ACE-031 peptide is a synthetic fusion protein designed to inhibit myostatin, a natural protein that limits muscle growth.  By blocking myostatin and related ligands like activin, ACE-031 promotes significant increases in muscle mass and strength, with studies showing up to a 40% increase in muscle volume in animal models and 3–3.4% gains in lean body mass and bone density in human trials. 
Key Health Benefits:
Muscle Growth & Strength: Inhibits myostatin to stimulate muscle cell proliferation, enhancing muscle mass and physical performance. 
Bone Health: Improves bone mineral density, with up to a 3.4% increase in lumbar spine density in postmenopausal women and significant gains in femur and vertebral bone density. 
Metabolic & Energy Benefits: Enhances muscle oxidative capacity, reduces fatigue, and may improve energy metabolism and vascularization of muscle tissue. 
Muscle Wasting Conditions: Shows promise in treating Duchenne muscular dystrophy (DMD), sarcopenia (age-related muscle loss), and other neuromuscular disorders by slowing muscle degeneration and improving function. 
Recovery & Rehabilitation: Supports faster recovery from injuries and surgeries by promoting muscle repair and reducing atrophy. 
Osteoporosis Prevention: Increased muscle mass helps maintain bone density, reducing fracture risk, especially in elderly or inactive individuals. 
Additional Notes:
Clinical Status: While early-phase trials showed efficacy, clinical development was discontinued by its developers (Acceleron and Shire), and ACE-031 is not approved for therapeutic use. 
Availability: Only available through research or underground labs, often sold as a "research chemical" with no regulatory oversight. 
Side Effects: Mild reactions include injection site pain, headaches, fatigue, and skin rashes. Serious adverse events like nose and gum bleeds were reported in some trials. 
Despite its potential, ACE-031 remains experimental, and its use outside clinical trials is not medically recommended.