A Novel High Intensity Interval Protocol

This one is for all the physiology geeks out there… Thought I’d start up a thread on an interesting paper from this 2019 EJAP paper. I think it’s been mentioned/shared previously in another thread, but wanted to follow up on it and attempt to model it (and try the protocol for myself) using Xert.

The topic of interval intensity versus duration has been an interesting topic for quite some time now - dating back to the HIIT intervals of Tabata (40-20 micro intervals) & Billat (30-30 micro intervals), through Seilers work (4x8 min), and with some of Ronnestad’s recent works (30-15 micro intervals & fast-start intervals).

The paper I’ve linked to above suggests merging a few concepts that Xert has actually been using for quite some time to further optimize the time that can be spent > 90%VO2max, which is thought to be a great indicator of performance gains in VO2max (see Seiler’s 2013 study). To do this, they use a couple longer intervals to quickly get HR/VO2 up towards 90% of max before switching into 3:2 pattern micro-intervals to maintain VO2/HR above 90%max.

Figure taken from Vaccari, et al., 2020

In several workouts (SMART - Iron Man, for example), Xert uses a longer initial Target MPA interval to draw down your MPA (which also increases HR & VO2) before performing more endurance or other high-intensity intervals. By bringing MPA down, we expect more strain (XSS) than compared to the same efforts done without bringing MPA down first. A similar effect could similarly be achieved using our fast-start XSSR intervals (like you’ll find in the SMART - Closer or SMART - Gasoline series of workouts).

Getting back to the paper…their proposed High Intensity Decreasing Interval Training (HIDIT) protocol was described as follows:

" 3 min at high intensity and 2 min at low intensity; 2 min at high intensity and 1 min and 20 s at low intensity; 1 min at high intensity and 40 s at low intensity; 45 s at high intensity and 30 s at low intensity; and finally 30 s at high intensity and 20 s at low intensity, repeated until volitional exhaustion of the subject. The high–low ratio intensity duration was always 3/2. "

…where high-intensity is defined as their 5 MMP (derived using their CP/W’). We can easily recreate this in Xert using 5 MMP as the intensity for intervals! :slight_smile:

I’ve re-created their protocol as a SMART, Mixed Mode workout, with only a few minor changes:

  1. I used Target MPA intervals for the initial two intervals, rather than using fixed 5 min power. I suspect this will increase compliance by reducing workout difficulty a little on the front end, especially since the initial 8 minutes of the proposed protocol calls for 5 min of riding at 5 min power.

  2. After concluding the initial 5 steps of the HIDIT protocol, I’ve utilized the Mixed Mode features of Xert, allowing you to complete the 30/20 efforts in SLOPE mode (2.0%), rather than ERG mode at 5 min power, which can sometimes lead to premature fatiguing from the ERG spiral of death. This part of the workout will likely feel similar to the SMART - Break on Through (To the Other Side) workout

It would be interesting to see if others wanted to try this workout and compare the workout difficulty/XSS to some well-established & effective HIIT protocols, like Ronnestad 30-15’s or Billet 30-30’s! I plan on trying it for myself sometime as well, but here would be some questions I’d be curious about:

  • How long did it take to reach ~90%max?
  • Were you able to maintain HR at/above 90%maximum?
  • Once reaching the 30/20 micro-intervals, how many repetitions were you able to complete?

I’ve shared the workout to the Shared Workout Community, which you can join by clicking the link: here!

Once you’ve joined the shared workout community, the actual workout is here: SMART - Bow Down

Curious to see where the discussion goes! Cheers!


Very interesting ! Thanks @ManofSteele for share !
And curious for try Break on Through (To the Other Side) Workout !(Xert - Login) workout
Have a happy new Year !


1 Like

Is a killer Workout :relaxed:

Especially the relative long intervals before the 30-20 intervals are - for me - very hurting.

This time I’ve failed - but I’ll try again when I’ve fresher legs. I had a long Zwift ride at Thursday (Mega Pretzl) and one day recovery is probably to less for this workout.

Xert did also recommend other types of workout - but I was too curious to try this one.



Double :grin:

And breakthrough :heart_eyes:

Today I reseted my my profile from no decay to optimal, which caused a drop of TP of 15W. Then I did this workout again. Now the “long” intervals were doable (of course),
I’ ve got at each of the last 3 short intervals - that I did - a breakthrough and a raise of TP of 10W. I assume now the “long” intervals would suck me again.

Interesting workout :joy:

So interesting to see so many Breakthroughs, but it looks like the recovery intervals are still just a bit too easy… you can tell by watching the trend in Heart Rate over time during the workout. Ideally, your HR should be as close to/above 90% of HRmax as much as possible during the high intensity efforts.

I have yet to give this workout a shot yet…

Hey Scott and others – tried this style workout today and was quite pleased. But I noticed in reviewing the research afterwards that the original protocol used unusually high base levels – 83% of CP. I used more typical 45-50% FTP. I varied the target wattage on the overs by the duration. In net, it didn’t give me more time at 90%+ HR than the 3x13 Ronnestad format, but I still liked it.

for comparison, 3x13 30-15s at 125%. From mid March.

Hi @TKskate , thanks for chiming in! You’re correct - the ‘recovery’ intervals are still pretty intense at ~83% CP, which is likely low tempo (Z3) for most athletes.

The authors noted that the work intensities and recovery intensities were mirrored above & below the athlete’s CP. Based on our math, athletes will fatigue asymmetrically with this type of riding… e.g. you will accumulate more fatigue riding 10% above TP then you can recover at 10% below TP for an equal amount of riding at both intensities.

I’m guessing that if you kept the recovery intervals just a little more intense, your HR wouldn’t “recover” as much between work efforts and you’d be able to accumulate more time >90%HRmax.

When I created our version of this workout in Xert (SMART - Bow Down), I intentionally left the recoveries at a relatively lower level, mostly to keep the overall intensity of the workout lower - even with the “easier” recoveries, this workout hits >150 difficulty in <45 min:

While there are targets presented for the athlete, all these intervals are done in SLOPE mode, so athletes can use their gears & cadence to control their efforts. Ideally, the goal is to ride at the highest sustainable power effort for many repetitions, NOT to sprint all out on the first 2 intervals.

If I followed exactly the guidelines in the original paper, then the HIDIT protocol is likely only sustainable for ~10 minutes of total work time because the athlete would become limited to MPA far quicker. Because of this, Difficulty Score also increases significantly more (literally off the chart) despite a shorter work time:

Therefore, I suspect there is some room for fine-tuning and improving on an individual level. It essentially boils down to this: which is better? Maintaining a near-maximal effort over a longer duration, or achieving an all-out/maximal effort over a shorter duration?

Decreasing the recovery intensity will allow you to prolong the 30:20 efforts, but will also make it harder to maintain >90% HRmax. On the other hand, increasing the recovery intensities will make it ‘easier’ to maintain HR at near-max levels, but will likely lead to reaching exhaustion sooner. I guess the only way to determine would be to look at the XSS for the session completed both ways and see which is greater.

Thanks Scott for your thoughtful reply. I got to 140 difficulty even with the lower than original target for the 3- and 2-minute blocks.

One interesting suggestion I saw New VO2max Intervals — High North Performance was to perhaps focus on the ‘longer’ side and do it twice (or 3 times!?) That suggestion actually correlates pretty well with your new chart showing MPA exhaustion right around when you’d reach the 1st or 2nd 30s effort. Maybe I’ll try that next week, TBD.