The American Heart Association recommends:

• All children age 2 and older should participate in at least 30 minutes of enjoyable, moderate-intensity activities every day.
• They should also perform at least 30 minutes of vigorous physical activities at least 3–4 days each week to achieve and maintain a good level of cardiorespiratory (heart and lung) fitness.
• If your child or children don't have a full 30-minute activity break each day, try to provide at least two 15-minute periods or three 10-minute periods in which they can engage in vigorous activities appropriate to their age, gender and stage of physical and emotional development.