Reference Values for Inspiratory Muscle Endurance in Healthy Children and Adolescents.

Cristhiele Taís Woszezenki,Isadora Levices,Taila Cristina Piva,Márcio Vinícius Fagundes Donadio,Fernanda Maria Vendrusculo,João Paulo Heinzmann-Filho,Stephen E Alway

doi:10.1371/journal.pone.0170696

Abstract

AimsTo generate reference values for two inspiratory muscle endurance (IME) protocols in healthy children and adolescents.Materials and methodsThis is an observational, cross-sectional study, in healthy children and adolescents from 4 to 18 years of age. Weight, height, maximal inspiratory pressure (MIP) and IME were measured using two protocols. A fixed load of 30% of MIP with a 10% increment every 2 minutes was used in the incremental threshold loading protocol. As for the maximal loading protocol, a fixed load of 70% of MIP was used and the time limit (Tlim) achieved until fatigue was measured.ResultsA total of 462 participants were included, 281 corresponding to the incremental loading protocol and 181 to maximal loading. There were moderate and positive correlations between IME and age, MIP, weight and height in the incremental threshold loading. However, the regression model demonstrated that MIP and age were the best variables to predict the IME. Otherwise, weak and positive correlations with age, weight and height were found in the maximal loading. Only age and height influenced endurance in the regression model. The predictive power (r2) of the incremental threshold loading protocol was 0.65, while the maximal loading was 0.15. The reproducibility measured by the intraclass correlation coefficient (ICC) was higher in the incremental loading (0.96) compared to the maximal loading test (0.69).ConclusionIME in healthy children and adolescents can be explained by age, height and MIP. The incremental threshold loading protocol showed more reliable results and should be the model of choice to evaluate IME in the pediatric age group.

Highlights

Inspiratory muscle endurance (IME) can be defined as the capacity of a muscle or a muscle group to sustain a particular task over time, being directly related to muscle fatigue [1, 2]
The regression model demonstrated that maximal inspiratory pressure (MIP) and age were the best variables to predict the IME
The reproducibility measured by the intraclass correlation coefficient (ICC) was higher in the incremental loading (0.96) compared to the maximal loading test (0.69)

Summary

Introduction

Inspiratory muscle endurance (IME) can be defined as the capacity of a muscle or a muscle group to sustain a particular task over time, being directly related to muscle fatigue [1, 2]. The evaluation of IME is a simple, non-invasive and easy to apply method, which can be measured through sustained maximal voluntary ventilation, incremental threshold loading test or maximal loading test [3]. The incremental threshold loading test is a method that initially uses low resistance loads, giving the individual a learning period during the initial steps, increasing the output load progressively until exhaustion [4]. As for the maximal loading, a fixed load of the maximal inspiratory pressure (MIP) is used throughout the test. The final result is defined as the time limit (Tlim) achieved until exhaustion [3]. Previous studies have demonstrated that both protocols are frequently used in the adult age group, even though some findings indicate that the maximal loading protocol presents a higher variability in the IME measurement when compared to the incremental threshold loading protocol [5, 6]

Methods

Results

Conclusion