Which of the following elements should be communicated clearly to members before starting a treadmill block?

Communicating the duration of the treadmill block to members before starting is essential for several reasons. Understanding the length of the workout helps members mentally prepare for the intensity and effort required during that time. It enables them to pace themselves appropriately and sets clear expectations about how long they will be engaged in the activity. This information also allows members to adjust their strategies for hydration, motivation, and recovery as they progress through the block.

In contrast, while aspects like the challenge rating or maximum achievable speed might enhance understanding of workout intensity, they are secondary to knowing how long members will be exerting effort. The recommended incline setting, though important for maximizing the workout's effectiveness, is also less critical than knowing the duration, which is a fundamental piece of information for planning and executing their exercise.