Final answer:
ACSM's recommendation of moderate to vigorous intensity exercise on the Category Ratio scale corresponds to RPE values of 7-9.
Step-by-step explanation:
The American College of Sports Medicine (ACSM) recommends moderate to vigorous intensity exercise. The corresponding RPE values on the Category Ratio scale are 7-9. This means that during exercise at this intensity, you should feel like you are working somewhat hard to hard, but still able to maintain a conversation without too much difficulty.