Comparação do desempenho cardiopulmonar, metabólico, da cinética de oxigênio e da ventilação de mulheres obesas durante testes de esforço cardiopulmonar em esteira e bicicleta ergométrica

Abstract

Introduction: Maximum cardiopulmonary exercise tests (CPX) performed on a bicycle or treadmill objectively measure functional capacity and quantify exercise limitation. In these tests, the analysis of peak oxygen consumption (VO2PICO) and ventilatory threshold (VT) are useful measures to evaluate cardiorespiratory performance in several populations. Several exercise protocols using a bicycle or treadmill are used for performance evaluation, however, for obese individuals, it is not known which of the ergometers leads to greater physical exhaustion, which better evaluates the physical performance of these subjects and is even more acceptably accepted by these individuals. Moreover, for this population, less is known about the behavior of oxygen kinetics and ventilation, i.e. its rate of increase (VO2 and VE kinetics) and the understanding of energy systems during an exercise using different types of exercise (cycling x pedaling). Objectives: To compare the cardiorespiratory, metabolic performance, oxygen kinetics and ventilation of obese women during cardiopulmonary exercise tests using a conventional treadmill and ergometric bicycle through incremental ramp protocols and constant load tests at two different exercise intensities. Materials and Methods: The sample consisted of 40 obese volunteers, based on sample calculations, randomized into two groups of 20 obese individuals, each of whom performed treadmill or bicycle CPX. We assessed the clinical, anthropometric and adiposity (weight, height, BMI-body mass index, BAI-body adiposity index, WBC-waist-hip ratio, HC-hip circumference, WC- waist circumference, NC- neck circumference) and spirometry (FVC-forced vital capacity, FEV1 -forced expiratory volume in the 1st second, PEF-peak expiratory flow, MVV-maximum voluntary ventilation). In both tests, ventilatory measures (VE-ventilation per minute, VE/VO2-ventilatory equivalent of oxygen, VE/VCO2-ventilatory equivalent of carbon dioxide, RER-gas exchange ratio) and metabolic (VO2-consumption of oxygen, VCO2-carbon dioxide production) of breath-by-breaths with respiratory gases (Cortex-Biophysik-Metamax3B), in addition to the variables of effort perception (fatigue and dyspnea - Borg6-20 ), HRmax (maximum heart rate) and systolic and diastolic blood pressures. Continuing with the evaluation protocol, 30 obese performed two constant load tests with different intensities (25% <VT and 25%> VT), with a 30-minute rest between the tests, to evaluate oxygen kinetics and ventilation. In these, measurements of the kinetics were taken as the time delay (TD), rate of increase (τ) of VO2 and VT and amplitude (A). Sigma Plot 11.0 software for kinetic analysis and Statistic 10.0 software were used for the statistical analysis of the other outcomes, with a significance level of 5% being assigned to test the hypotheses. Results: The studied sample presented a high degree of obesity (BMI = 43.5± 6.6 kg/m², but without ventilatory disorders.) Both groups presented homogeneity in relation to their anthropometric and ventilatory characteristics. During incremental CPX, the obese women in the treadmill group (TG) had the highest cardiopulmonary and metabolic response seen by VO2peak (18.1±3.3 ml/kg/min x 12.2±2.1 ml/kg/min) and VEpeak (62.9±13.5L x 42.1±8.3L), with p <0.05. However, it was the same group that interrupted CPX earlier (153.4s), and with a lower ventilatory reserve (42.3±19.4L x 58.7±27.1L) when compared to the bicycle group (BG). Correlations between the anthropometric measurements and the performance variables between the groups, observed that only the TG had the final performance of the test influenced by the anthropometric measures as weight r= -0.56, p=0.01) and BMI (r= -0.55, p=0.02). Analyzing oxygen kinetics and ventilation, (p<0.05) for the VO2 stable state (VO2SS), where the TG presented an increase in VO2SS in relation to BG (TG= 1.144 L/min, BG= 0.905 L/min; p<0.05). In the above VT test, we observed an additional ventilatory component (SLVE) for the obese women of the TG (TG= 10.0 L.min-1, BG= 5.2L.min-1; p = 0.02). Conclusion: In our study, it was evident in our sample that obesity seems to influence the test performed on a treadmill more negatively, causing obese women to stop this test earlier, requiring a higher oxygen consumption and a ventilatory response to complete the exercise. For oxygen kinetics and ventilation, apparently the type of exercise performed did not influence the response of the VO2 and VE curve when exercise was performed below VT. However, for the above VT test, an additional ventilatory component (SLVE) was required so that the obese could finish the activity, suggesting that this activity becomes more difficult for this population.