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. 

Farmer's Walk or Squat, Tire Flip or Bench Press, Stone Lift or Seated Row - Is Strongmen Training as "Anabolic" as Classic Hypertrophy Training and Which is "Best"?

Is he (or she?) going to be muscular when he grows up, or is this kind of exercise just making him strong?

I guess we all know that the most muscular guys are not necessarily also the strongest men in the gym - but why is that the case? And moreover, how does this fit in with the notion that you'd have to use heavy weights to induce skeletal muscle hypertrophy? Yeah, I know. Many scientists believe that's nothing but "broscience" (cf. Burd. 2013) and if you look at the muscle fiber composition of a bodybuilder in this previously published article, you will see that it is by no means type II and thus "strength-specific". And let's be hones does not the advent of blood flow restricted training signify that we are about to witness a "paradigm change"? With the classic approach (heavy weight and 8-10 reps) being on the upper end of a "optimal growth continuum"?

Notwithstanding this contemporary trend towards "making light weights heavier" (let's be honest, BFR for example does exactly that), a group of researchers from the Health and Human Performance Laboratory at the Hofstra University and the Gridiron Training Facility in Hempstead, New York, did actually dare to "waste" their time on research on the opposite extreme of the heavy vs. light lifting divide.

Don't forget: The paradigm determines the research design

Before we delve further in to the methodological issues, let me briefly get one thing straight. Ghigiarelli and his colleagues firmly believe in the significance of the immediate and early endocrine response to a workout. They specifically cite the work from Stuart Phillips lab, I have been referring to numerous times times, but (and this is science, guys!) politely disagree with the conclusion that the relationship between elevated endogenous testosterone levels and hypertrophy function was non-existent or at least irrelevant, stating that...

Suggested read "Anabolic Workouts Revisited"

"[...] a much larger body of evidence supports the integral role that the acute hormonal response to RE [resistance exercise] has on muscle hypertrophy (Schoenfeld. 2010; Vingren. 2010) and its role in strength training adaptation (Hansen, 2001;Kvorning. 2006). Those in support of an endogenous testosterone response stand by the belief that RE causes an initial downregulation on AR content in the target tissue (i.e., skeletal muscle) followed by a subsequent upregulation during the recovery period, thus increasing free testosterone uptake facilitating protein synthesis." (Ghigiarelli. 2013)

It is therefore not a design flaw, when the scientists take the acute testosterone response to the workout as a measure of it anabolic potential and speculate that a strongmen-esque workout, which engages much more muscle fibers than even a compound based bodybuilding workout does, would elicit a stronger hormonal response than a "classic" hypertrophy training (additional read => the Saturdaily installment of On Short Notice) .

Real trainees, real workouts, real (?) results?

To probe their hypothesis the scientists recurited trained athletes from various athlete backgrounds. The mean age of the

• tan recreational strength trainees (>4 training sessions per week, >2 years of training),
• one wrestler and one football player, 
• two competitive bodybuilders, 
• one competitive powerlifter and one competitive o-lifter

was 24 years, whose mean 3-RMs , i.e. the weight the participants can maximally perform for 3 reps, were 161kg for the squat and 126kg for the bench press.

Main result: Not superior, but "similar"testosterone responses

I guess, when you read the word "similar" (which is a real quotation from the full text) in the above subheading and take a loot at the actual data in figure 1 some of you may not without good reason complain that Ghigiarelli et al. use the word "similar" pretty generously.

Figure 1: Salivary testosterone response to immediately after (post) and 30 min after work-matched classic hypertrophy,  strongmen and mixed routines (Ghigiarelli. 2013)

If you look at the raw data on the left, it does after all look as if the classic hypertrophy workout with its squats, the leg presses, bench presses and seated rows was way more "anabolic" than

• its strongmen counterpart that consisted of tire flips, chain drags, farmers walks, keg carries and stone lifts, 

• the mixed protocol which was build around tire flips, squats, chain drags, bench presses and stone lifts 

when all exercises were performed for 3 sets x 10 reps with 75% of the weight the subjects could lift... and what should I say? You are right!

"Hold on! I don't see any 'similar' response!?"

What the average data in figure 1 (left) does yet not convey, are the large inter-individual differences. If you take those into account and use some statistical shenanigan to compensate for differences in the workout duration and the individual exercise intensity (whatever that may be, see Steele's recent paper on the absence of a clearcut definition of "intensity"), the superiority does turn into "a nonsignificant trend of greater testosterone release after the H protocol" (Ghigiarelli. 2013) - a trend, the researchers ascribe to the "abnormal response" they observed in response to the hypertrophy training (abnormal as compared to other studies, where the reponse hypertrophy training is usually in the 70% range, as well), which in turn would be attributable to 6 high responders with extreme spikes testosterone spikes of 165-493%.

Does true mastery of the exercise determine skeletal muscle anabolism?

Usually outliers like that are a problem, but sometimes there are cases where the exception from the rule has the greatest explanatory value and in this case, the latter may well be the case. How come? Well, the two hypothesis Ghigiarelli et al. come up with to explain the differences is simply too attractive to discard it as being irrelevant. Firstly, the scientists believe that it would be plausible that the anxiety level due to the unfamiliarity of strongman lifts may have reduced the testosterone spike.

You have no goals or don't track your results? Huge mistake (learn why)!

"This possibility is supported by previous literature examining the hormonal responses to different RE protocols in seasoned trainers (Beaven. 2008). Beaven et al. suggested that the novelty and stress of the situation are likely to be perceived based on experience. Thus, the stressors of the ST and XST sessions and the lack of familiarity of the exercises can suppress the actual physical nature of the stimulus. This psychological nature of the hormonal response in our subject pool may have caused a different response to protocols with which they were unfamiliar with or disliked." (Ghigiarelli. 2013)

Now, if you go one step further and expand on this idea by involving my mantra that training is not about moving weights from point A to point B and rephrase all that using a term Nicolas Burd et al. mentioned in their recent review in Applied Phyisology and Nutrition, in which they advance the idea that it does not really matter on which extreme of the low vs. heavy weight continuum you train, as long as your protocol elicits "high intensity contractions" (Burd. 2013), you could also argue that the subjects may have moved the weight for 3 sets of 10 when they did the farmer's walk etc., but did not to so using "high intensity contractions".

The intensity of the contraction determines the gains

Knowing the "101 of Pre Workout Protein Supplementation" can make a difference. Over all the supplement shenanigan many trainees do yet tend to overlook the basics and simply  assume that as long as they move weight from A to B the use of the right powders and popping the right pills at the right times would have the largest impact on their results - big mistake!

In other words, the calculated "intensity" and the real muscular tension, i.e. the intensity of the contraction, were not identical and certainly sub-optimal for those of the trainees who have never flipped tires or carried kegs before. The bodybuilders and certainly also most of the recreational athletes may well have been so focused on the novel exercise that they could not pay any attention to the one thing that's at the bottom of skeletal muscle growth the "high intensity contraction".

Now, it is probably undebatable that the actual work that is done by the muscle and not the physical work, you would calculate by multiplying the weight (respectively the force you would apply to it in an ideal scenario) and the length of the way along which you dragged, carried or flipped it, is the physiologically relevant number here. In this context it would also be irrelevant, if the endocrine response to a workout does actually correlate with the net gains in muscle size or strength, as long as the "intensity of the contraction" did. In the end, it is thus not the weight or the exercise that determines the actual growth stimulus, but rather your ability to use a given weight in a given exercise to induce those damn high intensity contractions.

---

Bottom line: For 90% of the trainees out there, the first step to improve their gains would thus to improve their game. To take the true meaning of "training", of which the venerable Oxford English Dictionary says that it is  "the sustained instruction and practice (given or received) in an art, profession, occupation, or procedure, with a view to proficiency in it." (OED Online. 2013). For the majority of trainees I see at the gym, it would thus be much wiser to follow Adelfo Cerame's recent advice and focus on a handful of exercises, instead of hopping from one exercise to the next, whenever a study says: Subjects, X,Y and Z gained 0.5% more mass doing farmer's walks vs. squats.

For others, it may yet be time to move on or to expand their arsenal of exercises with what Ghigiarelli et al. feel are "unique and exciting" exercises which provide "effective alternative to traditional resistance training, but require a lot of training to even master them "manipulate the specific combinations of rest intervals, loading, and volume toward [your] desired training goals" (Ghigiarelli. 2013).

References

• Beaven CM, Gill ND, Cook CJ. Salivary testosterone and cortisol responses in professional rugby players after four resistance exercise protocols. J Strength Cond Res. 2008 Mar;22(2):426-32.
• Burd NA, Mitchell CJ, Churchward-Venne TA, Phillips SM. Bigger weights may not beget bigger muscles: evidence from acute muscle protein synthetic responses after resistance exercise. Appl Physiol Nutr Metab. 2013 Jun;37(3):551-4. doi: 10.1139/h2013-022. Epub 2013 Apr 26.
• Ghigiarelli JJ, Sell KM, Raddock JM, Taveras K. Effects of strongman training on salivary testosterone levels in a sample of trained men. J Strength Cond Res. 2013 Mar;27(3):738-47.
• Hansen S, Kvorning T, Kjaer M, Sjøgaard G. The effect of short-term strength training on human skeletal muscle: the importance of physiologically elevated hormone levels. Scand J Med Sci Sports. 2001 Dec;11(6):347-54.
• OED Online. "training, n.". December 2013. Oxford University Press. < http://www.oed.com/view/Entry/204425 >  accessed March 04, 2013.
• Kvorning T, Andersen M, Brixen K, Madsen K. Suppression of endogenous testosterone production attenuates the response to strength training: a randomized, placebo-controlled, and blinded intervention study. Am J Physiol Endocrinol Metab. 2006 Dec;291(6):E1325-32.
• Schoenfeld BJ The mechanisms of muscle hypertrophy and their application to resistance training.J Strength Cond Res. 2010; 24: 2857–2872.
• Steele J. Intensity; in-ten-si-ty; noun. 1. Often used ambiguously within resistance training. 2. Is it time to drop the term altogether? Br J Sports Med. 2013 Feb 12. 
• Vingren JL, Kraemer WJ, Ratamess NA, Anderson JM, Volek JS, Maresh CM. Testosterone physiology in resistance exercise and training: the up-stream regulatory elements. Sports Med. 2010 Dec 1;40(12):1037-53.