A comparison of the effects of inspiratory muscle strength and endurance training on exercise capacity, respiratory muscle strength and endurance, and quality of life in pacemaker patients with heart failure: A randomized study

Introduction: Studies widely investigated the effects of inspiratory muscle strength training in heart failure (HF) patients. No study compared the effects of inspiratory muscle strength or endurance training in patients with pacemaker. Aims: To investigate the effects of inspiratory muscle strength or endurance training on exercise capacity, quality of life, peripheral muscle strength, respiratory (MIP, MEP) muscle strength and endurance, pulmonary function and dyspnea in HF patients with pacemaker. Methods: Sixteen patients received inspiratory strength training at 50% of MIP, 20 patients received endurance training at 30% of MIP 7days/8 weeks. Functional exercise capacity [6-min.walking test (6-MWT)], incremental shuttle walking test (ISWT)], pulmonary function (spirometry), respiratory muscle strength (mouth pressure device) and endurance (threshold loading), peripheral muscle strength (dynamometer), dyspnea (Modified Medical Research Council dyspnea scale (MMRC) and quality of life [Minnesota Living with Heart Failure (MLHFQ), SF-36 questionnaires] were evaluated before and after. Results: There were statistically significantly improvements were present in MIP, MEP, respiratory muscle endurance, peripheral muscle strength, 6-MWT and ISWT walking distances, MMRC, MLHFQ and SF-36 Scales within groups however there were no significant differences between groups (p≥0,05). Conclusions: Inspiratory muscle strength or endurance training similarly improves respiratory and peripheral muscle strength, exercise capacity, quality of life and decreases dyspnea and are safe, effective in HF patients with pacemakers.

Two distinct types of specific respiratory muscle training (RMT), i.e. respiratory muscle strength (resistive/threshold) and endurance (hyperpnoea) training, have been established to improve the endurance performance of healthy individuals. We performed a systematic review and meta-analysis in order to determine the factors that affect the change in endurance performance after RMT in healthy subjects. A computerized search was performed without language restriction in MEDLINE, EMBASE and CINAHL and references of original studies and reviews were searched for further relevant studies. RMT studies with healthy individuals assessing changes in endurance exercise performance by maximal tests (constant load, time trial, intermittent incremental, conventional [non-intermittent] incremental) were screened and abstracted by two independent investigators. A multiple linear regression model was used to identify effects of subjects’ fitness, type of RMT (inspiratory or combined inspiratory/expiratory muscle strength training, respiratory muscle endurance training), type of exercise test, test duration and type of sport (rowing, running, swimming, cycling) on changes in performance after RMT. In addition, a meta-analysis was performed to determine the effect of RMT on endurance performance in those studies providing the necessary data. The multiple linear regression analysis including 46 original studies revealed that less fit subjects benefit more from RMT than highly trained athletes (6.0% per 10mL · kg−1 · min−1 decrease in maximal oxygen uptake, 95% confidence interval [CI] 1.8, 10.2%; p = 0.005) and that improvements do not differ significantly between inspiratory muscle strength and respiratory muscle endurance training (p = 0.208), while combined inspiratory and expiratory muscle strength training seems to be superior in improving performance, although based on only 6 studies (+12.8% compared with inspiratory muscle strength training, 95% CI 3.6, 22.0%; p = 0.006). Furthermore, constant load tests (+16%, 95% CI 10.2, 22.9%) and intermittent incremental tests (+18.5%, 95% CI 10.8, 26.3%) detect changes in endurance performance better than conventional incremental tests (both p 0.05). The meta-analysis, performed on eight controlled trials revealed a significant improvement in performance after RMT, which was detected by constant load tests, time trials and intermittent incremental tests, but not by conventional incremental tests. RMT improves endurance exercise performance in healthy individuals with greater improvements in less fit individuals and in sports of longer durations. The two most common types of RMT (inspiratory muscle strength and respiratory muscle endurance training) do not differ significantly in their effect, while combined inspiratory/expiratory strength training might be superior. Improvements are similar between different types of sports. Changes in performance can be detected by constant load tests, time trials and intermittent incremental tests only. Thus, all types of RMT can be used to improve exercise performance in healthy subjects but care must be taken regarding the test used to investigate the improvements.

Respiratory muscle fatigue in asthma and chronic obstructive lung disease (COPD) contributes to respiratory failure with hypercapnia, and subsequent respiratory acidosis. Therapeutic induction of acute metabolic acidosis further increases the respiratory drive and, therefore, may diminish ventilatory failure and hypercapnia. On the other hand, it is known that acute metabolic acidosis can also negatively affect (respiratory) muscle function and, therefore, could lead to a deterioration of respiratory failure. Moreover, we reasoned that the impact of metabolic acidosis on respiratory muscle strength and respiratory muscle endurance could be more pronounced in COPD patients as compared to asthma patients and healthy subjects, due to already impaired respiratory muscle function. In this study, the effect of metabolic acidosis was studied on peripheral muscle strength, peripheral muscle endurance, airway resistance, and on arterial carbon dioxide tension (PaCO(2)). Acute metabolic acidosis was induced by administration of ammonium chloride (NH(4)Cl). The effect of metabolic acidosis was studied on inspiratory and expiratory muscle strength and on respiratory muscle endurance. Effects were studied in a randomized, placebo-controlled cross-over design in 15 healthy subjects (4 male; age 33.2 +/- 11.5 years; FEV(1) 108.3 +/- 16.2% predicted), 14 asthma patients (5 male; age 48.1 +/- 16.1 years; FEV(1) 101.6 +/- 15.3% predicted), and 15 moderate to severe COPD patients (9 male; age 62.8 +/- 6.8 years; FEV(1) 50.0 +/- 11.8% predicted). An acute metabolic acidemia of BE -3.1 mmol x L(-1) was induced. Acute metabolic acidemia did not significantly affect strength or endurance of respiratory and peripheral muscles, respectively. In all subjects airway resistance was significantly decreased after induction of metabolic acidemia (mean difference -0.1 kPa x sec x L(-1) [95%-CI: -0.1 - -0.02]. In COPD patients PaCO(2) was significantly lowered during metabolic acidemia (mean difference -1.73 mmHg [-3.0 - -0.08]. In healthy subjects and in asthma patients no such effect was found. Acute metabolic acidemia did not significantly decrease respiratory or peripheral muscle strength, respectively muscle endurance in nomal subjects, asthma, or COPD patients. Metabolic acidemia significantly decreased airway resistance in asthma and COPD patients, as well as in healthy subjects. Moreover, acute metabolic acidemia slightly improved blood gas values in COPD patients. The results suggest that stimulation of ventilation in respiratory failure, by induction of metabolic acidemia will not lead to deterioration of the respiratory failure.

Background:In patients with rheumatoid arthritis (RA), decreased respiratory muscle strength, exercise capacity, and increased dyspnea are indicative of cardiopulmonary deconditioning. Therefore, evaluating respiratory muscle performance is crucial in patients with...

Introduction: Individuals with cystic fibrosis (CF) have digestive, pulmonary and muscular system manifestations, resulting in functional and clinical repercussions, such as changes in the nutritional status, in the strength and endurance of the respiratory muscles and in the oxidative capacity. The objective of this study was to compare blood lactate level, respiratory muscle strength and endurance, peripheral strength and nutritional status among children and adolescents with CF and healthy ones, as well as to correlate the lactate level with respiratory and peripheral muscle forces and respiratory muscle endurance of children and adolescents with CF. Methods: In an observational, analytical and cross-sectional study, 22 children and adolescents (11 healthy and 11 with CF) were divided into two groups according to the diagnosis of CF. Blood lactate level, inspiratory and expiratory muscle strength, respiratory muscle endurance, peripheral muscle strength and nutritional status were evaluated. Data analysis was performed using Students t test, Mann-Whitney, Pearson and Spearman correlations, with SPSS (25.0), adopting a significance level of 5%. Results: Children and adolescents with CF presented high levels of blood lactate (p=0.000), decreased maximum inspiratory pressure (p=0.006), deterioration of nutritional status (p=0.000) and also they did not show any difference in peripheral strength (p=0.365) and respiratory endurance (p=0.716). Conclusions: Individuals with CF have high levels of blood lactate, with significant impairment of nutritional status and respiratory muscle function compared to healthy individuals. However, the high lactate levels are not related to respiratory and peripheral muscle strength and respiratory endurance.

This study aimed to explore how varying inspiratory muscle training workloads affect exercise capacity, health-related quality of life (HrQoL), depression, peripheral and respiratory muscle strength, pulmonary function, dyspnea, fatigue, and physical activity levels in hypertension (HT) patients. A randomized, controlled three-arm study. Forty-five patients (58.37 ± 8.53 y, 7F/38M) with HT received IMT (7 days/8 weeks) by POWERbreathe® Classic LR device and were randomized to control group (CG, 10% maximal inspiratory pressure (MIP), n: 15), low-load group (LLG, 30% MIP), and high-load group (HLG, %50 MIP). Exercise capacity, HrQoL, depression, peripheral and respiratory muscle strength, pulmonary function, fatigue, physical activity level, dyspnea, and sleep quality were evaluated before and after the training. Exercise capacity, physical functioning, peripheral muscle strength, and resting dyspnea were statistically significantly improved in HLG and LLG after the training compared to CG (p < 0.05). Similar improvements in perception of depression, fatigue, and sleep quality were seen within and between the groups (p > 0.05). Statistically significant differences were found within all the groups in terms of MIP and PEF values of respiratory functions (p < 0.05). The superior improvement in the physical activity level was found in the HLG (p < 0.05). Discussion. High-load IMT was particularly effective in increasing physical activity level, peripheral muscle strength, exercise capacity, and improved HrQoL. Low-load IMT was effective in reducing dyspnea and improving respiratory function. Device-guided breathing exercises decreased blood pressure, improved sleep quality, and strengthened respiratory muscles. IMT, an efficient method, is suggested for inclusion in rehabilitation programs due to its capacity to increase physical activity, exercise capacity, and peripheral muscle strength, enhance HrQoL and respiratory function, and alleviate dyspnea. Also, the efficacy of IMT should be investigated with different training protocols such as endurance IMT or functional IMT in HT patients.

The morphological determinants of respiratory muscle (RM) strength and endurance in non-athletic populations are well documented, but are lacking in athletic populations. The purpose of this study was to determine the kinanthropometric and pulmonary predictors of RM strength and endurance. 160 athletes (103 men) were recruited from eight different sports to participate in the study. All subjects underwent a series of kinanthropometric and RM function assessments during a single visit to the laboratory. RM function assessments included the flow-volume curve test to assess pulmonary function, maximum voluntary ventilation (MVV) to assess RM endurance and maximum inspiratory mouth pressure (MIP) and maximum expiratory mouth pressure (MEP) to assess RM strength. Multiple regression analyses revealed that gender, mesomorphy and exercise sessions per week predicted 35% (SEE = 26.6 cmH(2)O) of the variance in inspiratory muscle strength (MIP). Gender and mesomorphy predicted 24% (SEE = 28.3 cmH(2)O) of the variance in expiratory muscle strength (MEP), while gender, relative sitting height, forced expiratory volume in 1 s (FEV(1)) and peak expiratory flow rate (PEFR) predicted 78% (SEE = 18.2 L min(-1)) of the variance in RM endurance (MVV). Although the reference equations are still not adequate to predict MIP and MEP in an athletic population, they provide more suitable reference values than previously reported. The predicted values derived from the equation for MVV can be applied as adequate reference values for athletic populations.

Background Pulmonary involvement due to coronavirus disease 2019 (COVID-19) is common. Pulmonary involvement may affect pulmonary function. Moreover, structural alterations in the lungs may impair the extrapulmonary functions. Purpose This study compared respiratory functions, peripheral muscle strength, maximal exercise capacity, chronotropic incompetence (CI) (< 80% of maximal heart rate), physical activity level, and dyspnea in patients with post-COVID-19 who had lung involvement and healthy controls. Methods Forty-seven patients and 60 healthy controls were compared. Pulmonary function (spirometry), respiratory muscle strength (maximal inspiratory-expiratory pressures – MIP, MEP) and endurance, peripheral muscle strength (dynamometry), exercise capacity (cardiopulmonary exercise test – CPET), CI, physical activity(metabolic holter), and dyspnea (modified Borg Scale) were evaluated. Results Pulmonary function test parameters, MIP, MEP, respiratory muscle endurance, peripheral muscle strength, oxygen consumption, CI during CPET, total and active energy expenditures, daily physical activity duration, metabolic equivalents, and the number of steps were significantly lower in patients compared to controls (p < .001). In contrast, lying down duration (p = .027) and dyspnea on exertion (p < .001) were significantly higher in patients compared with controls. The diffusing capacity for carbon monoxide (DLCO) was 77.2% in patients, indicating mild diffusion impairment. Conclusion Respiratory functions, peripheral muscle strength, exercise capacity, and chronotropic response are considerably impaired in patients with post-COVID-19 with pulmonary involvement. The majority of patients demonstrate sedentary lifestyle and reported higher levels of dyspnea during daily living activities. Therefore, these outcomes need to be evaluated in patients with pulmonary involvement, and patients should be referred to comprehensive pulmonary rehabilitation to prevent long-term impairments. TRIAL REGISTRATION: NCT05381727 – Date: May 17, 2022

Background: In ankylosing spondylitis (AS), chronic systemic inflammation mainly affects the axial skeleton and involvement the costovertebral and costotransvers joints results in limitation of thoracic and spinal mobility (1,2). There is no study published to evaluate the endurance and strength of respiratory muscle and to investigate the relationship with pain. Objectives: The aim of the study was to investigate the functional status, quality of life, pain, pulmonary function, respiratory muscle strength and endurance patients with AS and compare to healthy controls. Methods: Standard pulmonary function tests, maximum inspiratory pressure (PImax), and maximum expiratory pressure (PEmax) for pulmonary volumes and respiratory muscle strength were applied. Respiratory muscle endurance was recorded using sustained threshold loading of 40% maximal inspiratory pressure. AS group were evaluated by using the functional status and quality of life, the Bath Ankylosing Spondylitis Functional Index (BASFI), Bath Ankylosing Spondylitis Disease Activity Index (BASDAI), Ankylosing Spondylitis Quality of Life Questionnaire (ASQoL). The severity of night pain, morning pain and morning stiffness were evaluated by Visual Analog Scale (VAS) in patients with AS. Mann Whitney-U test and Student-t Test were used to compare to groups variables. To evaluate the correlation in AS group Spearman’s Test was used. Results: A total eleven patients (6 female, 5 male; mean age: 41±9.4yrs, body mass index (BMI): 26.1±6.3kg/m2 and duration of disease 22±24.9months) and eleven controls (6 female, 5 male; mean age: 42.9±12.7yrs and BMI: 25±3.6kg/m2) were included in this study. There were no differences in age (p=0.554) and BMI (p=0.922) between the groups. No difference between FEV1% (p=0.069), FEV1/FVC% (p=0.243), PEF% (p=0.490), FEF25-75% (p=0.297), MVV% (p=0.450), PImax (p=0.694), PEmax (p=0.358) and respiratory muscle endurance (p=0.341) in both groups. But FVC% (p=0.041) significantly lower in AS group compare to controls. In addition to PImax (r= -0.800, p=0.003), PEmax (r=-0.683, p=0.021) and respiratory muscle endurance (r=-0.683, p=0.021) were correlated the night pain level in AS group. The respiratory muscle endurance (r=-0.675, p=0.023) was correlated the duration of disease. No correlations to the functional status, quality of life indexes and pulmonary functions in AS group. Conclusion: This study shows that patients with AS have clearly reduced maximal PImax and PEmax, indicating decreased respiratory muscle strength and endurance as night pain levels increased. If indeed the respiratory strength were to be unchanged or even increased the decreased respiratory muscle strength should be due to reduced strength or atrophy of intercostal or accessory muscles, or both. Although the present data do not provide the direct evidence of intercostal muscle atrophy, it is tempting to speculate that immobilization of these muscles due to thoracic rigidity and decreased inspiratory intercostal and accessory activation leading to disuse may be an important factor contributing to it.

Background: Patients with severe asthma need to be studied separately due to differences from less severe asthma. This is the first study to carry out a wide physical evaluation of children and adolescents with severe asthma. The objective was to evaluate maximal and submaximal exercise capacity, respiratory and peripheral muscle strength in children and adolescents with severe asthma. Methods: The study included children and adolescents (6 to 18 years) diagnosed with severe asthma, controlled in the last 4 weeks. The maximal exercise capacity was measured by the modified shuttle test (MST) and submaximal by the 6-min walk test. Respiratory muscle strength was evaluated by measuring maximal respiratory pressures and the peripheral strength through a handgrip. Results: Thirty patients were included, with mean age of 10.3 years, 63% female and 46.7% overweight or obese. Patients underperformed but reached more than 80% of expected in all evaluations. There was a moderate correlation between age and body mass index (BMI) with MST, maximal expiratory pressure and peripheral muscle strength. The correlation between MST and BMI was negative. There was a strong correlation between peripheral muscle strength and age. Peripheral muscle strength also correlated moderately with respiratory muscle strength and lung function. Conclusion: Children and adolescents with severe asthma had lower maximal and submaximal exercise capacity and reduced peripheral and respiratory muscle strength. These results are slightly below normal and very similar to patients with less severe asthma, allowing us to infer that patients with severe asthma have a good functional condition when the disease is controlled. Int J Clin Pediatr. 2022;11(3):76-84 doi: https://doi.org/10.14740/ijcp477

Effects of inspiratory muscle training in patients with heart failure

To assess the significance of changes in respiratory muscle endurance in relation to respiratory and limb muscle strength in patients with mild to moderate chronic heart failure using a threshold loading technique. 20 patients with chronic heart failure (17 male) aged 63.8 (SD 7.4) years and 10 healthy men aged 63.1 (5.6) years. Heart failure severity was New York Heart Association (NYHA) grade II (n = 11) and NYHA grade III/IV (n = 9). Respiratory muscle strength was measured from mouth pressures during maximum inspiratory effort (MIP) at functional residual capacity (FRC) and limb muscle strength was measured using a hand grip dynamometer. Inspiratory muscle endurance was measured using a threshold loading technique. The total endurance duration, the maximum threshold pressure achieved (P-Max), and the inspiratory load (% ratio of P-Max/MIP) were recorded in all subjects. Inspiratory muscles were weaker in patients with heart failure than in the controls [MIP 53.6 (16.5) v 70.9 (20.2) cm H2O, P < 0.05]. Hand grip strength was similar in both subject groups [31.6 (SD) v 36.1 (15.9) dynes]. Total endurance duration was significantly reduced in the patient group [494 (223) v 996 (267) s, P < 0.01], as was the maximal threshold pressure achieved [P-Max 18.5 (6.4) v 30.7 (6.6) cm H2O, P < 0.01]. When expressed as a percentage of MIP, P-Max was also lower in the patients [35.2 (11.8) v 44.8 (11.4)%, P < 0.05]. There was no significant correlation between any measure of endurance and limb muscle strength. Respiratory muscle endurance is reduced in patients with chronic heart failure. These changes probably reflect a generalised skeletal myopathy and provide further evidence of respiratory muscle dysfunction in patients with this disease. Respiratory muscle endurance needs now to be related to symptoms and the effects of treatment and respiratory muscle training should also be explored.

Patients with rheumatoid arthritis (RA) show lower cardiorespiratory fitness than normal subjects. This study was planned to investigate the pulmonary function tests (PFT), respiratory muscle strength and endurance, and aerobic capacity of patients with RA, as well as the relationship of these parameters to clinical and functional status. Twenty-five RA patients aged 25-71 (48.52 +/- 14.09) and 21 control subjects aged 25-66 (45.67 +/- 13.27) participated in the study. PFT, maximum volunteer ventilation, maximum inspiratory and maximum expiratory pressures and cardiorespiratory exercise tests were carried out in all subjects to evaluate the respiratory involvement, inspiratory and expiratory muscle strength and endurance, and aerobic capacity. Patients' duration of disease, smoking and alcohol habits, duration of morning stiffness, visual analogue scale scores, ARA functional classifications and Ritchie articular indexes were recorded. All the patients and control subjects were non-exercising individuals. As a result, we found that RA patients have normal PFT but reduced respiratory muscle strength and endurance, and also reduced aerobic capacity compared to controls. According to this result, respiratory and aerobic exercises may be recommended to improve respiratory muscle strength and endurance and aerobic capacity in these patients.

We read with great interest the study by Battaglia et al.1 which assessed the effectiveness of a new volumetric exerciser for improving some respiratory function parameters in patients with COPD. The purpose of this letter is to comment on what we consider to be important about the effectiveness of inspiratory muscle training (IMT) for improving the strength and endurance of respiratory muscles. Various studies in recent years have assessed the effectiveness of IMT for improving the strength and endurance of respiratory muscles in patients with COPD. When Threshold IMT equipment was not yet available commercially, Smith et al.2 published the first meta-analysis on the effects of IMT on the strength and endurance of the respiratory muscles, and the exercise capacity and functional status of patients with COPD. Little evidence was found for clinical benefits from IMT in patients with COPD. The authors suggested that the benefits of this training were related to the generation of adequate pressures in the mouth, considering that most studies included in the meta-analysis used a flow device for loading. Ten years later, Lotters et al.3 in a new meta-analysis that included 15 randomized controlled studies, concluded that IMT had significant effects on both the strength and endurance of respiratory muscles, thus raising the possibility of benefits from IMT in these patients. In a recent editorial, and later in correspondence between McConnell et al. and Hart et al.4 the pros and cons of the effectiveness of IMT were debated. Polkey et al.5 in a very interesting editorial, presented the scientific opinion of his research group concerning the insufficient evidence, based on the isolated use of dependent tests for assessing the function of respiratory muscles, that was used to support the possible benefits of IMT. In this editorial, the authors discussed the article of Weiner et al.6 They reported that several points are still unclear in relation to the results of IMT. Hart et al.7 recently introduced a new technique for assessing respiratory muscle endurance. These authors observed that the noticeable improvements in strength and endurance that are normally reported after IMT programmes, seem to be more related to an alteration of respiratory pattern, rather than a real increase in endurance capacity of the respiratory muscles.4,8 Curiously, Battaglia et al.1 after an intervention with a simple volumetric inspiratory exerciser, a device that stimulates volume without a target resistance, found an increase in maximal inspiratory pressure (MIP) of around 30% after 6 months of training. This result seems to corroborate the hypothesis that, in isolation, the dependent tests used to assess the strength of respiratory muscles (the MIP test being the most widely used) are insufficient for measuring the effects of IMT, thus supporting the results of Polkey et al.5 If a volumetric inspiratory exerciser device is used to train the respiratory muscles, it is expected that compliance of the rib cage will increase and muscle performance in the test will improve. The MIP test is a dependent test that is related to the compliance of the rib cage, and in turn to pulmonary volume. However, despite doubts in relation to IMT, Ramirez-Sarmiento et al.9 recently studied structural adaptations in the external intercostal muscle after 5 weeks of IMT in patients with COPD. This was the first, and as yet only, published study showing evidence for clinical and physiological effectiveness, and for structural adaptation of a respiratory muscle after IMT. Therefore, the following points remain obscure in relation to IMT: the techniques that should be used to assess the effects of IMT, given that the new technique proposed by Hart et al.7 is neither simple nor inexpensive to use on a daily basis in pulmonary function laboratories; the degree of improvement that should realistically be expected after IMT, given that the diaphragm of patients with COPD seems to be more active and more susceptible to fatigue than that of healthy subjects;10 and finally, can IMT be considered a valid alternative for improving functional capacity in patients with COPD?

Respiratory muscle function is considered as strength and endurance. Since respiratory muscles are used a submaximally in daily life, measurement of respiratory muscle endurance rather than respiratory muscle strength is a more functional assessment. Measurement of respiratory muscle endurance is recommended to be performed by controlling the respiratory frequency and recording the breathing parameters. The purpose of this study was to evaluate respiratory muscle endurance with the incremental threshold loading (ITL) test in healthy adults by recording breathing parameters. This observational, cross-sectional study included 112 healthy adult subjects aged between 18 to 35 years. The anthropometric characteristics (weight and height), pulmonary function testing including forced expiratory volume (FEV1), forced vital capacity (FVC), and maximal voluntary ventilation (MVV), maximum inspiratory pressure (MIP), and physical activity level (International Physical Activity Questionnaire-Short Form - IPAQ-SF) were evaluated. Inspiratory muscle endurance is assessed with ITL. The inspiratory muscle endurance (PImax) was 54.08±21.62 cmH2O. Correlations between the PImax showed weak positive results with height (r=0.392, P < 0.001), weight (r=0.382, P < 0.001), and FEV1 (r=0.386, P < 0.001), moderate positive results with FVC (r=0.446, P < 0.001) and MVV (%) (r=0.541, P < 0.001), while strong positive results with MIP (r=0.796, P < 0.001). According to the regression analysis results, the MIP and MVV% values explained 63% of PImax. Inspiratory muscle endurance in healthy adults can be explained with MIP and MVV. The ITL testing that is performed by recording respiratory mechanics, such as the inspiratory volume, inspiratory flow and work of breathing, can guide the determination of respiratory muscle training intensity.