AUTHOR=Oviedo Guillermo R. , Garcia-Retortillo Sergi , Carbó-Carreté María , Guerra-Balic Myriam , Balagué Natàlia , Javierre Casimiro , Guàrdia-Olmos Joan 

TITLE=Cardiorespiratory Coordination During Exercise in Adults With Down Syndrome

JOURNAL=Frontiers in Physiology

VOLUME=Volume 12 - 2021

YEAR=2021

URL=https://www.frontiersin.org/journals/physiology/articles/10.3389/fphys.2021.704062

DOI=10.3389/fphys.2021.704062

ISSN=1664-042X

ABSTRACT=Introduction: Down syndrome (DS) is a chromosomal disorder affecting simultaneously cardiovascular and respiratory systems. There is no research studying the coupling between these systems during cardiorespiratory exercise testing in population with DS. Cardiorespiratory coordination (CRC), evaluated through principal components analysis (PCA), measures the co-variation of cardiorespiratory variables during exercise. 
Objective: to investigate and compare CRC in adults with and without DS during maximal cardiorespiratory exercise testing.
Methods: Fifteen adults with DS and 15 adults without disabilities performed a maximal cardiorespiratory exercise test on a treadmill. First the slope, and afterwards the velocity was increased regularly until participants reached exhaustion. The time series of six selected cardiorespiratory variables (ventilation per minute, expired fraction of O2, expired fraction of CO2, heart rate, systolic and diastolic blood pressure) were extracted for the analysis. The number of principal components (PCs), the eigenvalues of the first PC (PC1), and the information entropy were calculated in each group (Non-DS and DS) and compared using t-test or, alternatively, a Mann-Whitney U test. 
Results: Two PCs in the Non-DS group, and three PCs in the DS group captured the variance of the studied cardio-respiratory variables. The formation of an additional PC in the DS group was the result of the shift of SBP and DBP from the PC1 cluster of variables. Eigenvalues of PC1 were higher in the Non-DS (U = 30; p = .02; d = 1.47) than in the DS group and entropy measure was higher in the DS compared to the Non-DS group (U = 37.5; p = .008; d = 0.70). 
Conclusion: DS adults showed higher CRC dimensionality and higher entropy measure than participants without disabilities. Both findings point towards a lower efficiency of the cardiorespiratory function during exercise in DS participants. CRC appears as an alternative measure to investigate cardiorespiratory function and its response to exercise in DS population.