Executing 4x8 Intervals

Is there a general rule of what percentage of your FTP, one should try to execute a 4x8 interval? I understand one should try to go as hard as possible, during the 8mins, keeping in mind you still have to complete all 4 intervals at the same or close to power as the others.

But in order to help figure out the first time without risking going too low or too high, where should I aim to keep it? 106% of FTP?

Thanks in advance

I usually will try to do mine in the 80-95% range and try to add an extra interval or two before adding power (or upping the power a bit on a final minute of an interval) or recalibrating my FTP/Threshold for training. To me I want to make sure I do each interval well and get a good progressing feel of getting fatigued and recovering over the course of the 4x8. If I were to do 100%+ I would really fizzle out and be a bit too fried the next few days for good work. Though, if there is a day you are feeling good and want to test yourself at a high %, do it. But know when you need to stop and dial it back. You may find that 105% is a good setting for you. I think if it if you have ever done any weight work. You would find a day and do your “max” and they you do your sets for the next few months at a smaller weight and progressing up each workout before trying to max out again.

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@AlexM370, great question on that. @bgkeen has excellent feedback. The one other piece I will add is that you can always adjust the recovery period to tune into the appropriate % for what you are trying to accomplish. So you can take a 4x8 and treat it a bit like Trevor’s famous 5x5 workout where there are very low rest periods (1 minute) and this allows you to spend a lot of time just below threshold to reduce the anaerobic contribution to the start of intervals and accumulate a lot of time at just below threshold. You can also extend those rest periods and focus more on a hard-start approach or working at >100% threshold, knowing that there are other benefits to gain by going to that level of intensity, but at the expense of taking more recovery from a session like that.

One of the blocks I’ll do is 2x per week 4-5 intervals of 4-5 minutes zone 5 with a hard start approach. I’ll knock out 6 sessions total, usually within ~3 weeks time, and then rest hard. There is absolutely no other quality work I can accomplish at that time, but when I come out of it I feel good and ready to race. Threshold bumps up, lactate becomes more tolerable, and time to peak power takes a step in the right direction.

I am in agreement with @bgkeen where he talks about being too fried to have any good work the next few days. Those can be very taxing sessions, and if we think about 32 minutes at 106% or greater, that may take a while before we have good legs back to go hard again, versus something a little more sustainable sub-threshold where we can accumulate more time. So yes, very individualized, and also specific to what you are looking to accomplish at that time. For testing, there will be those days where you feel really good and can knock it out. Like the day to do your “max” testing in the gym.

Coach Ryan

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My understanding of polarized training was that 4x8 were supposed to be done on hard days and that they should be done having all 4 intervals as “equal” in power as possible, going as hard as you could, so you don’t start too hard on the first interval and fate towards the others. Also, these workouts are supposed to be done 2x a week in most cases, which falls inline with what @ryan just described.

I understand the benefits of working sub-Threshold but I thought these were kind of “undesirable” under the polarized approach.

I agree that after a workout like that one would need a couple of days of recovery rides in order to execute another one.

I am intrigued by that 3 week 6 session block and have a 3 week coming up where that would fit perfect to try out. When you say “Hard Start” are you only starting hard (above Vo2 Max) and then settling into threshold/sub-threshold. Or is it starting hard and then bringing it down a bit and hang on til the end?

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Yeah, working sub-threshold does seem to fall outside of the strict polarized method but some work in the middle zone with the right focus is good. Depending on where you are in your training plan getting some of the work in that zone if beneficial. I will admit, I will sub them in for a “hard” workout in my plan and then will play with an 8 minute block to be a bit more intense with a 30/30s, 2x2s, to “tickle the higher intensities” (stolen from another topic in the forum :slight_smile: ) But that work is more beneficial to my strength, events I do and goals in those events. I mostly do events that are in the 100-200km range. Much of those events are done at an average power that is upper z1 and lower z2 (on 3 zone). Those 4x8 sub threshold reps along with the long z1 rides really helps my ability to sustain the needed effort over the distance and be able to get the z3 efforts in to hang with a group during the critical moments of the event.

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Brian, yes, that’s something I’ve stuck with pretty religiously over the years. When I have a key workout, I’ll aim for 6 sessions. How those are accumulated can vary greatly. It might be 2 weeks of 3 sessions blocked up per week with massive recovery, or it might be more like 2x per week and more sustainable to not dig too deep of a hole.

In any case, the “hard start” I mentioned - yes, it is along the lines of start hard, allow the fade to build in, and hang on until the end. This particular approach is almost exclusively done with Zone 5 sessions, and the reason I chose that is because it lends itself to my style of riding as a punchy rider with good acceleration capabilities. I’m no where near a good TT rider, so this type of approach is to keep sharp with the way in which I deliver power well. So with that approach in a Zone 5 workout, I would finish well above threshold (125% threshold power on average with peaks over the first 30-40 seconds being 140-150% threshold power). For more of a threshold interval session, I would tend to be more conservative starting above, but not looking for that peak power any longer - just a strong start and then more awareness around settling in at sub-LT and holding that while allowing the body to work on within-interval recovery.

You’ll have to let me know how it goes if you have a block where you can try it out!
Coach Ryan

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Thanks for the info. I have put in my plan to try this out in a few weeks before I go into a little low-intensity weeks before starting building a base for my early spring events. I will be sure to update with what I tried and how it went!

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Hi there!

We’ve just posted our first Live Q&A Session recording which includes a lengthy discussion of the 4x8 interval topic.

Live Members can see the recording: Q&A on Executing 4×8 Intervals, Using Scooters in Training, Recovery Walks, and Micro Training Camps.