Redbullet

In outdoors cycling, I had a basic method for simulating HIIT intervals: a digital watch that can handle intervals, set to beep at desired times, marking "full throttle" and "recovery" periods (no power meter available). Now, since bad weather keeps me a long period indoors, I was wondering whether there is a smarter way of doing HIIT intervals on smart trainer, maybe taking advantages of power reading and "erg" mode.
So: How do you approach HIIT on smart trainer?

clasher

I use https://zwofactory.com/ to make .zwo to load into zwift and do the workouts in that program. That site will also let you export workouts as erg or mrc files that can be used with various head units and likely also the phone app that some smart trainers have. I've used my bolt to run workouts on my kickr but it's not the most straightforward process. I am not sure how to do it on a garmin head unit since I don't have one anymore. I imagine most phone apps that come with a trainer have some way to use workout files but I've never used the wahoo app I have for my kickr.

unterhausen

I think it's a lot easier on the trainer if you have some idea what power level you want to achieve. But I usually do HIIT on trainerroad.

atwl77

It's pretty easy to just set the trainer at a specific amount of resistance, and then ride it like you do outdoors. But to take advantage of power, and ERG mode, then as unterhausen says, you need to have specific targets to achieve. e.g. 140% FTP, 200% FTP, etc - basically know your FTP and then target specific multiples above it. And then most training apps will have some sort of interval program based off your FTP. For me, I do HIIT stuff on The Sufferfest.

Redbullet

Thanks for the answers.
I checked https://zwofactory.com/ and, indeed, it is a very easy way to create own intervals. I can link the zwo file to a few roads, in the virtual cycling application I use. I also have a good aproximate of my ftp, after a number of longer and intense virtual rides. But I don't know what percentage of ftp is used in HIIT intervals, nor the duration. For example, I tested some "VO2max" intervals: they use around 120% ftp and they play with number of intervals (6-20), their duration (30-120 seconds) and recovery times.
But, as I understand, "HIIT" intervals are different.
So, what percentages of ftp are used in HIIT? Are there some examples of HIIT intervals, that I can replicate to obtain a "zwo" file and use the power meter and erg mode of the trainer?

Thanks

gregf83 

HIIT intensity levels are often specified as a function of Pmax where Pmax is the maximum power in the last 30S to 1min of a ramp test. The intervals can be done at 60% of Tmax where Tmax is the time you can sustain Pmax with a rest of a fixed time (120% of Pmax) or when HR drops to 65% of HRmax.

I don't think an FTP estimate is of much use for HIIT as the intensity a given rider can sustain for short durations is not well correlated to FTP, i.e. sprinter types can sustain relatively higher intensity for short durations than TT specialists.

Ref: Interval training program optimization in highly trained endurance cyclists

Personally, I find these types of intervals much easier to do outside on a hill. I get enough intensity with zwift races or group rides.

jpescatore

There are existing interval workouts on Zwift you can see - check out WhatsOnZwift and search on "interval" and you will see them. You can view the workout graphic either by watts or by % of FTP to get an idea of what they are doing.

Here's an example of 1 of the 9 Tabata interval workouts on Zwift viewed by % FTP:

atwl77

Huh? 70% FTP? What kind of tabata is that?

gregf83 

Definitely not Tabatas. I'm assuming there were also some high cadence targets in there but that's not HIIT

zen_

Good video on the subject, and a channel worth following if you care about training somewhat properly. The Cliff's Notes is that there is not a lot of difference between the traditional vo2 interval like a 5x5, or tabata type intervals that are 8-12x 40/20 or 30/30 type efforts done in sets. What matters is accumulation of time in zone, and being well rested so you can do the workout correctly. You also need to know your FTP to set the zone correctly, and it is "easier" to do them on smart trainer with ERG mode (particularly the tabata) because you are forced to ride at the specified power, or stop.

Redbullet

Thanks, interesting material. So, it is much more complicated than alternating for a number of times "full throttle" and resting periods: identify Pmax with ramp test, then identify Tmax as maximum time at Pmax, then calculate the elements of the intervals...
And, overall, none of those can be done without a power meter - either on the road or indoors with the trainer. Difficult topic.

gregf83 

Precision is not that critical. You just need to be in the ballpark. If the target power you come up with is too easy raise the target next time. Similarly, if you're unable to complete the planned intervals lower the target. The last interval in a set should be tough to get through. I just provided one example. There a plenty of other interval formats and it will be up to you to determine which ones you can do on a consistent basis.

For high intensity intervals, I do 6 - 5min intervals with 1 min rest in between each interval (6x5x1). Target power is supposed to be 106-108% of FTP but I just set a reasonable target and adjust as necessary. No need to measure FTP. I go all out on the last interval and if the final interval power is higher than the first 5 I raise the target next time. I still prefer to do these outside but do them inside when it's miserable or dark out. If I do these a couple times a week the target power naturally goes up over the weeks. I find them very effective.

caloso

Are you saying that you can’t do this specific protocol without a PM? Because you can absolutely do intervals with just a stopwatches and RPE. Maybe not these, if they’re so specific. But riders have been doing 30sec on/offs since the days of wooden rims.

Branko D

The idea is to spend the most time operating at or near VO2max to force the body to adapt, but the training effect isn't really down to time in power zone but rather physiologically getting you in the state near maximum oxygen consumption and keep you there as long as possible. There's more than one way to get there and you don't quite need to test and retest FTP frequently or ERG mode to do them correctly.

What's more indicative is getting the heart rate response to closely replicate what happens when you're doing more traditional longer intervals; if my block of 40/20s is giving me the same heart rate rise as doing longer VO2max intervals on the road does, the intensity of those 40 second work periods is pretty much right. For me (and looking at studies I'm not unique in that regard) the 40/20s interval format works better than the 30/30s where I'd have to really ratchet the power up more to get the same response.

Redbullet

Thanks for the answers.
I found a ready made "VO2max" workout in the application, having the format: 12 times 1+1 min, with the first minute at 135% FTP and the second minute at 55% FTP. It also offers the functionality to raise the power for the whole period. I felt it difficult but doable. Thus, next time I shall try the same format with around 5% power increase in both periods. And further increase another time, if the last interval is ok and if I fel I still have some power left.
Does it sound as a good approach for high intensity interval training?

atwl77

The 1 min on, 1 min off is a very common interval workout format. On The Sufferfest it's named Revolver and has you doing 16 sets. I'm pretty sure other platforms have different names and durations.

Do not increase the power for the recovery portion (e.g. the 55% FTP part). And on that note, instead of increasing the power targets of the interval, try to complete more sets first before changing power targets.