Geert Kleinnibbelink

Chapter 2 38 loops). Based on the presumed higher workload of the RV during hypoxic versus normoxic exercise, we hypothesize that exercise under hypoxia exaggerates RV to a greater extent than LV compared to exercise under normoxia. To investigate EICF, we examined pre- and post-exercise echocardiography at rest, but also during a standardized low-to-moderate- intensity recumbent exercise challenge (‘stress’). As the post-exercise recovery period is associated with persistent sympathoexcitation and peripheral vasodilation 17, 18 , evaluation of EICF could be confounded when evaluated solely at rest. Therefore, evaluation during stress echocardiography may better reflect cardiac function during exercise and offsets the key limitation of (para)sympathetic imbalance associated with echocardiographic assessment in recovery. 14 METHODS Study population Twenty-one participants (mean age , 22.2±0.6 years; 14 men; mean body mass index, 24.0±0.6 kg/m 2 ; mean maximal oxygen consumption [VO 2 max] per kilogram, 52.4±1.8 mL/min/kg) completed the study. Baseline characteristics are shown in Table 1 . Participants were eligible to take part in this study if they were able to run on a treadmill and if they trained < 2 hours a week at moderate to high intensity for the last six months. Exclusion criteria were a body mass index (BMI) < 18 or > 30 kg/m 2 , active smoker, any possibility of pregnancy, personal history of cardiovascular disease, positive family history of cardiovascular death ( < 55y), exercise-limiting respiratory disease, physical (i.e. musculoskeletal) complaints making completion of a bout of high-intensity running exercise impossible, abnormal resting 12-lead electrocardiogram (ECG) and abnormalities observed on resting transthoracic echocardiography. The procedures were in accordance with institutional guidelines and conformed to the declaration of Helsinki. The study was approved by the ethics research committee of Liverpool John Moores University (18/ SPS/065). Participants gave full written and verbal informed consent before participation.