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Title:	Cardiorespiratory coordination in repeated maximal exercise
Author:	Garcia Retortillo, Sergi; Javierre Garcés, Casimiro F.; Hristovski, Robert; Ventura i Farré, Josep Lluís; Balagué Serre, Natàlia
Other authors:	Universitat de Barcelona
Abstract:	Increases in cardiorespiratory coordination (CRC) after training with no differences in performance and physiological variables have recently been reported using a principal component analysis approach. However, no research has yet evaluated the short-term effects of exercise on CRC. The aim of this study was to delineate the behavior of CRC under different physiological initial conditions produced by repeated maximal exercises. Fifteen participants performed 2 consecutive graded and maximal cycling tests. Test 1 was performed without any previous exercise, and Test 2 6 min after Test 1. Both tests started at 0 W and the workload was increased by 25 W/min in males and 20 W/min in females, until they were not able to maintain the prescribed cycling frequency of 70 rpm for more than 5 consecutive seconds. A principal component (PC) analysis of selected cardiovascular and cardiorespiratory variables (expired fraction of O2, expired fraction of CO2, ventilation, systolic blood pressure, diastolic blood pressure, and heart rate) was performed to evaluate the CRC defined by the number of PCs in both tests. In order to quantify the degree of coordination, the information entropy was calculated and the eigenvalues of the first PC (PC1) were compared between tests. Although no significant differences were found between the tests with respect to the performed maximal workload (Wmax), maximal oxygen consumption (VO2 max), or ventilatory threshold (VT), an increase in the number of PCs and/or a decrease of eigenvalues of PC1 (t = 2.95; p = 0.01; d = 1.08) was found in Test 2 compared to Test 1. Moreover, entropy was significantly higher (Z = 2.33; p = 0.02; d = 1.43) in the last test. In conclusion, despite the fact that no significant differences were observed in the conventionally explored maximal performance and physiological variables (Wmax, VO2 max, and VT) between tests, a reduction of CRC was observed in Test 2. These results emphasize the interest of CRC evaluation in the assessment and interpretation of cardiorespiratory exercise testing.
Subject(s):	-Exercici -Fisiologia de l'exercici -Condició física -Sistema cardiovascular -Regulació de la respiració -Exercise -Exercise physiology -Physical fitness -Cardiovascular system -Regulation of respiration
Rights:	cc-by (c) Garcia Retortillo, Sergi et al., 2017 http://creativecommons.org/licenses/by/3.0/es
Document type:	Article Article - Published version
Published by:	Frontiers Media
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