Explaining on Instagram: "During a baseball pitch, the muscles in the human arm work together in a powerful, perfectly timed sequence to generate speed, accuracy, and control. ⚾💪 The motion begins with the shoulder and back muscles — especially the deltoids, latissimus dorsi, and rotator cuff — rotating the arm back. As the pitcher winds up, the biceps and forearm flexors help stabilize the arm. Then, during the explosive forward motion, the triceps, pectorals, and core muscles unleash stored e