Mistake in the last podcast?

@trevor, did you make a mistake in Fast Talk Episode 182 with Rebecca Gross when referencing Seiler’s 4X4, versus 4X8, versus 4X16min study?

You suggested starting with 4X4min intervals. In Seiler’s study, I thought that overall there was no significant difference to the groups but there was a trend toward better improvement in the group that went 4X16, then 4X8, then 4X4min. It makes sense to me to go from longer, lower intensity intervals progressing to shorter higher intensity (over threshold) intervals. I was planning on using this progressing for next year’s build.

I’m not Trevor, but I do know that:

  • if your fitness matches the fitness of the group in the research study, the study results might apply to you too
  • always base your interval design on your training goal and fitness level
  • the intervals in the study target the high-intensity part of the total training program, so the intensity is always high
  • as per the polarized concept, you can extend the duration of those high-intensity intervals as your anaerobic endurance improves during the season. And I think that is wat Trevor ment.

I think you are misinterpreting the intention behind Trevor’s approach. Seiler’s work concluded that organizing different interval sessions in a specific periodized mesocycle order or in a mixed distribution during a 12 week training period has little or no effect on training adaptation when the overall training load is the same. However, there is a function of adherence and capability that isn’t discussed in Seiler’s study. Taking someone out of for instance, a base phase or a sharpening phase and throwing them into 4x16s is likely a recipe for failure for a lot of riders. Sustaining 4x16 at threshold is difficult for a large portion of riders that are not acclimated for that type of work.

The sensible approach to periodization is to use 4x4s/5x5s and generating a potential lift to a rider’s threshold, then progress to longer intervals. Sure, the adaptation would be the same regardless of the periodization, as Seiler suggests, but that is making a pretty big assumption - that the athlete is 100% adherent to the workouts i.e. not failing the intervals. A variable that was not included in the 2016 study. The inclusion criteria for that study was pretty steep - The cyclists were all male with a VO2 max greater than 55, trained more than four sessions per week, had cycling experience of over 3 years and competed regularly.

I am not trying to impeach Seiler’s work by any stretch, it is a very good study, but not necessarily practical to the lion’s share of amateurs out there when used in a vacuum. I think Trevor’s approach as a coach is to take the training modality and right-size it to the everyday athlete.

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The 16 min intervals in the study I’m referencing were subthreshold. I agree that starting with 16 min intervals at threshold would be too hard. The 16 min intervals were done at 86% HR max, 95% 40 min TT power, 15 RPE. The 8 min intervals were done at 88% HR max, 106% 40 min TT power, 16 RPE. The 4 min intervals were done at 89% HR max, 117% 40 min TT power, and 17 RPE. That sounds like sweet spot, threshold, above threshold respectively. This progression from lower intensity/longer to higher intensity/shorter makes sense to me. I believe the study group with this progression showed trends towards better 40 min power, power at VO2 max, power at 4 mmol lactate, and a larger proportion of “responders” to training. I meet the inclusion criteria you mentioned, so I’m eager to give this a try. Maybe you’re right, it’s not appropriate for every athlete.

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Hi @robertehall1,

There was no significant difference between the two groups at the end of the 12 weeks, so this really comes down to your interpretation, but personally, I do think that the 4x4 to 4x8 to 4x16 (DEC group) progression proved to be a little better than the other way (INC group.) I have a few reasons for saying this.

First, remember that the study was conducted in the base season and ended at the start of the race season. So, it doesn’t address how the next 6-10 weeks of racing went for these athletes. But in the study, you saw the bulk of the improvements in the INC group in the first four weeks and then they plateau’ed:

In fact, you see a slight non-significant decrease in the aerobic parameters in the final four weeks. While in the DEC group, you see a steady rise in the aerobic parameters throughout the 12 weeks. So, even if the INC group finished at a slightly higher, non-significant, level, what is more important to me is the trend in their directions. And my interpretation as a coach is that the INC group plateau’ed early and may already be getting stale at the start of the season, while the DEC group is coming into the season just finding their form - better place to be.

Second, Seiler did mention in the study that the group which started with the 4x16s found it very hard. It was a real shock to the system. Again, as a coach, I don’t want to hit my athletes with that big a shock in the early base.

Finally, I think the INC protocol runs a bigger risk of pushing an athlete into an over-reach state. Here’s the graph of their cortisol and free testosterone-to-cortisol levels. Both are markers that have been used to measure over-reach:


Notice that particularly in the free testosterone-cortisol ratio, the INC group was consistently low while the DEC group did a good job of staying homeostatic.

So, again, we didn’t see how the race season played out for these athletes, but based on the trends, I think the DEC group came into the season fresher and just finding their form and likely were able to hold it better through their races. But that’s an educated guess.


@trevor, thanks very much for the interpretation. I understand your points and will look at adjusting my plans.

@trevor, just thinking about this a bit more… The 5X5 min intervals you like in the base period are just below or at threshold correct? The 4 X 4 min intervals in this study look like above threshold, more like “VO2” efforts. Starting with that in November seems iffy??

Hi @robertehall1, in the study, the 4x4s definitely would have been over threshold. The way I do the 5x5s, I doubt they are. That said, I don’t prescribe them by power. So, I can’t say for certain if they are a little above or a little below. I’d say they are right around threshold. As you know, I’m a big believer that our threshold is not a static number - it varies day-to-day and even over the course of a ride. So, I’ll give power ranges, but I never prescribe at a precise power.

The way I give the 5x5s is to first set a limit on their heart rate that’s 1 BPM over threshold. They are not allowed to exceed that heart rate. If they do, they have to back off. Second, the intervals have to be consistent. So, while I won’t prescribe a set wattage, whatever they average for the first interval is what they have to average for all five give or take 5 watts.

Those two rules keep the athlete right around their threshold on that day. On a day when they’re feeling good, they may be a little over. On a day when they’re feeling not-so-good, they may be a little under.

Also, in November, I start my athletes with 4x4s but make sure they are done below threshold. I don’t get them up to the full 5x5s until mid-December. November is just about getting them to remember what structured work feels like. The hard work doesn’t start until later.

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Thanks @trevor, that all makes sense to me.

I know Trevor has already chimed in on this topic with his particular flavour of interval progression, but with regards to the study, I had thought that the interval sessions were “effort matched”? Meaning that the prescription was to “go as hard as you can while still completing the interval and keeping the power similar from interval to interval”? If I am recalling correctly then I don’t know that I would necessarily look at the specific powers and heart rates as targets, but as outcomes from the effort you put in. You have to consider the intra-participant variation in the study and each participant would have different outcomes throughout the course of the protocol