Inclusion Criteria:  Be an AYA-CS, defined as ≤39 years of age at the time of cancer diagnosis; Be ≥18 years of age at the time of enrolment; Received cancer treatment(s) with known cardiovascular risks (e.g. anthracyclines, radiotherapy, trastuzumab, platinum-based agents, vascular endothelial growth factor inhibitors, tyrosine kinase inhibitors) in the previous 5 years;  Be cancer-free at the time of enrollment;  For Primary RCT:  Confirmed diagnosis of SBHF at baseline (LVEF<53/54%, GLS >-18%, left ventricular hypertrophy (LV mass/body surface area: >95 g/m2 for women or >115 g/m2 for men), concentric remodeling (>0.42 relative wall thickness), or diastolic dysfunction (≥ grade 1).  Exclusion Criteria:  Have an absolute or unresolved relative contraindication to exercise according to the American College of Sports Medicine guidelines; Have an untreated physical or mental health concern that precludes safe and effective exercise participation; Have established CVD (excluding mildly reduced LVEF as described above); Be pregnant at time of recruitment; Be currently engaging in frequent high-intensity exercise (>1 high-intensity exercise session per week); Have substantial barriers to participating, including (1) living too far from study centre or (2) being unable or willing to comply with the study protocol.