There is some limited evidence that reduced size of electrical complexes/traces of the heart on the electrocardiogram (ECG) may be associated with scarring in the heart muscle, which may predispose to serious life-threatening electrical abnormalities and sudden cardiac death (SCD). There is no current guidance on how young individuals and athletes with reduced ECG traces should be managed. Therefore, correct interpretation of this ECG finding is crucial for identifying athletes with disease and at risk of SCD. Some athletes experience SCD despite normal standard cardiac tests. The investigators, therefore, propose to study young healthy individuals and young athletes using cardiovascular MRI, cardiopulmonary exercise testing, 24 hour ECG monitoring and genetic analysis to determine the significance of reduced ECG traces and possibly revise current international sports recommendations.