If the Androgen Receptor Response to Training Determines Your Gainz, the Question is: How Can You Optimize 'ur AR Density? Training-, Diet-, and Supplement-Effects Reviewed

Your androgen receptor status may not just determine how much muscle you gain - the data from Morton et al. seems to suggest that it even determines if you make visible muscle gains, at all.
Unless you've missed following the SuppVersity on Facebook, yet, you will remember my recent, highly popular post which previewed the results of a recent study from the McMaster University in Ontario. Meanwhile, the full-text of the study has been published and it highlights what I pointed out before: It supports previous research, which showed that neither the acute increase in intramuscular free testosterone, nor dihydrotestosterone, or 5α-reductase predicts the muscle gains of resistance-trained men.

More importantly, however, it has the potential to shift the interest in post-exercise changes of testosterone, IGF1, GH & co. to the androgen receptors or rather how they (and maybe other receptors, like the IGF-1 receptor) respond to resistant exercise.
Read more about studies involving TRT/HRT & co on suppversity.com:

What to expect from normalizing Testosterone

Testosterone Gel Augments 'ur Gainz

PWO T-Increases Don't Determine Your Gainz

The Hormonal + Other Underpin-nings of Gainz

Impressive 12% T-Boost (+20% IGF1) W/ Tribulus

T +/- Exercise to Rejuvenate Old Muscle?!
As previously discussed, Morton et al. examined if there's a link between circulating hormones, intramuscular hormones, and intramuscular hormone-related variables in resistance-trained men before and after 12 weeks of RET. The study results speak for themselves:
"Unlike intramuscular free testosterone, dihydrotestosterone, or 5α-reductase, there was a linear relationship between androgen receptor content and change in LBM (P < 0.01), type 1 CSA (P < 0.05), and type 2 CSA (P < 0.01) both pre- and post-intervention. [Thus indicating that] intramuscular androgen receptor content, but neither circulating nor intramuscular hormones (or the enzymes regulating their intramuscular production), influence skeletal muscle hypertrophy following RET in previously trained young men" (Morton 2018). 
This result becomes particularly obvious if you take a look at the type-I & -II muscle fiber and lean body mass gains of the AR high vs. AR low responders. Effectivel, Morton et al. didn't just find that those with the highest- (HIR; n = 10) androgen receptor (AR) response made the greatest gains, it even suggests that those with a suboptimal AR response don't see any gains, at all.
Figure 1: When they stratify the 20 subjects according to their androgen receptor response to training, Morton et al. found that one group saw great, the other almost no gains and thus shed a whole new light on the previously known, but often ignored correlation between AR density and skeletal muscle hypertrophy (Morton 2018).
It should thus be obvious why the question from the headline is relevant for anyone busting his ass in the gym - the question "How do you make sure you're one of the guys in the 'high responders' group?" My review of the literature can give you some pointers:
  • Resistance training is probably the best-proven modulator of AR density - It may sound too good to be true, but many of you may probably already be following the best proven "androgen receptor density"-program there is: heavy, high(er) volume resistance training. Based on the results of previous studies that show how androgens can increase the AR density in myonuclei and satellite cells (Ferrando 2002Kadi 1999Syms 1985Gregory 2001), in vitro, many researchers seem to believe that the temporary exposure to exercise-induced increases in testosterone was the causative factor here.

    Personally, I don't consider this explanation to be true. If we assume that it's the transient increase in testosterone, the latter should also be a determinant of muscle gains - a significant number of studies does yet show that this is not the case.
    Figure 2: Changes in skeletal muscle androgen receptor content (mean ± sem) due to the heavy resistance exercise bout (5 × 10RM leg presses) in younger (n = 5 | 28 ± 3 yrs) and older men (n = 8 | 70 ± 2 yrs) before and after the 12-month experimental heavy resistance training period (Ahtiainen 2015) - on a side note: The study confirms the initially postulated correlation between correlated changes in fCSA and lean body mass.
    Furthermore, one would expect the positive effects to occur relatively soon after the workouts. The reality of scientific studies such as Ahtiainen et al. (2015 | see Figure 2), however, shows that this is not the case - at least not for young men such as the subjects in Morton's study.

    Figure 3: Protein expression of androgen receptor (B) in the skeletal muscle of male and female rats altered by acute exercise. Samples from male (n = 8) and female (n = 8) control rats and from male (n = 8) and female (n = 8) exercised rats (analyzed by immunoblotting | Aizawa 2010).
    For older men, the results look significantly different, but a significant increase in AR density wasn't observed for them either - no wonder in view of the statistical 'power' of this N=8 mini-study. In conjunction with a 2010 study by Aizawa et al. which found pronounced increases in AR density female, but no effect on ARs in male rodents (see Figure 3), and very similar effects in humans (Vingren 2009 | slight decreases and marginal increases in AR in trained men and women, respectively, immediately post and 70 minutes after the workout), one can still speculate that both, age and sex matter when it comes to (a) the AR response and (b) its downstream effects on skeletal muscle hypertrophy, which is - I don't have to tell you that - significantly less pronounced in women and elderly vs. young men.

    So, sex and age matter, but they cannot be the only factors to explain the heterogeneity of pertinent studies; and, more importantly, both are irrelevant for the Morton study, which is at the heart of this whole discussion.

    The first of two additional confounders that come to mind is the training volume. Vingren et al., who failed to record significant increases in AR density, for example, used a low-volume approach consisting of 8–10 repetitions of #squats at ∼50% of the subjects' estimated 1-RM followed by another set of 2–5 repetitions at ∼85% of the estimated 1-RM.
Check out my research update on BFR and compression garments from October 2018 | go ahead, read it!
Volume = stress, BFR = stress:  I think, at this point, it is worth mentioning that 'artificially' increasing the metabolic stress (an increase that usually comes with increases in volume) via #bloodFlowRestriction (BFR) seems to have a beneficial effect on your androgen receptor, as well. In their 2011 study, Loenecke et al. found that "the acute and chronic testosterone response to blood flow restricted exercise appears to be minimal when examining the current literature".

In view of the significant gains the authors observed that was odd - even though we know that the acute T-response is not a determinant of your gainz - accordingly, the scientists speculate that an increase in androgen receptor density following blood flow restricted exercise may explain why the same amount of testosterone can, when combined with BFR, produce increased gains - and you know what? In view of the way BFR seems to work and the overlap to high-volume training, this is not even totally unlikely.
  • Figure 4: People who do high volume training seem to indeed see greater benefits - at least that's what the small-scale study by Spiering et al. (2009) suggests. Bodybuilders who combine high volume training with periodic steroid abuse may even potentiate this effect - no wonder they're getting so big ;-) The chronic (ab-)use of androgens, on the other hand, seems to reduce the effects and will have the AR density return to baseline.
    A similarly low volume was used by Spiering et al. in the control group of their 2009 study, in which a standardized (low volume) knee extension workout was performed either on its own or after doing an upper-body workout (bench press, bench row, and seated overhead press at 4 sets of 10RM), which was specifically "designed to increase circulating T" (Spiering 2009).

    I have to say, though, that I personally doubt that the benefits are a consequence of the testosterone response to the upper body workout. If you asked me, I would venture the educated guess that it is rather a mere consequence of the increase in exercise volume and/or the total muscle mass that's involved in the workout.

    The volume hypothesis would obviously imply that the changes in androgen receptor density in the immediate and prolonged post-workout period increase with training volume - at least as long as the latter remains within "sane" limits.

    And even though I cannot prove the accuracy of this theory, it is corroborated by research from Willoughby & Taylor (2004). They tested the effects of 3x lower-body resistance exercise bouts, each separated by 48 h - all with a high volume of 3x10 on the squat, leg press, and leg extension exercise.

    Increases in AR density were observed in Willoughby & Taylor 2004 after only one workout (see Figure 5, sampling point 2), and the effects got significant (compared to control) after the 2nd and 3rd workout (see Figure 5, sampling point 3).
    Figure 6: Quantitative representation of the means (± SD) for the content of AR mRNA normalized to GAPDH. Numbers 1–4 indicate the four muscle sampling points (1 = immediately before exercise bout 1; 2 = 48 h after exercise bout 1 and immediately before exercise bout 2; 3 = 48 h after exercise bout 2 and immediately before exercise bout 3; 4 = 48 h after exercise bout 3; † sign. different from corresponding preexercise value; ‡ sign. dif. from CON; * sign. Group × Test interaction (P < 0.05 | Willoughby 2004).
    Moreover, the Willoughby study confirms that this increase goes hand in hand with increases in myofibrillar protein (P = 0.002) - with, and that's interesting, significantly greater increases in myofibrillar protein content 48 h after the third exercise bout (muscle sampling point 4) compared with sampling points 1, 2, and 3.

    Training at a high enough volume and with sufficient time for the androgen receptor rebound to occur (possibly after 24h, certainly after 48h) is #1 on the list of things that you can do to conserve and maximize your AR levels.

    Why's that interesting? Because this increase was observed in the biopsy in which you'd measure the effects of the most elevated AR levels after the 2nd workout (~60% over baseline | see Figure 5, again). A correlation analysis that would support a direct relationship between AR increases and gains wasn't conducted, though.
Figure 5: Biopsy timing may make all the difference - If measured 48h after exercise the AR density is significantly increased with either concentric or eccentric contractions .- without significant effects of the contraction mode, by the way (Bamman 2011).
The time-point at which the biopsies were taken in the various previously cited studies alone could explain the hetergoenous results. If we compare design and result of the study by Willoughby & Taylor to Ratamess' 2005 study, the first and only study that compared higher vs. low volume training (6x10 squats vs. 1x10 squats), the assumption that it's all about volume becomes highly questionable. After all, Ratamess and his colleagues from University of Connecticut didn't observe any beneficial effects of an increase in training volume - in fact, the higher volume squat program (10 sets vs. 1 set) actually produced a significant decrease in androgen receptor expression 1h after the workout, while the single set program left the AR density unchanged (Ratamess 2005).

Obviously, this doesn't mean that the AR levels of the subjects of Ratamess' study were not increased to a similar extent as it was observed by Willoughby & Taylor and confirmed by Bamman et al. (see Figure 5 & 6) who both took muscle biopsies 48h post workout - and that's also what Kvorning et al. imply in their 2006 paper when the authors refer to the timing "of the [muscle] biopsies" as a potential explanation for the "divergent results" of studies in this field.
  • What we shouldn't forget, here, is that the inconspicuous "after" refers to 48h after the workout in the context of the Willoughby study. It should thus be obvious that the timing of the muscle biopsies is at least a 2nd and potentially even more important confounder that may explain the heterogeneous results of the previously cited studies (see red box above), because, as Vingren et al. point out the "current paradigm says that there's a "stabilization followed by a reduction and then a rebound in the acute AR response" in response resistance exercise.

    If this paradigm describes the time-course of the AR response correctly and time is in fact 'of the essence', this has profound implications for your workout programming, sa well. A 24h-48h delay in the AR response does, after all, seem to favor a medium vs. high training frequency with at least 24h of rest between two bouts of high volume resistance training over classic bro-splits, where you train on a daily basis.
While we are waiting for more research to answer the (still) open question about the interaction of volume, recovery times, and the androgen receptor response to resistance training, let's briefly take a look at the little we know about the potential benefits of dietary and supplementary interventions.
  • Figure 7: In Kraemer 2006, twenty-one days of LCLT supplementation (2g/day) significantly (P < 0.05) increased pre-exercise vastus lateralis AR content compared with PL. When RE was followed by water intake, AR content increased compared with PRE for PL only. Feeding following RE significantly increased AR content compared with pre-RE values for both LCLT and PL trials.
    Yes, l-carnitine tartrate seems to increase AR density - but is it the only supplement? Before we answer the question, let's briefly revisit the often-cited 2006 study by Kraemer et al. in which the researchers complemented results from a 2003 study which revealed that #LCLT will improve the "number of intact [hormonal] receptors" and thus increase the potential of "hormonal interactions" (Kraemer 2003). The more-recent cross-over study was conducted in ten resistance-trained men (mean+/-SD: age, 22+/-1 yr; mass, 86.3+/-15.3 kg; height, 181+/-11 cm) supplemented with 4g LCLT (equivalent to 2 g of L-carnitine per day) or placebo (PL) for 21 d.

    L-carnitine l-tartrate (and only the l-tartrate) form is #2 on the list of proven promoters of exercise-induced AR expression and probably the only one you're not already using to your advantage.

    What you'll rarely hear about the study's results, though, is that the benefits were contingent on the consumption of a #postWorkout nutritional supplement containing 8 kcal/kg body mass from 56% carbohydrate, 16% protein, and 28% fat.
A remark on anabolic steroids and their effects on AR density: If you think about high volume training, you probably think about bodybuilders. Needless to say that, for them, the effects of doing plenty of sets and reps often are potentiated by anabolic steroids, of which in vivo studies have shown that they will upregulate the AR content acutely.  Bros should be warned, though, because studies have shown that the steroids lose this effect over time and - when they've been used for weeks or months - the AR density returns to baseline (Ferrando 2002). The use of steroids in shorter cycles (as it obviously is common practice in the real world), on the other hand, has been observed to provide sustained increases in the androgen receptor content of male skeletal muscle (Kadi 1999) - as usual, the effects in females are unknown.
  • In fact, the post-workout nutrient provision, alone, had beneficial effects on the androgen-receptor levels the scientists detected in the muscle biopsies they took from their subjects 48h after the last workout (see Figure 7).

    Adequate post-workout nutrition is thus #3 on the list and probably something you're already doing to conserve and maximize your AR levels.

    In that, it may be that incorporating creatine into this post-workout stack could have (as of yet unproven) extra benefits. How's that? Well, hypothetically, #creatine could exert some of its hypertrophy effects (partially) by an effect on the androgen receptor. Insane idea? Yeah, I admit I cannot prove it, but you will certainly all remember the "creatine increases DHT"-study (Van der Merwe 2009) that resurfaces once a year among a (then) panicking group of fitness enthusiasts. With DHT being four times more biologically potent than testosterone as an androgen receptor activator and its local production from testosterone via 5α-reductase being increased in response to resistance training alongside the androgen receptor content in the previously cited study by Aizawa, et al. (2010 | see Figure in original study), I don't think it's impossible that an interaction exists - if for nothing else in form of a second-order effect due to a creatine-induced increase in training volume.
Figure 8: While the provision of soy and whey did affect the change in skeletal muscle androgen receptor content, only the time effect, i.e. the effect of 12 wks of resistance training was statistically signif. in a recent study from the Auburn Univ. (Haun 2018).
Before anyone asks: 'No, soy protein doesn't negatively affect your androgen receptor density.' While the rumors that it will reduce testosterone are die hard, the evidence that it doesn't affect testosterone and - as of late - also its receptor is increasing. Only recently, Haun et al. (2018) published a study that acquits regular (not specialty = extra high isoflavone) soy protein of ruining your virility.

What Haun et al found, though, is that training increases the androgen receptor density of previously untrained, college-aged men (n = 47, 20 ± 1 yrs) that resistance trained for 12 weeks significantly - with greater increases in the soy vs. whey protein group -  non-significantly greater that is.
  • That's too hypothetical for you? Well, in that case, you will like #4 on the list. Although technically not a supplement, people take it for non-medical reasons, anyway: #T3, i.e. iodothyronine, the "active" thyroid hormone which has been found to directly stimulate the expression of androgen receptors in skeletal muscle (Clement 2002). 

  • Keeping your thyroid chugging along nicely (in particularly the levels of T3) is #4 on the list and, hopefully, a thing that you're already doing to conserve and maximize your AR levels.

    Now, I don't recommend using a prescription drug for off-label purposes (also because using too much will - irrespective of increases in AR density - put you at risk of hyperthyroid muscle catabolism). What I do recommend, though is to keep in mind that (over-)training and undereating can trigger a rapid decline in thyroid function and hence T3 levels (see my 2013 article on "self-induced hypothyroidism") - hence, the interaction with T3 makes adequate recovery and nutritional fuelling even more important for those of you who want to maximize their androgen receptor levels.
"That's not much, I am not already doing!" I know that the previous list is not exactly exciting, but if anything, I could add avoid #Nicotine and #alcohol (Basiri 2016) and #castration (Suzuki 1997) to the list of at least decently proven AR expression modulators. Both nicotine and alcohol have been observed to reduce the AR density, ... in rodents and both outside of skeletal muscle, though.

Hence, high(er) volume training, adequate recovery, nutrition, and l-carnitine l-tartrate (yielding 2g of carnitine per day) have - as of today - to be considered the only "proven" promoters of AR density.

Figure 9: Intramuscular (A) free testosterone concentration, (B) dihydrotestosterone concentration, and (C) 5α-reductase expression, didn't differ between AR high and low responders and neither of these hormonal parameters had any effect on the gains of the 20 subjects in Morton's 2018 study..
With creatine making the "potentially beneficial" criteria only hypothetically, this makes l-carnitine l-tartrate (LCLT) the only OTC supplement on the list (note: there's no evidence that other forms of carnitine will do the same and sine LCLT is ~50% tartrate you have to take 4g/d to get the effective dose of 2g carnitine). I have to warn you, though: I doubt that the downstream effects the LCLT-induced increase in AR density (which is relatively small | see Figure 7) on your gains are going to be visible - unless, you have been retired for years if not decades, because all studies showing actual increases in lean mass with carnitine have been conducted in the elderly (Piston 2003Malaguarnera 2007).

So what does that all mean? Well, if you want to see the often-marketed steroid-like gains, everybody is chasing, you will probably have to wait for a gene-drug that changes both, the baseline expression and exercise-induced increase of androgen receptors on your muscle tissue.

In the meantime, you can console yourself with the realization that in all the excitement about the results of the initially quoted study by Robert Morton, many seem to have forgotten that the scientists found nothing but a correlation between the AR response and increases in muscle size.

Practically speaking, this means: Even if this gene-drug already existed and effectively doubled your AR levels, it's (a) unlikely to double your gains and (b) not even guaranteed to have a significant effect on your gains, at all - and the researchers who emphasize that their data on the "androgen receptor correlation [is] an inflated estimate due to the choice of measuring only higher and lower responders to our training protocol" (Morton 2018) make it quite clear that this estimate was meant to "illustrate the difference in RET-induced muscle hypertrophy and investigate the influence of circulating and intramuscular hormone-variables on two distinct groups" (Morton 2018). In conjunction with other methodological limitations, which are likewise discussed in great detail in the corresponding section of the FT (read it), this 'illustrative' nature of the results leaves ample room for future studies to (a) confirm or refute the 'AR hypothesis of muscle gains' and to (b) quantify the interaction between AR expression and gainz  | Comment!
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