Geert Kleinnibbelink

Chapter 2 40 Figure 1. Overview of study design, where the dotted panel is highlighting visit 2 and 3 (test days). Baseline measurements. Participants were examined for height (SECA stadiometer, SECA GmbH, Germany), weight (SECA scale, SECA GmbH, Germany), oxygen saturation (SpO 2 , pulse oximetry; Ana Pulse 100, AnaWiz Ltd., UK), 12-lead ECG (Cardiovit MS-2010, Schiller, Switzerland) and maximal oxygen consumption (VO 2 max). Resting heart rate (HR, Polar, Kempele, Finland) and resting blood pressure (BP, Dinamap V100, GE Medical, Norway) were determined at the endof tenminutes of quiet rest in a supine position. A standardized maximal cardiopulmonary exercise test (CPET, Oxycon pro, CareFusion, VS) for VO 2 max assessment was conducted on a motorized treadmill (HP Cosmos, Nussdorf, Germany) after a 10-min warm-up and familiarization. VO 2 max was defined as the highest value of a 30-s average 29 , and attainment was verified according to previous recommended criteria. 30 Test days. Figure 1 outlines the details of a single test day. One of the test days was performed at normoxia (sea level, equivalent to fraction of inspired oxygen [FiO 2 ] 20.9%) and the other at normobaric hypoxia (FiO 2 14.5%; equivalent to a simulated altitude of 3,000m), separated by at least 48 hours of rest. Participants were subjected to 30 minutes of acclimation in a seated position followed by 45-minute of high-intensity (85% of maximumachievedHR during CPET) endurance running exercise on amotorized treadmill