Showing posts with label satellite cells. Show all posts
Showing posts with label satellite cells. Show all posts

Tuesday, November 12, 2013

Sulforaphane from Cruciferous Vegetables Inhibits Myostatin and Increases Cell Viability in Skeletal Muscle Satellite Cells

Chicken Egg Rolls with Red Cabbage, Mango & Lime (CleanEatingMag); small inset shows sulforaphane content (µg/ml) of a juice made cauliflower, broccoli, red and white cabbage and brussel sprouts (based on Totušek. 2011).
When I am looking at the currently top-rated posts (see box "Most Popular (last 30 days)" on in the right navigation bar), it appears as if someone must have found my older article on the myostatin boosting effects of clenbuterol and told all his facebook friends about it.
Don't forget to check out and tell your friends about the latest SuppVersity Facebook News, as well!
In case this hypothesis is right, he (or she?) and all the friends will probably be happy to hear that there is a virtually side-effect free over-the-counter alternative that can suppress myostatin and thus make your muscles grow faster: Broccoli, cauliflower, cabbage and co (see image on the right and realize Red Cabbare, not broccoli is the King!) - the sulforaphane in these cruciferous vegetables appears to make that possible.

Muscle building veggies... yamyol!

Back in the day Popeye was invented to convince children that it would be worth eating their spinach (unfortunately this advise was based on the false assumption that it was a good source of iron and would thus help build the kids' stamina). I guess when the inventors of Popeye get wind of the soon to be published paper we are going to look at, today, we are soon going to see a digital avatar of Mr. O. munching broccoli in a 3D animated cartoon.

Sulforophane protects muscle against exercise induced damage: Although pertinent studies on the myostatin inhibiting effects of sulforophane outside of the petri dish have yet to be conducted, a rodent study from 2009 did already observe another, likely related effect of sulforophane  supplementation in intact animals. Administered at dose of 25mg/kg (human equivalent: 4mg/kg ~ 300-400mg for an average adult) it exerted significant ameliorative effects on exercise induced muscle damage (Malaguti. 2009). Against that background it does not seem to be exactly unlikely that chronic sulforophane supplementation or cruciferous vegetable consumption could give you a slight edge over those who don't eat their greens.
Whether the digital broccoli munching Mr. O Popey will be able to bring more scientifically sound arguments to the table than his predecessor, popeye does however still have to be determined. After all, the scientists from the Animal Breeding and Husbandry Group at the University of Bonn in Germany did not study the real-world effects of sulforaphane (SFN), but only the in vitro effects the exposition of porcine satellite cells to, of which every SuppVersity reader knows that they function as skeletal muscle stem cells and support muscle growth and regeneration following injury or disease, when they found that...
"[...] SFN treatment significantly represses MSTN expression, accompanied by strongly attenuated expression of negative feedback inhibitors of the MSTN signaling pathway. miRNAs targeting MSTN are not implicated in posttranscriptional regulation of MSTN." (Fan. 2013)
If you take a closer look at the data in figure you may notice that this increase in myostatin went hand in hand with a decrease in MyoD expression. With MyoD being a protein that is involved in the very first step of satellite cell recruitment (it stops the proliferation of stems cells and initiates their transformation to muscle cells) this may seem awkward at first.

In view of the MyoD promoting effects of trichostatin A, which basically stops cell development in its tracks it can however be explained by the fact that less new satellite cells are needed, because their survival is increased so that the proliferation rate does not actually suffer (figure 1, left).
Figure 1: Cell viability, proliferation, MyoD, Myostatin and (total) Follistatin mRNA expression in porcine stem cells (satellite cells) from semimembranosus muscles from 6 purebred Pietrain piglets after exposure to DMSO (control),  trichostatin A or different concentrations of sulforaphane (SFN; data based on Fan. 2013)
This explanation does not only stand in line with the previously reported increase in MyoD expression in aging muscle (in this case unfortunately in the absence of increased cell viability; Alway. 2013), but is also supported by the concomitant downregulation of the pro-apoptotic (=initiating cell death) caspase enzymes (not shown in figure 1) in the SFN treated satellite cells.

In conjunction with the decrease in myostatin, which is, as I am sure you all know the 'myocyte hypertrophy break' of your body, the data from this in vitro study clearly suggests that SFN treatment could well have a growth promoting effect on skeletal muscle, which is -- and this may be one of the most important messages here -- more prononce at lower concentration used in the study.

Figure 2: Appearance of SFN in serum (triangles) and its metabolite in the urin of one of 10 healthy, normal-weight adult (34 +/-13 y) male volunteers after the ingestion of 200g of raw (top) or cooked (bottom) as part of a warm meal (Vermeulen. 2008)
Bottom line: After you have read about the potent anti-adiposity effect of antibiotics which are used in poultry fattening, yesterday, and today's news about the myostatin inhibiting effects of cruciferous vegetables, or more precisely, their sulforphane content, the infamous 'chicken breast, broccoli and rice diet' does actually begin to shine in new splandor! I mean, if only 50% of the aforementioned in vitro effects could actually be achieved by eating like this day in and day out, these recent findings could well explain, why generations of bodybuilders thrived on these spartan foods. And in case you wondered why the guys get freakier year by year - that's simply the availability of broccoli extracts and the increased use of antibiotics in poultry fattening... ;-)

I am obviously just kidding. If we go by the bioavailability data of raw (figure 2, top) and cooked (figure 2, bottom) broccoli, 200g of broccoli served as part of a warm meal will get your blood SFN levels up to only 2.5% or 1.2% of the most effective dose (5µM) used in the study. So, it's pretty certain that you'd have to gobble copious amounts of red cabbage juice (see picture on top of the article) to get there.

In view of the fact that lower concentrations yielded greater effects, it is however not totally unlikely that even concentrations as low as 1µM would yield results. With additional supplements, it does therefore not appear to be unrealistic to achieve blood levels like that (although you should not expect the increase to be linear).... anyway, I will let you know as soon as the first pertinent rodent or even human trials are available.


References:
  • Alway SE, Degens H, Lowe DA, Krishnamurthy G. Increased myogenic repressor Id mRNA and protein levels in hindlimb muscles of aged rats. Am J Physiol Regul Integr Comp Physiol. 2002 Feb;282(2):R411-22.
  • Fan H, Zhang R, Tesfaye D, Tholen E, Looft C, Hölker M, Schellander K, Cinar MU. Sulforaphane causes a major epigenetic repression of myostatin in porcine satellite cells. Epigenetics. 2013 Oct 23;7(12).
  • Totušek J, Tříska J, Lefnerová D, et al. Contents of Sulforaphane and Total Isothiocyanates, Antimutagenic Activity, and Inhibition of Clastogenicity in Pulp Juices from Cruciferous Plants. Czech J. Food Sci. 2011; 29(5): 548–556.
  • Vermeulen M, Klöpping-Ketelaars IW, van den Berg R, Vaes WH. Bioavailability and kinetics of sulforaphane in humans after consumption of cooked versus raw broccoli. J Agric Food Chem. 2008 Nov 26;56(22):10505-9.

Wednesday, October 23, 2013

When Rodents Squat, Scientists Gain Insights into How Muscles Grow. IGF-1 Response to Exercise Does Matter - Locally, not Systemically, of Course!

You want to build big wheels? Look no further get yourself the "Squat T-Bar" with integrated 15mA electrical 'motivator' (Aguiar. 2013)
"A rodent study investigating strength workouts?" Yeah, I know it does not sound like that would be in any ways news-worthy, but if you take a look at the image on the right, you will immediately realize: This study is different! Instead of using a treadmill or simply stitching down (or rather up) one of the hindlimbs of the rodents to induce a chronic overload on the other one (don't laugh, many rodent studies have done just that), the study at hand (Aguiar. 2013), which is going to be published in the next issue of the International Journal of Sports Medicine, used a not innovative, but unfortunately largely forgotten (or overlooked?) torturing device that has been developed by Japanese researchers roughly 20 years a ago (Tamaki. 2013).

The rodent torture... ah pardon squat rack ;-)

After being fitted with a canvas jacket in a way that would enable the researchers to limit the twisting and flexion of their torsos (no, that was not a weight lifting belt ;-), the 32 male Wistar rats (80 days old, 250–300 g) were suspended in a standard position on their hind limbs and "encouraged" to exercise by "electrical stimulation [...] that was applied to the rat’s tail through a surface electrode"  (Aguiar. 2013).

Using their neat little toy, the eight researchers from the University Estadual Paulista, in Botucatu, Brazil, were able to submit the rats to a relatively realistic progressive resistance training regimen for either 8 or 12 weeks. Three times per week each rodent had to do 4 sets  of squats for 10-12 repetitions at 65-75% of its individual 1-RM (maximal weight the rodent could handle). During the study period, Aguiar et al. adjusted the weights twice a week to ensure the same training intensity throughout the experiment (something I would highly recommend to anyone of you, as well; try to pack on 1.25lbs - 2.5lbs at least every other week).
Figure 1: Body weight, muscle weight (plantaris, only) and food intake relative to body weight of the control (C8, C12) and trained (T8, T12) rats before and after the 8-week (C8, T8) and 12-week (C12, T12) intervention (data adapted from Aguiar. 2013)
As you can see in figure 1, this minimalist approach to leg training lead to an increase in both body weight and muscle weight that may initially look as if it was strongly linear. You do yet have to be careful about statements like that, because (a) the rodents did gain weight irrespective of whether they were training or not (80 day old rats are still growing!), so comparing the four bars next to each other and saying "yep, linear!" is not feasible, because this would mean linear as in not training for eight weeks < training for 8 weeks < not training for 12 weeks < training for 12 weeks, which is obviously nonsensical. That being said, there is simply (b) insufficient data to say anything about the linearity -- after all, we do have only three data points per group.
"All groups started the experiment with similar body weight. There was a significant increase (p < 0.05) in the body weight of the 4 groups in the resistance training program (C8: 35.5 %; T8: 27.7 %; C12: 46.9 %; and T12: 40.1 %) and final body weights were not significantly (p > 0.05) different between groups. Furthermore, no significant (p > 0.05) differences in the weekly food intakes were observed between the groups."(Aguiar. 2013)
What does yet stick out, is that the obviously age-dependent weight gain in the control groups C8 and C12 did not increase the weight of the plantaris muscle to a weight anywhere near to the muscle weight, the rats in the trained groups achieved.

Muscle gains and strength gains went hand in hand

In the rats who were subject to the three-times-per-week exercise regimen, on the other hand, those increases in muscle size went hand in hand with highly significant improvements in 1-RM squat power; While all groups had begun the training protocol with similar absolute 1-RMs of ~450g (that's about 130% body weight, pre) ...
"[...] training for 8 and 12 weeks promoted a significant (p < 0.05) increase in the RM/BW ratio in the T8 (pre- vs. post-training: 35.7 % increase, p < 0.05) and T12 (pre- vs. post-training: 57.1 % increase, p < 0.05) groups, while no statistical (p > 0.05) difference was observed in their respective control groups." (Aguiar. 2013)
Consequently, the ratio of 1-RM to body weight was 36.1 % and 57.7 % higher in the groups who had been training fot the last 8 or 12 weeks than in the lazy controls and the time-effect yielded another +22% increase in strength in those rodents who trained for 12 and not just 8 weeks.
Figure 2: Strength gains (left) and increases in cross sectional area, as well as intramuscular IGF1, myogenin and myoD expression (data adapted from Aguiar. 2013)
Now you may have heard all that before, what really makes this study stand out, however, is the observation of statistically highly significant correlations of intra-muscular IGF1, myogenin and myoD  mRNA expression, which speaks in favor of my previous hypothesis (read up on that in the Intermittent Thoughts on Building Muscle) that muscle growth is triggered, driven and maintained almost exclusively at a local level.

What are myogenin and myoD? Both are myogenic regulation factors with myogenin actually being part of the myoD family of transcription factors that will make stem cells develop into myocytes (myo D is highest in recently activated satellite cells).
So, when you are looking for "hormonal" (or other pro-anabolic) ghosts (Phillips. 2013), it is imperative to look for them right where the spook, or, in this case, the muscle building magic happens. If you do just that (see figure 2) and correlate the intra-muscular mRNA expression of IGF-1, myogenin and myoD, you will find the "ghostly" explanation for strength and size gains, as well as the confounding structural changes in the architecture of the muscle, with corresponding correlations between the increases in muscle cross-sectional area (CSA) of r = 0.85 (p = 0.0001), r = 0.87 (p = 0.0001) and r = 0.88 (p = 0.0001) for myoD, myogenin and IGF-1, respectively.

Fiber type changes take their time and occur only within the type II spectrum

A neat side-finding, which is actually no news, though, pertains to the fiber-type conversions that took place in response to the exercise regimen. Firstly, the scientists confirmed the notion that these changes occur exclusively within a certain fiber type. In other words, while Aguiar et al. observed conversions from the metabollically more flexible type IIX/D to the highly glycolytic (power) IIA type, no conversions of the highly oxidative type I to type II fibers were observed. And though the results would generally suggest that fiber IIX/D-to-IIA type conversion, as they 
"[...] also appear to occur during endurance training in humans, so that it would [be] reasonable to think that any exercise stimulus (e. g., endurance or strength) that is sufficient in duration and/or intensity can potentially induce conversions within the fast fiber population from type IIX/D to type IIA" (Aguiar. 2013),
the time-frame in the course of which these changes took place -- namely 12 weeks -- would confirm that the common fear of strength and endurance athletes could provoke negative structral adaptations from doing a "cardio" or "strength" workout from time actually is actually unwarranted. Neither will the former turn a powerlifter into a weakling, nor will the latter make a marathon runner "bulky". Both powerlifter and marathoner are on the contrary going to benefit from the conditioning effect and increase in strength, respectively -- not to mention the important effects on overall health both and not as mainstream stupidity will tell you only the powerlifter can derive from, figuratively speaking, "killing some game in the other's territory"

Bottom line: More food for intermittent thoughts on building muscle ;-)

Figure 3: Correlations between acute GH (A), free testosterone (B), IGF-1 (C)  and cortisol (D) responses (area under the curve—AUC) and gains in type II fibre CSA (Burd. 2013).
Eventually, this study is an excellent example of a way to design a rodent study in a way that will render its results actually meaningful. And what's more, in this particularly case these results are not just meaningful, but can also help us to make some sense of a couple of things we have not fully understood / appreciated, as of yet.

What I am particularly thinking about here, is the contrast between the in-vitro effects of IGF-1 and the (more or less absent) real-world effects of the IGF-1 response to exercise (=systemic increase), as it was observed by West and Phillips in a 2013 study. In their well-powered longitudinal study, neither the acute increase in systemic testosterone, nor the exercise induced increases in systemic IGF-1 showed significant correlations with the gains in type II CSA in a cohort (n = 56) of young men in response to 12 weeks of resistance training (West. 2013; see figure 3).

Another interesting finding of the West study was that, contrary to the circulating testosterone and IGF-1 levels, GH and cortisol did show direct correlations with increased muscle cross sectional areas in type II fibers.

And while the former correlation may be explained by the influence of growth hormone (GH) on the local expression of IGF-1 (Hameed . 2004), there is another open question left: How does cortisol actually figure in here? I mean, the chronic elevation / exogenous adminstration of cortisol, has been show to do the exact opposite, i.e. it decreases the local IGF-1 mRNA expression (Inder. 2010).

Figure 4: Graphical summary of what you should have learned Intermittent Thoughts on Building Muscle ... you didn't 'cause you are new to the SuppVersity or simply forgot about it? No problem read the preliminary summary and browse the individual chapters here!
What was missing in the Inder study, however, was the exercise component: Working out does not just exert protective effects against the negative side effects of the provision of exogenous "cortisol" (in this case Dexamethason), as they were observed in the afore referenced study by Inder et al., exercise will also lead to profound increases in local IGF-1 mRNA expression (e.g. +60% in Bamann. 2001), despite the fact that it will also increase the release of the falsely vilified anti-inflammatory glucocorticoid, cortisol... acute vs. chronic, local vs. system, peak values and amplitudes vs. plateaus and AUC values - you got to keep all these contrastive, yet complementary pairs in mind, when you are thinking about the endocrine and intracrine (within the cell) mediators of skeletal muscle hypertrophy.... what? Sounds familiar? Well, you must have been following the Intermittent Thoughts on Building Muscle, then ;-)

References:
  • Aguiar AF, Vechetti-Júnior IJ, Alves de Souza RW, Castan EP, Milanezi-Aguiar RC, Padovani CR, Carvalho RF, Silva MD. Myogenin, MyoD and IGF-I Regulate Muscle Mass but not Fiber-type Conversion during Resistance Training in Rats. Int J Sports Med. 2013 Oct 11.
  • Bamman MM, Shipp JR, Jiang J, Gower BA, Hunter GR, Goodman A, McLafferty CL Jr, Urban RJ. Mechanical load increases muscle IGF-I and androgen receptor mRNA concentrations in humans. Am J Physiol Endocrinol Metab. 2001.
  • Ding H, Gao XL, Hirschberg R, Vadgama JV, Kopple JD. Impaired actions of insulin-like growth factor 1 on protein Synthesis and degradation in skeletal muscle of rats with chronic renal failure. Evidence for a postreceptor defect. J Clin Invest. 1996 Feb 15;97(4):1064-75. 
  • Inder WJ, Jang C, Obeyesekere VR, Alford FP. Dexamethasone administration inhibits skeletal muscle expression of the androgen receptor and IGF-1--implications for steroid-induced myopathy. Clin Endocrinol (Oxf). 2010 Jul;73(1):126-32.
  • Phillips SM. Strength and hypertrophy with resistance training: chasing a hormonal ghost. Eur J Appl Physiol. 2013 May;112(5):1981-3-
  • Sculthorpe N, Solomon AM, Sinanan AC, Bouloux PM, Grace F, Lewis MP. Androgens affect myogenesis in vitro and increase local IGF-1 expression. Med Sci Sports Exerc. 2013 Apr;44(4):610-5.
  • Tamaki T, Uchiyama S, Nakano S. A weight-lifting exercise model for inducing hypertrophy in the hindlimb muscles of rats. Med Sci Sports Exerc. 1992 Aug;24(8):881-6.
  • West DW, Phillips SM. Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. Eur J Appl Physiol. 2013 Jul;112(7):2693-702. 

Tuesday, September 17, 2013

Anabolic Workouts Revisited - Testosterone, GH, Prolactin & Co: Differential Effects of Workout Type, Volume & Density

Ronnie Coleman is just one of the pros who trained with crazily high volume and weights - is that the way to go, or does it require too many "supplements"?
"What's the most anabolic form of training?" To answer that question we would actually have to initially define how we are planning to measure "anabolism". If we go by the more or less confuted paradigm that the immediate hormonal response to a workout is one, if not the, fundamental determinant of it's effectiveness, today's blogpost provides you with a whole host of already known and novel insights that could come handy, when you're setting up your next workout routine.

Please keep in mind, though, that the study by West et al., in which the researchers found no correlation between exercise induced increases in testosterone and only weak correlations between growth hormone and fast twitch muscle fiber size and cortisol and overall lean mass, over a 15-week period, as well as my dissertations on the complexity of "building muscle" in the Intermittent Thoughts on Building Muscle, while I am taking you through the latest results.

Part I - Shorter rest times = greater "anabolism"

I'd like to start out with the results,Villaneuva et al. recently published in the Journal of Strength and Conditioning Research (Villanueva. 2013). The scientists from the University of Southern California conducted a 2x2 randomized trial involving strength and hypertrophy oriented total body workouts on Tuff Stuff Performance Series equipment with different different set/rep schemes and rest times, but identical exercises for both:
  1. maximum strength protocol (S)
    8 x 3 (sets x reps) at 85% of predetermined 1-RM for all resistance training exercises; 60 seconds (S60) or 90 seconds (S90) rest in-between sets
  2. muscular hypertrophy protocol (H)
    3 x 10 (sets x reps) at 70% 1-RM for all resistance training exercises; : performed with either 60 seconds (H60) or 90 seconds (H90) rest in-between sets 
    Exercises
  • smith machine barbell back squat
  • flat barbell bench press 
  • narrow/neutral grip lat pulldown 
  • seated unilateral knee extension
The six study participants were young men, who volunteered for the study (age 26+/-2.4 years, 178.6 +/-5.9 cm, and 86.4+/-1.2kg) were healthy and described as "recreational resistance trainees who trained at least 2 days per week (>2 years)" (Villanueva. 2013).None of them was yet a competitive weight lifters or did engaged in any other sport-specific training. Furthermore none of the 6 participants took any medication or dietary supplements that could potentially have skewed the results, i.e. the change in cortisol and total testosterone levels, I plotted in figure 1:
Figure 1: Change of total serum testosterone concentration from rest (PRE) to immediately post-exercise (POST), Pre to 15 minutes post-exercise (15 MIN), and Pre to 30 minutes post-exercise (30 MIN) for strength and hypertrophy protocols with short (60s) and "long" (90s) rest period (* indicates significant difference - p < 0.05; based on Viallaneuva. 2013).
The overall message here should be clear: If you want to ramp up your testosterone levels, hit it fast and in the classic hypertrophy range with 3 sets of 10 reps!

Exercise-induced increase in testosterone = anabolism?

While we cannot exclude that the exercise induced increase in testosterone (and other "anabolic" hormones) is a necessary and facilitative part of the adaptive cascade at the end of which you may in fact have gained another inch on your arm, the results of the initially mentioned study from Phillips lab at the McMaster University in Ontario, do at least suggest that there is no linear, nor otherwise proportional relationship between exercise induced increases in testosterone and gains in lean muscle mass (West. 2013).
Figure 2: Differential endocrine response to high vs. low volume squatting in healthy trained men - androgen receptor content of vastus lateralis (left), total testosterone levels (right; data based on Rattames. 2005)
The notion that intracrine (=within the cells) processes, proteins and hormones are the actual driving forces and controlling factors in skeletal muscle growth is further supported by observations Ratamess et al. made in 2005. The researchers from the Human Performance Laboratory at the University of Connecticut found a 45% reduction in androgen receptor expression in response to high (figure 2, MS: 6x10, 2min rest in-between) vs. low volume (figure 2, SS: 1x10) squatting sessions in healthy, resistance-trained men with a minimum 3 years of experience with the back squat exercise. At first sight, this does certainly seem as if the testosterone response was pretty useless, after all, even this proven muscle builder (see "Zoning In On the Big T" and "Quantifying The Big T") cannot do its muscle building job, if there is no receptor to bind to, right?  Correct! ... but follow up studies by Spiering et al. and Vingren et al. have shown that the testosterone release in and out of itself will illicit increases in receptor density which do however need some time to take place: In that, the +14% increase in testosterone in response to a high volume upper body workout in the Spiering study increased the androgen receptor expression 3h after the workout by 40% over control (Spiering. 2009).

Strength vs. Hypertrophy - Check... Endurance exercise & Sprinting?

Before we discuss the implications of these findings, let's briefly take a look at another even more recent study trying to discover the complicated hormonal response to different types of exercise that could help us to grasp a better notion of "The latest on working out for anabolism". Now, I would venture the guess that 99% of you are probably thinking about "3,2,1" vs. "5x5" vs. "HST" and a couple of other classic strength training or bodybuilding routines, right now. The results the already mentioned study which have been published only 4 days ago in the Journal of Applied Physiology do yet bring two unexpected training types to the play: Sprinting and endurance training. I see, you are surprised. Well, at least for the first one, i.e. sprinting, you actually should not be; after all, I have been writing about the protein anabolic effects of HIIT (=multiple sprints) before (see "The Anabolic Effects of HIIT"). So, if it increases muscle protein synthesis by >40%, why shouldn't sprinting also be able to establish an overall more anabolic milieu? But endurance training?
Figure 3: Prolactin, insulin (in the absence of a "control" AUC, I calculated the value relative to the mean), testosterone, cortisol and growth hormone (GH) area under the curve (pre to 60min post) in 8 healthy young men in response to 4 separate trials involving resting (control, relative to which all the other values - except insulin - are expressed to), resistance training, sprinting and endurance training (for details see text; data based on Stokes. 2013)
Yeah, it sound counterintuitive, but if you take a close enough look at the data in figure 3 and take into account growth hormone (GH) bars at the right hand side of the colored graph have their own scale you will have to concede that the 8.4x increase in growth hormone expression in response to 30min cycling at 70% of the VO2max are pretty impressive. Specifically, if you consider that the competition, i.e. a...
*the scientists write it the other way around, but honestly I have not et come across a study, where the rest between sets was longer than the one between exercises, so I assume this is a typo
  • 30min total-body resistance training regimen - bench press, leg press, bench pull; 75% 1RM 5 sets 10 reps, each; 60s rest* between sets, 180s rest* between exercises, and an
  • all out 30s sprint that was performed subsequent to a warm-up that consisted of cycling for 4 min at 60 W, 30 s at 80 W, and
    then 30 s at 100 W and a 5-min pause on a friction-loaded cycle ergometer at 7.5 % (75 N/kN) of the subject’s body mass
were training regimen you would probably rather associate with the term "growth" as in "growth hormone". Now, if you ask the "bros" about their reasons for taking GH, I guess that few of them will still be falling for the idea that it was a great muscle builder (when used appropriately, it can be a exponentiate the anabolic effects of superphysiological doses of testosterone, though).

Most of them will probably tell you that it helps you lean out... and why does it do that? Simply because it helps with fatty acid mobilization and oxidation. And when is the need for the latter the greatest? When you sleep, yeah... when you fast, ok... but also when you expend huge amounts of energy from fat! And that's exactly what's happening during the 30min of cycling at 70% of the VO2 max, an undertaking that does not simply burn relatively, but most importantly absolutely significantly more energy and thus fat, than either the strength training (82% less energy expenditure) session, or the sprint session (94% less energy expenditure).

Fine, so a drop in FFA will increase GH, but what's that about prolactin?

Figure 4: GH response of young men in response to exhaustive endurance (15min, targer HR 160bpm) and resistance training (total-body, 5 exercises, 4 sets classic pyramid, 1-2min rest) and combined training (crossfit-style + 6x10m sprints) from Akbari. 2013
These remarks on growth hormone do yet not answer a question of which I suppose that it's already preying on your minds: What's that about sprinting induced increases in prolactin? Well, if
  • higher volume weight lifting in the hypertrophy range (8-12 reps) increases testosterone, and
  • energy consuming endurance exercises with a tendency to reduce free fatty acids in the purported "fat burning zone" (70% VO2Max) increases GH
the straight forward answer to this question would be: A ...
  • higher mean work rate [=energy expenditure per time unit of exercise] maintained only over a very short timespan increases prolactin
And just to make that clear, the work rate during the sprint was 430% higher than during the resistance training session and still 260% greater than during the 30min of cycling.

On a side note: The drop in insulin after the endurance trial (>60% immediately post) supports the view that the associated GH response is primarily fat-catabolic and not muscle anabolic. Moreover, it's IGF-1 it's splice variants MGF & Co, not it's parent GH which are mainly responsible for the muscle building effect. And at least the synthesis of IGF-1 is in a hitherto not fully elucidated way related to insulin (click here to learn more), the villain of the last decade that was once, and is still hailed among many hardcore bodybuilders as "the most anabolic hormone of all"!
In view of the fact that this rise in prolactin (actually somewhat of an acute stress response, of which we don't yet know what exactly it's role wrt to training adaptation is) went hand in hand with a temporary increase in insulin this may sound as if sprinting was a bad thing, but the spike in insulin may have been significant compared to the steady insulin levels of the control, let alone the declining insulin levels in the endurance trials, but was almost identical to the one that occurred in response to the resistance training regimen (the AUC for insulin was even higher in the 60min after the resistance training protocol). And has, as Stokes et al. point out unquestionable benefits:
"Increased insulin concentrations as seen following the sprint trial [...] might facilitate muscle glycogen synthesis during recovery through insulin’s actions on both glucose transport and on glycogen synthase activity. The significant increase in insulin concentrations following sprint exercise in the present study is followed by a suppression of blood glucose concentrations to levels below pre-exercise. This finding might have implications for individuals who have difficulty regulating blood glucose concentrations, such as individuals with impaired glucose tolerance." (Stokes. 2013; my emphases)
The post-exercise increase in the universally and wrongfully demonized insulin could thus not just come handy for the the 8 young recreationally active men who participated in the study at hand, but also for the average and extraordinary gymrat (like yourself?) and even the obese type II diabetic who has finally found his/her way to physical culture! And this is not simply a vague assumption, but an already empirically validated hypothesis (e.g. Richards. 2010; Whyte. 2010).

So what does all this tell us then?

Did we even answer our question? By now you should actually notice something. The question "What's the most anabolic workout?" cannot be answered with only one definition of "anabolism" on your mind. The classic body part split with 3-5 sets of 5-10 reps per exercise is probably still the way to go, if your perspective on anabolism relates to increased skeletal muscle hypertrophy based on both, endocrine (testosterone), as well as intracrine (mTOR) responses to your workouts. If you want to build your brain and thus interpret "anabolism" as "neurogenesis", you will have to either sprint or do extra-long endurance work (Rojas Vega. 2013) or have lot's of sex to up your prolactin levels . And if your mitochondrial density is what's on your mind, when you think of "anabolism", HIT and HIIT should be your best friends.
Aside from the time-delayed increase in testosterone receptor expression, of which you could either argue that it could be evidence for a shift from an intracrine to an endocrine anabolic response, and the beneficial effects of an increase in insulin at the right time, namely post-workout when your muscles are ready to take up the glucose that could otherwise end up being converted to triglycerides and stored in one of the numerous fat depots of your body, there are two other imho important reasons not to simply fall into the opposite extreme and say "Wtf if exercise induced increases in anabolic hormones don't correlate with muscle growth they are completely worthless!":
  1. Real world, not lab evidence: High(er) volume training with short(er) rest periods was and still is the way the majority of using and non-using athletes are "building" those physiques on, people actually have on their minds, when they are looking for the "most anabolic workout"
  2. Effects on intracrine factors of anabolism: From mTOR-dependent local protein synthetic response over the many, hitherto not fully understood intracrine growth factors, the role and function of inflammatory cytokines and the immune response to exercise, up to the maintenance and incorporation of satellite cells into new myonuclei and the PGC1-alpha driven increase in mitochondrial density, all of the things, we are training for show some correspondence with the exercise induced systemic expression of "anabolic" or "catabolic" hormones.
The main problem is therefore, as Stokes et al. state, that we still have an "over-simplistic" concept of the "anabolic (e.g. testosterone and growth hormone) and catabolic (e.g. cortisol) hormones" (Stokes. 2013), in which things like the prolactin response to exercise, which has only recently been implicated as a driving force of exercise induced neurogenesis (Rojas Vega. 2013), have not even had a place, until now... apropos prolactin, you should be aware that having an orgasm will likewise elicit a temporary spike in prolactin levels and sex is therefore "brain-o-bolic" (see my post on the matter on the SuppVersity Facebook wall)!

References:
  • Akbari A, Mojtahedi H, Marandi SM, Movahedi A, Ramsheh SFR. Comparing the Effects of Three Types of Exercise (Exhaustive Endurance, Intensive Resistance and Combined Exercise) on the Secretion of Growth Hormone in Active Men. World Journal of Sport Sciences. 2013; 6 (3): 247-253. 
  • Ratamess NA, Kraemer WJ, Volek JS, Maresh CM, Vanheest JL, Sharman MJ, Rubin MR, French DN, Vescovi JD, Silvestre R, Hatfield DL, Fleck SJ, Deschenes MR. Androgen receptor content following heavy resistance exercise in men. J Steroid Biochem Mol Biol. 2005 Jan;93(1):35-42.
  • Richards JC, Johnson TK, Kuzma JN, Lonac MC, Schweder MM, Voyles WF, Bell C. Short-term sprint interval training increases insulin sensitivity in healthy adults but does not affect the thermogenic response to beta-adrenergic stimulation. J Phys-iol (Lond). 2010; 588(15):2961–2972 
  • Rojas Vega S, Hollmann W, Struder HK. Influences of exercise and training on the circulating concentration of prolactin in humans. J Neuroendocrino. 2013; 24(3):395–402.
  • Spiering BA, Kraemer WJ, Vingren JL, Ratamess NA, Anderson JM, Armstrong LE, Nindl BC, Volek JS, Häkkinen K, Maresh CM. Elevated endogenous testosterone concentrations potentiate muscle androgen receptor responses to resistance exercise. J Steroid Biochem Mol Biol. 2009 Apr;114(3-5):195-9.
  • Stokes KA, Gilbert KL, Hall GM, Andrews RC, Thompson D. Different responses of selected hormones to three types of exercise in young men. Eur J Appl Physiol. 2013 Sep 13.
  • Villanueva MG, Villanueva MG, Lane CJ, Schroeder ET. Influence of Rest Interval Length on Acute Testosterone and Cortisol Responses to Volume-Load Equated Total Body Hypertrophic and Strength Protocols. J Strength Cond Res. 2013 Jul 12. 
  • West DW, Phillips SM. Associations of exercise-induced hormone profiles and gains in strength and hypertrophy in a large cohort after weight training. Eur J Appl Physiol. 2013 Jul;112(7):2693-702. 
  • Whyte LJ, Gill JMR, Cathcart AJ. Effect of 2 weeks of sprint interval training on health-related outcomes in sedentary over-weight/obese men. Metabol Clin Exp. 2010; 59(10):1421–1428.

Sunday, July 14, 2013

On Short Notice: 15% Stronger With Kineso Tapes, HIIT With 30-20-10, Combined Training vs. Diabetes, Coffee vs. Scars, Peanuts & Pregnancy, Phosphate & Insulin + More!

Image 1: You like it fast? Then the novel SuppVersity column SuppVersity "On Short Notice" is right for you. So don't forget to bookmark, subscripe to the RSS feed or the email updates (see bottom right of the page) or simply start following me on facebook and/or twitter
Actually I am quite happy that most of you liked last Saturday's first installment of SuppVersity "On Short Notice" - it turned out that just writing down one of those mini-items, whenever I have a couple of minutes to spare yields more great content than a single post can hold. So, despite the fact that I have stockpiled 11 items for you in today's installment I have already written the first ones for next week's installment of this new column. Before we start with those of the past week, I would just like to remind everyone that you can simply add the RSS feed (all SuppVersity posts, only "On Short Notice" posts) to your favorite RSS reader, or start following me on facebook and/or twitter if you like those informational quickies and thus make sure that you won't miss any information from the realms of exercise science, supplementation and nutrition!

30 - 20 - 10  HIIT for maximal conditioning

As a regular at the SuppVersity you have already learned one or two things about the benefits (and in many cases superiority) of high intensity interval training (HIIT) for fat loss and cardiovascular conditioning (read all about HIIT).
Figure 1:  The 30-20-10 protocol consists of a inner 5x1min 30-20-10 'acceleration'-cycles followed by a 2min period of active rest; those 5x 30-20-10 low-, moderate-, and high-speed running + 1x 2min active rest pairs are repeated 3-4 times.
A recently published study by Gunnarson et al. does now show that even moderately trained individuals can benefit from a very simple yet intense 15-20min interval training (see figure 1) similar to the one the 3 women and 7 men in the active arm of the study performed (total number of participants N=20). And I would say that 4% higher VO2max, 21s faster 1,500-m and 48s faster 5-km running times are nothing you would want to miss, either. Specifically, if those come with a 30-20-10 decrease of systolic blood pressure and reductions in total and low-density lipoprotein (LDL) of -0.5 ± 0.2 and -0.4 ± 0.1 mmol/l, respectively - am I right? No, well you should better stick to your arduous treadmill walks in the non-existant  fat-burning zone, then.

Add strength training to your 10-20-30 aerobic regimen and rid yourself of type II diabetes

I guess it goes without saying that the exercise approach to diabetes won't work without other lifestyle interventions, such as dietary modifications and stress reduction / management (e.g. "Chronically Fatigued? Do Qigong!". After all, you would not have gotten into the mess if your nutrition had been in check and your stress-management effective - and don't give me the "bad genes excuse", I hear that from my type II diabetic grandma often enough!
Figure 2: fasting glucose and glycolosated hemoglobin levels before and after a 20-week exercise intervention consisting of either 3x per week of combined resistance and aerobic training or aerobic only training of the same volume (based on Moro. 2013)
As far as exercise goes, a recently published study has (once again) confirmed that a combined aerobic + resistance training protocol is more effective with respect to longterm (20-week) improvements in glycemia than the regular "walk" or even worse "jog an incline for 40-60min everyday" regimen - in the study at hand the aerobics regimen employed one of those classic 'ramps' starting at 15min @ 40-50% in the first week and ramping up volume + intensity to 60 min at 60-70% (Moro. 2013): What is particularly striking about the results (see figure 2) is the differential effects on simple fasting blood glucose levels and the amount of glycolosated hemoglobin, an index for the long-term (24h) glucose stability, which improved significantly more (p < 0.05) with the combined (3x split training with 3 sets à 10-12reps + 20min of light aerobic exercise afterwards), than with the aerobics only 3x per week exercise program.

Assuming that the additional strength training component is also going to help the 24 formerly sedentary participants (men and women aged 60,41 ± 7,87y) to build or at least maintain "metabolic currency" (= muscle) you can bet money that those differences would have been even more pronounced if the trial had lasted 6 or more instead of just 5 months. Remember: You are in this for life!

And if you want do get stronger, just tape your biceps

If you train in one of the gyms, where professional athletes go in and out, you will probably already have seen people come in with those blue, green or pink "package tapes" on their limbs. Usually their coaches and or physiotherapists apply those and send them to the gym, when they are still recovering from an injury and thus cannot perform their regular training sessions.
Figure 3: Concentric and eccentric elbow peak torque with and without kineseo or placebo taping ( (Fratocchi. 2013)
As the data in figure 3 goes to show, this practice could turn out to be the kinesiologic analogon to creatin... well, aside from the fact that it works instantaneously, maybe (Fratocchi. 2013). Done right, the taping can increase your concentric and eccentric peak torgue on a simulated biceps curl (performed on an isokinetic pulley machine) by 13-15%. Whether these results, Fratocchi et al. observed in trained, but not (upper body) strength trained young men and women will translate in similar pronounced strength improvement on real curls - let alone permanent gains, once you remove the tape - remains to be seen. But let's be honest, what do you have to lose? As long as you don't apply the tape wrong (see figure 3, green-framed photo), I would say that the worst thing that can happen is that people laugh at your novel 'gymwear'.

On ultra-short notice:
  • Your red blood cells can produce testosterone and other androgens - Believe it or not, but according to a recent study from the Universidad de Chile in Santiago, Chile, human platelets can produce sex hormones from circulating DHEA-S (Garrido. 2013). They can also take up estrone-sulfate and convert it to 17b-estradiol (the most active form of estrogen); taking your DIM does therefore not necessarily prevent that your platelets avail themselves of the estrone your liver is spilling out and convert it back to estrogen, when they "feel that's necessary". If you don't care about that, you may be interested that DHEA can also ramp up insulin sensitivity and help you lose weight and protect your muscle against exercise induced damage - even when you train like a maniac. 
  • Image 2: Better smear some coffee paste onto your wound than special creams if you don' want nasty scars.
    Coffee paste applied to a closed wound could prevent scarring - Although the paper does not mention this explicitly (Perez-Aso. 2013), the discovery that the pharmacological blockade of the adenosine A2A receptor prevents scarring suggests that a paste made of/with fresh coffee should actually do the exact same thing. After all, coffee is a natural pan-(=across many)adenosine receptor antagonist. It goes without saying, though that you cannot apply the coffee onto the open wound, right? Well, I guess you can, but it is at least questionable if that would not rather increase your chance for infections that decrease your risk of developing ugly scars. Find out more about coffee!
  • EPO increases muscle repair by ramping up satellite cell activity - According to Jia et al., endogenous EPO, i.e. erythropoietin that is produced by your body, plays an important role in satellite cell proliferation and thus the repair and the "structural expansion" of muscle tissue. Based on their studies in wild-type and EPO overexpressing mice, the researchers speculate that exogenous erythropoietin could thus be used to "contribute to increasing satellite cell number following muscle injury, improve myoblast proliferation and survival, and promote repair and regeneration" (Jia. 2013). Read more about EPO or sattelite cells, and the commonly overlooked role of estrogen in satellite cell replenishment and activation.
  • IGF-1 from colostral whey is orally active and ameloriates high blood sugar - I have addressed the question whether the more or less complex peptides from milk (see "Colostrum & Milk"), deer antler (see "Ask Dr. Andro: Does Deer Antler Velvet Work?") & co can even work, when they are administered orally several times before - a recent discovery by scientists from the Republic of Korea does now suggest that, at least in diabetic rodents, the IGF-1 fraction in colostral whey exerts similar blood sugar lowering effects as its recombinant (artificial) human cousin (Hwand. 2011). Since this is nothing but another rodent study, the non-negligible blood sugar reductions of 11 and 33 % at weeks 2 and 4, respectively, are yet sill only something for the "ultra-short notice" section of the "on short notice" column of the SuppVersity (if you have not done so already, don't fotget to read up on the anti-diabetic effects of camel milk here).
  • People with reactive hypoglycemia shouldn't follow a low carb high protein diet - I knew that from my experience with others (esp. women), but when the issue of reactive hypoglycemia surfaced again in one of the comments, I dug up a 1975 study which clearly shows that avoiding carbs altogether (50-60g /day in the study) will only add impaired glucose tolerance on top of the existing and persistent symptoms (Anderson. 1975). More on potential pitfalls with very low carbing: "Carbohydrate Shortage in Paleo Land" and "Half As Heavy, but Twice As Fat: 'Atkins-Style' No-Carb Diet + Exhaustive Exercise Compromise Body Composition"
  • Image 3: Craving peanut butter? The sugar (and thus increased gestational diabetes risk) is probably more of a problem than the "allergens". At least that is what the ~20% reduced asthma and allergic rhinitis risk a recent study reports based on data from the Danish National Birth cohort reports would suggest.
    Peanuts during pregnancy not a problem, but rather beneficial - While real junkies harm their unborn babies by irresponsible consumption of cigarettes, alcohol and other drugs, health junkies could be doing the same by totally avoiding exposure to any kind of potential allergens. At least this is what a recent analysis of data from the Danish National Birth Cohort would suggest. According to the results of Maslova et al., the consumption of potentially pro-allergenic pea- and tree-nuts did not only elicit any changes in terms of future allergies, it was also "inversely associated with a medication-related asthma diagnosis (OR, 0.81) and self-reported allergic rhinitis (OR, 0.80)" (Maslova. 2013) - or put simply: not the consumption, but rather the abstinence of potential pro-allergens appears to dispose unborn children to develop respective allergies in later life.
  • High-normal TSH good predictor of visceral obesity; irrespective of insulin resistance - "Your TSH is somewhat high, but no reason to be concerned." If that's what your Dr. told you, you better get another one. After all, a recent study by Muscogiuri et al. shows that those "somewhat high TSH levels" are a pretty good indicator of increased visceral adiposity, and all its potentially fatal health consequences (Muscogiuri. 2013). And if you want to improve your thyroid function naturally, I suggest you read my previous post "Dietary Thyroid Treatment: Beef, Green Vegetables, Full-Fat Milk & Butter Normalize TSH in Subclinical Hypothyroidism"!
  • High phosphate content of meal increases postprandial blood glucose and insulin - What are two characteristics of coke and similar soft drinks? Right: They contain tons of high GI sugar and phosphate. A combination of which a group of researchers from the Department of Clinical Nutrition at the University of Tokushima in Japan has recently shown that it leads to a profound increase in postprandial (hours after the meal) blood glucose and insulin levels compared to low GI, but also compared to high high GI low phosphate (400mg vs. 1200mg) meals in 11 young, healthy volunteers. Bottom line: If high GI is bad, high GI + high phosphorus is even worse (Taketani. 2013). I am not sure how much phosphor the sports drink I wrote about roughly two weeks ago contain, but certainly less than coke, and still the average body fat gain per energy drink was ~18g ("Fat Content Per Energy Drink 0g, Body Fat Gain Per Energy Drink 18g!").
References:
  1. Anderson JW, Herman RH. Effects of carbohydrate restriction on glucose tolerance of normal men and reactive hypoglycemic patients. Am J Clin Nutr. 1975 Jul;28(7):748-55.
  2. Fratocchi G, Di Mattia F, Rossi R, Mangone M, Santilli V, Paoloni M. Influence of Kinesio Taping applied over biceps brachii on isokinetic elbow peak torque. A placebo controlled study in a population of young healthy subjects. J Sci Med Sport. 2013 Jul 6.
  3. Garrido A, Munoz Y, Sierralta W, Valladares L. Metabolism of dehydroepiandrosterone sulfate and estrone-sulfate by human platelets. Physiol Res. 2013 Jun 6.
  4. Gunnarsson TP, Bangsbo J. The 10-20-30 training concept improves performance and health profile in moderately trained runners. J Appl Physiol. 2013 Jul;113(1):16-24.
  5. Hwang KA, Hwang YJ, Ha W, Choo YK, Ko K. Oral administration of insulin-like growth factor-I from colostral whey reduces blood glucose in streptozotocin-induced diabetic mice. Br J Nutr. 2011 Oct 10:1-7.
  6. Jia Y, Suzuki N, Yamamoto M, Gassmann M, Noguchi CT. Endogenous erythropoietin signaling facilitates skeletal muscle repair and recovery following pharmacologically induced damage. FASEB J. 2013 Jul;26(7):2847-58. Epub 2013 Apr 9.
  7. Maslova E, Granström C, Hansen S, Petersen SB, Strøm M, Willett WC, Olsen SF. Peanut and tree nut consumption during pregnancy and allergic disease in children-should mothers decrease their intake? Longitudinal evidence from the Danish National Birth Cohort. J Allergy Clin Immunol. 2013 Jun 26.
  8. Moro AR, da Rosa R, da Silva FC, Filho PJBG. Effect of combined and aerobic training on glycemic control in type 2 diabetes. Fisioter. mov. [online]. 2013, vol.25, n.2 [cited 2013-07-13], pp. 399-409.
  9. Muscogiuri G, Sorice GP, Mezza T, Prioletta A, Lassandro AP, Pirronti T, Della Casa S, Pontecorvi A, Giaccari A. High-normal TSH values in obesity: is it insulin resistance or adipose tissue's guilt? Obesity (Silver Spring). 2013 Jul 3.
  10. Perez-Aso M, Chiriboga L, Cronstein BN. Pharmacological blockade of adenosine A2A receptors diminishes scarring. FASEB J. 2013 Jul 5.
  11. Taketani Y, Yamazaki M, Ueda H, Mori Y, Tanaka T, Horie D, Ominami H, Okumura-Yamanaka H, Yamamoto H, Takeda E. Interaction between dietary phosphate and carbohydrate on glucose and phosphate metabolism in healthy young men. Kidney Research and Clinical Practice. Volume 31, Issue 2, June 2013

Tuesday, March 12, 2013

Understanding Muscle Hypertrophy - Study Sheds More Light on Process of Satellite Cell Recruitement: SRF, IL-6, STAT3, COX2, IL4 + More Funky Acronyms With Important Roles in the Structural Component of Muscle Growth.

No pain inflammation, no gain? In the long(er) run this could in fact be true.
All of you who followed my advice to "like" the SuppVersity Facebook page and are thus keeping up with the numerous additional news I am posting there, should actually have seen the news item on the non-significance of the exercise-induced interleukin-6 (IL6) response for the exercise induced improvements in glucose metabolism (read more). The mere fact that the glucose metabolism of IL6(-) mice, which are mice who simply cannot express IL6, is still improved by "working out" does yet by no means preclude that the demonized cytokine does play a fundamental role in the exercise-induced systemic and local benefits. In fact, an even more recent rodent study would suggest that a certain degree of inflammation and the respective increase in IL6 immediately after a workout is even essential for persistent skeletal muscle hypertrophy.

As you may remember from the Intermittent Thoughts on Building Muscle Series there is more to skeletal muscle hypertrophy than the simple messages such as "increases protein synthesis by X%" that are printed in shiny letters on the boxes of hundreds of the currently available "natural muscle builders" on the real and digital shelves of the supplement vendors. One of these "mores" is the recruitement of satellite cells, muscle stem cells that are incorporated into the musculature to replace damaged myonuclei or increase the myonuclear density to allow for greater protein accretion (learn more).

Decreasing domain sizes = better function + higher growth propensity

"Hold on those are rodents and rodent studies are not relevant!" While it is a good thing to critically assess whether the results of a certain study can be species specific. The contemporary practice to question all rodent studies which are not part of your own cherry picked arsenal is getting onto my nerves. So, please check out the pretty analogues (short term unfortunately) human study by McCay from 2009 (McCay. 2009), before you stop reading after spotting the word "rat" in this article.
It is this process of satellite cell activation and incorporation of which Gwenaelle Begue and her colleagues from the University of Montpelier have now confirmed that it depends on the activation of the IL-6/STAT1/STAT3 signaling pathway in a prolonged 10 weeks resistance training scenario. In the course of the latter,  36 male Wistar rats were randomly assigned to one out of the following six groups:
  • CTL2, CTL4, CTL10 (CTL = non-training controls, n = 6 in each group) and 
  • TR2, TR4 and TR10, which were rats trained for 2, 4 and 10 weeks. 
The rodents in the TR-X groups were supposed to climb an apparatus with initially 50% later up to 210% of their body weight strapped to their back, five times a week. The load was increased every two days, if the rodents still managed to do "10 reps" = climb 10 steps and reached quite impressive levels of 120% of the body weight after two, 150% of the body weight after four and 210% after ten weeks of training.

Where is the rodent squat machine?

No rodent squat in the study at hand, but the "stair climbing" is a better full-body workout, anyways.
Now, this may not be as "realistic" a program as the rodent squat Aguiar et al. used in their 2013 study, but is is - and this is interesting - very similar to a test that has been done by many researchers with myostatin negative mice. As you will remember from the Intermittent Thoughts on Building Muscle Series (click here to read the pertinent part) those heavily muscled mice are unable to lift their own bodyweight, mainly because of the fact that the myonuclear domains within their muscle grew beyond a threshold where they absence of an adequate number of myonuclei per volume unit enders the muscle useless.

"Healthy" muscle growth does therefore require both, protein synthesis (increase in volume), as well as structural adaptations, so that the domain size does remain constant - at least!

"10 weeks of resistance training did not affect the myonuclear domain"

Against that background the last subheading, which is in fact a direct citation from the full text of the Begue paper is - contrary to what a non-SuppVersity reader could believe - good news. Very good news, to be precise:
Figure 1: Changes in fiber type ratios (left), cross sectional diameter according to fiber type (middle) and  fiber area per myonucleus (right; Begue. 2013)
As you can see in figure 1 (right hand side), there was even a small, yet statistically non-significant decrease in the fiber area each myonucleus had to control and that despite quite impressive increases of 77%, 92% and 100% in the cross-section of the type-I, type-IIa and type-IIx fibers of the animals (figure 1, middle).

Satellite cell recruitment, necessary of optional if you want to get big?

In this context, Begue et al. speficially point out that the "recruitment of additional nuclei derived from SC incorporated into muscle fibers" occurs parallel to the better known "resistance training induced enhancement of protein synthesis" that occurs "after the training session and last[s] up to 24–48 h in humans" (Bengue.2013). 
"Indeed, several works in humans have evidenced an increase in the number of myonuclei per fiber when fiber size increases approximately more than 25% (Kadi. 2004; Petrella. 2008). Thus, the myonuclear domain (i.e. the theoretical amount of cytoplasm supported by a single myonucleus in a muscle fiber) remained constant although a large increase in fiber CSA via the addition of SC-derived nuclei occurs." (Begue. 2013)
Since estrogen plays an important role in the regeneration of the satellite cell pool, it's pretty likely that you can literally "SERM your growth potential away" (learn more)
Notwithstanding the heavily quoted results of the 2011 study by McCarthy et al. in which the reasearchers were able to demonstrate that rodent muscle can grow even when it is satellite cell depleted, my personal conviction is that the latter process, i.e. the incorporation of new (not just even the replacement of damaged myonuclei is an obligatory prerequisite for persistent gains.

With +40% increased domain sizes, after only two weeks, it would have been interested to see how things would have developed in the subsequent weeks. I bet(!), the normal mice would have kept growing while their satellite cell depleted peers would have hit a plateau, where their own body woul have pulled the emergency brake aka myostatin (in this context, it's also interesting to remark that myostatin stops the proliferation of satellite cells and does thus indirectly divert the existing ones towards differentiation and incorporation into the muscle, cf. figure 2)



Bottom line: The study at hand delivers further evidence for the intimate connection between "inflammation" or rather the expression of the still demonized inflammatory cytokine interleukin-6 and the incorporation of "fresh" satellite cells into the muscle. With the latter being a necessary prerequisite to keep the domain sizes within functionally optimal limits while the cross section of the fibers is expanding (the muscle is growing), it is likely an (I want to emphasis that!) not yet disproven that continuous muscle growth requires satellite cell recruitment.

Basically you can think of it like the Army. While it is (or at least has historically been) relatively easy to find any recruits (=increase protein synthesis), people who are qualified to become officers and coordinate the actions of the rank and file are hard to find and without an adequate number of them you will end up with a chaotic mess instead of a powerful army. That's actually pretty much what happens to the myostatin negative mice, who may be able to recruit officers,... ah, I mean to recruit satellite cells, but simply outgrow the maximal pace of satellite cell incorporation.

Figure 2: IL-6 is the first myokine you should remember, it "wakes" the quiescent satellite cells up, he COX-2 activated IL-4 is myokine #2 and initiates the differentiation / incorporation process which will eventually result in the formation of a new nucleus. .
What, oh yes, of course! I had almost forgotten the unfortunately quite complicated connection to IL-6. If you take a parting look at the figure on the right, you will realize that a diagram explains things much better than I could. In fact, the "motor" of the whole growth business is the contraction induced expression of serum responsive factor, of which Guerci et al. have found in 2013 that it is the previously missing link between muscular contractions on the one hand and the expression of myokines, who happen to be the same molecules we know as "inflammatory cytokines" in other contexts. Il-6 and the COX-2 activated IL-4 are then getting things rolling (Guerci. 2013)... what? No, I cannot tell you whether taking antioxidants will block that, but I can promise you that you will learn more about this tie-in within the next 7 days, so stay tuned ;-)

What I can tell you in advance, though, is that strength and size gains of IL-6(-) mice are compromised (Serrano. 2008). So even if I would have to qualify my previous statement that satellite cells are necessary for continuous growth - one thing is sure: Their activation by IL-6 is necessary for optimal growth.

References:
  • Begue G, Douillard A, Galbes O, Rossano B, Vernus B, Candau R, Py G. Early Activation of Rat Skeletal Muscle IL-6/STAT1/STAT3 Dependent Gene Expression in Resistance Exercise Linked to Hypertrophy. PLoS One. 2013;8(2):e57141. 
  • Guerci A, Lahoute C, Hébrard S, Collard L, Graindorge D, Favier M, Cagnard N, Batonnet-Pichon S, Précigout G, Garcia L, Tuil D, Daegelen D, Sotiropoulos A. Srf-dependent paracrine signals produced by myofibers control satellite cell-mediated skeletal muscle hypertrophy. Cell Metab. 2013 Jan 4;15(1):25-37.
  • Kadi F, Schjerling P, Andersen LL, Charifi N, Madsen JL. The effects of heavy resistance training and detraining on satellite cells in human skeletal muscles. J Physiol. 2004; 558: 1005–1012.
  • McCarthy JJ, Mula J, Miyazaki M, Erfani R, Garrison K. Effective fiber hypertrophy in satellite cell-depleted skeletal muscle. Development. 2011; 138: 3657–3666
  • McKay BR, De Lisio M, Johnston AP, O'Reilly CE, Phillips SM, Tarnopolsky MA, Parise G. Association of interleukin-6 signalling with the muscle stem cell response following muscle-lengthening contractions in humans. PLoS One. 2009 Jun 24;4(6):e6027. doi: 10.1371/journal.pone.0006027.
  • Petrella JK, Kim JS, Mayhew DL, Cross JM, Bamman MM. Potent myofiber hypertrophy during resistance training in humans is associated with satellite cell-mediated myonuclear addition: a cluster analysis. J Appl Physiol. 2008. 104: 1736–1742
  • Serrano AL, Baeza-Raja B, Perdiguero E, Jardí M, Muñoz-Cánoves P. Interleukin-6 is an essential regulator of satellite cell-mediated skeletal muscle hypertrophy. Cell Metab. 2008 Jan;7(1):33-44.