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.

"80-85% 1RM, 6-10 Reps"? Changes in Muscle Fiber-Type in Response to Classic, Super Slow and Light Training Confirm "Old School Training" Rules and Will Always Prevail!

Image 1: If you don't want to be strong and look good naked, you better not train like "old school" like Arnold, Franco Columbu (img), Dave Draper, Frank Zane & Co.

Although, I do assume that you just dropped everything, went home from work early, or simply did not leave the house at all to be able to listen to my appearance on Carl Lanore's Super Human Radio, yesterday, I know that sometimes more important things (whatever that may be) get into one's way and will thusly give you a second chance, today (click here to download the podcast)... well, so far for the humorous part of this post. Assuming that by now, you did listen to the podcast you should remember that I promised to have something about exercise and strength training in the news, today. And as Carl will probably assert, Super Humans usually stick to their promises, although - and I did mention that yesterday, as well - the number of significant studies, i.e. studies that do not involve frail elderly or morbidly obese people, is relatively scarce.

Bro, you know the revolutionary new "GHRWZAR-642421 training principle"?

Image 2: If you are looking for a collection of proven routines, instead of bunch of old hats with funky new names, the Blueprint would be a good choice.

Beside the fact that our interest in improving our health and the way we look by diet and nutrition is not getting all too much love in the major scientific publications, another factor, which in all fairness should not be forgotten is that we do actually know what works, don't we? Sleep, eat, train... with the "common wisdom" with respect to "what is the best diet" being in constant flux, I guess, we are simply expecting to see similarly paradigm changes in the realms of exercise physiology, but aside from the occasional letter salad people are trying to sell you as the latest and greatest new training technique, which then turns out to be the 1001 iteration of what the fathers of physical culture have been doing for ... I guess, centuries, would be correct... the basics, which are to pick up a heavy weight move it through time and space for about 6-10 reps and rack it, never change - for a good reason as the pretty detailed results of a freshly published (actually still ahead of print) study from Mark D. Schuenke and his colleagues just confirmed anew (Schuenke. 2012). 

Lifting heavy objects makes women ... dunno, but not bulky, to say the least ;-)

I guess, I better mention it right away in order to avoid that you get all to psyched out and are disappointed in the end: The study participants were 34 untrained young women (21.1 § 2.7 years). And just to make sure there are no misunderstandings, here - the downside for physical culturists is that these women were untrained not that they were women! The latter, is, as the scientists point out, actually an advantage, because "in pre-vious studies, it has been easy to find eager, untrained female subjects with excellent compliance to protocols", which by the way is another thing, Carl and I talked about in yesterday's installment of Super Human Radio ;-)

The reason that the subjects training status ("untrained") is somewhat of a downside, is yet that the early adaption which occur once you first pick up the weights, are fundamentally different from the painfully slow gains of an advanced trainee or elite athlete. In the end, the latter is yet also part of the reason that scientists don't recruit athletes for studies like this, after all the gains" (both strength- as well as muscle-wise) these subjects would have made over the course of the 6-week study period, in which the ladies in this study performed a total of 17 training sessions (two in the first week, three per week in the subsequent 5 weeks), would have been hardly "significant" - and in this case we are talking about both, statistical, as well as real-world significance.

Figure 1: Graphical illustration of the three experimental conditions / training regimen in the study.

Figure 1 should give you the general idea of the three different training regimen the women were randomly assigned to. With the first one being heavy + fast (TUT was in fact 1-2s for both concentric and eccentric part of the movement; verbal count was provided to make sure the tempo was correct) representing what has worked pretty well for generations of strength athletes, the second one being a variety of the Super Slow principle and the third one representing the "I don't want to build muscle"-approach to weight lifting that is unfortunately still very popular among women, we have the whole spectrum from tried and proven to tried and worthless in here ;-) I guess, it should be mentioned that the number of sets (3 sets, to failure) and the exercises, which were leg presses, squats and knee extensions (I suppose the latter is identical to "leg extensions", but I thought I rather stick to what Schuenke et al. wrote) were identical so that the effective parameters which influenced the study outcome were time-under-tension (TUT + reps) and intensity (% of 1RM) - or to make a long story short: Lift heavy and fast, give yourself a hard time by lifting slow or just pump away with lousy weights to "shape your body" (I hope you see the irony wrt to the last point).

Everyone who believes in "shaping your body with high reps and light weights" raise your hand!

I guess, for most of you it won't  come as a surprise, when I am telling you that there were no changes in total body mass in the course of this 6-week training intervention, but what I guess will be surprising is that the body composition of the women did not change either (cf. figure 2)!

Figure 2: Fat mass (in kg) and fat free mass (in kg) before and after 6 weeks with a total 17 leg training sessions (data adapted from Schuenke. 2012)

If you scrutinize the data in figure 2 you could make a point that there was a 0.1% increase here and a 0.025% decrease there, but I guess, even if you have no clue how those p-values, which indicate if the change in a measured parameter could be mere coincidence are calculated, it is quite obvious that none of these changes reached statistical, let alone real-world significance.

If we take a closer look at what happened "inside" the vastus lateralis muscle from which the scientists took muscle biopsies before and at the end of the study period, it does yet become obvious that our "conventional exercise wisdom" is in fact much more reliable than its nutritional counterpart.

Figure 3: Changes in relative fiber composition in vastus lateralis muscle in response to 6 weeks of leg training with different loading / TUT / rep schemes (data adapted from Schuenke. 2012)

As you would expect, the muscle fiber-types shifted according to the load and the TUT / reps that were used with a generally more pronounced increase in the still highly glycolytic type IIA and type IIAX fibers in the classic standard RT group and a shift towards a more oxidative type II fiber type (type IIC) in the super slow group. As those of you who have read the Intermittent Thoughts on Building Muscle will know, the former precipitates both strength and size gains, while the latter would be something a "strength-oriented endurance athlete", as maybe a rower, could be interested in. What all three training regimen have in common though, is the decrease in the exclusively glycolytic type IIX fibers, of which those of you who have followed the aforementioned series will know that they are quasi-nonexistent in elite bodybuilders.

Training light does work, but does not really do the job

What is also noteworthy, is that the light, yet fast training with high reps, induced what you may call a "transition status", with initial changes in the type IIX fibers (becoming type IIAX), but without the a complete switch from the "unflexible" glucose guzzling type IIX fibers to the cornerstones of strong and big muscles - the type IIA fibers. In view of the fact that the scientists did not quantify the strength gains and that the "higher growth propensity" of type IIA fibers is somewhat of an urban myth, the study outcome with the greatest real-world significance is unquestionable the increase in fiber size, which, as the data in figure 4 goes to show was maximal in all three major fiber types in response to the classic training protocol.

Figure 4: Changes in cross sectional area of the different fiber types (data adapted from Schuenke. 2012)

If that is not enough to convince at least the male part in the audience that there is good reason that the good old "6-10 reps in the 80-85% 1RM range" is still around, I guess they must be beyond help... and as far as the ladies are concerned: I know you don't "wanna get big", but let me tell you this - "strong is the better sexy", and as Carl Lenore would probably add "muscle is metabolic currency". So, if you want to stay mobile into your old days, do your joints and bones a favor by strengthening them in time. Moreover, with the mitochondrial powerhouses in full-gear, a few fixes to your diet should suffice to make those "problem areas" not magically, but gradually disappear.

Apropos diet, while the subjects did not have to log their calorie let alone macronutrient intake, I would bet that with a simple protein shake after their training and some general tweaks to their diets, those favorable changes in body composition, i.e. decreases in fat and increases in lean mass, which are at the heart of "looking good naked" would have come about... with the "I love my pasta and red-meat gives you cancer"-diet from the latest cosmopolitan, on the other hand, you better stick to baggy jeans and huge sweaters instead of bikinis and speedos, ladies and gentlemen ;-)