Intermittent Thoughts on Building Muscle: The Skeletal Muscle Hypertrophy 101 - Part 2: Getting Big Means Growing Beyond Temporary Physiological Limits.

Image 1: This is another type of "dysfunctional muscle"; distinct from the one we are talking about, here

Although I assume that you all have read the last installment of the Intermittent Thoughts, I took FatFree's comment that he (or she?) was missing the "too comlicated check box" from the old design to the heart (I do so with every comment, btw, so keep them coming) and kick off today's installment of "The Thoughts" with a brief and even more "dumbed down" summary of what we have learned about the (possibly) ascertained and, even if human skeletal muscle hyperplasia existed, dominant factors in the trinity of skeletal muscle growth: Protein synthestic increases in myonuclear domain sizes and the satellite cell driven incorporation of new myonuclei.

Getting big goes beyond ballooning up

You probably will remember the balloon-metaphor, I introduced in the red infobox toward the end of the last installment. Let's briefly get back to that and use it to reavaluate the results from the Quaisar study (Qaisar. 2011, see also "What is Hypertrophy"). Rizwan Qaisar and his colleagues from the Uppsala University in Sweden had analyzed the differential effect of insulin-like growth factor 1 (IGF1) over- and myostatin-underexpression on muscular size and function (the latter is important, since we know that a complete lack of the "muscle growth blocker" myostatin leads to huge, but disfunctional / weak muscles). 

Figure 1: Domain sizes of EDL and soleus muscle fibers in wild-type control, myostatin negative and IGF1 overexpressing mice (data based on Qaisar. 2011)

Now to really understand the meaning of what may be the main message of the study, it is imperative to understand the basic architecture of muscle fibers. If you think about a complete muscle fiber as a bundle of ballons that is wrapped into a strechable net, then each balloon would represent one myonuclear domain. The owe their name to the fact that they actually are the "domains" which surrounding a single myonucleus (lat. plural "myonuclei") within a given skeletal myocyte, which - contrary to other cells in your body - has the ability to hold multiple nuclei. Now, the most obvious determinant of the myonuclear domain size is the ratio of protein in- to protein efflux. And it is this connection on which researchers base their belief that by simply measuring the protein synthetic response to exercise and/or supplementation would suffice to predict long-term increases in muscle size (and subsequently strength / performance).

Growth is limited and myostatin is not just a pain in the ass of anyone who wants to "get big"

Image 2: Sketch of a mammalian skeletal muscle fiber - myonucleus (turqouis), mitochondria (blue),  sarcoplasmic rectilium (buff), tubules (orange), myofibrils (pinkish)  - Artist: Lesley Skeates. Originally from Gray's Anatomy 29th ed. Elsevier. 2008

If you take another look at the data from the Qaisar study (cf. figure 1), you will notice that uncontrolled growth in "one dimension", i.e. exclusive increases in domain size, generates larger muscles, but at the same time renders them dysfunctional, a process of which Qaisar and his colleagues believe that it is caused by a decrease in the number of strongly attached cross-bridges, which are the primary source of the small specific force in muscle fibers with very large MNDs. This hypothesis is by the way supported by a lowered myosin (contractive motor-protein) content per muscle volume in the myostatin negative mice.

In order to really understand why this is the case, it may help if you take a look at the (awesome) sketch of a mammalian skeletal muscle fiber on the right (image 2). The myonuclei are colored in turquois-green, they are connected to the mitochondrion (blue) and the sarcoplasmic rectilium (buff), which is traversed by transverse tubules (orange, and not easy to distinguish). The major part of the muscle fiber is yet made up by myofibrils, which are protein chains containing actin, myosin, and titin...

Ah... wtf. Before someone wants to click the "too complicated"-button again, let's just say the myofibrils are the ones who do the actual work. Now, with the increased domain size (obviously the domain is the "zone" comprising all the aforementioned components that a single nucleus is "responsible" for) and the consequent decrease in myosin content (per volume), as well as the reduced number / density of cross-bridges, i.e. links between the myofibrils to coordinate their action, the muscle loses its functionality. Just like a labor brigade with 5 smaller, smart guys who listen precicely to what their foreman says and work hand in hand can get the job done more efficiently than 5 big, but dump guys, who do not even listen to what their foreman tells them, this type of one-dimensional growth, i.e. an exclusive increase in domain sizes, goes at the expense of muscle function.

From satellite cells to broadcasting towers and back again

Image 3: Myonuclei have a domain, similar to the broadcasting area of a transmitter mast.

So, the myonuclear domain, has nothing to do with some sort of "fenced off" area that is protected by a cell membrane. In physics, we would probably talk about a field, a field of influence, just like an electromagnetic field, with the exception that the signalling from the nucleus does not work via EM radiation, but via gene-signalling... mTOR & Co says hello ;-) Satellite cell recruitment and the "installation" of new myonuclei would thusly be equal to the installation of new broadcasting towers, which make the existing system more effective and allow for further expansion. If you are a mobile communications veteran, who knows the "good" (or rather bad) old days of poor reception you'll know what I mean.

In this context it may be interesting that a very recent study by Antonios Matsakas et al. was able to show that the voluntary wheel running or swimming was able to restore the function of the "over-blown" muscle of myostatin-null (MSTN-) mice (Matsakas. 2011). Another clear cut evidence that exercise induces structural changes which go well beyond the accrual of protein that is not adequately controlled in the MSTN- mice.

Do you take my point now? Ok, then let's get on...

The expression of myostatin, which prevents the myonuclear domains from further expansion is thusly a means by which your body maintains muscular function. Contrary to my friend Adelfo, your body has no interest in looking like Phil Heath... the only reason it has to grow is to be able to survive and survival requires functional strength, not size. There is yet some leeway as far as increase in domain sizes are concerned and it is this leeway that explains the "exorbitant" gains you have been making when you first hit the gym. The lazy bastard (sorry ;-) you have been before, your myonuclear domains were probably far beyond their "functional" limit and, consequent to the acute protein synthetic response to your 1001 biceps curls, "ballooned up" until, just as Darryn S. Willoughby observed it in his 2004 study (Willoughby. 2004), the contemporary increase in skeletal muscle myostatin content brought the expansion of the "bloated" myonuclear domains to an "abrupt halt" (at least that was probably your perception).

Figure 2: Relative myofibrillar protein content and myostatin mRNA expression in the thigh muscles of 11 previously untrained subjects in response to a 12-week (3x per week) resistance training regimen with 3 sets of leg presses and knee extensions à 6-8 reps @85-95% of the 1RM (data calculated based on Willoughby. 2004)

As the relative amount of myofibrillar protein content and myostatin mRNA expression in skeletal muscle from the previously 22 untrained male subjects of the Willoughby study shows (cf. figure 2), the myofibrillar protein accretion is accompanied by profound increases in the expression of muscular myostatin. Or, put simply, the bodies of the subjects, whose thigh volume increase by roughly 16% in the course of the 12-week study period, were sensing that without structural changes, this type of muscle growth would eventually lead to huge, yet dysfunctional muscle fibers - something that obviously would not promote survival and is thusly not part of our genetic program.

Structural changes facilitate new growth

On the other hand, the constant overload to which (I hope) you are exposing yourself in the gym signals your body that without increasing strength (again, your body does not care about size), it will not last much longer is the "adverse environment" of the gym. So, the only way to "survive" is to rebuild / restructure the muscles, a process of which we have seen in the last installment of this series that it goes hand in hand with decreases in the number of purported hypertrophy prone "ultra-fast" twitch type IIb muscle fibers (or rather the content of respective myosin heavy chains within your muscles). Whether the resulting phenotype is that of a bodybuilder, characterized by increases in both the number and size of slow-twitch type I and fast-twitch (intermediate) type II-x fibers, or that of a powerlifter, characterized mainly by increases in the number and size of (intermediate) type II-x fibers, depends on the training stimulus, alone:

Image 4: Our bodies respond to different training routines by distinct changes in the muscular structure.

• Wanna get strong like a German Olympic gold medalist Matthias Steiner? Then goto the gym, 10x a day and do a 1-rep max plus minimal auxiliary work like people the Bulgarian O-lifters are supposed to do. 
• Wanna get big like Arnold? Then follow his example and break into your local gym on Sunday (Arnold's was not open 24/7 back in the day, but that did not stop him from training) and pump out rep after rep, after rep to make sure your body understands that you want to maximize both type-I as well as type-II fiber size.

This does not mean that you cannot get big and strong, it does yet mean that a competitive bodybuilder will - per pound of lean body mass - always be weaker than a powerlifter.

"I need YOU!" ... to pick my brain and steer this series in the right direction

The sixty-four-thousand-dollar question now is: What is the "best" way to let your body know what you (not even your brain, but rather your mind) wants? And even at the risk that I am losing my "guru status" now, I want to be honest with you: I don't know the answer... at least not yet ;-) I thusly depend on your help, on people like Steven Acerra, who is constantly picking my brain with interesting questions and studies on facebook, Mike T Nelson, who lately jumped in on an interesting discussion on training stimuli, "Fat Free", Aaron, Matt, Erik Istre, Lerner (whose comments I have been missing lately) and all the rest of you who chime in with questions, suggestions or the simple assessment that the "good Dr. Andro" is once again making things only more complicated ;-)

And as a food for thought, I give you a sneak peak at what should come next in this series: It is the intricate relation of protein and endocrine signaling by which your muscles and no central governor or transient elevations in isolated systemic testosterone, growth hormone or insulin levels regulate the concomitant increases in muscle protein synthesis and satellite cell recruitement and changes in the myosin heavy chain composition. So, assuming that this installment of the Intermittent Thoughts did not raise further questions as far as the basics are concerned, the next installment will revolve around the role of IGF1 and its local (=intra-muscular) cousins MGF and IGF-IEa, which appear to play a key role in the the coordination of the restructuring process that will keep your muscles functional, even when you are approaching a Olympia stage ready bodybuilding physique.

Intermittent Thoughts on Building Muscle: The Skeletal Muscle Hypertrophy 101 - Part 1: What is Hypertrophy?

Image 1: Governator, Arnold Schwarzenegger, as a teen and in his early twenties. What - puberty aside - were the underlying mechanisms of the obvious increase in sleeve-size? I mean on a strictly myocellular level, of course ;-)

Those of you, who have been following the Intermittent Thoughts series over the last weeks will probably already have realized that I finally dropped the "Intermittent Fasting" from the title... this is something I have been thinking about for quite some time now. After all, the series has evolved way beyond its initial focus on a specific dietary protocol and has become more of an educational "how do you find your way to success"-series. With the format, intermittent thoughts, being still the same, the upcoming posts in this series, which will certainly touch on the topic of intermittent fasting, again, will be titled "Intermittent Thoughts on..." whatever the topic of the week may be... and for this week's installment the latter is going to be "Building Muscle: The Skeletal Muscle Hypertrophy 101".

I can already foresee that this is only the first in yet another series of posts. An introduction into the myocellular mechanisms that turn a normal teen like into a symbol of physical culture, or, to put it simply:  

What actually is skeletal muscle hypertrophy? 

Before I even try to answer this question let me remind you of something you have learned about "growth" in one of the previous installments of this series. In "Building Muscle Starts With Losing Weight" you have learned that one of the greatest fallacies of "classical" bulking, as in "eating everything that cannot escape your ravenous hunger for mass", is adipocyte hyperplasia. You may also remember that this increase in the number of fat cells occurs, when your existing fat stores are ready to burst and your body is in need of new storage capacities. Analogously, you would expect your muscle fibers to "hypertrophy" (from mechanical overload and constant nutrient abundance) until they are "ready to burst" and then divide and form new muscle fibers. (Un?)fortunately, myocytes are not adipocytes and thusly things are working somewhat different, here.

Figure 1: Overview over the three (?) pathways by which your skeletal muscles "grow".

If you take a look at the graphical overview I have come up with in figure 1, you will see that there are two, maybe three distinct pathways which contribute to what the average trainee subsumes under "hypertrophy".

1. Pathway A - hypertrophy via satellite cell recruitment and increases in the number of myonuclei per muscle fiber,
2. Pathway B - hypertrophy via increases in myonuclear domain size within an existing muscle fiber, and
3. Pathway C - hyperplasia, which would be the increase in muscle size by cell division and thusly an increase in the number of muscle fibers

The existence of different fiber types, or to be precise, the co-existence of different fiber types (fast twitch, slow twitch and various sub-types) at varying ratios within a single muscle group complicate things even further. Instead of giving you the usual theoretical lowdown on type I and type II fibers and how the former are supposedly used for endurance and the latter for strength training, I want to discuss the matter from a more practical perspective and first pose the question: What is that we actually want? 

I mean, you do not want "hypertrophy", but you want to get big and buffed, right?

Assuming that this is the case we should initially define "big and buffed" on a myofibrillar level by taking a look at how the muscles of the forerunners of physical culture actually look like - and I promise, what you will be learning today will, once again(!), go against conventional wisdom. Or would you have expected that bodybuilding is a sport that is characterized by a loss in highly glycolytic type IIb fibers and increases in both the intermediate type IIa, as well as the "endurance type" slow-twitch muscles? No? Well, then you should have a look at the data in figure 2:

Figure 2: Fiber composition of bodybuilders, recreational lifters, endurance rowers and sedentary control; determined via myosin heavy chain (MHC) isoform content of the triceps brachii muscle (data adapted from Jurimäe. 1997)

The results of the 1997 muscle biopsies by Jurimäe et al.  (cf. figure 2) clearly show that "getting big and jacked" is by no means about maximizing the "hypertrophy-prone type II fibers", as you may have read it numerous times on one of the thousand bulletin boards, or the numerous blogs of self-proclaimed fitness experts (Jurimäe. 1997). A bodybuilder is rather a person who has maximized the expression of myosin heavy chain I and IIa. Specifically with reference to the latter, the authors write:

It is interesting to note that Kraemer et al. (1995) have reported a lack of change in the area of fibres consisting predominantly of MHC type IIb proteins (i.e. FTb fibres) as a consequence of a 12-week resistance training programme. This suggests that a shift from MHC type IIb proteins to type IIa MHC isoforms may be a necessary prerequisite for FT fibre hypertrophy to occur. Consistent with this was the significant negative correlation (r = -0.67) between the percentage of MHC type IIb isoforms and arm circumference. Similarly, the smaller arm girth of the C group may have been partially due to the greater content of MHC type IIb isoforms in this group.

Or put simply,  the "strong" type IIb fibers have a very limited (if any) propensity for hypertrophy. So that, in order to maximize growth, it is necessary to trigger a shift towards the more "intermediate" type IIa fibers. If you take into consideration, how almost all bodybuilders got, where they are now, i.e. by a volume training approach, this is actually something you should have been able to infer simply from what has been and is still working for 99% of the trainees.

Figure 3: Intercorrelations between myosin heavy chain (MHC) isoforms and isoinertial (1-RM max), isometric (extension) and isokinetic (extension peak torque) strength indices (data adapted from Jurimäe. 1997)

Moreover, the data in figure 3 shows that this does not necessarily mean that they have to sacrifice their strength, as the percentage of type IIa fibers does not only correlate with increased muscle size, but also with increased isoinertial (1-RM max, r=0.66), isometric (workload, r=0.51) and isokinetic (peak torque, 0.61). strength. Getting big and buffed and getting strong thusly both require a profound shift in the "God given" fiber composition, but why?

Skeletal muscle hyperplasia - yes or  no? While there are a handful of studies which speak of hyperplastic responses to stretch or other form artificial overload, many (if not all) of them have been done on avian myofibers (Kelly. 1996), which, due to their special make-up, make it a) very difficult to distinguish between increasing overlap due to the longitudinal growth of intrafascicularly terminating skeletal muscle fibers and "real" hyperplasia and b) may not even translate to human beings. That's the reason, why I will disregard the issue of hyperplasia in the following discussion.

A very recent study by an international group of scientists from Sweden and the USA, may provide some insights, into why these fiber-transformations are necessary if you want to grow tree-trunk legs and sleeve-bursting arms. In this study, which was published on November 28, 2011, in the FASEB Journal (Qaisar. 2011), Rizwan Qaisar and his colleagues provide a detailed analysis of the the muscle fiber composition of mice who are either myostatin-negative or over-express the muscle building growth hormone IGF1 (we are talking about intra-muscular IGF1, here! More on that in future installments of the series).

Figure 4: Cross sectional area (CSA), number of mynuclei and myonuclear domain size of myostatin negative mice and mice overexpressing IGF1 relative to wild-type control (data calculated based on Qaisar. 2011)

As you would expect, both the myostatin-negative, as well as the IGF1 mice were more muscular than their wild-type cousins. There were, as you can see in figure 4, yet significant differences in fiber sizes (CSA), the number of myonuclei per fiber, and the domain sizes of the individual myonuclei in the exclusively fast-twitch extensor digitorum longus (EDL) and the predominantly slow-twitch soleus muscle.

Image 2: The balloon metaphor of skeletal muscle hypertrophy.

Note: If you picture a muscle fiber as a number of balloons which are held together by an elastic net, then the myonuclei would be within the individual balloons, which, in turn, would represent the myonuclear domains. You could thusly increase the muscle size, i.e. stretch the net, by either inflating the balloons, i.e. increasing the domain size, or simply adding more balloons to the net. The latter would then be equivalent to the recruitement of new myonuclei from the satellite cell pool in the sarcoplasma of the muscle fibers.

If you take a closer look at the data you will notice that in the IGF1 mice the predominantly fast-twitch EDL muscle growths mainly by increases in myonuclei number, a feature that is absent in the predominantly slow-twitch soleus fibers. The profound increases in myonuclear domain size that occur in the myostatin-negative mice, on the other hand, result in profound reductions in muscle function.

Figure 5: Specific force, stiffness and myosin content (secondary axes) of EDL and soleus muscle in wild-type control, myostatin negative and IGF1 overexpressing mice (data based on Qaisar. 2011)

Both specific force, as well as as muscle stiffness, are profoundly reduced in the EDL muscle of the myostatin negative mice (cf. figure 5), because they have surpassed the maximally sustainable domain size and have thusly become dysfunctional.

Figure 6: Domain sizes of EDL and soleus muscle fibers in wild-type control, myostatin negative and IGF1 overexpressing mice (data based on Qaisar. 2011)

This becomes even more obvious if we take a look at the domain sizes in isolation (cf. figure 6). It is the "uncontrolled" growth that is partly a result of a lack of satellite cell recruitment and consequent increases in myonuclei number, which cripples most of the animals with mutations in the myostatin gene.

Muscle hypertrophy = increases in myonuclear number & domain size

Healthy muscle growth, that is the intermittent take-away of this installment of the Intermittent Thoughts on building muscle, is thusly a direct result of "hypertrophy", as it is commonly associated with increased protein synthesis (and decreased or constant protein breakdown) and the subsequent expansions of individual myonuclear domains and the recruitement of satellite cells, which will then form new myonuclei.

As you may have noticed from the increasing amount of typos, of which I have probably overlooked 50% (sorry for that), my Sunday time-budget is already exhausted, so that I will have to postpone the discussion of what triggers these processes to the next installment. I do yet hope that the stuff you learned today provides enough food for thought to get you through the week ;-)

Ursolic Acid and The Narrow Line Between Anabolism and Myotoxicity: +25% Increased Protein Accretion in In-Vitro Study, But Cell Death With 2x "Effective" Dose

Image 1: "An apple a day keeps the doctor away!" And though the ursolic acid in its peel may be part of the underlying mechanism, this does not make it a "natural anabolic", but rather another item on the list of "healthy stuff from real food"

The number of purported natural anabolics increases year by year. Against the background that most of these products are nothing but supplemental nonstarters in shiny bottles and boxes with "non-FDA approved" promises of "unparalleled muscle growth" on them, the recent release of a broad range of ursolic acid supplements must already be considered a "highlight". With a peer-reviewed rodent studies backing its anti-catabolic, pro-anabolic properties (Kunkel. 2011), it appears as if ursolic acid could be more than another potent placebo. And if we put things into perspective, in the end its potential beneficial effects on skeletal muscle hypertrophy are rather negligible compared to its previously proposed role as a therapeutic compound in various conditions such as Alzheimer’s diseases (Wilkinson. 2011), cancer (Kim. 2000; De Angel. 2010; Pinon. 2011), and diabetes (Zhang. 2006; Jayaprakasam. 2006).

More ain't more, but toxic! And even less is probably more than you can get.

Only recently, Vandré Casagrande Figueiredo and Gustavo A. Nader were able to confirm the muscle building effects in an in-vitro study using C2C12 myoblasts which were incubated with different concentrations of ursolic acid for 72h (Figueiredo. 2012).

Figure 1: Protein content and cell viability after 72h incubation with different concentrations of ursolic acid (in µM); light bars p > 0.05, statistically non-significant (data calculated based on Figueiredo. 2012)

As you can see in figure 1, this treatment lead to dose-dependent increases in protein accretion in the muscle cells. These increases reached statistical signficance only in the 10µM group (their real-world significance is even more questionable, as we don't know if similar concentrations can even be achieved by oral administration of ursolic acid).

The profound loss of protein in the higher dose groups and the subsequent decrease in cell viability, on the other hand, are statistically highly significant. Their real world significance does yet appear to be even more questionable, after all, it is rarely possible to double the serum concentration of a given substance by just ingesting twice as much. At the dosages that are present in the currently available supplements myotoxicity, as it was observed in this in-vitro study, is thusly probably not a real concern.

No reason to be afraid, but no reason to expect grandiose results, either

Image 2: These muscles were not build on ursolic acid - that's for sure.

In other words, while the study at hand did help us to elucidate the underlying mechanism of previously reported benefits under mostly atrophic (=muscle loss) conditions, its overall real-world significance in view of the negative, but also in view of the positive effects appears to be more than limited. If you also take into consideration that the scientists were able to rule out that ursolic acid exerts hyperplastic (cell proliferation) effects on skeletal muscle tissue, that its "muscle building" effects (referring to the increased protein accretion observed in the study at hant) was highly dependent on the presence of additional growth factors in the culture medium and that ursolic acid did not increase the myocyte RNA levels, it remains questionable whether the ingestion of respective (most certainly underdosed) supplements will produce any significant improvements in training and diet induced skeletal muscle hypertrophy.

In the end, the new data stand in line with the observations of Kunkel et al. who identified an increase in skeletal muscle insulin sensitivity and subsequent upregulation of the IGF-1 induced growth response as the underlying cause of the atrophy-inhibiting effects or ursolic acid. What can be said for sure, however, is that the currently available OTC supplements are in no way "muscle builders". According to the currently available research, they should rather be filed under "health supplements", along with alpha lipoic acid and the like. Now, that does obviously not exclude that the health improvements - above all the improvements in insulin sensitivity could not help you build muscle - the label "natural anabolic" does yet still appear largely misplaced.