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Belgian Blue cows have been bred to have a myostatin deficiency, which makes them absolutely jacked. YK-11 is a myostatin inhibitor.

Over the past few months we’ve been examining selective androgen receptor modulators (SARMs) in detail. The best place to start is here, with our master article on the subject. In addition, we’ve covered all the major SARMs in detail in individual articles, including chemicals such as MK-677 and cardarine, which are not true SARMs, as well as considering stacks, post-cycle therapy (PCT) and side effects, and Click Here to Get 11% off SARMs with Promo Code “HS11”

What is YK-11?

YK-11 is a lesser known but very powerful SARM. Its unique selling point is that it acts as a myostatin inhibitor as well as a SARM. We’ll discuss how it works in detail below.,ret_img,w_510,h_510/https:/

SARMs were initially created to help cancer patients combat muscle wasting, but bodybuilders, strength athletes and others quickly realized that they could also experience steroid-like anabolic effects, without most of the side effects.

In all of our previous articles, we have touted the anabolic potential of SARMs for athletic performance and aesthetics, but we have also been at pains to ensure you understand that they have specific uses that will some suit individuals and contexts more than others. That caveat applies to YK-11 too. If you put it to the right uses, you will see positive results, with fewer of the side effects associated with the use of performance-enhancing substances like steroids. 

You must, however, be in no doubt of the potential risks and side effects, which we will discuss below. 

There is much less clinical evidence for the efficacy or safety of YK-11, but in both cases there is plenty of anecdotal evidence in favour of both.


The reported benefits of YK-11 include:

  • Serious muscle growth, including increased muscle density
  • Increased strength
  • Enhanced libido

Do I want to take the advice of u/bleached_booty_hole? Not really. Thankfully there are lots of other users who report tremendous results on YK-11

How YK-11  works
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The testosterone molecule

SARMs induce anabolic activity – growth – by directly stimulating the body’s androgen receptors. These are specific sites within the body to which androgenic (i.e. male) hormones, including testosterone and androsterone, bind. 

The activity of these androgen receptors, and the binding of androgens to them, is crucial to the proper expression of male characteristics, including muscle growth and reproductive function. In the womb, androgens are responsible for sexual differentiation, and then during puberty they regulate the development and function of the penis, prostate and other sexual organs, as well as inducing growth spurts, larynx development and growth of skeletal muscle. For adults, androgens regulate behaviour, the production of sperm, muscle growth, bone function and aspects of the cardiovascular system. Androgens regulate sexual function and are responsible, in part, for aggressive behaviour in men. As a result, disregulation or blocking of the androgen receptors can lead to all sorts of conditions. 

(10) YK-11 Explained!!! SARM? – YouTube

As a SARM, YK-11 binds to the androgen receptors and mimics the effects of testosterone, increasing protein synthesis and therefore muscle growth. This is also what steroids do, but SARMs generally have an advantage over steroids, because they only bind to receptors in skeletal muscle tissue. Steroids, by contrast, work on other tissues in the body and have, as a result, been linked to all sorts of side effects, including prostate and heart problems.

SARMs are also non-aromatising, meaning that they aren’t converted to estrogen by the body in an attempt to maintain the body’s testosterone-to-estrogen balance. By contrast, aromatisation can occur when using steroids or testosterone injections, which upset that balance, leading to problems such as gynecomastia (formation of breast tissue).


What YK-11 does that other SARMs don’t do is inhibit the body’s production of myostatin. Myostatin limits how much muscle you can produce naturally. By inhibiting the production of myostatin, which it does through stimulating muscle cells to produce follistatin, YK-11 potentially raises the roof in terms of muscle-building potential.

(10) YK11 Myostatin Inhibitor – Increased Follistatin, Results & Side Effects – YouTube

Although there haven’t been any studies of the effects of YK-11 on humans, increased levels of follistatin have been shown to have seriously anabolic effects on mice. Mice with low levels of myostatin have been shown to have on average twice the muscle mass as mice with normal levels.


Unfortunately, there are no studies on the effects of YK-11 that have been performed on humans. Instead, there is lots of anecdotal evidence, which is easily found on Reddit in forums like r/sarmssourcetalk. Many users report gaining 15 or 20lbs of lean mass during a single cycle.

For a detailed testimonial, see the following video by Russo Lifts, who has extensive experience of SARMs.

(10) FREAKY Results/Side Effects With YK11 HIGH DOSAGE Inject | Sarms Review – YouTube


As we’ve already pointed out, since there are no human studies, there are no established medical dosage guidelines for YK-11. 

The general consensus amongst body builders is that 10 mg is a good dosage for muscle growth and performance enhancement. An intermediate dose might be 15mg a day, and a higher dose 20mg.

While some users have reported taking dosages as high as 30 mg per day, most agree that taking between 10 mg and 15 mg to start is a much better idea.

YK-11 is usually administered orally.


Side effects

As we’ve already noted, the side effects of SARMs in general are much milder compared to those of traditional androgenic agents including steroids. Even so, you are likely to experience some suppression of natural androgen levels at the very least.

It’s worth saying that Ostarine, Ligandrol and RAD 140 have been flagged for potential liver damage, as indicated by elevated liver enzyme levels. Users of these SARMs report mood swings, acne, small amounts of hair loss and reduced libido. Some report experiencing more or less no side effects whatsoever, though.

Some users will report no side effects and others like, ahem, u/bangedvajayjay (ed: where do we find these people? Answer: Reddit!) provide strange, sometimes incomprehensible, side-effect testimonials

Some of the reported symptoms of SARMs are clearly associated with reduced natural testosterone levels. As with steroids, the use of SARMs including YK-11 will reduce natural testosterone levels. The reduction will correspond with the amount you take and for how long. You may notice some visible shrinkage of the testicles.

As a result, after a SARM cycle, it may be wise to engage in a round of post-cycle therapy, as many steroid users do. Note, though, that because the side effects, at least in the short term, appear to be much less serious than for steroids, the post-cycle therapy will almost certainly need to be less severe. Post-cycle therapy helps to restore your natural testosterone levels, and may last up to six weeks. Various supplements and medications are available, which we will discuss in a separate article on SARMs stacks. You can begin post-cycle therapy as soon as you stop taking SARMs.

The side effects of myostatin inhibition are also unknown at this stage, especially in the longer term (here are some speculations). This is true for SARMs more generally: we just don’t know what the long-term effects of these new chemicals are. 

It’s worth reiterating that SARMs aren’t legally certified as a dietary supplement. You are taking a risk if you use them; but you are also taking risks lifting heavy weights, running – or even just stepping outside your front door. Ultimately, it is a decision for you to make, based on willingness to balance the risk against the potential rewards.

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