Tuesday, September 20, 2011

Ripped & Buffed vs. Skinny and Sinewy: Training Velocity, not Load, Appears to be Sole Determinant of Exercise Induced Shifts from Slow- to Fast-Twitch Muscle Fibers.

Image 1: Who would you like to be?
And how do you train to achieve
his physique?
Sprinter or marathon runner? Ripped and buffed or skinny and sinewy? Although this is, after all, a question of muscle vs. fat, bone and tissue mass, it is upon closer examination as much a qualitative question, as it is a quantitative one - a question that may well be influenced by the way you train!

Unlike our adipose tissue which has almost unlimited capacity to grow, the size of our muscles appears to limited by a number of factors, among which the individual fiber-make-up, i.e. the ratio of slow-oxidative endurance-type fibers (type I) to fast-twitch type IIA (fast-oxidative glycolytic), and fast twitch IIX (fast glycolytic) seems to play an important role, when it comes to getting big and buffed or skinny and sinewy.
Figure 1: Slow- and fast-twitch faber composition in athletes and non-athletes (data based on Carrol. 1998; Widrick. 2002)
As the data in figure 1 goes to show, athletes, unlike untrained individuals, who have about the same amount of fast and slow-twitch fibers, exhibit discipline specific adaptations in muscle fiber composition, with sprinters having the lowest and middle distance runners the highest ratio of slow to fast twitch muscle fibers. According to data from Aagard and Andersen, Bergh et al. and Fry et al. (Berg. 1978; Aaagard. 1998; Fry. 2003), the range of slow to fast twitch fiber ratios extends from ultra-endurance runners with a 90:10 slow to fast twitch ratio down to weight lifters and sprinters with a minimum of 20:80 slow to fast twitch fiber ratio.
Muscle fiber type and weight loss: Contrary to what you may have guessed, or read elsewhere, obese patients with a higher amount of oxidative slow-twitch fibers have been shown to lose weight easier than their "heavier muscled" peers. In a 2002 study Tanner et al. report (Tanner. 2002):
With weight loss intervention, there was a positive relationship (r = 0.72,P < 0.005) between the percentage of excess weight loss and the percentage of type I fibers in morbidly obese patients. These findings indicate that there is a relationship between muscle fiber type and obesity.
Image 2: For someone who already got morbidly obese, a higher ratio of type II fibers may well be counter-productive if his/her overall goal is weight loss.
Another result of the same study, which could easily be misinterpreted as politically incorrect is the genetically determined higher raio of type II muscle fibers within the African American part of the female study population, which made it increasingly harder for these women to burn the fat. And just in case, you still wonder why a type I fiber, something obviously only skinny people have in excess would help with losing fat, just think about the term "oxidative muscle fiber" for a moment, then add to that the experimental observation that type I fibers have greater mitochondria volume densities than type II fibers (Sullivan. 1978) and you will realize that a highly oxidative muscle fiber is more valuable when it comes to burning fat than a glycolitic one, reagardless of whether or not the latter may "look" better ;-)
In a recent review of the literature Wilson et al. provide the following biological explanation for the differences that exist between endurance and strength athletes (Wilson. 2011):
[...], type I fibers have been observed to have both greater mitochondria volume densities as well as capillary-fiber contact length when compared to type II fibers.  In addition, mitochondria volume density was highly correlated (r = 0.99) with O2 diffusion coefficients across three different muscle groups (retractor, sartorius, soleus) suggesting greater aerobic capacity in type I fibers.
While type I muscle fibers will thus figuratively carry their owners in 80 days around the world, type IIX and IIA fibers exhibit a 10x and 6x greater peak power and a 4x and 3.3x greater contractile velocity than their oxygen-hungry slow twitch cousins.
Figure 2: Relative peak power and contractile velocity of fast twitch fibers vs. slow twitch fibers (data based on Wilson. 2011)
The reason that the two guys from image 1 do not only perform but also look completely differently, lies yet in the greater capacity of type II fibers for exercise-induced hypertrophy (Schoenfeld. 2000). The relative number of type II to type I fibers is thus of paramount importance, if you want to look like a sprinter - not like a marathon runner and if you want to lift heavy weights instead of running cross-country. Fry et al., for example found strong correlations (r = 0.94; almost "causative") between the percentage of type IIA fibers and 1 repetition max snatch performance in national caliber Olympic athletes (Fry. 2003). Now the obvious question is: "How can I influence my individual fiber composition, or is this simply genetically determined?"

It stands to reason that genetics is a major determinant of fiber composition, but, hardgainer or not, with appropriate training and nutrition everyone can - at least to a certain degree - shift his muscle fiber make-up from a slow-twitch oxidative to a fast-twitch glycolytic type, even without the use of clenbuterol and other beta-2 agonists which hav been shown to trigger respective shifts from type I to type II muscle fibers in a rodent model (Zeeman. 1988).

Training for shifts in fiber composition

From Wilson et al.'s review of the literature it becomes quite obvious that standard exercise regimen, like jump squats at either 30% or 80% do not provide satisfactory results for someone looking to increase the number, not the size of his glycolytic muscle fibers (Wilson. 2011). In a study by Liu et al. (Liu. 2008), a 5x3RM bench press protocol, performed 3 times per week for 6 weeks, on the other hand, triggered a shift within the type II fibers. It increased the percentage of type IIA fibers from 44.9% to 66.7%, but decreased the type IIX fibers from 33.4% to 19.5%, thus leaving the percentage of slow twitch type I fibers unchanged. A second group from the same study who used a more versatile routine, with the same 5x3 regimen on Mondays, 10x concentric-repetition bench press throws at 30% of their 1RM on Wednesday and 10 stretch-shortening type push-ups on Friday for 5 sets, each, were able to increase the number of type IIA muscle fibers (from 47.7% to 62.7%) without decreases in the number of type IIX fibers, but a profound -50% reduction of slow-twitch oxidative fibers (from 18.2% to 9.2%). Wilson et al. go on and cite several other studies that were able to show the modulatory (increase in type II, decrease in type I) effects of high-velocity contractions on muscle fiber composition (Wilson. 2011) and corroborate that results with findings from other studies which corroborate these results with ...
[...] findings that the percentage of type I fibers may be increased with various types of aerobic training protocols such as endurance cycle training (+12% Type 1) and long distance running (+17% Type 1), [where, on the other hand] studies indicate that sprint training may facilitate the change of slow twitch fibers to fast twitch fibers.
Interestingly, Hortobagyi et al. were able to show that laziness taken to the extreme, i.e. 3 weeks of knee immobilization, also reduced the amount of type I fibers (-9%) and increased the number of type IIX fibers (+11%) in 48 recreationally active men and women (Hortobagyi. 2000). These results should yet be treated with appropriate caution and I would strongly advice against lying on the couch to increase your propensity for muscle growth by decreasing the number of slow twitch and increasing the number of fast twitch muscle fibers, because "recreational activity", for most people, consists of aerobic type of exercises, playing soccer, tennis or whatever - all sports that by and out of themselves would trigger shifts towards a more oxidative (predominant type I) muscle composition. It is thus not surprising that refraining from such activities for 3 weeks would reverse those changes.

So how should you train, then?

In view of the paramount importance of speed, not load in the few experiments which challenge the hitherto established paradigm that muscle fiber composition was largely determined by genetics and transformation was possible only within type II fibers, i.e. from type IIA to type IIX and vice versa, the incorporation of respective training techniques, e.g. concentric-repetition bench press throws at 30% of your1RM, as they were used in the study by Liu et al. (Liu. 2008), into a more versatile hypertrophy-specific routine which would
  1. trigger a hypertrophy response, on "classic" strength training days (like 3x5 or 3x8-10), and
  2. increase propensity for growth, on "speed-rep" days with exercises like plyometric push-ups, concentric-repetition bench press throws at 30% 1RM, etc.
would appear to be the most reasonable way to train for anyone out there, who does not belong to the "genetic elite" of born sprinters.


  1. Looks like I can always trust this RSS feed to make me stay up late scourging for more info...

    So speed-rep days would be just plyo days? Most of the plyo exercises I know involve legs, how would you train for example biceps explosively? Medicine ball throws with arms only?

  2. Couldn't the use of various vascular occlusion techniques like Kaatsu, isometrics, reduced time between sets on a exercise and reduced range of motion when performing a exercise to maintain tension produce similar effects?

  3. Hi Doc,
    Quick question, just wondering what nutritional changes or habits would support a change from type I to type II fibres? Or is it really just dependant on training type?

  4. Very interesting blog post once again. It would be interesting to know if the plyometrics have to be done on a separate day or if I can just incorporate them in to my workout routine in order to achieve optimal results. Besides that, do you think the benefits of a plyometrics day can really compensate for the missing hypertrophy day (assumes that you replace an existing hypertrophy day with the plyometrics day)

  5. 1) you can do concentric reps for biceps and in fact this is what I see many people do. explosive on the way up... similarly you can do boxing type exercises for triceps like holding a barbell in front of your head and "boxing" it towards an imaginary enemy ...

    2) I don't see benefits of Kaatsu, which would be in line with (http://journals.lww.com/acsm-msse/Abstract/2003/07000/Resistance_Training_with_Vascular_Occlusion_.20.aspx), reduced range of motion or continous tension (the latter could even be detrimental), but maybe you have read studies I am not aware of?

    3)as far as I know only beta-2 agonists have hitherto (in rodent experiments) shown to directly trigger such shifts... otherwise you would obviously benefit from supps that work for sprinters, i.e. increasing / sustaining maximal speed and performance in the gym

  6. wrt to 3) I forgot to mention that in the next installment of the Intermittent Thoughts on Intermittent Fasting Series I will start out with some elaborations on AMPK which are of relevance here, because chronic AMPK elevation could induce the reverse effect, i.e. reduce the amount of type II fibers

  7. the latter being said, everything that keeps mTOR up (Leucine, BCAA, protein, weight training) etc. would at least ward off any (re-)conversion from type II to type I

  8. and another one on 2) I just realized that you were probably thinking of occlusion training = greater recruitment of type II fibers = more type II fibers? I would not think so... its rather like "isolation training" for type II fibers... if you ONLY did that, maybe some type Is would atrophy, but would the desired shift take? I doubt that...


  9. 3) You should also watch out that you have a healthy throid (not eat soy, other goitrogens) "Of all hormones, thyroid hormones appear to have the greatest effect on muscle fiber phenotypes. In general, hypothyroidism causes fast-to-slow transitions (Fitts
    et al. 1980; Ianuzzo et al. 1977; Nwoye and Mommaerts 1981), while hyperthyroidism elicits transitions in the reverse direction. Reduced levels of thyroid hormone cause
    fast-to-slow shifts in MHC isoform expression, whereas high levels of thyroid hormones cause low-to-fast shifts (Caiozzo et al. 1992; Canepari et al. 1998; d’Albis and
    Butler-Browne 1993; Fitzsimons et al. 1990; Izumo et al.
    1986; Kirschbaum et al. 1990; Larsson et al. 1994; Li et
    al. 1996)."

  10. http://www.jstage.jst.go.jp/article/ijktr/4/1/4_1/_article




    Many more studies since 2003 on ischemic training.

  11. Hmmm, may have to add a few sets of speed work in on my rest days.

    Good post as usual. Keep it up!

  12. This may interest you as well.


  13. while I see your point, Anonymous, as far as building muscle is concerned. you are sort of off topic with your Katsuu type of training, because it DOES NOT CHANGE muscle composition

    * change in fiber composition not measured
    * no change in relative strength which would be a results we should expect if the number of type II fibers increased

    * mTOR signaling - if that worked, you could as well take leucine, so again muscle growth, yes... fiber changes, no
    * same here > http://jap.physiology.org/content/103/3/903.short

  14. http://www.jstage.jst.go.jp/article/ijktr/4/1/4_1/_article Since Kaatsu effects are more a local metabolic/hormonal training rather than a strength/neurological loop program, you would expect more rapid hypertrophy with strength effects occurring later. Six days of training and expecting large strength changes?

  15. http://www.jstage.jst.go.jp/article/ijktr/1/2/1_65/_article

    No fiber changes? " We concluded that skeletal muscle and fiber hypertrophy, especially type-II fiber, occur after high frequency KAATSU training."

  16. the problem I am seeing here is that this is absolutely identical to normal strength training - the hypertophic response in type II fibers is greater, thus any form of strength training will shift the ratio if you just look at muscle size, but there is no shift from type I to type II fibers involved. It's as I have pointed out before that the type II fiber grow, say 50% faster and thus you shift the ratio - you do not "convert" type I to type II no matter how long, severe or whatever you restrict blood flow

  17. Yasuda et al (2005) observed a
    7.8% and a 1.8% increase in quadriceps muscle CSA
    in KAATSU and no-KAATSU groups, respectively,
    after a 2-week training (at 20% 1-RM) program. Type
    I and Type II muscle fiber CSA increased 5.9% and
    27.6% following KAATSU training, whereas changes
    in Type I and Type II fiber CSA were -2.1% and 0.5%
    after no-KAATSU training, respectively. The findings
    suggest that skeletal muscle hypertrophic responses
    may not only be due to changes in water balance
    created by blood flow restriction, but due to increased
    protein synthesis.

    This ratio increase in type II fibers is what I think most trainees are looking for in the promotion of hypertrophy.

    My view is that the "normal" strength training is a difficult physical program to maintain. As someone who has trained for over 45 years and known others of the same ilk, higher load lifting for many is a non-sustainable activity. I also treated many lifters over 20 years and have seen the damage of higher load lifting. The use of techniques that will stimulate or at least maintain hypertrophy using lesser loads is my area of interest. The use of different forms of isometrics, reduced range of motion, shorter rests between sets, etc that reproduce Kaatsu effects which has demonstrated potential near high load lifting is I think a more sustainable form of resistance training. Your thinking may differ.

  18. actually my thinking is not diffrent, I am 100% on par that Katsuu has its place where "normal" lifting hits a wall. That being said, my point was that there is no FUNDAMENTAL difference between the outcome of the two and that neither "transforms" muscle fibers, while both increase the ratio of the type II to type I fibers, because the latter RESPOND BETTER to the training stimulus.

    btw: I don't know who you are, but since I am very interested in occlusion training myself, but have no practical experience whatsoever, I would be pleased if you would provide the SuppVersity readers with some insights into your own practical experience (and the science behind your approach), or in other words: write a guest post, in which you could obviously plug any services (I assume you are a trainer) you are offering as long as the whole thing does not turn into an ad

  19. I have no services to plug and no entrepreneurial goals. I do make comments on other sites in regards alternative ways to perform resistance training especially in regards to the use of lighter loads. I have done comparison work using a blood pressure cuff and experimented using different training techniques without artificial external devices to try to simulate the Kaatsu type experience. I have attempted to marry the work of many authors. Part is from Kopov with the use of short range work. Much is from research on different forms/hold times of isometrics finding the short oscillating form most useful due to the high frequency of short contractions that may better sustain occlusion. From the studies that I reviewed on isometrics, there appears to be a strong pressure/intramuscular effect with the starting contraction then some "leakage" afterward as the hold continues. Also reviewed were studies on blood lactate and other metabolic products produced by different rest times between sets. The mix of many elements has produced several training models that I have posted on other sites.

    I wonder if some of the success with muscle protein synthesis and signaling coming out of McMaster U. using low intensity training is due to the higher metabolic buildup from the high rep training?

  20. hi anonymous, sorry I did not get back to you before. Plenty of work to do... while you did not provide an answer on my initial question on whether you would be inclined to write something up, I thank you for the reference points ;-)

    Stuart Philips group at McMaster has done a hell lot of interesting work, and you are right wrt to the fact some of their data suggest that the mantra to hit it hard is not really scientifically sustainable (or at leas only part of the picture); they have for example shown that the increases in GH are negligible and it is (in part) due to their work that the non-hormonal signaling cascades have now become the focus of scientific attention. Dunno if you already have, but if not, I suggest you dig deeper into HSP (heat shock proteins; my best bet they are involved in the benefits of Katsu & co, as well > http://www.ncbi.nlm.nih.gov/pubmed/19885776 < a starter)

  21. In reference to the study you posted, I have had communication with Loenneke and discussed aspects of blood flow restricted training and personally have started utilizing the technique. I have his full papers,"Blood flow restriction: The metabolite/volume threshold theory" and "A Mechanistic Approach to Blood Flow Occlusion". The latest studies about the effects of blood flow restricted training on myostatin and signaling http://journals.lww.com/acsm-msse/Abstract/publishahead/Strength_Training_with_Blood_Flow_Restriction.98840.aspx and http://jap.physiology.org/content/108/5/1199.abstract?sid=9ecb7b20-687e-416c-bb45-399059651472 gives even the older lifter some hope.

  22. I am familiar with the paper "A Mechanistic Approach to Blood Flow Occlusion", but must concede that we still don't really know how blood flow restriction does its magic... I would yet think that one of the reasonable explanations Loenneke cites is actually NO, which has been shown to faciliate satellite cell recruitement in aged muscle


  23. I have used Kaatsu in my own training and I am of the opinion it's an IGF-1 mediated effect - the increased lactic acid build up during sets should result in greater cleavage to the more anabolic IGF-DES peptide, and the high GH signalling from the ischemia should stimulate more endogenous IGF production in the liver. That's why, I think, doing Kaatsu exercises with more FREQUENCY is key - you'll get a lot of GH responses that are typical of normal training. Granted, there are some studies (I saw the takedown on the biceps-after-legs you did) that suggest maybe this is not a large effect, but hypoxia is a definite trigger of anabolism, and I think the IGF-1 cleavage is an intriguing candidate.

    I did this write up a bit ago, it seems to be an effective program:


  24. Some of the problems interpreting the Kaatsu studies is if the use of momentary failure was utilized or just a 30-15-15-15 pattern of reps using a low 1RM. This new study shows some of the stronger effects if the training is performed to failure-http://www.unboundmedicine.com/medline/ebm/record/21947453/abstract/Contractile_function_and_sarcolemmal_permeability_after_acute_low_load_resistance_exercise_with_blood_flow_restriction_

    I believe the width of the wrap/tourniquet may be a factor that is overlooked.

  25. I was curious as to how KAATSU got started and found:

    written by the creator, Sato. It seems it all began when one day his leg fell asleep at a Buddhist mass.

    It's also noteworthy that during his early experimentation while in college he gave himself a Pulmonary Embolism (PE), which is a blood clot that formed in a leg and traveled to a lung. A PE can be fatal.

    And btw, here's a video showing use of belts, rather than the cuffs that I've usually seen:

  26. Question of safety-


    Kaatsu has been successfully used in other studies on patients with different health disorders.

    As with any procedure or approach, abuse can lead to potential problems.

  27. I agree with anonymous on the safety issue. I would rather expect some severe damage to your lower back from heavy duty squatting to build muscle than a blood clod forming from appropriately performed Kaatsu training.

    A pros pos "appropriate", why would you think the breadth of the cuff would make a difference? I would rather think that the position could make a difference... although that would obviously "change" with wider cuffs, as well.

  28. Some of my studying on Kaatsu included looking at some of the variables that may effect the results which included the device used and exercise cadence. Exploring research on the effects of different tourniquets I found studies showing that wider units produced more and deeper compression.