Exercise prescription refers to the specific details of a workout plan, including the types of exercises, the number of sets and repetitions, and the rest periods between sets. It's a primary determinant of the adaptations your body will make in response to the exercise. The choice of exercise is important because it determines the muscle groups you'll be working and the movement patterns you'll be using. For example, if you want to work your quads more, you might choose a front squat variation. The intensity of the exercise is another key variable, referring to either a percentage of your one-rep max for strength-based exercises, or a percentage of your maximum heart rate or VO2 max for cardio-based exercises.