The purpose of this study is to determine which is the most effective intervention for increasing lifestyle physical activity in Fontan patients: an education (stage of change) intervention or a physical activity (mastery experience) intervention.

Over 100,000 Canadian children are living with congenital heart defects and approximately 1.5% of them have a univentricular heart. The Fontan procedure allows children with functionally univentricular hearts to live relatively normal lives. However, the cardiopulmonary physiology remains abnormal and chronic complications, including myocardial dysfunction, arrhythmias, pathway abnormalities, hepatic dysfunction, obstruction of the ventricular outflow tract or pulmonary veins, and pulmonary arteriovenous malformations may significantly reduce maximal exercise capacity and quality of life. Quality of life and life-long heart health are, therefore, critically important for Fontan patients as their survival depends on the continued functioning of an already sub-normal cardiopulmonary physiology.

Inclusion Criteria:

• have undergone a successful Fontan procedure prior to 5 years of age
• 6 to 10 years of age at the start of the study
• sufficient cardiopulmonary function (based on pulmonary function tests prior to the standardized cardiorespiratory exercise test) for safe participation in moderate to vigorous physical activity

Exclusion Criteria:

• disabilities or medical conditions that may influence physical activity participation.