MK-677 gym results at week 4: what the science says

What did @whereis_tarzan actually say?

In week four of their documented cycle, the creator reports running three compounds simultaneously: MK-677, RAD140, and YK11. Their specific observations were "a lot more solid pumps while lifting" and "increasing strength and appetite." That is the full extent of the claims here. No dosing was mentioned, no bloodwork was referenced, and no health outcomes beyond gym performance were stated. Give credit where it is due: the creator kept the claims narrow and personal.

What they did not say matters too. There was no suggestion these compounds are safe for general use, no dosing advice, and no before-and-after framing designed to sell anything. For a TikTok gym post, that restraint is worth noting, even if the underlying stack itself carries real risks that a four-week progress update will not capture.

Does the science back this up?

Partially, yes. The effects described, better pumps, increased strength, and elevated appetite, are consistent with what these compounds are known to do pharmacologically. But "consistent with" is not the same as proven safe or legal for human use.

MK-677 (ibutamoren) is a ghrelin receptor agonist that stimulates growth hormone secretion. Appetite increases are well-documented and not surprising: ghrelin is literally the hunger hormone. A 2008 study by Nass et al. in the Journal of Clinical Endocrinology and Metabolism confirmed MK-677 increases GH and IGF-1 levels, along with appetite. RAD140 is a selective androgen receptor modulator (SARM). Early animal data from Jayaraman et al. (2014, Endocrinology) showed anabolic tissue selectivity. YK11 is even less studied and is sometimes classified as both a SARM and a myostatin inhibitor. The pump and strength observations are biologically plausible, but four weeks of subjective self-reporting is not a clinical trial.

What did they get wrong, or right?

The creator did not get the pharmacology wrong, exactly. The effects they described align with the known mechanisms of these compounds. But there is a significant omission problem here. RAD140 has been linked to drug-induced liver injury in case reports, including a 2020 case documented by Flores et al. in ACG Case Reports Journal. YK11 has almost no human safety data at all. Running all three compounds together amplifies the unknown risk profile substantially.

The word "appetite" being tied to MK-677 is accurate and well-supported. The "solid pumps" observation is harder to attribute cleanly to any one compound in a triple stack. It could reflect increased nitrogen retention from RAD140, elevated GH from MK-677, or simple placebo and training adaptation. Self-reported week-four updates cannot disentangle those variables. The creator did not claim they could, so that is not a criticism of them specifically, but viewers should understand the limitation.

What should you actually know?

None of these three compounds are approved by the FDA for human use outside of clinical trials. MK-677 has investigational history but remains unapproved. RAD140 and YK11 are not approved for any human indication. Purchasing them is legal in some jurisdictions as "research chemicals," but that label is largely a regulatory workaround, not a safety certification.

The stack this creator is running combines a GH secretagogue with two androgenic compounds. Even if each compound carried modest individual risk, stacking them without medical supervision and routine monitoring (LFTs, lipid panels, hormone panels) is playing a guessing game with your endocrine and hepatic health. A four-week window is also too short to see the downstream consequences. Lipid changes from SARMs, for example, can worsen meaningfully over 6 to 12 weeks of use, as noted by Jayaraman et al. and corroborated in later reviews. If you are curious about GH-axis optimization through a legal, monitored pathway, that conversation belongs with a licensed clinician, not a TikTok comment section.