The beginning of any year is a good time to assess where you’ve been and where you want to go.
In January 2024, Dr. Stephen Seiler tweeted a simple post (above) which included what he described as “30 years of thinking about and studying endurance training distilled down to 12 lines.”
Now, with Dr. Seiler’s help (and slides from his presentation), we will look at each of these “12 Truths” a bit more closely. Consider them Dr. Seiler’s endurance training best practices, based on a lifetime of observation and experimentation.
1. Start with universal good practices, then be sport specific, then add individual optimization
There are universal practices that carry through all endurance sports. However, not all sports are created equal. What a runner might do, in terms of volume, is not the same as what a cyclist might do, which is not the same as what a cross-country skier might do. It isn’t an apples to apples comparison, as illustrated below.
Next, remember that what works in general doesn’t necessarily work for the individual. The best training plan is one that takes into account the specific needs of the athlete, the given attributes he or she possesses, and the demands of the event he or she is preparing for.
2. Training is an optimization challenge, not a maximization challenge
Athletes are always training their cardiovascular systems, their brains, and all the way down to their muscle tissue. But the training process is two-fold: it is both a signal for adaptation at the cellular level, and a driver of physiological and psychological stress responses at the systemic level. The former adaptations take the form of biochemical and molecular changes; the stress can lead to muscle damage, inflammation, psychological fatigue, and a host of other issues.
Therefore, the training process is not a process of maximization, but rather optimization. It is about finding the right balance between signal and stress over time.
3. Focus on the big things first, not marginal gains. Think Maslow’s Hierarchy. That solves many problems.
Maslow’s hierarchy of needs is a psychological theory that outlines five levels of human needs, starting with the most basic physiological needs (like food and water) and progressing to higher levels like safety, love and belonging, esteem, and finally self-actualization, where individuals strive to reach their full potential; essentially, the idea is that lower needs must be met before moving on to higher ones.
Dr. Seiler has taken this hierarchy of needs and applied it to endurance training priorities (below). On the right side he also indicates the strength of the effect and the strength of the evidence that supports his conceptualization.
To simplify this further, Seiler stresses a three-part recipe for endurance training:
- Frequency
- Duration
- Intensity
And the order conveys the importance. To build a foundation for performance, you have to start with frequency. Once you solidify both the habit of getting out the door “X” times per week, and the ability to recover and manage the stress of this habit in your life, only then should you start lengthening some of these training sessions.
After you extend the duration—and you are able to recover and manage the stress of this habit within the context of your life—then you can begin to work in more intensity.
4. A consistent and sustainable training process eats epic interval workouts for breakfast.
The real foundation for success in endurance training and performance is staying healthy (acknowledging that health is a relative term). If intervals lead to significant gains but also increase the risk of injury, that must be taken into consideration.
Training methods that place an emphasis on consistent good habits and health-first practices yield the highest potential return on your investment. This is building with intention, rather than with impact.
There are many factors that come into play when considering the physical and mental health of a training athlete (below). Think like an engineer to methodically craft your progress, instead of hitting yourself with the jackhammer each and every time you do a workout.
5. Simple metrics like program compliance tell us a lot. Keep the monitoring simple.
Why do we monitor training? Dr. Seiler believes there are four reasons to use simple metrics to track your progress.
- Verify prescription execution—because prescription does not equal execution!
- Individualize and revise the training prescription
- Detect any deviation and deterioration from the prescription (and do it early). Ever the minimalist, Seiler likes to color code this self-assessment: GREEN = muscular fatigue; YELLOW = autonomic nervous system imbalance; RED = endocrine function disruption. Which color are you feeling each day?
- Quantify development and document the process.
Throughout the training process, you should ask yourself simple questions:
- How do I feel?
- How am I responding to the training?
- Should I (and my coach) make adjustments?
Finally, at the end of a season, count up the number of training sessions that went as planned. How many green days? How much time spent in the yellow zone? Did you ever tip into the red?
In Dr. Seiler’s illustration of the monitoring technology “Stairway to Heaven” (below), he walks through his ideal stepwise logic of training assessment.
Start with an effective tool for measurement. Make sure it’s easy to use so you are more likely to use it consistently. This will have a positive effect on your behavior and your ability to make informed decisions. And this, of course, will lead to better health, function, and, ultimately, performance.
6. Good scientists, coaches, and athletes all share curiosity, deliberateness, and intelligent failures.
For a bit more context, we refer you to Joe Friel’s thoughts on what makes a good coach.
7. Triangulation and “heads-up displays” help pilots and athletes alike stay on target.
Athletes and coaches now have a host of devices, meters, algorithms, and good old-fashioned feeling (RPE and other scales) to help them understand internal cost versus external output.
For more explanation, listen to Dr. Seiler describe the “holy trinity” of training feedback in this presentation at the ITU World Triathlon Edmonton 2020 Science and Triathlon Virtual Conference.
8. Detailed periodization models are generally overrated and under-validated.
As you likely know, periodization comprises evolving one’s training over the course of a season, and in specific ways, with the intention of causing fitness to increase.
When it comes to periodization schemes, Seiler doesn’t believe the details matter much. What does matter is that: 1) the overall training workload (as a function of both the volume and the intensity of training) rise, and 2) the most challenging race-specific workouts come as your fitness is near its peak and a target event draws near.
The relevant research suggests that within these broad parameters, the various periodization practices yield similar results. In other words, when it comes to periodization, there’s “more than one way to skin a cat.”
9. Rest days are highly UNDERRATED.
Dr. Seiler has no well designed and executed research studies to back this up. However, he does have a lot of experience working with and talking to high performance athletes. And the trends he sees are telling.
The importance of rest, and specifically of sleep, can’t be overstated. It is essential to turn the hard work of training into the outcome of performance gains. The status of sleep isn’t new. But our understanding of how we monitor and change our sleep, to get the most out of every night, continues to develop.
10. Physiology is COMPLEX but training prescriptions should NOT be.
The fact of the matter is that there is significant overlap between “energy systems” in our bodies. Changing training intensity by a watt here or there will not have you training one system then another.
This is illustrated in the below figure, which is redrawn based on educational material developed by the Olympiatoppen, or the Norwegian Olympic Federation, whom Dr. Seiler works closely with.
Training effects on cardiovascular pump function may be centralized in zone 4, for example, but they are also seen in zones 2, 3, 5, and 6.
Peripheral muscular adaptations are focused in zone 2, but that doesn’t mean you won’t also impact them when riding in zone 3, 4, 5, and even 6.
Likewise, other specific endurance adaptations take place over a wide range of intensities.
Extrapolating from there just slightly, not only is physiology complex, but properly executing intervals that “target” certain intensities is very difficult. Therefore, training prescription should remain simple.
11. Think fewer intensity zones, not more.
As the physiologist who popularized the polarized training method, it’s no surprise that Dr. Seiler likes to reduce the complexity of the zone system of training prescription to basic elements: green, yellow, and red zones.
From lab testing, we know these three zones align with a typical five-zone model used in training practice, as illustrated below.
Polarized training suggests that you spend 80% of your training time in the green (low stress training), and 20% in the red (and sometimes yellow, which are both high stress training). Think of your training as various buckets, and it would look like this:
12. If the training PROCESS balances deliberate efforts, deserved recovery, and daily smiles, the results will follow.
Intention. Balance. Fun. In three words, that’s Seiler’s recipe for endurance development, based on 12 truths he’s gleaned from over three decades of observation, experimentation, and intuition.
