5X5 min versus 4X8 min threshold intervals

Thanks for the videos on 5X5 min and 4X8 min threshold intervals. The key points of execution and the intent of the intervals seem very similar to me. @trevor, do you view these as interchangeable or would there be any reasons to choose one over the other?

1 Like

I know Trevor is traveling now, so will give my quick thought. I would differentiate these two sessions in terms of time at intensity. 5x5 will get you ~25 minutes at a target intensity, whereas 4x8 will get you ~32 minutes. Overall I would look at this as the progression to build from a lower work time to a higher work time in order to generate that overload.

Yes I see the math…LOL… but I’m curious why so keen on the 5X5min with it having the lower time at intensity.

I look at it as a starting point - 25 minutes of intensity is completely reasonable for generating aerobic adaptations if you’re doing it consistently or starting up your training with that, say 2x per week. And then building from that to 4x8 becomes the next step. Note sure if that’s what you’re asking, but where my mind is going at the moment.

Oops! We forgot to include the 4x8-minute threshold interval workout .fit file and the 5x5-minute threshold intervals workout .fit file with their corresponding workshops.

Those files are now available as downloads on each workshop!

4x8-Minute Interval Execution

5x5-Minute Interval Execution

@robertehall1 @ryan Sitting at an airport - thought I could send a quick response. Overall, the 4x8s are a little harder. I generally give these to my athletes as a progression - do 6 weeks of the 5x5s and then six weeks of the 4x8s.

That said, I do find the 5x5s are a little better at raising power while the 4x8s are better for learning to sustain power. So it does depend on where your focus is. For example this winter I switched to the 4x8s for about two weeks, but wasn’t happy where my power was at, so I went back to the 5x5s and continue to push my power up.


I don’t have access to the video, but I’m assuming the 5 min intervals are similar to what have been referred to as ZeCanon Intervals in the past?

It’s a nice thread to review if your interested in this type of work. The consensus is 6 x 5 min w/ 1 min RBI - all at 103% - 108% FTP. They work. Here’s a link to the academic research I believe led to this workout design.

Metabolic and performance adaptations to interval training in endurance-trained cyclists


I am having trouble downloading the .fit files. When I go to upload them into TP I get the error message “No workouts found in this file”. Any help?! Thanks!

@murphyy12, I had to do some digging, but here’s the scoop on the .FIT files.

  • TrainingPeaks will allow you to build your own workouts using their workout builder and then export any extension (.FIT., .ZWO, .ERG, .MRC)
  • They do not, however, seem to allow you to import a structured workout (a file that contains no training data, only the pre-build structure of the workout) from outside sources

It looks to me like there are some options (not great ones, but I think this is what we’re stuck with at the moment):

  1. If you want to have a 5x5 workout in your TP calendar for future training, you would have to build that file yourself in the workout builder and save it in your library
  2. If you’re looking to import that file anywhere else to run the workout (e.g., Zwift, Garmin, etc.) you can do that and then follow the structured session that way. The completed workout file can then of course go into your TP calendar as a completed workout (since it will contain training data). Potentially at that point you can do a copy & paste on future days to show that structured session in your calendar? (not sure, I haven’t confirmed that approach yet)

I’ll admit I was a little surprised. It seems like workout files that you build in TP are ok to be exported, but unless you build a file within TP itself, there seems to be no easy way to import such a file to your TP library.

Our workout files were meant to be primarily used to guide your sessions on a variety of platforms that communicate with your trainer or cycling computer, so I hope that .FIT file is still useful if you are utilizing another platform like TrainerRoad, Zwift, etc.


@ryan - thanks for the response. Seems silly, but makes sense. I will try loading the .fit into Zwift and see what happens.

@ryan would you give a refresher on loading a .fit file into the TrainerRoad workout creator. I’ve gotten the same results as when I tried uploading to Training Peaks, i.e. nothing.

1 Like

I found exporting the ZWO format works best for importing to Intervals/Zwift, and the for it to push to the Garmin calendar.

Think of your goal before choosing your intervals.
5x5 and 4x8 means nothing if you don’t stick to the intensity level that fits your training goal.

To purposefully specify and interval session, include the intensity of both the work and rest bout.

10 x 10 seconds @ max load with 5 minutes hr zone 2 in between. (Goal: strength development while maintaining max volume)

4 x 4 minutes @ 90% HR max, with 30 seconds rest and 3 minutes zone 2 recovery.
(Goal: vo2max development while maximizing volume)

8 x 1 minute @ 80@ of HR max, with 5 minutes zone 2 in between.
(Goal: technique development, strength development, aerobic capacity, kill the zone 2 boredom, maximize volume)

Just to add, volume is key.

@trevor not sure if this is the place for it, but is there a reason to believe 5 x 5 intervals are better than simply doing 25 minutes at the same pace? As I’m fortunate to live close to a long and steady climb it’s simple(r), if not easy, for me to go and ride at that pace for 25 minutes. Does doing it in intervals make subsequent recovery easier? Or is is as you extend it at some point it likely won’t be possible to hold that pace?

The idea of the repeats is indeed to replenish energy in the muscles, so you can again to to a high heart rate.
Shorter interval are indeed less stressful for muscles which implies shorter recovery.

Exactly! Having a one minute recovery gives both a mental rest and allows some physiological “recharge” while not giving the aerobic system time to ramp down. So the idea is that you can do a higher quality 25 minutes of aerobic work than you could if you did a 25 minute time trial.

If you’re able to hit the climb at the same power and quality, then yes, you’re basically going to get the same gains, but I haven’t seen very many athletes be able to match the quality without the rest.

As an example, I have plenty of 25+ minute climbs around me, but when I do threshold work on the climbs, I still do eight minutes at most and use the descents to recover. I personally can’t do the full climb on a workout day at the same power that I do the eight minute segments. .

thanks @trevor. I did a 5 x 5 session yesterday and it was pretty hard. I ended up at around 92% of my max hr towards the end of the first intervals and pretty much from the off for the last two. I had three minute recovery periods as I believe from listening to Seiler in an episode (don’t remember which one) that this would allow all the systems to fully recover. I wasn’t aware that the protocol you suggest requires less than full recovery. I think I would really struggle to hit the power numbers - 103 - 108% of my ftp - with such limited recovery time. Is the point that I should really be targeting HR and power will do whatever it does?

@Mr.B, I personally like the 1 minute recoveries because it turns the workout into a pretty pure aerobic workout. In effect, it’s like doing a 25 minute threshold effort but at higher quality.

Reading your description, it does seem that you’re doing them too hard. I don’t prescribe these by power, but typically my athletes end up around threshold power when they do them.

The two prescriptions I give are that the athlete isn’t allowed to exceed threshold heart rate (well, I let them go up to 1 BPM above threshold) and all five intervals have to be the same intensity/power. That tends to put them right around threshold power.

Hope that helps!

1 Like

@Schils, in my research putting together some refreshers on these different file types, it seems that TrainerRoad only accepts .ERG or .MRC files. Do you have one of those extensions available for some of the structured workouts? If not, I’m happy to get those posted on the site so you can have all available formats.

@ryan thank you for the refresher regarding the file types and why I was having difficulties getting the workouts created. As for posting the workouts on the site in every flavor of file type, please provide them if others are requesting this. I already created versions of the 5x5 and 4x8 workouts based off of information gathered from the podcasts and the forum. It seems that next on my list is creating the 4x4 version for early base season. :smiley:

In reality, I’m rather old school (could be due to my age). All of my bikes have rim brakes and mechanical shifting. My “gravel” bike even has down tube shifters and is older than some of your members. Similarly, my trainer and rollers are “dumb;” just like the operator. So every workout is more of a “guideline.” There’s no reason I couldn’t just write my workout on a white board and get on with it.

Ok, I’m not a complete luddite. I do have a power meter on the road bike and I find it useful to align my reality (RPE) with data.

1 Like