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In response to the augmented haemodynamic load placed upon the heart by intense and prolonged exercise, various forms of physiological remodelling are elicited. The resultant cardiac structural, functional and electrical adaptations are coined the athlete’s heart. Due to the nature of the remodelling, in some cases these adaptations may however overlap with the diagnostic criteria for varying pathological conditions, often related to sudden cardiac death. Several variables are associated with the athlete’s heart including age, sex, sport, body size, and ethnicity. Ethnicity is of particular importance as athletes of an African/Afro-Caribbean ethnicity demonstrate a greater prevalence of abnormal changes suggestive of pathology. There is however paucity in the literature of the athlete’s heart among other ethnicities. For this reason Study 1 investigated the impact of Arabic ethnicity upon the structure, function and electrophysiology of the heart in male athletes. Study 1 identified that while Arabic athletes had larger hearts than Arabic controls, they had significantly smaller hearts than their Black and Caucasian athletic counterparts. While Black athletes had a significantly greater prevalence of training unrelated/abnormal ECG findings, Arabic and Caucasian both had similar levels of training unrelated/abnormal findings, suggesting the European Society of Cardiology guidelines for ECG interpretation in athletes are applicable for the ethnicity. Study 2 investigated another important facet of the athlete’s heart, which is body size. Study 2 identified that while there was a progressive relationship between body size and cardiac dimensions, the previously identified upper limits of cardiac structural remodelling were applicable even among those with a body surface area (BSA) over 2.3m2. Among the cohort of athletes with a BSA >2.3m2, Black athletes demonstrated significantly greater wall thickness’ than Caucasian and Arabic athletes. The second aspect to the thesis highlighted how the findings of Study 1 and 2 impact upon pre-participation screening. While debate still exists around the most effective methodology to screen for pathological cardiac conditions, several organisations mandate the use of the echocardiography alongside the resting 12-Lead ECG. Study 3 established that should echocardiography be limited to use as a follow up investigation, significant cost benefits could be elicited (47% reduction). The premise of this significant cost reduction was that no pathological case was identified by echocardiography in isolation. While still found to be useful in confirming pathology, significantly, in our study the investigation failed to identify two cases of hypertrophic cardiomyopathy. Study 4 investigated the implications of adopting modified ECG interpretation guidelines in light of the criticism that ECG screening should be avoided due to a high false positive rate. Utilising an ethnically diverse cohort, Study 4 demonstrated that using the ‘Refined’ criteria reduced the false positive rate from 22% when using the 2010 ESC guidelines to 5%. Importantly both criteria achieved 100% sensitivity, highlighting the importance of the ECG in cardiovascular screening.