Geert Kleinnibbelink

Chapter 3 82 Limitations. We did not include a control group(s) who either; did not perform exercise or performed exercise under normoxic conditions. Whilst this may have provided additional insight into the role of hypoxia in mediating cardiovascular adaptations, we believe this does not impact the primary finding of our study, that exercise training may lead to RV structural adaptation, which seems to relate, at least partly, to acute baseline exercise- induced changes in cardiac function. A further limitation is that we did not collect blood samples to assess haematocrit and haemoglobin. Although, the participants were exposed to very short durations of intermittent hypoxic exercise training session (maximum of 1 hour including acclimation), this may have led to a change in haematocrit and haemoglobin. 35 In addition, the RV loop is based on area while volume would be more suitable given the complex RV geometry. However, the technique to derive the RV volume loops is not yet validated and will require 3D echocardiography. Finally, LV strain- volume loops were only constructed from an A4C view and not in the A2C and APLAX views. CONCLUSION 12-week high-intensity running hypoxic exercise training induced right-sided structural remodelling, which was, in part, related to baseline cardiac increase in RV fractional area change to acute exercise. These data suggest that acute RV responses to exercise are related to subsequent right ventricular remodelling in healthy individuals upon hypoxic training.