Chapter 3 covers exercise prescription, which is tailored fitness plans designed by specialists, including recommendations for activity type, intensity, duration, and frequency. It distinguishes between physical activity and exercise while introducing the F.I.T.T principle (Frequency, Intensity, Time, Type) for structuring workouts. The chapter also emphasizes the physical activity pyramid, detailing levels of activity from daily movement to sedentary behavior, and outlines the foundational principles of training, such as overload, progression, and specificity.