Which type of run is characterized by a sustained normal pace that is neither too long nor too short?

The type of run that is characterized by a sustained normal pace, which is neither too long nor too short, is known as a base run. This type of run is essential as it helps in building a solid foundation for runners by improving aerobic capacity and endurance. Base runs typically occur at a comfortable pace that allows the runner to maintain a conversation, making it an important component for overall fitness and stamina development.

In contrast, a progression run involves gradually increasing the pace throughout the workout, while a tempo run is performed at a faster, more challenging pace aimed at improving speed and endurance for racing conditions. A recovery run is generally done at an easier pace, primarily to facilitate recovery after more intensive workouts. Each of these types serves a specific purpose, but the base run's focus on a steady, moderate pace distinguishes it as the choice that best fits the description given in the question.