Emma, a 27-year-old female, begins a cardiovascular training program. to achieve the maximum benefits from exercise, how often will she need increase the intensity and duration of her workout? once a month once a week once every three weeks once every two weeks

It is a questions that depends on many variables. The one you give is the age of Emma, but more is needed like her physical constitution, diet, target, frequency of training and so forth. You also need to control the heart beat rate to make sure is not low or too high but it remains in a safe 80-90 per minute to ensure correct cardiovascular workout.

Explanation:

If you want a blind answer with what you tell me in the question, I will say once a week but again, more is needed to make your workout effective. Please consult with a trainer so he can help you monitor your progress and increase the intensity without you hurting yourself. Thanks

i believe it would be the lungs.