Avaliação não invasiva da fadiga e recuperação de músculos inspiratórios da parede torácica durante testes de endurance em indivíduos saudáveis

Abstract

Introduction: One way to analyze the function of the respiratory muscles is through the respiratory endurance test that can be performed in different ways, being associated with the ability to maintain high levels of ventilation under isocapnic conditions (normocapnic hyperpnea,HN) or to breathe against a determined resistance ( inspiratory pressure threshold load, IPTL) over a period of time (Tlim) until task failure. Objective: Our aim was to non-invasively assess fatigue and recovery of inspiratory chest wall muscles during two different endurance tests in healthy individuals. Methods: This is a crossover study, with a quantitative approach in which healthy individuals of both genders were studied. The subjects were evaluated before, during and after performing the respiratory endurance test that was performed in the normocapnic hyperpnea modality and with an inspiratory pressure threshold load. A period of 7 days was respected between their achievements and the order of execution of each modality was randomized. During the performance of the protocol, the subject was monitored by optoelectronic plethysmography, surface electromyography and by NIRS. Results: A total of 22 subjects participated in the study, 11 men and 11 women, aged 24.36 ± 2.06 years, BMI 22.40 ± 2.02 kg / m². Regarding the relaxation properties, the subjects showed a decrease in the maximum relaxation rate (MRR) and an increase in the time constant (τ) after the IPTL test (p <0.05). There was a decrease in the peak pressure (cmH2O) generated in the post maneuvers in both tests (p <0.05). Regarding the shortening speed and mechanical power, there was a decrease in ∆VCTp / Ti, Winsp and WCTp in the IPTL test (p <0.05). There was a linear drop in the median frequency in the IPTL test and an exponential drop in the HN test, which was not significant for the presence of fatigue. In addition, there was a linear increase in the NIRS variables in both protocols. Conclusion: In view of the results found, it can be concluded that the inspiratory muscles of the chest wall undergo changes in behavior after performing an endurance test with normocapnic hyperpnea and inspiratory pressure threshold load. In addition, the development of fatigue in these muscles and their consequent changes are more evident in the protocol with IPTL that recruits more inspiratory muscle actions.