The recommendation of the American Heart Association and the American College of Sports Medicine for all healthy adults 18 - 65 years of age is: (30 seconds)

At least 10 minutes of vigorous intensity physical activity 3 days a week
No more than 10 minutes of moderate intensity physical activity 2 days a week
At least 20 minutes of moderate intensity physical activity at least 5 days a week
At least 30 minutes of moderate intensity physical activity at least 5 days a week
At least 30 minutes of moderate intensity physical activity 7 days a week