muscle builder pre workout - AMINO ACIDS 1000 MG, Pre Workout - l-arginine amino acid, 3 Bottles (300 Capsules) Amino acids can support joints. Together with other amino acids found in bone broth (especially proline), glycine plays a part in the formation of collagen, promoting the growth and function of joints, and tendons. Leucine, in particular, has been shown to regulate and improve muscle protein synthesis after exercise.