Too much HIIT impacts health negatively

Don’t think this has been posted before.

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This paper comes to a similar conclusion.

So…what is excessive HIIT? How many times or how many hours per week?

seems like 3 straight weeks of progressively harder HIIT. lol. Even TR plans don’t expect that! I’m not to worried about my one VO2 max workout a week.

One of the referenced studies shows this protocol.

I am actually surprised how much it takes.

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From what I understand it is a highly variable thing largely depending on muscle fiber composition. Athletes with predominantly fast twitch muscle fibers are more fragile and must be careful with high intensity. Athletes with predominantly slow twitch fibers are more tolerant to high intensity.


One might argue that SSB fits the bill. Especially if you have a slightly inflated FTP.

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i only do two “hard” workouts a week, so no trouble there either.

This article is fantastic. But mostly just because of their Figure 1:


@stonerider they did two types of HIIT workouts…5x4min and 5x8min. 5x4min were executed at a workrate that equalled ~95% of VO2max. VO2max usually happens a little before MAP…so if you had a 300W ramp-test-derived FTP that would mean 5x4min at 360W. That’s HITT workout #1.

HIIT workout #2 was 5x8min @ ~90% of VO2max. So that would be something like 340W 5x8 if you had a 300W FTP.

Pretty tough workouts!

If you had a 300W FTP that week 4 schedule might look something like:

Monday: 5x8min @ 340W w/3min rest
Tue: off
Wed: 5x8min @340W w/3min rest
Thu: 5x4min @360W w/3min rest
Fri: off
Sat: 5x8min @340W w/3min rest
Sun: 5x4min @360W w/3min rest

Sounds crazy! On the other hand…how many of us have done some sort of crazy routine like this before a business trip or vacation? Thinking we can cram 2 weeks of training load into the 1 week before a trip & then let the trip be 100% recovery. :rofl: :joy: Maybe not such a good idea!

I went back and found this discussion from the TR podcast. Good commentary on the nuanced difference between over reaching and over training.

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Are you sure? Here’s a screenshot of mine. During the build and specialty phases (criterium low volume plan) it’s 3 weeks of increasingly more difficult HIIT.

Overtraining makes you overtrained? Woah!


Here is Ronnestadt talking about a more sane way to approach HIIT periodization. 5x/week blitz followed by a few weeks of ~maintenance level work. The periodized approach produced superior results. Don’t make me an advocate for this type of training approach…I’m just throwing some info out there. The original post was a super interesting paper about how NOT to do it…here is an example(s) of some approaches that seem to be a better way.

I guess there can be a thin line between overreach and overtrain.

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lol, good point. TR plans are hard, but I took it to mean daily progression, so 3 days a week still has 4 off days.

I was considered tryng a similar block periodisation on my next VO2 block. I’ll probably do Mon/Tues/Weds of week 1 and then decide what to do for next two-and-a-bit weeks based on how close to a date with the grim reaper I feel on Thursday morning.

Those workouts don’t fit the protocol definition of HIIT, and even if they did it would be the “Moderate training” phase.

“ The training load during the ET phase consisted of almost daily intervals at the all-out effort and must be considered a rather extreme type of exercise training that only highly motivated individuals can tolerate for more than a few days in a row. Therefore, we do not see a high risk that people wishing to improve their health through exercise enter the state of mitochondrial impairment and glucose intolerance due to ET volumes.”

I think it would be a short argument.

This I thought was more interesting (of national endurance athletes:

Athletes spent 41 min per 24 h in the hyperglycemic range (>8 mmol·L−1) compared with 22 min for the controls (Figure 7A) (t test, p = 0.005), 1,284 min in the normoglycemic range (4–8 mmol·L−1) compared with 1,384 min for the controls (Figure 7B) (t test, p = 0.001), and 115 min in the hypoglycemic range (<4 mmol·L−1) compared with 34 min for the controls (Figure 7C) (t test, p = 0.04). In the athletes, hyperglycemia seemed to occur in the early afternoon and hypoglycemia mainly occurred during sleep between 3 and 7 a.m.

Well, I have first hand experience and I’m not the only one in this forum.

If you, like me, are anaerobically gifted and rely on the ramp test, an inflated FTP is more or less certain. Add to that some “sweetspot” at 95% and you end up with a lot of work at threshold.

Fast twitch fibers are easily fatigued, much more so than slow twitch and can’t handle nearly the amount of fatigue slow twitch fibers can handle.

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Ok….but what does any of that have to do with comparing the study protocol to TR SSB?