TheStack Baseball is a free iPhone application designed to help players improve their bat speed and overall performance at the plate. Developed by sports scientist Dr. Sasho MacKenzie, the app features dynamic training programs that utilize customized variable inertia speed training, based on extensive research. This systematic approach enables players of all levels, from amateurs to professionals, to swing faster and hit harder, enhancing their success in the game.

Inside the app, users will find a personal speed trainer that guides them through scheduled workouts while tracking essential metrics. The app monitors factors like Stack weight, rest periods, and performance gains, allowing for tailored adjustments to future workouts. Additionally, users can track and share key performance metrics such as Stack Speed and Grit Score, making it easier to visualize progress and improvements over time.