From The “Just A Hunch, Can’t Prove It” Catagory – Fiber Type Expression From Detraining

If you’ve noticed that I’ve not been on facebook or twitter lately, that’s because I haven’t. I’ve found that I can communicate with those I like to communicate with just fine without “social” media. Also it only serves to make me angry so instead of see how much I can tolerate because getting furious, I’ve substantially reduced my time on social media. I’ve not “missed out” on anything and found that I have much more time for things that might actually make me a better human being: Dual N-back training, mindfulness meditation, and reading books, like Self Comes To Mind. My livelihood doesn’t depend on being all over social media so I’ve no need to spend much time there. Find me here or by email.


So I was reviewing some old PDFs I had lying around (inasmuch as a digital file can “lie” around) and I came across an article from Scientific American regarding fast twitch motor units and training as it pertains to athletes. In this article, there is the discussion of how, in the authors’ particular study, they found that after a group trained for a period of time and then was detrained, their relative percentage of fast twitch muscle fibers increased dramatically. The designations used in this article are Type IIa to Type IIx however, while even my exercise physiology textbook designates a IIx sub-catagorization, more recent studies have used this designation:

Back to the study at hand. Take a look at the relative amount of fast twitch motor units that are created (or rather, that the body adapts toward) after detraining:

So the relative amount of IIx fibers doubled after 3 months of detraining. Damn you Art De Vany for being right about everything.

The Hunch

So here’s the “just a hunch” part, where the labcoating begins: maybe people who get great results with HIT do this better than those that do not. I’ve been thinking about this a lot as I’ve ventured into my new experiment and thinking about gains in the past. I’ve been freaky-strong training only once a week and bigger than I am now, albeit not by a huge amount (~10lbs lean mass). It could be that my physiology is spendthift but it also could be that by training so infrequently you’re creating a miniature version of the curve shown above, changing the relative amount of fibers toward a fast myosin expression thus getting way stronger and perhaps a bit larger. Lots of anaerobic stimulus from the incredibly intensive, very brief workouts may have the potential to express a fast twitch machine without adding much mass.

What if you want more mass? I’m looking forward to testing this on myself as well but maybe the periodic, drastic upregulation of volume ala a blitz-type burst becomes the way to a bigger engine. Hypertrophy seems to be muscle more “here and now” when it comes to the stimulus. Perhaps all of this fast-twitch turnover primes the pump for a short period of much higher volume. You have a much larger percentage of fast motor units at your disposal thus any effort you exert for a given volume has the potential to create a much larger homeostatic disruption. You’ve got these giant engines, occasionally you should run them through the rev range. Not only is the alarm state reaction (ala a flu shot) much greater than if you had been training all of the time and reduced the relative amount of fast motor units, but your ability to endure such workouts for very long is physiologically truncated by your fiber ratios (more fast than slow).

Can I prove this? No. Is there some evidence that I can daisy-chain together that at least suggests plausibility? Perhaps, if you believe the study above. This is the extent of my testing for the next few months. The bodpod will tell the tale.


8 thoughts on “From The “Just A Hunch, Can’t Prove It” Catagory – Fiber Type Expression From Detraining

    1. No particular protocol, just a short 2 week blitz that doubles or triples the volume compared to my once-per-week training. Bodpod will be taken before and after.

    1. According to my calipers, I’m leaner and more muscular, just a pound or 2 though. I’ve been intentionally dieting and have dropped 2% bodyfat (3.5lbs) but my weight is only 1.5-2lbs lighter, so a slight improvement in that regard.

      However, part of what I’ve learned since I posted this is that the reason for the shift to Type IIx fibers is because of the inactivity and the relative difficulty, from a CNS perspective, in recruiting these fibers. It’s a lot of effort to get these things firing, which is why from an ease of use standpoint, they convert back toward Type IIb fibers. I suspect that pure power athletes at the highest levels (think high jumpers/long jumpers) have a higher percentage of these fibers and the CNS to carry it. If you’re built like a quarterhorse, all of your fibers better be powerful!

      1. Thanks for that Skyler.

        It’s an interesting example to use, the jumpers. I can’t see them doing super hard sessions, but only doing them infrequently; as far as I’m aware, athletes like these do either long daily sessions or multiple daily sessions, that seems quite the opposite to what your proposing.

        I wonder how you make sense of that?


      2. It’s a sport and they’re not doing what they’re doing to get in better shape. They’re doing it to do what they do better because jumping (in this case) is a skill. Massive numbers of repetitions are necessary to make the jump so engrained in their neuromuscular maps that they could do it in their sleep. By making the skill so engrained, they can maximally recruit all available fibers.

        This of course has nothing to do with training for better health and muscular hypertrophy; they only resemble each other.

      3. Thanks Drew; I thought it might be a bit wordy but apparently I was mistaken!

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