Geert Kleinnibbelink

Chapter 5 120 Baseline and follow-up measurements . The measurements included determination of height (SECA stadiometer, SECA GmbH, Germany), weight (SECA scale, SECA GmbH, Germany), oxygen saturation (SpO 2 , pulse oximetry; Ana Pulse 100, Ana Wiz Ltd., UK) and maximal oxygen consumption (VO 2 max). Resting heart rate (HR, Polar, Kempele, Finland) and resting BP (Dinamap V100, GE Medical, Norway) were determined at the end of ten minutes of quiet rest in a supine position. Resting HR was averaged over 1 minute of continuous recording. Resting BP determination involved three serial measurements from the right arm taken 30 seconds apart. Cuff size was adjusted to arm circumference. A standardized maximal cardiopulmonary exercise test (CPET) for VO 2 max assessment was conducted on a motorized treadmill (HP Cosmos, Nussdorf, Germany) after a 10-min warm-up and familiarisation. The test started at a speed of 7 km/h for 3 minutes followed by speed increments of 1 km/h every minute until subjects’ volitional exhaustion. Careful calibration of flow sensors and gas analysers was performed before each measurement according to the manufacturer’s instructions (Oxycon pro, CareFusion, VS). VO 2 max was defined as the highest value of a 30-s average 22 , and attainment was verified according to previous recommend criteria. 23 Test days. Figure 1 gives an overview of the test days described below. Participants were randomly allocated to one of two groups in a counterbalanced design and blinded for the order of testing days. One test day was performed at normoxia (sea level, equivalent to FiO 2 20.9%)) and the other test day at normobaric hypoxia (3,000m simulated altitude, equivalent to FiO 2 14.5%), separated by at least 48 hours and maximal 72 hours of rest. Participants were subjected to 30 minutes of acclimation in seated position followed by 45-minute of high-intensity endurance running exercise on a motorized treadmill (HP Cosmos, Nussdorf, Germany) and 60 minutes of recovery in seated position. Exercise intensity was set by using 85% of maximal heart rate for both hypoxia and normoxia sessions. HR, SpO 2 and BP measurements were performed at the end of acclimation (baseline) and at 15, 30, 45 and 60 minutes during post-exercise recovery in the seated position. HR was averaged over 1 minute of continuous recording. BP determination involved three serial measurements from the right arm taken 30 seconds apart. To assess PEH, post-exercise BP measurements were averaged to calculate the decline in BP from baseline. Participants remained in a seated upright position with back support and BP