that the long interval group had statistically significantly larger improvements.  This again suggests there may be a high intensity training sweet spot - slightly above the anaerobic threshold, but not quite all-out.  Looking back at the case study with Bente Skari, her training intensity distribution of moderate to high intensity training over her entire career was as follows:

  • 3.5% of her training time in zone 3

  • 6% in zone 4.<1% in zone 5


This shows that zone 4 may be a sweet spot, but more research is still needed to confirm this.  If putting an emphasis on intervals, aim for slightly longer intervals slightly above the anaerobic threshold.


3. Training intensity distribution


Training intensity distribution is also a well established factor that is considered important for endurance training. This comes back to the concept of polarised training, which Stephen Seiler is a pioneering researcher in.  Polarised training is defined as having most of your training time below your aerobic threshold - in Zone 1 in a three-zone system.  According to this model you do very little training between the aerobic and anaerobic thresholds (moderate intensity, zone 2) The high intensity training you do is at or above the anaerobic threshold (zone 3 if using 3 zones, zone 4-5 if using 5 zones). 


There are studies from Portuguese and French elite marathoners that show their training distributions as:

  • 78% in zone 1