Intermittent Thoughts on Building Muscle: IGF-1 and its Splice Variants MGF, IGF-IEa & Co - Master Regulators or a Bunch of Cogs in the Wheel of Muscle Hypertrophy?

Image 1: With regard to IGF-1 and its splice-variants like MGF, there is probably 10x-100x more bro- than pro-scientific data out there - this does not help us, though, since you never know which of the bro-reports is bogus and which is not.

In view of the fact that we have not covered much ground with the last installment (we did build a pretty solid foundation, though ;-), I will try my very best to steer a middle course between presenting impressive amounts of facts and explaining the complex and in part not even completely elucidated physiological underpinnings of skeletal muscle hypertrophy, or, as the bros would say, getting big and buffed! A pros pros Bro, you will unquestionably have read on one of the myriads of bodybuilding-related bulletin boards how the injection of X amounts of IGF-1 right into the muscle made BigGuns, or whatever the poster's pseudonym may have been, grow "3 inches in 2 weeks"... ok, his profile picture looks impressive, but is that credible? Does IGF-1 really have such profound effects on muscle growth? And about what type of growth are we talking here? The myostatin-negative "ballooning up" of the muscle, which leaves you with overblown myogenic domains and dysfunctional muscles?

IGF-1: Insulin, growth hormone, or what?

To be able to answer these and related question we will first have to understand what exactly this "insulin-like growth factor 1" actually is. From a (bio-)chemical perspective it is nothing but a bond of 70 amino acids which are entangled into a specific peptide structure that is characteristic for somatomedin C, as IGF-1 is also called. Both the "growth" in IGF-1, as well as the "somato" in its old-fashioned appellation already suggest that what we are dealing with, here, is a "growth hormone related" polypeptide. And in fact, the synthesis of IFG-1, which, in the case of the systemically available fraction, takes place primarily in the liver, and is triggered by systemic growth hormone (somatotropin) levels.

Figure 1: Changes in systemic IGF-1 levels after 5-weeks on either a "normal" (=55:15:30 carbs:protein:fats) or a low carb "high protein" (=20:30:50) diet in 8 men with untreated type II diabetes (data adapted from Nuttal. 2006)

The "insulin" in its name, however, is pretty misleading... or I should say people mislead themselves, by not reading  the name correctly: It's not "insulin-growth factor", but "insulin-like growth factor" and the "like" refers to the structure of the molecule and does not imply that it is released in response to insulin spikes, as you may have read it on one of the aforementioned bulletin boards. If you do take a look at the growth hormone and IGF-1 levels of eight male subjects in a 2006 study on the metabolic of 5-weeks on what the scientists call a "high protein, low carbohydrate diet" (Nuttall. 2006), you will see that an increase in protein and fat from 15% to 30% and 30% to 50%, respectively elicited an 34% increase in serum IGF-1 levels over the treatment period, a finding that is corroborated by the recently published results of Matthew B. Cooke and his colleages from the Department of Health, Human Recreation and Performance at Baylor University.

Figure 2: Serum IGF-1 levels in response to whey vs. maltodextrin supplementation and subsequent lower body resistance training (data adapted from Cooke. 2011)

In their randomized double-blinded cross-over study, Cooke et al. had a group of 10 recreationally active men (2-3 non-resistance training exercise sessions per week) perform a lower body exercise program (leg presses and knee extensions, 4 sets, 8-10 reps at 80% of the individual 1RM) with either 10g of maltodextrose or 10g of whey 30 minutes before the exercise bout (Cooke. 2011). The results of the study (equal IGF-1 response regardless of whey or carbohydrate supplementation) imply that even in the short term, in healthy subjects and in conjunction with exercise the ingestion of carbohydrates is not superior to the provision of fast acting protein sources as a means to either increase or maintain systemic IGF-1 levels.

On a side note: The insulin-mediated induction of Akt, which subsequently triggers the phosphorylation of the mammalian target of rapamycin (mTOR) and thusly does its bit to elevate protein synthesis, has no direct relation to IGF-1, which - I cannot emphasize that enough - has a structure resemblance to insulin, nothing more, nothing less. And what's more, the insulin response in the aforementioned study by Cooke et al. was identical in the whey vs. maltodextrin arm of the study.

Systemic vs. local IGF-1 expression: A crucial distinction

If you have been following the daily research updates here at the SuppVersity over the last months, you may now be wondering why I am even caring about those growth hormones (after all you should, after reading the first paragraph, realize that IGF-1 is something like the active incarnation of somatotropin), when Stuart Phillips lab has quite conclusively shown that even the exercise induced elevation of testosterone does not correlate with subsequent increases in muscle protein synthesis. Certainly a good question, but nevertheless not difficult to answer:

1. The previous installments of the Hypertrophy 101 (Part 1, Part 2) should have made it quite clear that protein synthesis alone is not sufficient to grow. Without intra-muscular restructuring / reorganization and the recruitement of new myonuclei from satellite cells, you would sooner or later grow beyond the maximally allowed myonuclear domain sizes (assuming that by whatever means you block the healthy upregulation of mystatin that will prevent that) and end up as an over-muscled but completely dysfunctional wrack.
2. In a very recently published study, the results of which I have actually been holding back, because I thought I would get to them much earlier in this series, the very same Stuart Phillips whose studies are "responsible" (in fact it is the way they are discussed by the lay-press and abused by the supp-companies that is actually "responsible") for the current over-emphasis on acute increases in the protein synthetic response to exercise and/or supplements, reports that there actually was a statistically significant correlation between exercise induced growth hormone release and increases in mean type I fiber (p<0.06) and type II (p<0.04) cross-sectional area (CSA) in 56 healthy previously non-resistance trained healthy young men in response to a 12-week, 5-day per week resistance training regimen (West & Phillips. 2011).
3. While we have hitherto been talking about systemic IGF-1, it has become evident in the course of the last decade that the hepatic IGF-1 output, which is the main determinant of circulating IGF-1 levels, has little to no impact on the IGF-1 induced increases in skeletal muscle mass and remodeling of muscle tissue that has been previously studies in Petri dishes. In fact, recent research suggests that, just like the liver produces IGF-1 for "the whole body", muscles produce their own IGF-1, or I should say, their own IGFs-1, whenever they are challenged to grow and/or repair (Velloso. 2010), and that the decline of muscle mass with age is at least in parts attributable to a defect / reduction in the expression of local IGF-1 splice variants (for an explanation of what this is, see red box below).

If we now count 2. and 3. together the result is not 5. but rather that it is the growth hormone mediated, exercised-induced local expression of IGF-1 splice variants, which drives the repair and restructuring process that allows for continuous (healthy) muscle growth.

Did you know that the intra-muscular (=autocrine, meaning directly in the tissue where it is supposed to work) "construction process" of the mature 70 amino acid polypeptide IGF-1 gives rise to three different splice variants of insulin-like growth factor (note: the structure of IGF-1 gene does theoretically allow for 6 variants)? And though we are just beginning to understand the physiological roles of IGF-IEa, IGF-IEb and IGF-IEc, also known as MGF (mechano-growth factor), their distinctly timed expression in response to physical overload appears to constitute one of the major driving forces of myocellular hypertophy.

In order to fully understand the role "the" insulin-like growth factor 1 plays in the physiology of muscle growth, it is thusly important to realize that the common perception of IGF-1 as a systemic hormone is, at best, incomplete - I would even venture to say that it is totally flawed.

MGF?! Yeah, I have heard of that one!

Figure 3: Stained myocyte migration (top) and infiltration (bottom) essays for IGF-1 and MGF; more stains = greater effect (taken from Mills. 2007).

Of the three primary splice variants that are expressed in skeletal muscle, IGF-IEc, or MGF (Mechano-Growth Factor) has probably received the greatest attention - so much attention that even the aforementioned bros, will probably have grasped the notion that this is somewhat of a local isoform of IGF-1 which is expressed in response to exercise induced muscle damage and could potentially be the magic bullet to grow beyond what we have hitherto believed to be possible... and, guess what, in essence this appears to be correct.

In one of the earlier studies on the cellular effect of MGF, Yang et al. were able to show that MGF stops the IGF-1 mediated cell differentiation process (in practice this means that it stops the satellite cells from differentiating = specializing and becoming muscle cells) and increases their proliferation. Or put more simply: While in vitro exposition to IGF would suffice to build muscle, as long as there are enough progenitor cells (satellite cells) available, MGF is necessary to replenishes the satellite cell pool of which you have learned in the previous installments that it is necessary to a) repair damaged muscle tissue and b) increase the number of myonuclei in order to grow beyond the physiological growth limit that arises due to the muscle-type-specific upper limit to the myonuclear domain size (cf. previous installments).

Figure 4: Cell proliferation data in response to MGF treatment after blocking the IGF-I receptor.

As the data in figure 4 goes to show the effects of the complete polypeptide IGF-1 and its splice variant MGF appear to be mediated, at least partly via distinct receptors. And while recent research suggest that MGF also exerts similar effects on tendon (Olesen. 2006), brain (Dluzniewska. 2005) and nervous tissue (Aperghis. 2004), our primary concern here, is its pivotal role in muscle repair, which involves the activation of satellite cells, their proliferation (Yang. 2002) and migration (Mills. 2007).

A series of studies by Hammad et al., which was originally intended to investigate the effects of age on the expression of the different IGF splice variants, goes to show that the "muscle (re-)building effects" of MGF are not restricted to the test tube. In their 2002 study (Hamed. 2002), the researchers were able to show profound increases in the MGF expression in the quadriceps muscles of 8 healthy young men (age 29.5 ± 1.5 years, body mass 81.1 ± 2.4 kg, height 179.3 ± 1.8 cm) 2.5h after a single muscle-damaging leg-extension exercise (10 sets of 6 repetitions at 80% 1-RM, 2 min rest between sets):

Figure 5: MGF (ng mRNA / 10^8 µg RNA) and IGF-IEa ng mRNA / 10^5 µg RNA) expresion in quadriceps muscle of young subjects before and 2.5h after 10 sets of 6 repetitions at 80% 1-RM on a leg-extension machine with 2min rest between sets (data adapted from Hamed. 2002)

If you take a closer look at the data in figure, you will probably notice that there was one subject with an extreme MGF response, the scientists explain by a particularly high type-IIx fiber content of the quadriceps of this individual. If you remember the mouse studies and the analysis of the muscle composition of bodybuilders from the previous installments, you will be aware that the shift from type IIb to type IIx muscle fibers is one of the main characteristics of "getting real big". The extreme MGF response (>10x higher than the mean MGF expression across the other subjects) in this subject thusly suggests the increased growth capacity of type IIx muscle fibers is in part due to their ability to release MGF in response to strenuous exercise and thusly multiply / replenish their satellite cell pool to prepare for future growth.

Figure 6: MGF (ng mRNA / 10^8 µg RNA) and IGF-IEa ng mRNA / 10^5 µg RNA) expresion in quadriceps muscle of young subjects after eccentric HIIT exercise on cycle ergometer (data adapted from Hamed. 2008)

Interestingly, a 2008 follow up study (this time involving nine healthy young men aged 20–27 years, cf. Hamed. 2008) with a completely different training protocol that consisted of

60min of opposing the rotation of the pedals down to 60 r.p.m. Subjects performed the following program of six working intervals: six working intervals: 0–6min at 50%, 6–12min at 75%, 12–20min at 100%, 20–25min at 130%, 25–40min at 100% and 40–60min at 75% of the load  eliciting concentric VO2max

illicited surprisingly similar results (cf. figure 6). And in both cases, it appears to be the MGF splice variant not the IGF-IEa variety that drives the short term (hours to days) response to strenuous exercise.

HIIT and resistance training a dynamic duo for MGF expression

Assuming that you are following each and every post here at the SuppVersity (you know you should be ;-), this should remind you of a previous blogpost of mine (cf. "HIT Your Satellite Cells to Increase Your Gains!"), in which I explained that one of the many advantages of high intensity training (not even interval) over classic "cardio" training is that it can increase satellite cell proliferation. Now, with this installment of the Intermittent Thoughts you finally understand, why this is the case.

Image 2: This is not the kind of muscle damage you should be aiming for in the gym.

Now, while protein synthesis and increases in domain size are partly mediated via nutrition, the intra-muscular expression of the IGF-IE splice variants appears (at least based on the current research) to depend solely on exercise, or I should say the wear and tear that goes hand in hand with heavy exercise. In that it seems to be less important, whether you are "pumping away" or "cycling like maniac", as long as its "hard" - to put that into perspective, in the 2008 study by Hamed et al. the subjects underwent ~3600 eccentric muscle contractions in only 1 h, their creatine kinase (CK) levels (marker of muscle damage) increased by +183% and all subjects reported profound muscle soreness.

This controlled amount of muscle damage ties in nicely with the topic of next week's installment which will center around the the intricate relation of the inflammatory response to exercise, the expression of the well-known and less known inflammatory cytokines, TNF-alpha, IL-6 and IL-15 (sorry, Trevor, I have already gone overtime, so your question will have to wait till next week ;-) and the muscle (re-)building effects of IGF-1 and its intra-muscular children.

D-Finitively Relevant News: Vitamin D Supplementation Speeds Up Strength Recovery and Lowers Markers of Muscle Damage in Vitamin D-Sufficient Young Subjects

If we were all training at "Muscle Beach", we would probably not need any vitamin D3 caps to get our 25(OH)D levels into the recovery friendly 50ng/ml zone. They would already be there!

Ok, I know this looks odd, but it's really total coincidence that all the interesting vitamin D research is published in the last weeks of the year. Unlike the latest vitamin D articles, i.e.

• "Vitamin D Builds Muscle: 70% Reduction in Myostatin, 45% Increase in Myotube Size in 10 Days" |  learn more
• "Leucine, Insulin & Vitamin D*: A Hypertrophy Boosting Triplet That Does Not Make It From the Dish to the Gym?" | read more

today's SuppVersity article does yet leave little room for speculations about it's real-world significance. I mean, how could it, if the paper it discusses is titled "Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise" (Barker. 2013).

You can learn more about vitamin D at the SuppVersity

Vitamin D Builds Muscle

Leucine, Insulin & Vitamin D

Vitamin D = Fat Synthesizer

Overlooked D-Sources

Vitamin D For Athletes!

Vitamin D Helps Store Fat

The title does yet not "say it all". Moreover, what it doesn't tell you is the most important piece of information. The study period was short (35 days) the dose of vitamin D was relatively high (4,000IU) was conducted with "reportedly healthy and modestly active (30 minute of continuous physical activity at least 3 time/week) adult men with low, albeit normal vitamin D levels (25(OH)D ~ 30ng/ml)! The otherwise almost obligatory question about the potential relevance in "normal" human beings does thus become superfluous - and this is true for all the observations the scientists made, i.e.

• ... the linear relationship between baseline 25(OH)D levels and the increase in serum vitamin D in response to the with an up to 150% increase in subjects in the deficiency zone and less than 50% increases in subjects in the >40ng/ml range, ...
• ... the steady serum calcium levels, which make concerns about potentially kidney damaging increases in calcium from vitamin D3 supplementation obsolete, ...

... and, not to forget, the enhanced recovery in peak isometric force the researchers observed in their subjects after these had performed 10 sets of 10 repetitive eccentric-concentric jumps with a load of 75% of their respective body mass on their shoulders and a 20 sec rest period between each set.

For the researchers this is a model of a "muscle damaging event" (P< 0.05; ≈8% at 24-h), which was, as it was to be expected, associated with an increase in the circulating levels of the "liver enzymes"  alanine (ALT) and aspartate (AST) aminotransferase, of which many medical textbook will tell incorrectly tell you that they would indicate a strain on the liver / liver damage, when they are actually only markers of increase amino acid catabolism. The attenuation (P< 0.05) of the immediate and delayed (48-h, 72-h, or 168-h) increase in these enzymes in the vitamin D supplemented group  is thus an indicator of "muscle protective" or at least general protein sparing effects of supplementally increased vitamin D levels.

Figure 1: Strength recovery (%) from immediately post to 24 post workout, left; serum ALT values immediately after, 24h, 72h, and 168h after the exercise test (Barker. 2013).

The fact that the alleged decrease in muscle damage did not correlate with a decrease in muscle soreness does or doesn't negate the purported muscle protective effects of vitamin D. There is, as you should remember from Alex' excellent articles about DOMS, after all no direct link between ALT, AST, muscle damage and delayed onset muscle soreness, aka DOMS (learn more about DOMS). What is clear, though is that there was no consistent trend in the subjective measures of muscle soreness in the study at hand, so that Barker et al. are right, when they state that "[s]upplemental vitamin D was ineffective at abrogating muscle soreness in the SSC leg" (Barker. 2013). If it's an improvement in pain you are looking for, you'd be better off with one of the techniques Alex' discussed in part I of his article series.

Figure 2: It looks boring, but the linear association between the subjects baseline levels and the change in 25(OH)D and the ceiling effect at ~50ng/ml are also important results of the study at hand (Barker. 2013).

Bottom line: I guess you can't have it all, so I would not mourn over the lack of effect on muscle soreness. I mean, come on (!), this is one out of thousand (literally!) vitamin D studies with real-world relevance for you and me. A study that confirms that getting your 25(OH)D levels into the 50ng/ml range can actually have small, but stat. significant beneficial effects on your exercise performance (without negative effects on calcium, btw).

Furthermore, the fact that this increase to the 50ng/ml+ was achieved in all subjects with "only" 4,000IU D3 within only 35 days and was directly associated to their respective baseline level is an intruiging result on its own (see Figure 2). It does after all provide you with a rough guideline of what you have to do if your next 25(OH)D blood test comes back way below the 50ng/ml margin.

Against that background, there is no reason to frown about the fact that we still don't really know what vitamin D actually does to elicit its ameliorative effects on the performance decline in response to potentially muscle damaging stretch-shortening contraction. This was beyond the scope of the study at hand and cannot be investigated in isolated muscle cells... much contrary to the previously reported anabolic effects in the Petri dish, by the way, which may be exciting, but more or less irrelevant, if we can't observe corresponding increases in muscle hypertrophy in the real world.

References:

• Barker, T., Schneider, E. D., Dixon, B. M., Henriksen, V. T., & Weaver, L. K. (2013). Supplemental vitamin D enhances the recovery in peak isometric force shortly after intense exercise. Nutrition & Metabolism, 10(1), 69.

High and Low Dose BCAA Supplementation Have Minimal, Non-Significant Effects on Markers of Muscle Damage 24h and 48h Post Heavy Resistance Training

Image 1: Cover of the September issue of the International Journal of Wrestling Science - don't tell me you don't have a subscription, yet!

I don't know about you, but I feel that it's quite interesting to look at the highly heterogeneous dosage suggestions on the labels of the ever-increasing number of BCAA supplements on the market. Interestingly, almost every producer claims in his "non FDA-approved" statements that his supplement contains "scientifically supported" or "clinically validated" amounts of branch-chained amino acids in the "optimal" (whatever that may be) ratio of 2:1:1, 3:1:1, 4:1:1, 8:1:1, ... and all the other variations that appear to be limited only by the patent applications and lawyers of the financially more potent players in the business. From a scientific perspective, however, this "optimal" amount has still to be elucidated - at least to my knowledge, no respectable scientist has yet claimed to have found the "optimal" amount and composition of free form amino acids for a given subgroup of athletes, let alone strength athletes, bodybuilders or figure competitors, in general.

At this point I would like to add that no respectable scientist would ever dare to make the claim that he or she has found the "optimal free form amino acid supplement" for all, or even a significantly large group of athletes, unless he or she would be interested in losing his reputation as a "respectable scientist" ;-)

In a recently published study scientists from the Department of Physical education and Sports Science University of Tabriz in Tabriz, Iran, set out to establish whether there is at least a significant difference between the effects of ~15g (210mg/kg) or 33g (450mg/kg) of branched chain-amino acids taken before and after the completion of an intense resistance training regimen comprised of 7 exercises à 3 sets of 10 repetitions (Amirsasan. 2011). Yet, despite the fact, that even the "low dose" of 15g of BCAAs (in the customary 2:1:1 ratio, i.e. 7.5g of leucine + 3.75g of iso-leucine + 3.7g of valine) was about 1.5x higher than what I have seen as "suggested dosing" or "serving size" on very high-dosed commercial supplements, the effects of this amino acid overkill were "sobering", to say the least.

Figure 1: Effects of "low" (210mg/kg) and "high" (450mg/kg) dose BCAA supplement on enzymatic markers of muscle damage relative to pre-values in the placebo group (data calculated based on Amirsasan. 2011)

As the data in figure 1 goes to show both the "low" as well as the "high" (or should I say "overkill" ;-) dose of pre- and post-workout BCAAs had only marginal, and certainly statistically non-significant effects on creatine kinase (overall - CK; muscle specific - CK MB) and lactate dehydrogenase activity, both established indicators of (exercise-induced) muscle damage.

Comparison of results between groups in mean and amplitude changes of serum indexes of cell damage (CK-LDH-CKMB), 24 and 48 hours after the exercise performance showed no significant difference between the 3 groups. In other words, different amounts of BCAA did not significantly affect the serum cell injury indexes (CK-LDH-CKMB), 24 and 48 hours after the heavy resistance activity.

These results are interesting, because they contradict previous findings by Sharp et al. who reported "significantly reduced" creatine kinase levels with BCAA supplementation in likewise previously strength-trained athletes on a similarly intense (8 exercises; 3x 6-8 repetitions) resistance training protocol (Sharp. 2010), as well as the results of studies in endurance athletes and previously untrained subjects, where the provision of BCAAs decreased creatine kinase and lactate dehydrogenase enzyme expression, across-the-board (Greer. 2007; Koba. 2007; Matsumoto. 2009).

"To supplement or not?" This question may arise if you have a look at the data from this study. Thor, in a comment to this posts poses the question whether his "personal experience" that "having the fast digesting aminos seemed to increase [his] ability to have a more successful work out" is, after all "only in [his] head" and while I cannot say for sure how much of it may be the result a placebo-effect in his case, I can provide you with the results of a 2011 study by Greer et al. who found no increases in exercise performance despite reduced perceived rates of exertion with BCAA supplementation after a 90-minute cycling bout (Greer. 2011). These results seem to confirm the "central fatigue hypothesis" according to which BCAAs exert their beneficial effects agains (perceived) fatigue via modulation of the availability of the serotonin precursor tryptophan. In a 2007 review of the literature, Meeusen and Watson do yet conclude that the "nutritional manipulation of these systems [neurotransmitter] through the provision of amino acids has proven largely unsuccessful" (Meeusen. 2007)... All that does not take away from the established beneficial effects of chronic low-dose BCAA (in particular, leucine) supplementation on endurance performance and strength adaptations to exercise (e.g. Crowe. 2006; Matsumoto. 2009). In the respective studies, dosages in the 1.5-3.0g/day range have yet been sufficient, to elicit these beneficial effects - and that in subject groups that are not particularly well-known for their exorbitantly high protein intakes ;-)

Image 2: When bought in bulk and without the addition of a ton of fancy extras BCAAs have become reasonably priced - whether they are a "necessary" part of your supplement regimen may yet depend on your dietary protein intake.

Probably - this would at least be my first guess - the outcome of these studies was not so much affected by the actual study protocol, but rather by the habitual dietary protein intake of their subjects. With endurance athletes (Koba. 2007; Matsumoto. 2009),  recreationally active (Sharp. 2010) and untrained (Greer. 2007) we usually see much lower dietary protein intake than with professional wrestlers, which prompts me to repeat my previously stated skepticism towards the usefulness of large boluses of additional free form amino acids in a group of athletes whose habitual dietary protein intake is way beyond the 1.5g/kg level, anyway... but hey, that's just the opinion of a brainy physicist; so if your brawny guru says you need those 150g of BCAAs on top of your 5x50g whey protein shakes and your 3 pound of lean meat - go for it!

"10x3 = 3x10 < 20x3"? The Mathematics of Optimal Set and Rep Ranges for Maximal Increases in Sleeve Size

Image 1: Going for the pump was Arnold's way
to biceps peak and size, but is that "optimal"?

How many sets do you do, when you are at the gym? How many repetitions (reps) each? And are you sure that this is the "right" way to train? No? Well I guess then you will be interested in the results of a study from the School of Exercise, Biomedical and Health Sciences at the Edith Cowan University in Joondalup, Western Australia ( Chan. 2011), for which Roy Yang Han Chan (I hope I did not mix up name and surname, here ;-) recruited 10 non-resistance trained men to investigate the effects of different set/rep schemes on muscle strength, range of motion  (ROM),  muscle  cross  sectional  area  (CSA),  muscle  soreness  and  plasma  creatine kinase  (CK)  activity after two bouts of eccentric biceps curls (see illustration 1 for exact study setup).

Illustration 1: Setup of the 4 training bouts the 10 subjects of the study participated in (according to Chan. 2011)

Now, "non-resistance trained" subjects (mean ± SD age: 26.1 ± 4.1 y, height: 173.1 ± 6.1 cm, body weight: 72.4 ± 9.1 kg)  and training on just two occasions, are not exactly constituents of a highly significant study protocol. In view of the scarcity of data on what some trainers consider the holy grail of training theory, the finding that

Maximal  voluntary  contraction  strength,  ROM,  biceps  brachii  CSA [cross sectional area],  muscle soreness and plasma CK [creatine kinase - leakage of this enzyme from the muscle is a measure of muscle damage] activity changed significantly after the first bouts without significant differences  between  3x10  and  10x3,  and  changes  in  the  measures  following  20x3  were similar  between  arms.  No  significant  differences  in  the  changes  of  the  criterion  measures were  evident  between  bouts.the  set-repetition  configuration  had little effect on muscle damage, which was likely to be due to similar peak torques produced during  exercise  between  the  3x10  and  10x3  bouts.

The question we have to answer now, is "How representative is this data?" In the previous paragraph I already mentioned the first fundamental flaw of the study: the subject selection. "Why on earth", you may be asking yourself rightly, "Why did this Australian exclude resistance trained subjects from his study and chose subjects with 4.5inch arms? Isn't it obvious that these bonsai-guns will grow no-matter what those guys would do in the gym?" And, yes that is exactly the case and, at the same time though, also the reason why, time-and-again, we see those studies done with "resistance training virgins" - due to the completely novel stimulus their muscle simply grow like crazy, no matter how short your study period, how flawed your exercise program or how useless your supplement may be - and that, in turn, reduces your costs and the threat of observing a null-result dramatically. You better keep these general objections in mind, especially if you look at absolute values of studies like this one.

Figure 1: Relative increase in biceps cross sectional area [CSA] of 3 sets a 10 reps (3x10) and 10 sets a 3 reps (10x3) compared to 20 sets of 3 reps (data calculated based on Chan. 2011)

With the afore-made objections in mind, the relative results depicted in figure 1, do still provide some insight into the differential time-course of the effects of a high intensity training with 10 sets a 3 reps (10x3) and a classic hypertrophy regimen with 3 sets a 10 reps. The greater increase in muscle CSA on the first day (both are expressed relative to the 20x3 regimen that both group A and group B performed) in what I would like to call the hypertrophy group (3x10), as well as the delayed response in the high intensity 10x3 group appear to support the commonly cited hypothesis that due to the greater myofibrilar damage the high intensity 10x3 protocol would inflict, it takes longer for the muscles to recover and thus grow.

Figure 2: Relative elevation of creatine kinase over baseline in group A (3x10 vs. 20x3) and group B (10x3 vs. 20x3) 4 days after eccentric biceps training (data calculated based on Chan. 2011)

The creatine kinase [CK values are generally accepted as markers of muscular damage] values in figure 2 suggest another conclusion, though. While the CK values in what I labeled the hypertrophy group were still +60% elevated over baseline, they had returned to normal (+8%) in the HIT group already. While this would go against the idea that a 10x3 training regimen requires longer recuperation times than a rather hypertrophy oriented regimen of 3x10 sets, these results would obviously warrant longer term studies in well-trained athletes to be of reasonable significance for any bodybuilder or fitness athlete - especially in view of the marginal and statistical non-significant difference in overall strength and size gains I already cited at the beginning of this post.

For the time being you could however try to switch things up for a week or two and see whether and how a rather unorthodox 10x3 regimen impacts your sleeve size, since even if it may not be the "optimal" training regimen, changing the training stimulus from time to time is always a good idea... ah, and if you wake up four days later with an +2inch increase in your biceps size, please let me know ;-)

Is Hydrolized Whey, the New Way to Go? 12 Week Human Study Suggests: Yes, If Your Goal is to Ward Off Oxidative Damage. No, If You Want to Build Muscle & Lose Fat

The typical soccer player is no longer a stick on muscular legs, these days. The sport has changed and so have the physiques of the players.

I guess ever since I published the article "The Glucose Repartioning Effects of Isoleucine: Falsely Underappreciated BCAA and Its Dipeptides Maximize GLUT-4 Expression and Ramp Up Muscular Glucose Uptake" (read it) that discussed the beneficial effect of the small isoleucine peptides in hydrolized whey on glucose metabolism, some of you may have been wondering, whether theh previously sneered at even more insulinogenic fast-digesting, bad-tasting, highly-processed whey protein hydrolysates (WPHs) may not be an alternative, if not the better alternative to whey concentrates or isolates.

Personally, I have always favored the "whole" over its individual parts, but the evidence that there is something special about WPH is accumulating.

"So what kind of new evidence is accumulating here?"

That being said, the latest evidence that would support this notion comes from the Universidade Estadual de Campinas in São Paulo, Brazil (Lollo. 2013). Where Pablo Christiano B. Lollo et al. investigated the effects the provision of whey protein (WP), hydrolysed whey protein (WPH), or a non-protein placebo (maltodextrin, MALTO) would exert on selected biochemical, anthropometric and performance parameters in 24 soccer player over the course of 12 weeks.

The iso-caloric supplements which contained 0.5g of protein (or placebo) per kg of body mass had to be before and after each training session, as well as on rest days (i.e. on Monday). The overall protein intake was relatively low (typical of a sport with a clear endurance focus) and was designed so that the protein of the diet plus that of the supplement would represent 15% of the total daily caloric intake. Both, the diets, as well as the sleep and training schedule were standardized. The intensity and training volume were identical for all individuals having plaing the same position (e.g. striker, defender, etc.). And the amino acid content of the two whey supplements was identical, so that the only difference between the WP and the WPH group was the chain-length of the proteins and peptides in the drinks they ingested.

Figure 1: Changes in markers of exercise induced damage (left) and body composition changes (in %) over the course of the 12-week study period (Lollo. 2013)

As you can see in figure 1 this minute difference was yet enough to result in significantly different responses to the protein supplement in the WPH and WP groups.Only, in the former, i.e. the whey protein hydeolysate group did the scientists observe significant decreases in the muscle damage indicators, creatine kinase (-42%) and lactate dehydrogenase (-30%). The minimal changes in the whey protein group, on the other hand, were not superior to the maltodextrin control.

"The foremost features of this investigation were greater than 40% and 30% decrease in CK and LDH, respectively, obtained after 12 weeks of supplementation with the hydrolysed whey protein. This outcome contrasted even more with the increase of CK, which was approximately  +35% obtained by supplementing with maltodextrin alone." (Lollo. 2013)

As you would expect there were no apparent adverse effects observed in either of the groups whose total total protein intake remained below 2.3 g/kg per day. The renal function and protein metabolism parameters, uric acid and creatinine remained within the physiological limits of normality in all groups. 

WPH the whey for elite athletes? 

In their discussion of the results, Lollo et al. make an interesting point, when they compare their observations to those in previously conducted studies and state:

Right from the archives: "Looking at Fast, Slow & Total Protein Intake. More Than 2g/kg Protein = Madness?" (read more)

"Since studies of the effects of protein supplementation have normally been carried out with non-athlete volunteers in acute experiments (Bolster et al., 2005; Pennings et al., 2011; Tipton & Ferrando, 2008), it was interesting to note that the data collected from elite athletes engaged in a real championship pointed to hydrolysed whey protein being the only form of supplement that effectively diminished the levels of muscle damage biomarkers.

Those results could be understood in light of the high antioxidant capacity of the hydrolysate." (Lollo. 2013)

If that could be confirmed for other elite athletes and highly trained gymrats, as well, the question I raised in the headline of this article may well be answered affirmatively: "Yes, for elite athletes with a high training workload, hydrolized whey proteins may in fact be the better way to go."

If you take a closer look at the data in figure 1 (right hand side), you will have to concede that this could well be a question of the kind of athlete we are looking at. A bodybuilder for example would fare better with regular whey. While soccer training is an allegedly bad model for bodybuilding, the way in which regular whey has the most favorable effects on body composition, i.e. a statistically significant 3.4% increase in muscle mass and non-significant 6% decrease in fat mass, is something I personally would not ignore (on a side note, you did see that the fat loss maxed out and reached statistical significance with the pure maltodextrose, right?). 

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Metabolic ward study shows: Higher than RDA protein intake turns weight loss into a fat loss diet, yet still it's not the more the better (learn more)

Bottom line: Despite or maybe even due to its high anti-oxidant prowess whey hydrolysate may not be the ideal protein for the average gymrat trying to build muscle, lose fat and improve his overall body composition. Allegedly, a study in soccer players and above all one with only 24 subjects is certainly not a reliable gauge, but why would you quit using what has worked for you before, if the evidence that the alternative may be good, but not exactly conducive to your primary goals?

Moreover, let's not forget, if you are simply trying to pack in some additional protein into your diet, price and taste are certainly things you want to consider, as well. And let's face it the taste and mouth-feel of the few true hydrolysates out there (most supplement producers mix various forms of whey and will still sneak a "hydro" into the name) are not exactly what you would expect from something you'd consume as a "liquid snack", right?

References: 

• Bolster DR, Pikosky MA, Gaine PC, Martin W, Wolfe RR, Tipton KD, Maclean D, Maresh CM, Rodriguez NR. Dietary protein intake impacts human skeletal muscle protein fractional synthetic rates after endurance exercise. Am J Physiol Endocrinol Metab. 2005 Oct;289(4):E678-83.
• Lollo PBC, et al. Hydrolysed whey protein reduces muscle damage markers in Brazilian elite soccer players compared with whey protein and maltodextrin. A twelve-week inchampionship intervention. International Dairy Journal. August 2013 [epub ahead of print]
• Tipton KD, Ferrando AA. Improving muscle mass: response of muscle metabolism to exercise, nutrition and anabolic agents. Essays Biochem. 2008;44:85-98.
• Pennings B, Koopman R, Beelen M, Senden JM, Saris WH, van Loon LJ. Exercising before protein intake allows for greater use of dietary protein-derived amino acids for de novo muscle protein synthesis in both young and elderly men. Am J Clin Nutr. 2011 Feb;93(2):322-31.

Rhabdo & Liver Failure or Just an Intense Leg-Workout? What Your Doctor Does not Know About AST, ALT and CK - CK-Values of 10,000 IU+ Will not Necessarily Kill You

Intense training sessions will always increase ALT, AST & CK. Unfortunately doctors will never learn that in med-school.

I don't remember the exact number, but I am afraid that I have promised to write and post this article at least a dozen of times. After getting another three questions pertaining to elevated AST, ALT and CK values on the last lab report within the last two weeks, only, I think it's about time to live up to this promise and translate + update an older, German article, I've written about the very same subject several years ago (note: I decided against translating it, but will write a complete new article - with updated facts, obviously).

Let's first see what we are actually talking about. Typically you went for a routine blood work and get a call from the nurse that there was something wrong with your "liver"- or "muscle-enzymes". You are summoned into the doctor's office, where your concerned doctor is already waiting at his desk looking at you as if you were a criminal and an idiot: "Do you do steroids?"

No, creatine is not the reason your creatine kinase levels are increased?

Creatine Doubles 'Ur GainZ!

Creatine, DHT & Broscience

Creatine Better After Workout

ALA + Creatine = Max Uptake?

Creatine Blunts Fat Loss?

Build 'Ur Own Buffered Creatine

That's the standard questions you will hear, when you enter the office - usually with this accusing undertone that says: "There you have it, now you have to suffer the consequences". Usually, this is the moment, when your mind starts racing: "What does he want, I did never... oh, my! Maybe the wise-asses over at the FDA were right after all? Was one of the supplements I took tainted..."

*STOP!* Agonizing about what you could possibly have done wrong is not going to help you here. This is all the more true if we take into account that tit is very likely that you did not do anything wrong at all. Against that background I'd suggest you stop panicking and start reading today's SuppVersity article, which will inform you about (1) what exactly AST, ALT and CK are, (2) why your doctor is so concerned about their elevation, and (3) how you can find out if he is rightly concerned or you are in the midst of a fitness version of Much Ado About Nothing.

What exactly are AST, ALT and CK & how do you read them (in contrast to your Dr)

On the text-book level this question is easy to answer. I guess it'd be best if we started with the proper name, of which you'll see that they already give away half of the solution to the mystically ALT, AST and CK elevations and the rarely measured but often likewise elevated lactate dehydrogenase and myoglobin levels.

Table 1: Time in h before ALT, AST, etc. (➚) exceed reference, (☆) peak, (➘) are back to normal (Petterson. 2007)

• ALT - alanine transaminase
  formerly SGPT, serum glutamic-pyruvic transaminase
• AST - aspartate transaminase
  formerly SGOT, serum glutamic oxaloacetic transaminase
• CK - creatine kinase
• LD - lactate dehydrogenase
• Myoglobin - iron- and oxygen-binding protein

Instead of tackling them alphabetically, we will start with "C" as in "creatine kinase", because this muscle enzyme, every SuppVersity reader knows as a frequently used, but pretty unreliable indicator of muscle damage is - at least in my experience - the #1 reason you may receive an overanxious call from your doctor's receptionist.

Elevated CK = Intense workout ↛ rhabdomyolysis ⇆ cardiac infarction

Did you ever notice that most lab reports list two types of creatine kinase? No? Usually they are listed as CK-MM and CK-MB and denote two out of a total seven isoforms scientists and doctors who specialize in muscular disorders are regularly testing for:

• 

  Suggested Read: "Why training over the full ROM counts" | more

  CKB ➫ brain | BB-CK
• CKBE ➫ ectopic expression | n.a.
• CKM ➫ all muscle | MM-CK
• CK-MM  ➫ mostly skeletal muscle
• CK-MB ➫ mostly heart muscle
• CKMT1A, CKMT1B ➫ ubiqu. mitochondrial CK
• CKMT2 ➫  sarcomeric mitochondrial CK

For your purposes the funky mitochondrial CK values are irrelevant and testing brain CK levels is usually not necessary either. Knowing your CK-MM and CK-MB, however, can come very handy to exclude identify which muscles are affected (note: Being lovesick does not lead to elevated CK-MB levels ;-)

The CK-MM differntial diagnosis: Have you sustained a cardiac infarction?

I should have mentioned it before, but I believe you are smart enough not to take this article as an invitation to recklessly ignore your Dr's calls. The first thing you would want to do, when the doctor's receptionist is calling it to ask her for the exact CK-MM and CK-MB values.

Tip #1: Always insist on a print-out of all your lab values. The receptionist may say that she cannot pass confidential health information via the telephone, but neither she nor your doctor have the right to keep all or parts of your medical records from you. You paid for the lab report, so it's your property and the least your doctor can do, is handing you a copy or printout of the results. File the sheets in a folder for reference and make sure you never lose that folder.

Their ratio, i.e. the ratio of "skeletal specific" and "heart speficic" creatine kinase, can tell you whether it makes sense / is necessary to further investigate the presence of weak and not even noticeable cardiac infarction.

• A follow up on your heart health is indicated, if CK-MB is elevated and higher than 5% of the total CK (CK-MM) value | example: CK-MB = 200 + CK-MM = 1000

Despite the fact that the 'text-book' ratio of CK-MM to CK-MB for muscle is 99:1, the balance can be slightly off in response to intense exercise, even in the absence of cardiac damage. On the other hand, ca. 25% of the patients with acute myocardial infarctions and symptoms like chest pain, shortness of breath etc. don't even have elevated CK-MB levels, when they present in the ED (Karras. 2001).

Irrespective of all uncertainties, it is very unlikely that your heart has actually taken a beating, if you are and have always been symptom free and have a high CK-MM:CK-MB ratio. This is particularly true if you have been training in the days before the blood draw.

Figure 1: Serum creatine kinase levels (in µkat/L) of perfectly healthy young men after a single intense full-body workout (left); exercise selection (right) - all exercises were performed for 3 sets à 12 reps with 70% of the 1-RM max, the average total weight moved during a single workout was >10 metric tonnes (Petterson. 2007)

As the data in Figure 1 goes to show you, increased levels of creatine kinase in response to strenuous physical activity, such as the standardized resistance training regimen (full body, 3x12 reps on each exercise, training to failure, 60s rest between sets; total training volume in weight units 10,500kg) in a 2007 study by Petterson et al. are perfectly normal. If you look closer, you will also relize that ...

1. the creatine kinase elevations peaked 3-4 days after the workout
2. the peak values vary from 'well within range' (= within the green box) to 6x above normal

In subjects 9, 11, 12 and 15, who had CK values that peaked 158x-278x higher than the official upper reference limit for the tests Petterson et al. used (note: most labs will use IU references, where the 3.2 µkat/L from Petterson's study would equal 206IU/L), the amount of myoglobin, which is likewise an indicator of severe skeletal muscle damage, was even above the upper detection limit (2999µg/L). Without the accompanying information that the previously untrained subjects have been hitting the weights, it is thus more than likely that most doctors who are looking solely at the lab raport would assume the 15 subjects from the study at hand were suffering from borderline to full-blown Rhabdomyolysis (Greek: ῥαβδω rhabdo- striped; μυς myo- muscle; λύσις –lysis).

Tip #2: Tell your doctor, when you've been lifting before the blood draw! If your medical practitioner does not know you and your training practices you can hardly blame him for being concerned about your health, when your creatine kinase levels are 10x-200x elevated.

It goes without saying that neither the 'low -', nor the four 'high responders' in the Petterson study had to be transferred to the emergency room for impeding kidney damage in response to full-blown rhabdomyolysis and that despite the fact that their levels were - due to their low training status - much more pronounced than those of the average athlete.

If you train like an athlete you will have the creatine kinase levels of an athlete

Irrespective of the protective effects of regular exercise, even professional athletes have chronically elevated creatine kinase levels. Yet, despite the fact that a 1984 study by Jaffe et al. was by no means the first to conclude that a substantial fraction of professional athletes have elevated CK-MM and CK-MB levels (Jaffe. 1984), Vassilis Mougios' 2007 paper "Reference intervals for serum creatine kinase in athletes" was the first to present a set of scientifically verified reference intervals for creatine kinase levels in athletes (Mougios. 2007). 

Figure 2: Experimentally verified CK values in male and female athletes and calculated CK reference ranges for athletes and non-athletes (Mougious. 2014))

If you are training like an athlete, the reference values Mougious calculated based on data from 483 male athletes and 245 female athletes (aged 7–44 years; see Figure 2) are thus a much better benchmark to determine whether you should or shouldn't be concerned about the red exclamation mark on your lab report.

What you (could) have learned today: Before we are about to take a closer look at the "liver values" ALT and AST, next week, let's briefly summarize what you you could have learned today that may help you, when you're summoned to the doctors office and your doctor wants to call the ambulance to save your kidneys from the consequences of your "rhabdo":

• Elevations of >10,000IU can occur and last for days after intense workouts.
• Regular training lowers the exercise induced CK leakage from the 10,000+ range back to the 500-1,500IU range.
• Nevertheless, the CK levels of athletes will always be higher than that of sedentary controls.
• It can take up to a week for your CK levels to return to baseline. If you want to make sure that your high CK levels are caused by exercise and nothing else, you will have to take a full week (best 14-days) off, before you retest.

Before you go, I would like to point out that your doctor is right to be concerned. Even if he knew about the effects of exercise (most doctors don't), 99% of his patients are not going to the gym and doing breathing squats for reps. For those people CK-values in the 1k+ range are a serious cause of concern.

Reference:

• Jaffe AS, Garfinkel BT, Ritter CS, Sobel BE. Plasma MB creatine kinase after vigorous exercise in professional athletes. Am J Cardiol. 1984 Mar 1;53(6):856-8.
• Karras DJ, Kane DL. Serum markers in the emergency department diagnosis of acute myocardial infarction. Emerg Med Clin North Am. 2001 May;19(2):321-37. Review.
• Mougios V. Reference intervals for serum creatine kinase in athletes. Br J Sports Med. 2007 Oct;41(10):674-8. Epub 2007 May 25.

Melatonin the Anabolic On-Switch!? Is Supplementation Necessary for Older and Beneficial for Younger Trainees?

Whatever sleeping position you and your partner prefer, you better make sure you do get some sleep. There'll still be time for life's other pleasures, don't worry  ;-)

If you are - as I would highly suggest - following the 6-12 SuppVersity Short News on Facebook, you will be aware of the accumulating evidence suggesting that a lower resistance to the inflammatory assault of exercise is at the heart of the age-induced decline in muscle gains.

We all know that especially those of us, who are still in good shape in their 60s and beyond are already having a hard time to keep the status quo, and only a handful of them appears to be able to make constant progress. But is this something you just have to accept or can the latest research help you overcome or at least lower the "anabolic" resistance? And if so, could young(er) individuals benefit from the same or similar interventions?

Age, inflammation, recovery and supercompensation

In a soon-to-be-published study from the University of Alabama at Birmingham an analysis of the vastus lateralis muscle gene expression and protein cell signaling of the IL-6 and TNF-α pathways in myoblasts from young (AGE28) and old (AGE64) donors, which have been pre-treated with TNF-α revealed that ...

"[i]ndices of activation for the pro-inflammatory transcription factors STAT3 and NFκB were highest in AGE76. Resistance loading reduced gene expression of IL-6 receptor, MuRF1, and atrogin-1, and increased TWEAK receptor expression. Donor myoblasts from AGE64 showed impaired differentiation and fusion in standard media, and greater NFκB activation in response to TNF-α treatment (compared to AGE28)".(Meritt. 2013; you know it already, if you are following www.facebook.com/SuppVersity)

These findings show for the first time that the aging process alone is associated with a hightened susceptibility to muscle inflammation.

Graphical illustration of what you should have learned by now, if you read the previous installments of the Intermittent Thoughts; note: while I have used the arrows rather indiscriminately (they do not necessary mean "causes"), the stops at the end of other lines indicate an inhibition, eg. the line from exercise to myostatin indicates that exercise inhibits myostatin, which would inhibit increases in myonuclear domain sizes, if it was not "switched off" by exercise... (learn more)

In view of the importance of "controlled inflammation" in the context of muscle damage, repair and supercompensation (learn more in the Intermittent Thoughts on Muscle Building, spec. this episode), the goal should thus be to (a) lower the inflammatory load to a level that allows the aging body to cope with it and (b) improve your body's ability to cope with a certain (yet to be determined) amount of inflammation that's necessary for the hormetic response to exercise to take place.

As alluded to in the introduction to this article, the same 500mg+ of vitamin C + 400IU+ of mixed tocopherols per day that are - at best - useless for a young trainee could in fact make a smart and valuable addition to the supplement stack of an older physical culturist, who is more reliant on exogenous ROS scavengers than the young grasshopper, for whom the exercise-induced inflammation is part of the training: A training for his endogenous defense system and a potential prerequisite for the structural remodeling process of the muscle (check out the figure on the right and learn more).

Melatonin: Protection beyond ROS scavenging

At least for the well-educated SuppVersity student you are ;-) It should be obvious that the "classic" anti-oxidants like vitamin C and E are not the only venues molecules to control inflammation. In fact, the emerging science shows that alternatives to these "Kamikaze"-inhibitors (ROS scavengers) can, in this, as well as other contexts, deliver much better results.

As a SuppVersity reader you'll know that melatonin is also an Alzheimer protectant, can help you shed body fat, could be the goto-supplement for ultra-marathon runners, figures in the cardio-protective and controls the circadian rhythm, the disturbance of which is involved in "all things bad" ranging from metabolic syndrome over diabetes to cancer.

Think of DHEA, for example. The adrenal hormone, which happens to decrease from year to year once you've passed your late 20s can even help young men to cope with the muscle damage of 5 days of concomitant combined endurance, strength and HIIT training in young men (read the whole story).

Or - and now we are finally zoning in on the actual news - think of melatonin, which has been shown to boost your anti-oxidant defenses, reduce the oxidaton of the lipids in your cell walls and modulate the immune response to intensive training, when it is supplemented in relatively high amounts of 6mg (learn more; don't forget to check out the links in the infobox to the right, as well).

It will therefore only come as a minor surprise for a diligent SuppVersity reader like yourself that a recent rodent study that has just been accepted for publicaton in the Journal of Pineal Research comes to the conclusion that..

[...a]dequate levels of circulating melatonin are [...] necessary to improve energetic metabolism efficiency, reducing body weight and increasing insulin sensitivity [in aging animals]. (Mendes. 2013)

Ah, and just to make that clear, I am not willing to start the "mice are no little men"-debate, here, but will take it for granted that you keep in mind that results, I have plotted for you in figure 1 have to be verified in future human trials (personally, I am confident, they will).

Figure 1: Relative levels of visceral fat, triglycerides, change in distance covered from month 0-2, running speed, citrate synthase activity, muscle & liver glycogen and glucose AUC during tolerance test; all data expressed relative to sedentary (S-) unsupplemented (-C) control, SC (Mendes. 2013)

So what are we seeing here in figure 1? Well, first of all there is a surprisingly significant (compared to the SC group) decrease of total, but more importantly visceral fat weight in both, the sedentary (SM), as well as the trained (TM) rodents. The latter goes hand in hand with

• 

  Expression of the muscle anabolic enzymes PI3K, p-AKT, as well as AMPK and GLUT4 in muscles of the supplemented (SM & TM) and non-supplemented (SC & TC) rodents in arbitrary units (Mendes.2013)

  significant improvements of the amount of triglycerides (a if not the no1 risk factor for CHD) even in the absence of exercise (compare the SC vs. SM groups)
• a mind boggling increase in the distance covered and the running speed of the animals in both the trained and the sedentary rodents "on" melatonin (in view of the fact that this increase remains statistically significant even when you compare it to the baseline levels, similar effects may even occur in young animals)
• almost 3x respectively 4x elevations in citrate synthase activity, a maker of fatty acid oxidation in the sedentary and trained melatonin treated rodents
• a 6x and 12x increase in muscle glycogen levels and an ameliorative effect on the exercise induced glycogen increase in the liver, both of which could not just explain the massive increase in exercise tolerance, but the previously observed beneficial effects on glucose tolerance, as well
• a 30-40% reduction in the glucose AUC that corresponds with the increased glycogen storage mentioned in the previous bulletin point

and lastly and for many of the physical culturists in the posterior half of their lives maybe most importantly, highly significant increases in the activity of the pro-anabolic PI3K, MAPK and AKT that were not increased at the expense of the fat-burning, anti-cancer, anti-diabetes AMPK energy switch (see figure 2).

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Bottom line: It is beyond doubt that the small amount of exercise corresponding to the four to five sessions at 0.3 – 0.5 km/h running on a 0% grade treadmill [questionable whether this is a typo on the speed, by the way] for 10 min/day in the study at hand alone are good for aging individuals. It's also almost certain that the addition of supplemental melatonin ameliorates these exercise-induced benefits and induce benefits on their own.

Don't forget t take appropriate time off, otherwise even 15g of melatonin are not going to help you overcome a growth plateau. Why? Well "Chronic Resistance Training Reduces the Anabolic Signaling in Response to Exercise - 12 Days of Detraining Restore It" (read more)

What is yet highly questionable still is the optimal dosage. The 1mg/kg body weight that were used in the study at hand would translate to roughly 0.16mg per kg for a human being and thus ~13mg for an adult (male) human being. Personally, I don't think this is exorbitantly high, but I know that real and pseudo-experts would be bashing me, if I even remotely suggested that you consume similar as much supplemental melatonin on a regular basis... what all of us would probably agree on is the fact that future human studies are necessary, and if you asked me not so much to avoid potential harm, but rather not to miss what Mendes et al. believe would be an outstanding chance to "improve the beneficial responses induced by regular exercise in aging individuals, promoting a better quality of life and a healthier aging process" (Mendes. 2013).

 References:

• Mendes C, de Souza Lopes AM, Gaspar do Amaral F, Peliciari-Garcia RA, de Oliveira Turati A, Massao Hirabara S, Scialfa Falcão JH, Cipolla-Neto J. Adaptations Of The Aging Animal To Exercise: Role Of Daily Supplementation With Melatonin. Journal of Pineal Research. 2013 [accepted manuscript]
• Merritt EK, Stec MJ, Thalacker-Mercer A, Windham ST, Cross JM, Shelley DP, Tuggle SC, Kosek DJ, Kim JS, Bamman MM. Heightened muscle inflammation susceptibility may impair regenerative capacity in aging humans. J Appl Physiol. 2013 May 16.