Geert Kleinnibbelink

Chapter 10 200 10.1.1 – Exercise-induced cardiac fatigue In Chapter 2 , we investigated the impact of a bout of 45 minutes high-intensity running exercise under hypoxia versus normoxia on EICF in a randomized cross-over design in 21 healthy individuals. Interestingly, one of our observations was that EICF was only present when measured during a low-to-moderate exercise challenge (stress echocardiography) and not at rest ( Figure 2 ). Similarly, several studies did not observe any signs of EICF at rest following short duration and prolonged bouts of exercise in both the RV and LV. 10-16 In the context of our novel finding, it couldbehypothesized that these studiesmay havedetected EICF when using stress echocardiography. For example, researchers in our laboratory did not detect any deterioration of RV and LV function following prolonged single and three- day walking exercise in 10 cardiac patients and 10 age- and sex-matched healthy controls suggesting absence of EICF. 10 However, close inspection of the post-exercise heart rate and blood pressure data advocates a (para)sympathetic imbalance. Namely, a higher heart rate and lower blood pressure was observed post-exercise compared to baseline. These inequalities may have biased the evaluation of EICF and masked the actual presence of EICF (if assessed during exercise). By adopting a designwhere evaluation during exercise is integrated, a potential bias of (para)sympathetic imbalance could be prevented. Recently, others proved the value of stress echocardiography in the evaluation of the athletes’ heart. Stress echocardiography has a better discriminatory capacity to differentiate physiological from pathophysiological conditions compared to rest echocardiography and has the ability to unmask any potential cardiac dysfunction. 17-19 These novel insights contribute to the rationale that evaluation of cardiac function during the haemodynamic stress of exercise has additional value compared to evaluation at resting conditions only. Namely, such evaluation would improve its sensitivity and discriminative capacity between different types, modes or intensities of exercise. Such as an athlete is judged by his or her performance during competition, functioning of their hearts should also be judged during exercise.