Question

why is it important to monitor your heart rate during exercise?
to make your heart work as hard as possible to increase endurance
to maintain a heart rate that is below 50% of your maximum heart rate (mhr)
to reduce the intensity of your workout to avoid reaching a level of exertion entirely
to ensure you are working within a heart rate range that is safe and effective

Explanation:

Monitoring heart - rate during exercise helps in keeping the heart rate within a range that is both safe (to avoid over - exertion and potential health risks) and effective (to achieve fitness goals like endurance building). Working the heart too hard can be dangerous, and working it too little may not provide fitness benefits. A heart rate below 50% of MHR is too low for effective exercise, and completely avoiding exertion defeats the purpose of a workout.

Answer:

to ensure you are working within a heart rate range that is safe and effective