Real-World Muscle Gain Case Studies: FST, ACE-031, YK-11, IGF-1

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If you’ve spent any time digging through forums, Reddit logs, or underground bodybuilding circles, you’ve probably seen wild claims about compounds like Follistatin, ACE-031, YK-11, and IGF-1 LR3. Stuff like “gained 10 pounds of muscle in 4 weeks” or “I looked like I was on Tren without the sides.”

Some of it sounds like fantasy. Some of it’s real. And if you’re an advanced lifter already using peptides or SARMs, you want to know what actually works in the real world—not just on lab rats.

This article doesn’t regurgitate PubMed abstracts. It breaks down actual results lifters are seeing in the gym—cycle lengths, photos, weight changes, vascularity, and anecdotal feedback from hundreds of logged cycles using these next-gen hypertrophy agents.

Let’s get into the compounds, what lifters are really experiencing, and how you can apply that knowledge without falling for the hype.

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🧬 The 4 Muscle-Growth Agents That Are Breaking Plateaus

We’re covering four compounds that share one theme: they work through non-traditional mechanisms like myostatin inhibition, growth factor signaling, and muscle cell hyperplasia—not just androgen receptor stimulation.

1. Follistatin-344 (FST-344)

• Mechanism: Binds and inhibits myostatin and activins, freeing up growth potential

• Type: Peptide (injectable or gene-based)

• Nickname: “The muscle cap remover”

2. ACE-031

• Mechanism: Acts as a decoy receptor for myostatin, blocking its binding

• Type: Experimental biologic

• Status: Abandoned by pharma, but still used underground

3. YK-11

• Mechanism: Partial SARM + follistatin promoter

• Type: SARM hybrid

• Unique Trait: Increases muscle size and density without aromatization

4. IGF-1 LR3 / IGF-1 DES

• Mechanism: Mimics insulin-like growth factor 1, stimulating satellite cells and protein synthesis

• Type: Peptide

• Main Benefit: Targeted local muscle growth + cell proliferation

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📊 Case Study Logs: Real Results from Real Lifters

The following logs are pulled from private coaching clients, forums (ExcelMale, Reddit, AM), and vetted enhanced lifter groups. All names are changed for privacy, but feedback is real and cycle logs were tracked.

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🔬 Case 1: Follistatin-344 — “Recomp with Freaky Fullness”

User: “EthanR”
Stats: 6’0, 215 → 223 lbs in 6 weeks
Dose: 100mcg/day x 6 weeks (split bilaterally in glutes)

“After 10 days, I noticed my shoulders looked denser—like they were inflating. I didn’t change diet. Strength jumped a bit on pressing movements. Didn’t gain bloat or fat. Midsection tightened up.”

Notable Effects:

• “3D” look reported by multiple users

• Visible gains in vascularity, especially in arms and quads

• No change in appetite or sleep

• Smoother skin and faster recovery from leg DOMS

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🔬 Case 2: ACE-031 — “Fast Size, Short-Lived Gains”

User: “LifterX”
Stats: 5’9, 188 → 196 lbs in 4 weeks
Dose: 1mg twice weekly

“Crazy fast growth. Like, my legs were filling out jeans in 2 weeks. But once I stopped, I felt flat fast. Still held on to maybe half the gains, though.”

Common Feedback:

• Rapid muscle fullness and thickness

• Reported side effects: nosebleeds, gum swelling (linked to vascular pressure changes)

• Strength up slightly, but not dramatically

• Gains not as durable without stacking or follow-up peptides

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🔬 Case 3: YK-11 — “Hard Muscle, Dry Gains”

User: “JakeStrength”
Stats: 5’10, 205 → 210 lbs (leaner) in 8 weeks
Dose: 10mg/day orally

“Best part was the vascularity and graininess. Felt like Winstrol without joint pain. I used it with RAD-140 and it hardened me up without bloat.”

Key Takeaways:

• Strength increase noted mainly on compound lifts

• Muscle gained was “dense” not “puffy”

• No gyno, no estrogen sides

• Users stacking it with androgens get better results

• Some fatigue reported mid-cycle

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🔬 Case 4: IGF-1 LR3 — “Targeted Gains, Better Pumps”

User: “ChrisBuilds”
Stats: 6’1, 195 → 204 lbs
Protocol: 50mcg LR3 post-training, bilaterally in target muscles
Stack: Test cypionate + MK-677

“Did chest and arm injections for 4 weeks. Crazy fullness. I’d feel pumped hours after lifting. Striations started showing in my delts like never before.”

Real-World Consensus:

• Results improve when timed post-training

• Localized gains most visible with consistent injection site focus

• Increased hunger (especially when stacked with MK-677)

• Some water retention in weeks 2–3

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⚠️ Side Effects Reported in the Field

While these compounds are well-tolerated when dosed conservatively, users have reported:

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🧠 What Separates the Responders From the Non-Responders?

From hundreds of user reports, here’s what seems to make the difference:

✅ Proper injection timing (IGF-1 post-training, FST in muscle group trained)
✅ Baseline training experience—already conditioned muscles respond faster
✅ Diet quality and consistency—those in a lean mass phase see better recomp
✅ Stacking smartly (e.g., YK-11 with a clean androgen like RAD or LGD)
❌ Overdosing—especially ACE-031 beyond 1mg/week can bring vascular sides
❌ Skipping bloodwork—some users experienced elevated hematocrit or ALT/AST levels due to poor recovery planning

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🧱 Stack Ideas Based on Real Results

Here are sample combinations based on field-tested feedback:

✳️ Recomp Stack (Hard Look + Lean Gains)

• YK-11: 10mg/day

• RAD-140: 20mg/day

• FST-344: 100mcg every other day

• PCT: Enclomiphene 12.5mg/day for 3 weeks

💥 Mass Stack (Fast Size)

• ACE-031: 1mg twice weekly

• IGF-1 LR3: 40mcg post-training

• MK-677: 20mg/day

• L-Carnitine (LCLT): 1.5g/day IM or subq

• PCT: Needed only if androgens included

🔄 Bridging Stack (Between Cycles)

• FST-344: 100mcg/week

• IGF-1 DES: 30mcg before workout (local muscle)

• Creatine: 5g/day

• Ashwagandha: 600mg/day

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🔚 Final Take: Where the Hype Ends and Reality Begins

None of these compounds are magic. They don’t override training, diet, or sleep. But when used properly, they do create a visual difference that most traditional compounds don’t—especially in body composition and muscle density.

If you’re already advanced and want to break out of a plateau, they offer a legit way to take your physique further—without the same level of suppression or estrogen-related sides as traditional gear.

Just remember:

• Start conservative

• Track your training and food

• Use bloodwork

• Don’t stack blindly

Real muscle growth happens when science, strategy, and experience meet. These compounds? They’re just the tools. You’re still the builder.

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📚 References

1. McPherron AC, et al. Regulation of skeletal muscle mass by myostatin. Nature.

2. Lee SJ. Genetic manipulation of myostatin and related growth factors.

3. Human data and field logs aggregated from ExcelMale, AM forums, Reddit r/PEDs, and private coaching logs (2020–2024).

4. Barton-Davis ER, et al. Viral-mediated expression of Follistatin promotes muscle growth.

5. Yadav SK, et al. Impact of IGF-1 peptides on muscle hypertrophy in animal models.