Exercise physiology and cardiac function. Aspects on determinants of maximal oxygen uptake

Although the athlete's heart has been of interest for over 100 years, further characterization of the athletes heart is needed in order to understand how training affects cardiac dimensions and function. Few studies have investigated the effects of training in female athletes and few have compared males and females. Therefore, the aim of this thesis was to characterize the physiologically enlarged athlete's heart and the healthy respiratory response to exercise in both males and females, in order to facilitate the differentiation between the physiologically enlarged heart and the pathologically enlarged heart. Paper I showed that the total heart volume (THV) increases with training in both males and females, with a balanced enlargement of the left and right ventricle. Furthermore, THV was a strong, independent predictor of peak oxygen uptake (VO2peak). Males had a larger left ventricular mass (LVM) normalized to THV when compared to females of similar fitness level. In Paper II, THV in relation to VO2peak was compared between 31 patients diagnosed with heart failure and a control group consisting of athletes and normal subjects. The ratio between VO2peak and THV (VO2peak/THV) was defined as the cardiac reserve index. Cardiac reserve index was significantly lower in patients when compared to athletes and controls. This difference also remained when only patients with normal ejection fraction were compared with the control group. Paper III investigated three different respiratory indices (Dx, Px and Pq) in triathletes and controls. The sequence in which the indices occurred during an incremental exercise test differed between well trained and untrained subjects. This difference was shown to be caused by the well trained subjects' ability to metabolize fat at high workloads. In Paper IV cardiac pumping mechanics was compared between athletes and controls matched for age and gender. Cardiac pumping was divided into longitudinal pumping and radial pumping. Except for the longitudinal contribution to the left ventricular stroke volume in males, the results of Paper IV showed that there were essentially no difference in cardiac pumping mechanics between males and females, and between athletes and controls. This emphasizes the results from Paper I that it is the total heart volume that is the dominant determinant for cardiac performance

Left ventricular AV-plane displacement is preserved with lifelong endurance training and is the main determinant of maximal cardiac output.

Age-related decline in cardiac function can be prevented or postponed by lifelong endurance training. However, effects of normal ageing as well as of lifelong endurance exercise on longitudinal and radial contribution to stroke volume are unknown. The aim of this study was to determine resting longitudinal and radial pumping in elderly athletes, sedentary elderly and young sedentary subjects. Furthermore, we aimed to investigate determinants of maximal cardiac output in elderly

Atrial remodelling is less pronounced in female endurance-trained athletes compared with that in male athletes.

Objectives. Little data exists on atrial adaptation to training in women. Furthermore, data on right atrial (RA) volumes is lacking for both male and female athletes. The objective of this study was therefore to investigate atrial volumes in male and female athletes. Design. A total of 75 athletes (33 women) and 53 controls (21 women) underwent cardiovascular magnetic resonance imaging. Left atrial (LA) and RA volumes were measured by manual delineation. The atrial appendage was included in the volumes, and pulmonary veins were excluded. Results. Atrial volumes were larger in athletes compared with those in controls (males: LA 116 ± 19 ml versus 93 ± 19 ml, RA 166 ± 32 ml versus 133 ± 23 ml, p < 0.0001, females: LA 90 ± 15 ml versus 83 ± 17 ml, p < 0.05, RA 119 ± 24 ml versus 108 ± 18 ml, p = 0.07). When normalized for body surface area, atrial volumes remained larger in athletes. However, when normalized for total heart volume (THV) there were no differences between groups except for LA volumes in females where controls had higher LA/THV compared with those in athletes (p < 0.05). Conclusion. Atrial volumes were significantly larger in athletes. Atrial volumes normalized for THV did not differ between athletes and controls indicating a balanced enlargement. There was only a small difference between female controls and female athletes, suggesting that atrial adjustment to training is more modest in women