Geert Kleinnibbelink

Chapter 10 204 10.3 – Acute and chronic exercise: right does not mirror left La Gerche et al . stated: “cardiac output is only as good as your worst ventricle” . 43 This means that both ventricles, rather than just the LV, can serve as the potential Achilles’ heel, and that both should be examined separately in relation (and in conjunction) to acute and chronic exercise responses. 10.3.1 – Exercise-induced cardiac fatigue EICF may affect the RV and to a lesser extent the LV. It has been hypothesized that the disproportionate increase in end-systolic wall stress in the RV, when compared to the LV, during exercise explains the difference in presence and magnitude of EICF in both ventricles. 21, 23 In Chapter 2 , we demonstrated that EICF occurred to the same extent in both RV and LV. One other study reported similar reductions in cardiac function post- exercise 22 while others showed reductions in cardiac function to a greater extend in the RV compared to the LV. 23, 44-47 These differences may be explained by difference in sport discipline, participant characteristics, exercise intensity or duration. Nevertheless, the magnitude of EICF is greater in the RV compared to the LV in the majority of the studies. This indicates that not only in-exercise responses vary between both ventricles but also affects both ventricles to a different extent (i.e. right does not per se mirror left). Association of exercise-induced cardiac fatigue with level of training A gap in the literature is the effect of the level of training on the magnitude of EICF. Whilst some have attempted to compare participants with lower or higher cardiorespiratory fitness (cross-sectional design) little data exists exploring prospective intervention studies that directly alter fitness. 22 The data of Chapter 2 and Chapter 3 are suited to address this question as we performed rest and stress echocardiography prior to and post a 12-week hypoxic training program. In this cohort, 15 individuals (N=6 drop-outs) completed the training program and significantly increased their cardiorespiratory fitness. Both RV free wall and LV global longitudinal strain significantly reduced post-exercise (RV: E, p < 0.001; LV: E, p < 0.001) but did not differ in magnitude following the 12-week training program compared to baseline (RV: E*T, p=0.36; LV: E*T, p=0.25) ( Figure 3, Table 1 ). Also, when observing with stress echocardiography, there was no difference in magnitude of the EICF (RV: E*T*S, p=0.89; LV: E*T*S, p=0.28). This exploratory analysis suggests that the changing