4 x 8 Syndrome: Everyone's Doing It, Should You?

Polarized Cycling 4 x 8 Minute Intervals

After the extremely popular VeloNews Podcasts with Dr. Stephen Seiler from Norway, we wrote up our thoughts on Polarized Training for Cycling in 2018 and Polarized Training for Cycling in 2019. A lot of listeners started Googling this doctor’s work, and this is where you can find the main study that he references in the slide presentation.

The biggest takeaway that I’ve heard riders making is his proof that 4 x 8 minute training in cycling was the best way to improve one’s Functional Threshold Power (FTP). Of course, with this being one of the main metric’s based around cycling performance, as well as one that can be tested relatively easily, you’ll often hear athletes talking about their FTP and how they can improve it.

When you look at the study, the 3 main groups of riders perform 4 x 4m, 4 x 8m, and 4 x 16m intervals sessions, aiming to hit the highest average wattages possible. The results show that the riders who performed 4 x 8m intervals had the largest change at VO2peak (l/min), power at VO2peak (W), and Power at 4mM blood lactate concentration (W).

With results like these, should we just ride some 4 x 8m intervals over and over again and we’ll reap all of the greatest benefit for our Zone 4 and 5 performance? After all, isn’t this what everyone needs to excel at in order to be at their best for cycling?

Athletes Going All In On 4 x 8 Minute Intervals

Luckily I ran into an athlete who had been doing these intervals over and over again but didn’t really seem to have much of a game plan.

“Why are you doing just these interval durations?”
“Well, I listened to that podcast and it said that they had the biggest results.”
“How often are you doing them?”
“Twice a week. And then easy rides.”
“What’s the plan after here?”
“Well, I’m not really sure.”

4 x 8 over and over.png

So, it’s very polarized in nature. If you’ve read our other blogs here and here, you can see what we like and dislike about them. One thing that you must take note of: everything at Zone 4 and above is Use It or Lose It, and an athlete can only maintain the results for a finite amount of time, whereas Zone 2 riding can be done over and over and over and you just continue to build massive aerobic efficiencies. Are we saying that you should just ride Zone 2? Definitely not; read on.

If you train at 100% FTP or above and aren’t using that training for a specific event coming up, you will make gains, not use the results (since you don’t have an event), come off a higher level of fitness (or peak), and then be back to where you started, but slightly more tired.

Yes, training FTP is important because you also learn how to dig deeper each time and there are not only mental gains to be made, but also the physiological growth, but these training blocks take a month or two to see results, so realistically you only have 3 (maybe 4) opportunities to go through these cycles when you consider the following:

October through January is base building and preparation for the upcoming spring and summer, leaving eight months left to work with, and this is when you are racing and resting for the next events on your schedule.

So, back to this athlete. While he may make some gains in January, it’s too early, as he won’t be wanting to use this fitness until April or so. He’d be much better off working on his aerobic efficiencies and system with Zone 2 and 3, start incorporating some burst efforts, and THEN hitting these 4 x 8m intervals before the race season.

Should We Forget About 4 x 4 And 4 x 16 Minute Intervals?

Definitely not.

All three of these durations are in the Functional Reserve Capacity and FTP System, and in order to avoid stagnation by only doing 4 x 8 minute intervals, you want to work the edges of that, as well as the other systems that you will be utilizing as a competitive cyclist! While Max Aerobic work will be improved, don’t forget to lengthen out your intervals beyond 16 minutes...WAY BEYOND...like to 40, 60, and 90 minutes, with decreasing intensity, to develop Intensive Aerobic and Extensive Aerobic capabilities.

What Wattage Do I Do My Intervals At?

When you look at Stephen Seiler’s study, the athletes were supposed to give 100%. If you have accurate data, you can shoot for 95% of your 8 minute best, as this is most likely the most repeatable wattage that you can hit. If you’re hitting 100% four times in a row, there’s a good chance that your max wattage number is just a little low. It won’t ruin your training, but it’s not optimized.

What Happens To Fitness When I Do 4 x 8 Minute Intervals?

This was interesting. I was curious what the athletes Chronic Training Load (CTL) and Acute Training Load (ATL) looked like on the Performance Manager Chart (PMC). While I think the importance of this chart is overrated due to people’s obsession with CTL, it still can have some importance. Take a look at this graph below. The first red arrow is really the last time the athlete fully rested (like 12/31 or 1/1), and then went until 1/20. 3 weeks on is normal, but it was so much intensity at 95% of hard watts. In this example it was 95% of his 8 minute max twice a week...too much intensity all at once, especially because he didn’t have a large base of aerobic training before.

The athlete mentioned that he had been feeling tired, and wasn’t sure why. This one snuck up on him, but luckily we held an #EvolveOurIQ Mastermind and the conversations there led him to reconsidering this repetitive 4 x 8 routine. Follow Us On Facebook to learn about this Live events coming to your town as we train and race around the country.

One thing this athlete needs now is rest. An easy way to "view rest" on the PMC Chart is when your CTL (blue line) dips below your ATL (pink line)...imagine it as "coming up for air". Said differently, this is actually when you are getting stronger. His ATL almost trends like a build phase, but because of the intensity of the workouts and polarized nature of the following easy rides, it’s more mountainous and doesn’t build fitness (his CTL only moves from 33 to 36 points). He does build from 8 minute effort adaptations after he rests, but don’t forget, if he doesn’t use it, he’ll lose it. Therefore, the timing is off on this training block in terms of what intensities he is doing and the dosage.

BLOG no rest 12.31 to 1.20 and no CTL build.png

Should I Do 4 x 8 Minute Intervals At 95-100% FTP?

Yes. Just make sure of the following rules:

  1. Have accurate data at that duration and around the edges of it. Test it before you start this protocol with relatively fresh legs

  2. Do this 4-6 weeks before an event that requires this type of training. This will be beneficial for almost ALL types of cycling, but don’t do it so much that you ignore Event Specific Training

  3. Don’t substitute this training for Aerobic Building Rides, like long endurance rides on the weekends

  4. Don’t hyper focus on just one duration for too long; your body gets used to that stimulus and stops responding with growth. Change things up, but make sure you are fresh enough for the new stimulus as well

Thanks for reading, and please let us know your thoughts with comments and direct messages.

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