Benefits
- Activates satellite cells for muscle repair — triggers the proliferation of muscle stem cells essential for post-exercise recovery and regenerationmoderate
- Localized muscle growth at the injection site — allows targeted stimulation of specific muscle groups when injected intramuscularlypreliminary
- Enhanced post-exercise recovery — accelerates repair of exercise-induced micro-damage by amplifying the natural MGF responsepreliminary
- May promote new muscle fiber formation (hyperplasia) through satellite cell fusion and myonuclear additionpreliminary
- Neuroprotective potential — MGF has shown protective effects on neurons in ischemic brain injury modelspreliminary
Dosage Protocols
| Route | Dosage Range | Frequency | Notes |
|---|---|---|---|
| Intramuscular injection (standard MGF) | 200 mcg per muscle (bilateral) | Immediately post-workout | Standard (non-PEGylated) MGF should be injected directly into the target muscle within minutes of completing training due to its extremely short half-life (~5–7 minutes). Split the dose bilaterally (e.g., 200 mcg per quad). Only inject on training days, into muscles that were trained. |
| Subcutaneous injection (PEG-MGF) | 200 mcg | 2–3× per week | PEG-MGF has a much longer half-life and acts systemically rather than locally. It is injected subcutaneously rather than intramuscularly. Best used on non-training days to avoid competing with the natural MGF pulse that occurs during exercise. |
| Intramuscular injection (targeted protocol) | 100–200 mcg per site | Post-workout, targeting lagging muscle groups | Used specifically for site-specific growth enhancement. Inject into each head of the target muscle. Rotate injection sites to prevent tissue buildup. Typical cycle: 4–6 weeks. |
Medical disclaimer
Dosage information is provided for educational reference only. Always follow your prescriber's instructions and consult a qualified healthcare provider before starting any peptide protocol.
Side Effects
- Injection site pain, swelling, or irritation — particularly with intramuscular administrationcommon
- Localized inflammatory response at the injection sitecommon
- Limited human safety data — long-term effects of exogenous MGF are unknown and there are no completed human clinical trialsserious
- Potential for localized fibrosis or scar tissue with repeated injections at the same siterare
- Mild fatigue or flu-like symptoms reported anecdotally during initial userare
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Frequently Asked Questions
What is the difference between standard MGF and PEG-MGF?
Standard MGF has an extremely short half-life of approximately 5–7 minutes, meaning it must be injected immediately post-workout directly into the target muscle to have any effect. PEG-MGF has a polyethylene glycol (PEG) chain attached, which dramatically extends its half-life to several hours and allows systemic distribution. Standard MGF is preferred for localized, site-specific effects; PEG-MGF is used for general systemic recovery. They should not be used simultaneously — standard MGF on training days (post-workout) and PEG-MGF on rest days is a common protocol.
Why is timing with exercise so important for MGF?
Naturally, MGF is produced in response to mechanical loading — your muscles splice the IGF-1 gene to create MGF as part of the immediate repair response. Exogenous standard MGF mimics this natural pulse. Injecting it post-workout when satellite cells are already being primed by exercise-induced damage appears to amplify the natural repair signal. Injecting at other times may be less effective because the satellite cells may not be in a receptive state. This timing-dependent mechanism is what makes standard MGF unique compared to other growth factors.
How do I properly perform site-specific muscle injections?
Standard MGF is injected intramuscularly using an insulin syringe (29–31 gauge, 0.5 inch needle). The injection should go directly into the belly of the muscle that was just trained. For bilateral muscles (quads, biceps, etc.), split the dose evenly between left and right. Rotate exact injection points within the muscle to prevent tissue buildup. Inject slowly and massage the area gently afterward. Sterile technique is essential — use alcohol swabs and never reuse needles.
What are the different IGF-1 splice variants?
The IGF-1 gene produces several splice variants: IGF-1Ea is the primary systemic form produced by the liver in response to growth hormone. IGF-1Eb (in rodents) and IGF-1Ec (in humans, a.k.a. MGF) are the mechano-sensitive variants produced locally in muscle tissue after exercise or damage. Each variant has the same mature IGF-1 peptide core but different C-terminal E-peptide extensions that determine their tissue distribution, receptor interactions, and biological activities.
What realistic muscle growth can I expect from MGF?
Expectations should be modest. MGF is a signaling peptide that amplifies natural repair processes — it is not a steroid and will not produce dramatic transformations on its own. Users who combine MGF with intense training and adequate nutrition typically report improved recovery speed, reduced soreness, and gradual improvements in muscle fullness over 4–6 week cycles. It is best viewed as a recovery enhancer that may provide a modest edge, not a game-changing muscle builder. The most dramatic results in animal studies involved gene overexpression, not injectable peptides.
References
Last updated: 2026-02-14