Satellite cells & local repair

What actually decides this outcome, in order of size

This page claims something narrower than the rest of the muscle estate: not more anabolic tone, but more myonuclei in the tissue you just damaged. Ranked by how much of the outcome each one owns:

1. The mechanical damage itself, because it is the trigger the whole pathway is trying to amplify. Satellite cells respond to loading. Nothing here initiates that response; every item claims to enlarge one that training has already started, which makes the training variable the largest term and the protein intake the second. Both are quantified in the meta-analysis and meta-regression on protein and resistance training Morton 2018.
2. Whether the peptide reaches the cell type it is supposed to act on, which for the headline molecule has been tested and answered. The mechano-growth factor peptide, the carboxy terminus of unprocessed IGF-1, had no apparent effect on myoblasts or primary muscle stem cells in a published study Fornaro 2014. That is a direct negative in the exact system the mechanism requires, and it is the single most important citation on this page.
3. Whether the argument is repair or maintenance, because they are different claims with different timescales. A peptide proposed to restore age-declined expression in existing tissue is making a maintenance claim; a peptide timed to a training session is making a repair one. Gotratix belongs to the first group and everything else here to the second, and the pages that argue the first properly are at Organ-specific bioregulation.
4. Half-life, because for two items here the pharmacokinetics are the entire theory of use. Native mechano-growth factor is cleared in minutes and the pegylated version exists only to change that; IGF-1 DES is short-acting by design so that it acts at the injection site before clearing. If those exposure profiles are wrong, the site-specific argument collapses into a systemic one, which is a different risk profile entirely.
5. Whether recovery capacity is the real lever, which for most readers it is. The cytoprotective pentadecapeptide has a body of preclinical work in striated, smooth and heart muscle Staresinic 2022 and in tendon and muscle healing through angiogenesis Brcic 2009, reviewed within a broader cytoprotection framework Sikiric 2020. Thymosin beta-4 has a European prospective randomized study in venous ulcers Guarnera 2007, which is human data in a healing endpoint and not a musculoskeletal one.
6. The two supplements here, which are the only items with human trials in a training population. Increasing skeletal muscle carnitine content in older people increased whole-body fat oxidation Chee 2021, undenatured type II collagen has a knee osteoarthritis review Gupta 2025, and epicatechin with resistance training in sarcopenic older adults moved strength alongside follistatin and myostatin Mafi 2019. Joint comfort and recovery are hypertrophy inputs because they decide whether you train again.

The order to run these in, and what has to be true first

Create the stimulus, feed it, remove the thing stopping you training, and only then consider the peptides. The order is set by what the pathway itself depends on rather than by evidence tier.

1. Progressive overload and adequate protein first, for at least twelve weeks. The pooled evidence is the comparator every item below has to beat Morton 2018, and without the damage signal there is no satellite cell response for anything here to amplify.
2. Then remove the limiter, because most people are not myonucleus-limited, they are pain-limited. UC-II Collagen works through oral tolerance rather than substrate supply and has a knee review behind it Gupta 2025; L-Carnitine L-Tartrate has human trial evidence in a training context Chee 2021. Both are cheap and both act on whether you can load the tissue next week.
3. BPC-157 (inj/oral) and TB-500 next among the peptides, because they are the two with the largest bodies of work, and the work is preclinical. The cytoprotection literature is extensive Sikiric 2020 Staresinic 2022 Brcic 2009; the one randomized human study in this group used a wound endpoint in a different tissue Guarnera 2007. Read that gap rather than around it.
4. PEG-MGF and MGF only with the null result in front of you. The peptide had no apparent effect on myoblasts or primary muscle stem cells Fornaro 2014. If you use it anyway, the honest framing is that you are betting the in-vivo context supplies something the culture did not, which is a real possibility and is a hypothesis rather than a finding.
5. IGF-1 DES is the site-specific argument and inherits a systemic risk. Any IGF-1 analog that escapes the injection site carries hypoglycemia risk, which is why glucose is on the read-out below rather than in a footnote.
6. ARA-290 is the most interesting mechanism here and has the cleanest falsification test. It was engineered from erythropoietin to keep tissue protection and drop the erythropoietic effect, and it has human data in type 2 diabetes with neuropathic symptoms Brines 2015. Nothing musculoskeletal has been trialed. If hemoglobin rises on it, the engineering claim has failed, and that is a full blood count away.
7. Actovegin last, because the active fraction has never been identified. There is in-vitro neuroprotective work Elmlinger 2011 and a large randomized trial in post-stroke cognitive impairment Guekht 2017, which is a real evidence base for a product whose contents are undefined. Both things are true and reasoning about dose is impossible.

What gets bought for this that cannot move it

The category that fails structurally is the injectable amino acid blend. Amino Recovery Blend bypasses digestion, and digestion was not the limiting step in anybody whose gut works. The rate-limiting term after training is the myofibrillar synthetic response, which is driven by leucine availability and mechanical signaling and is already saturated by an ordinary protein dose Morton 2018. Paying for a needle to solve absorption is paying to fix a step that was not broken.

The surrogate on this page is soreness, and it points the wrong way. Delayed-onset muscle soreness tracks damage and inflammatory signaling; the outcome the page wants is myonuclear addition, which is invisible without a biopsy. A product that reduces soreness has reduced soreness, and it may have reduced the damage signal that recruits the cells this page is named after. Nothing here resolves that trade, and the honest read-out below is therefore a performance measure rather than a comfort one.

The specific miss is treating a published null as an absence of evidence. The mechano-growth factor peptide was tested in myoblasts and primary muscle stem cells and did not do what the pathway claims Fornaro 2014. That is not the same as untested, and a page that lists the peptide without the result is telling half the story. The umbrella review of performance-enhancing drugs in healthy athletes is the right calibration document for the whole category Warrier 2023.

If the goal underneath is different, so is the page. If the limiter is systemic anabolic signal, Androgen & anabolic-receptor signaling or GH / IGF-1 axis. If it is sleep and between-session recovery, Recovery, sleep & the anabolic window between sessions. If there is an actual injury rather than training damage, Collagen & matrix synthesis and Inflammation resolution (not suppression) are written for that time course. And none of these peptides is licensed for this use, so the vial contents are an assumption before the mechanism is.

How you would know it was working, on a real read-out and a real timescale

This page makes two predictions. On ARA-290 the Complete Blood Count (CBC) with Differential hemoglobin should not rise, because the molecule was engineered specifically to lose that effect Brines 2015, so a rise falsifies the product rather than the theory; and any IGF-1 analog reaching the circulation shows up as a falling fasting glucose before it shows up anywhere else.

• A fixed strength or work-capacity test every four weeks. Same lift, same rest intervals, same time of day. This is the endpoint the page is about, and it is the only one that distinguishes recovered from comfortable.
• Complete Blood Count (CBC) with Differential at baseline and 8 weeks on ARA-290. Hemoglobin and hematocrit specifically. Eight weeks because a red cell response needs most of that to become visible, and this is a product-integrity test rather than a safety formality Brines 2015.
• HbA1c (Hemoglobin A1c) with Fasting Insulin at baseline and 8 weeks on anything in the IGF-1 family. Systemic IGF-1 activity lowers glucose, so this pair is the early warning that a site-specific claim is not holding.
• IGF-1 (Insulin-like Growth Factor 1) at baseline and 8 weeks on the same agents. A rise means systemic exposure, which is exactly what IGF-1 DES and MGF are sold as avoiding.
• hs-CRP (High-Sensitivity C-Reactive Protein) at baseline and 8 weeks. Not an efficacy endpoint. It is here because a persistent rise in somebody injecting an unlicensed product is worth noticing early.

What will fool you. Starting a peptide at the same time as a new training block makes the two inseparable, and the block is the larger variable. Soreness falls with repeated exposure to the same session regardless of what is injected, which is the repeated-bout effect and not a drug effect. Carnitine changes fat oxidation without changing strength Chee 2021, so a metabolic improvement is not the endpoint this page claims. Actovegin has real trial data and an unidentified active fraction Guekht 2017 Elmlinger 2011, so batch differences cannot be reasoned about. And an unlicensed vial has no assay, so a null result may be a product result rather than a mechanism result.

Sources read for these sections

• Fornaro M, et al. Mechano-growth factor peptide, the COOH terminus of unprocessed insulin-like growth factor 1, has no apparent effect on myoblasts or primary muscle stem cells. American Journal of Physiology: Endocrinology and Metabolism 2014 · PMID 24253050
• Staresinic M, et al. Stable Gastric Pentadecapeptide BPC 157 and Striated, Smooth, and Heart Muscle. Biomedicines 2022 · PMID 36551977
• Brcic L, et al. Modulatory effect of gastric pentadecapeptide BPC 157 on angiogenesis in muscle and tendon healing. Journal of Physiology and Pharmacology 2009 · PMID 20388964
• Sikiric P, et al. Stable Gastric Pentadecapeptide BPC 157, Robert's Stomach Cytoprotection/Adaptive Cytoprotection/Organoprotection, and Selye's Stress Coping Response: Progress, Achievements, and the Future. Gut and Liver 2020 · PMID 31158953
• Guarnera G, et al. Thymosin beta-4 and venous ulcers: clinical remarks on a European prospective, randomized study on safety, tolerability, and enhancement on healing. Annals of the New York Academy of Sciences 2007 · PMID 17495250
• Brines M, et al. ARA 290, a nonerythropoietic peptide engineered from erythropoietin, improves metabolic control and neuropathic symptoms in patients with type 2 diabetes. Molecular Medicine 2015 · PMID 25387363
• Elmlinger MW, Kriebel M, Ziegler D. Neuroprotective and anti-oxidative effects of the hemodialysate actovegin on primary rat neurons in vitro. Neuromolecular Medicine 2011;13(4):266-274 · PMID 21983748
• Guekht A, Skoog I, Edmundson S, Zakharov V, Korczyn AD. ARTEMIDA Trial (A Randomized Trial of Efficacy, 12 Months International Double-Blind Actovegin): A Randomized Controlled Trial to Assess the Efficacy of Actovegin in Poststroke Cognitive Impairment. Stroke 2017;48(5):1262-1270 · PMID 28432265
• Chee C, et al. Increasing skeletal muscle carnitine content in older individuals increases whole-body fat oxidation during moderate-intensity exercise. Aging Cell 2021 · PMID 33464721
• Gupta A. Undenatured type II collagen for knee osteoarthritis. Annals of Medicine 2025;57(1):2493306 · PMID 40253594
• Morton RW. A systematic review, meta-analysis and meta-regression of the effect of protein supplementation on resistance training-induced gains in muscle mass and strength in healthy adults. British Journal of Sports Medicine 2018;52(6):376-384 · PMID 28698222
• Warrier AA. Performance-Enhancing Drugs in Healthy Athletes: An Umbrella Review of Systematic Reviews and Meta-analyses. Sports Health 2023 · PMID 37688400
• Mafi F, et al. Improvement in Skeletal Muscle Strength and Plasma Levels of Follistatin and Myostatin Induced by an 8-Week Resistance Training and Epicatechin Supplementation in Sarcopenic Older Adults.. Journal of Aging and Physical Activity 2019 · PMID 30299198