Geert Kleinnibbelink

Post-Exercise Hypotension in Hypoxia 5 121 measurements were obtained using an appropriately sized cuff. HR was measured continuously throughout (Polar, Kempele, Finland), and rate of perceived exertion (RPE) wasmonitored during exercise. 24 Echocardiography (Vivid E9; GEMedical; Horten, Norway) was performed at baseline and at 60 min of recovery to obtain cardiac haemodynamic parameters (stroke volume (SV), cardiac output (CO)). EstimatedTPR (TPR est ) was calculated from the echocardiography-derived estimate of CO and mean arterial pressure (MAP) at baseline and at 60 min of recovery (TPR est =MAP/CO). Measurements were performed at the same time at both days to control for diurnal variation, and fluid intake was controlled by providing the same amount of water to participants during both testing days. Training program . Following the test days, subjects took part in a 12-week normobaric hypoxic exercise endurance-training program consisting of 2x45 minute sessions a week in the first four weeks and 3x45 minute sessions in the last eight weeks. This running exercise was performed on a motorized treadmill at 3,000m simulated altitude (equivalent to FiO 2 14.5%) at high-intensity (85% of maximal heart rate). Environmental chamber and safety . All exercise tests and training sessions were conducted in an environmental chamber (TISS, Alton, UK; Sportingedge, Bastingstoke, UK), which was set-up by a qualified technician. Normobaric hypoxia was achieved by a nitrogen dilution technique. Ambient temperature, carbon dioxide (CO 2 ) and oxygen (O 2 ) levels were controlled in all sessions (20°C; FiO 2 14.5%; CO 2 0.03%), whilst a Servomex gas analysis system (Servomex MiniMP 5200, Servomex Group Ltd., UK) was used inside the chamber to provide the researcher continuous information regarding O 2 and CO 2 levels. Acute mountain sickness symptoms (AMS, measured by Lake Louise Score (LLS) 25 ) were monitored during testing and training sessions every 20 minutes. The subject was removed from the environmental chamber if oxygen saturation levels dropped below 80% or severe AMS was suspected (LLS ≥ 6). Statistical analysis Statistical analysis was performed using SPSS Statistics 24 (SPSS Inc., VS). All parameters were visually inspected for normality and tested with Shapiro-Wilk normality tests. Categorical variables were presented as proportions and continuous variables were reported as mean±SD, unless indicated otherwise. A two-way repeated measures ANOVA