Cardiac structure and function in obesity: effect of aerobic exercise

Introduction: Obesity is a major risk factor for cardiac related morbidity and mortality particularly in women. Excess body fat induces detrimental LV structural and functional alterations that can potentially be reversed by aerobic exercise training, however the optimal exercise type has not been determined. Firstly the assessment of the impact of excess body fat, on LV structure and function in healthy overweight/obese women was undertaken. Next, the acute LV systolic and diastolic functional responses to heavy-intensity exercise were compared between healthy obese and non-obese women. Finally, the long-term effects of interval and continuous heavy-intensity training on LV structure and function in overweight/obese women were assessed. Methods: In chapter 4, 85 females were assessed for anthropometric characteristics and LV structure and function then divided into 3 groups; normal weight, overweight and obese. The allometric relationships between each pair of anthropometric and cardiac variables were assessed and the 3 groups were compared for absolute and allometrically scaled LV structural and functional data. In chapter 5, 16 females (8 obese and 8 non-obese) completed a 10-min heavy-intensity exercise session. LV systolic and diastolic function were assessed at rest, 8 min into exercise and 5 min post-exercise and compared between both groups. In chapter 6, 20 overweight/obese females were assessed for LV structure and function before and after completing 12 weeks of either interval or continuous heavy-intensity training. All measures of LV structure and function were assessed by echocardiography. Results: In chapter 4, excess visceral fat was associated with LV concentric hypertrophy as well as reduced LV diastolic filling velocity, diastolic myocardial velocity and systolic and diastolic myocardial deformation. Fat-free mass (FFM) was identified as the most appropriate scaling variable to normalise for body size without masking the impact of excess fat. In chapter 5, obese woman displayed greater exercise-induced systolic deformation and diastolic filling compared to non-obese women. In chapter 6, both continuous and interval heavy-intensity training resulted in improvement in LV structure, diastolic myocardial velocity and systolic and diastolic myocardial deformation with no difference between both training interventions. Conclusion: Excess visceral fat is associated with LV concentric hypertrophy and reduced systolic and diastolic function in healthy overweight and obese women. Heavy-intensity exercise enhances LV systolic and diastolic functional response to exercise in overweight/obese women and results in long-term improvements in LV function regardless of exercise type provided it is performed at the heavy-intensity domain.