Respostas cardiorrespiratórias e hemodinâmicas de adultos com síndrome de Down durante o teste de caminhada de seis minutos em esteira

Abstract

INTRODUCTION: Cardiorespiratory fitness in individuals with Down syndrome (DS) is often reduced, and this condition may be associated with cognitive, musculoskeletal, neuromuscular, endocrine, metabolic, respiratory, and cardiac alterations. Knowledge about physiological responses in submaximal tests for individuals with DS is still limited. Therefore, analyzing cardiorespiratory and hemodynamic responses during the six-minute treadmill walk test allows for the exploration of typical physiological demands and the determination of specific cardiorespiratory response patterns in this population. Thus, the objective of the present study is to analyze cardiorespiratory and hemodynamic responses during the six-minute treadmill walk test at an individualized fixed speed in adults with DS. METHODOLOGY: This is a descriptive and quantitative cross-sectional study, including people with DS (GDS) and without DS (GC), of both genders, aged between 18 and 40 years, with low cardiovascular risk stratification in the case of DS volunteers. Participants underwent anthropometric evaluation, test and retest of the six-minute walk test (6MWT) on a court, 6MWT on a treadmill with individualized fixed speed with exhaled gas analysis, and subsequently, the cardiopulmonary exercise test (CPET). To achieve all objectives, the study was divided into stages and included familiarization and adaptation of participants to the different equipment and resources presented. For statistical analysis, the Shapiro-Wilk test was used to assess data normality, the independent t-test or Mann-Whitney U test for comparison between the cardiorespiratory and hemodynamic variables of the groups, Pearson's correlation to evaluate the relationship between maximal oxygen consumption (VO2) variables measured by different methods, Bland-Altman plot for VO2 agreement analysis between methods, and simple linear regression to investigate the association of VO2 values between 6MWT on treadmill and CPET. RESULTS: The GSD presented higher BMI (GSD: 27,89 ± 4,94 kg/m2 vs CG: 25,22 ± 4,03 kg/m2, p= 0,084, d=0,05) and inferior performance in the 6MWT on indoor (GSD: 413 ± 69,5m vs CG: 633 ± 47,2m; p < 0,01; d=0,37) resulting in a lower VO₂ 6MWT on treadmill (GSD: 13,57 ± 4,04 mL/kg/min vs. CG: 19,47 ± 2,86 mL/kg/min, p < 0,01; d=1,68), CPET (GSD: 24,68 ± 8,09 mL/kg/min vs. 37,41 ± 6,27 mL/kg/min; p < 0,01; d=1,75) and under predicted values (GSD: 14,35 ± 2,71 mL/kg/min vs. 16,69 ± 1,47 mL/kg/min; p < 0,003; d=1,07). Using the Bland-Altman plot, a good agreement can be observed between the measurement method of predicted VO2 and measured VO2 with gas analysis. The Pearson correlation revealed a moderate positive correlation between the predicted and measured VO2 values by the 6MWT on treadmill (r=0.60; p=0,007). Simple linear regression indicated that approximately only 16% of the VO₂peak value from TECP can be explained by the variation found in the 6MWT on treadmill (r²=0.16). CONCLUSION: The GSD had differences in cardiorespiratory and hemodynamic responses compared to the control group at peak exercise. VO2 from the 6-minute walk test on the treadmill showed agreement and was moderately correlated with predicted VO2; the regression model did not demonstrate statistical significance (F = 3.0; p= 0.10).