MYOS Canine Muscle FormulaMYOS has worked wonders for our dogs, and we are proud to say that tens of thousands of dogs are experiencing the benefits of our unique product. Simple. Natural. MYOS uses a single, all natural ingredient called Fortetropin. No additives or artificial ingredients. Fortetropin has been shown in multiple clinical studies to accelerate gains in muscle mass, improve mobility and enhance recovery from injury. Veterinarian Recommended Veterinarians