As I frequently note, I have simplified my cycling life by focusing on a single coach, Coach John Hughes. Similarly, I mostly follow just one exercise scientist, Dr. Stephen Seiler. Seiler is most known as the father of polarized training. Casually, polarized training has come to mean that one should train at low Intensity (Zone 2) or very high Intensity (Zone 4 or 5) with nothing in between. In my opinion, "easy or hard with nothing in between" was never a good description of Dr. Seiler's ideas and has become an even worse description as Dr. Seiler has refined his understanding of polarized training. The one sentence summary of polarized training that I would give is that one should spend 80% of one's training sessions riding at low intensity (Zones 1 or 2) and 20% at higher intensity. That is, if one trains 5 days a week, 4 of those days should be low intensity and 1 at higher intensity. But what is low intensity? What is higher intensity? Is there a region of intensity in between those two one should avoid? Dr. Seiler is frequently interviewed by podcasters, making it easy to follow the evolution of his thinking, and recently he was interviewed on the 'Inside Exercise' podcast.
So what was new in this podcast? The most exciting thing to me was that Seiler explicitly stated that polarized training is not about avoiding middle intensity but about spending lots of time at low intensity. I had gotten the impression from previous podcasts that this is what he believed but this podcast was the clearest statement of this idea that I have come across to date.
A second point Seiler made was that the 80 and the 20 in the 80:20 rule referred to the percent of sessions done at low intensity. He explicitly noted that higher intensity sessions are, in general, shorter in duration than low intensity sessions so that if one expressed this rule in terms of time instead of number of sessions, it might be a 90:10 rule. I would take this even further. The bulk of a typical high intensity session is spent warming up, cooling down, or recovering from high intensity efforts. The Gillen et al. interval session I talk about a lot is 90% Zone 1 and only 10% Zone 5. Thus, if one rides five days a week and four of those rides are in Zone 2 and one of those rides is a high intensity interval session as recommended by the 80:20 rule and if the interval session is half as long as the Zone 2 rides as Seiler suggests, and if the Zone 5 ride is only 10% Zone 5 riding as in the case of the Gillen et al. session, the amount of time spent in Zone 5 is only 1% of the total time spent riding.
What is the unique value of the low intensity rides that are supposed to make up 80% of the rides athletes do? Dr. Seiler explained this as a cost benefit issue. Every ride generates a signal to to the body causing it to improve fitness. But it is also the case that every ride generates fatigue. For the same amount of fitness provided, higher intensity rides produce more fatigue than low intensity rides. Thus, for an athlete who is able to train for long hours, whose training is limited by fatigue rather than time, they can get more benefit from low intensity rides. Why, then do any high intensity rides at all? Because high intensity rides provide specific benefits that cannot be provided by low intensity rides.
I still have a number of questions about Zone 2 training, one which is relevant to this post. That is, is it the total amount of Zone 2 riding that is valuable, or is it necessary that a Zone 2 ride be "pure", to not contain any riding of higher intensity? The most radical version of the purity argument I have come across is that one short sprint at the end of a ride is enough to undo all the value of a long Zone 2 ride. Seiler has made remarks suggesting he agrees with some version of this, but I eagerly await clarification, perhaps on a future podcast.
Dr. Seiler works mostly with top athletes who devote many hours to training. He notes that the same rules may not apply to more casual athletes. I think about that and wonder if an amateur athlete with many work and home responsibilities whose training is limited by how much time they have rather than fatigue might benefit from more high intensity exercise. Interestingly, if this is correct, I am more in the category of the top athletes in that regard. Being retired, I have lots of time. Being old, I have very little energy and become fatigued quickly. Thus, for me, prioritizing low intensity riding would seem to be extremely important. How successful have I been at doing at doing that? Not very, as it turns out. The problem is that where I live is hilly, and I find it difficult to avoid going above Zone 2 on a hilly ride.
I have talked about the hilly ride problem before and have even claimed to have solved it. Here is an example of a ride I did on my Cañada route about a year ago where I did a pretty good job not going above Zone 2:
The two horizontal white lines indicate the boundaries of Zone 2. Here is a more recent ride on the same route where I didn't do as well:
I plan to write a future post on the factors that determine whether I can stay in Zone 2 or not but for this post I want to focus on this question: does the difference between the above two rides matter? If the strict version of the purity argument were true, even the first ride might not be good enough, those peaks in Intensity that go above Zone 2 at the end of the ride might cancel the benefit of all the Zone 2 riding that came before. At the other extreme, if all that matters is the total amount of time I ride in Zone 2, perhaps even the second ride provides significant Zone 2 benefits. Even if the latter hypothesis is correct, it is still the case that I could get more benefit by doing more rides like the first one and so I have been thinking about how I might do that.
