Resistance exercise training improves mucociliary clearance in subjects with COPD: A randomized clinical trial

Silva BSA, Ramos D, Bertolini GN, et al. Resistance exercise training improves mucociliary clearance in subjects with COPD: A randomized clinical trial. Pulmonology. 2019;25(6):340-347. doi:10.1016/j.pulmoe.2019.01.001

Key Points

- This study aimed to evaluate the effects of two resistance training (RT) programs on mucociliary clearance in subjects with chronic obstructive pulmonary disease (COPD).

- Nineteen subjects with COPD completed the study and were included in the analysis.

- The results showed that both RT with elastic tubing and conventional weight training promoted similar improvements in mucociliary transportability.

- No differences were observed between the two training groups in terms of mucociliary clearance.

- The study highlights the importance of exercise in improving airway clearance in COPD patients, as impaired mucociliary clearance can lead to lung infections and exacerbations.

- Future research is needed to further explore the chronic effects of exercise on mucociliary clearance in subjects with COPD.

Introduction

Peripheral muscle dysfunction is common in individuals with chronic obstructive pulmonary disease (COPD) and is associated with exercise intolerance, impaired quality of life, and increased healthcare utilization. In addition to muscle dysfunction, individuals with COPD may also have impaired mucociliary clearance, which can lead to lung infections and exacerbations. Saccharin transit time (STT) is a non-invasive measure of nasal mucociliary transport (MCT) that can be used to assess the efficiency of clearance. Pulmonary rehabilitation, specifically resistance training (RT), has been shown to improve muscle strength and functional exercise capacity in COPD patients. The researchers suggest that RT may also have a positive influence on MCT due to its modulation of autonomic control. Understanding the effects of RT on MCT is important for enhancing pulmonary rehabilitation strategies and reducing the risk of respiratory infections and hospitalizations in individuals with COPD. Aerobic exercise has been shown to improve the mucociliary system by altering nasal mucus viscosity, and it is recommended as an adjunctive treatment to respiratory physiotherapy techniques. While the effects of RT on the mucociliary system have not been reported, it is reasonable to hypothesize that RT may have a positive influence on MCT. Evaluating the effects of two RT programs on MCT in individuals with COPD is the aim of this study, and the findings could guide strategies to improve mucociliary clearance and reduce respiratory infections and hospitalizations.

Methods

Design of the study

To evaluate the effects of two resistance training (RT) programs on mucociliary clearance in individuals with chronic obstructive pulmonary disease (COPD), a randomized clinical trial was conducted. The study included subjects referred to an outpatient pulmonary rehabilitation program who met the diagnostic criteria for COPD and were clinically stable. Patients with nasal trauma or deviated septum, severe cardiac disease, or musculoskeletal disorders that hindered the experimental protocol were excluded. The study was conducted between 2014 and 2015 in Brazil and approved by the local ethics committee.

Twenty-eight subjects were randomly assigned to either the conventional RT group (GCT) or the RT using elastic tubing group (GET), based on quartiles of lower limb strength. The allocation was performed by a researcher unrelated to the study. Although therapists and subjects were not blinded, data analysis was conducted by a researcher not involved in data collection. The study was part of a larger project, with knee extension strength as the primary outcome measure.

Sample size calculation determined that 20 patients (10 per group) were needed to achieve 80% power, taking into account an expected difference of 45 N between groups, a standard deviation of 36 N, and a dropout rate of 20%. Evaluations were conducted before and after the 12 weeks of RT. Initial assessments included vital signs, lung function, and confirmation of smoking abstinence. Mucociliary transport analysis using the saccharin transit time test (STT) was performed on a separate day. The initial workload of the training groups was determined using the repetition maximum (RM) test.

This study aims to determine the effects of RT programs on mucociliary clearance in individuals with COPD, providing valuable information for the development of effective pulmonary rehabilitation strategies to reduce the risk of respiratory infections and hospitalizations.

Pulmonary Function Test

A simple spirometry was used to measure pulmonary function prior to the protocols of training based on the standards of the American Thoracic Society (ATS) and European Respirator Society (ERS).

Measurement of hemodynamic parameters

The researchers collected vital signs including respiratory rate via observing the number of expansion of the rib cage for 1 minute, heart rate via a heart rate monitor, and blood pressure via the auscultation method using an aneroid sphygmomanometer on the left arm.

Measurement of nasal mucociliary transport (saccharin transit time)

The researchers conducted a study to evaluate the effects of two resistance training (RT) programs on mucociliary clearance in individuals with chronic obstructive pulmonary disease (COPD). They used saccharin transit time (STT) as a non-invasive measure of nasal mucociliary transport (MCT). The STT test involved introducing 250 g of granulated saccharin through a plastic straw into the right nostril of seated subjects with overextended heads. The subjects were instructed not to engage in various activities such as walking, talking, coughing, or blowing their nose during the test. They were also instructed to swallow a few times per minute until they tasted the saccharin flavor in their mouth, at which point they would gesture to the examiner and the time would be recorded. Prior to the test, the subjects were advised to avoid certain medication and substances such as anesthetics, barbiturates, analgesics, anxiolytics, antidepressants, alcohol, and caffeine. The STT assessments were conducted before the start of training and after a minimum of 48 hours following the completion of the final training session, along with measurements of hemodynamic parameters. The researchers consider understanding the effects of RT on MCT important for enhancing pulmonary rehabilitation strategies and reducing the risk of respiratory infections and hospitalizations in individuals with COPD.

Training protocol

Both groups in the study followed a 12-week training program, consisting of three sessions per week, for a total of 36 training sessions. Each session lasted approximately 60 minutes and began and ended with vital sign checks and stretching of the trained muscle groups. Prior to starting the training, participants familiarized themselves with the exercises during separate visits.

The training was structured in a periodized and progressive manner. For the group undergoing general exercise training (GET), resistance was provided using elastic tubing, while the group undergoing conventional exercise training (GCT) used a conventional weight machine. The specific dynamics of the training varied throughout the 12 weeks. In the first to third weeks, the participants performed two sets of 15 repetitions maximum (RM) for each exercise. From the fourth to sixth weeks, they increased to three sets of 15 RM, and from the seventh to ninth weeks, they performed three sets of 10 RM. Finally, in the last three weeks (tenth to twelfth weeks), the participants completed four sets of six RM.

Overall, the training programs followed in this study were consistent for both groups and had a progressive nature, gradually increasing the intensity and resistance over time. The use of different resistance methods allowed for comparison between the two groups. These training protocols were implemented to evaluate their effects on mucociliary clearance in individuals with chronic obstructive pulmonary disease (COPD) and to determine whether resistance training may positively influence autonomic control and enhance pulmonary rehabilitation strategies.

The repetition maximum (RM) test

In this section of the research paper, the repetition maximum (RM) test was used to determine the initial workload and progression for both groups. The RM test was performed at the beginning of each session and involved participants determining the maximum number of repetitions they could do with a given load.

The load for each session was maintained if the maximum number of repetitions performed was within ±2 of the expected number. Otherwise, the load was adjusted to achieve the expected number of repetitions. For example, in the first week, participants aimed for 15 repetitions (15 ± 2), while in the seventh week, the target was 10 repetitions (10 ± 2), and in the twelfth week, the goal was 6 repetitions (6 ± 2).

The load adjustment was done by increasing or decreasing the weight in the group circuit training (GCT) and by changing the tube resistance in the group elastic tubing training (GET). The objective was to find a resistance level that allowed participants to complete 15 repetitions.

This approach allowed for individualized progression throughout the twelve-week resistance training program. By adjusting the load based on the participants’ performance, the researchers ensured that the exercises remained challenging but feasible. This method of load adjustment is important in resistance training as it helps to optimize muscle adaptation and strength gains.

Overall, the repetition maximum (RM) test was used as a tool to determine the appropriate workload and progression for each session and to ensure that participants were adequately challenged in their resistance training program.

RT with elastic tubing

In the study, elastic tubing was utilized in the resistance training program called GET. The researchers used different tubes with progressive resistance levels, where a higher reference number indicated a larger diameter and increased resistance. To support the training of various muscle groups, a specific chair with elastic tubing supports was employed. Metal rings and plastic cable ties were used to secure the tubing to the rings. In determining the initial selection of tube diameter for each movement, the researchers relied on dynamometry data obtained from a pilot study. The initial tubing lengths were determined based on the distance between the subject's upper or lower limb and the fixed point on the chair. Each patient had unique tubing lengths that were consistent throughout all training sessions. The muscle groups targeted for training were the same as those evaluated during dynamometry.

Statistical analysis

In this study, the researchers used the statistical package SPSS v.22, to analyze the data. They first checked for normal distribution of the data using the Shapiro-Wilk test. The results were presented as mean values with standard deviations or as median values with interquartile ranges, depending on the data distribution.

To compare the effects of training, the researchers performed an analysis of variance (ANOVA) for repeated measures using a two-factor scheme for each group. They also checked for violation of sphericity using the Mauchly test and applied the Greenhouse-Geisser correction when sphericity was violated.

To compare changes between groups, both at baseline and after training, the researchers used the Student t test for independent samples for parametric data or the Mann-Whitney test for nonparametric data.

Categorical variables, such as training frequency, were analyzed using the chi-square test. The threshold for statistical significance was set at p < 0.05.

Overall, the researchers used a range of statistical tests to analyze the data and compare the effects of training between groups. This rigorous approach ensures that any observed differences are statistically significant and not due to chance.

Results

This research study evaluated the effects of two resistance training (RT) programs on mucociliary clearance in individuals with chronic obstructive pulmonary disease (COPD). A total of 28 COPD subjects were included and allocated to one of the two groups, but 9 subjects dropped out, leaving 19 subjects to complete the study. The sample characterization showed no significant differences between the groups at baseline. Lung function remained unchanged after interventions in both groups. The analysis of hemodynamic parameters also showed similar changes between the two training groups. In terms of mucociliary clearance, there were no differences between the baseline evaluations of the training groups. However, there was a significant reduction in saccharin transit time (SST) values after 12 weeks in both training groups. There was no interaction between the type of training and SST decrease, and no differences between the groups in the magnitude of SST changes after interventions. Overall, the study suggests that resistance training may have a positive influence on mucociliary clearance in individuals with COPD. However, more research is needed to further explore the effects of resistance training on mucociliary clearance and to enhance pulmonary rehabilitation strategies for COPD patients.

Discussion

This research paper evaluates the effects of two resistance training (RT) programs on mucociliary clearance in individuals with chronic obstructive pulmonary disease (COPD). The study found significant improvements in mucociliary transport (MCT) after RT in both the conventional weight training and elastic tubing methods. Previous studies have shown the importance of physical exercise in improving airway clearance in individuals with COPD. While some studies have examined the effects of exercise on MCT, the chronic effects have remained unclear. The present study suggests that RT may increase autonomic nervous system activity, release adrenergic mediators, and increase the velocity of MCT. The improvement in MCT observed in the study may be related to the behavior of the autonomic nervous system after RT, including improvements in the parasympathetic and sympathetic components. The improved muscle strength in the study groups may also contribute to the improved autonomic function and MCT. Additionally, low-grade chronic inflammation may impair mucociliary function in individuals with COPD, and RT may decrease inflammation and help repair mucociliary function. The study acknowledges limitations such as a small sample size and lack of a control group, and calls for further research to understand the chronic effects of exercise on MCT in individuals with COPD. Overall, the study suggests that both conventional and elastic tubing RT programs can promote improvements in MCT in individuals with COPD, and that further research on the physiological mechanisms is needed.

Opportunities for Future Research

1. Investigate the long-term effects of resistance training (RT) on mucociliary clearance in subjects with chronic obstructive pulmonary disease (COPD) using alternative methods such as aerobic exercise or other modalities of RT.

2. Examine the potential mechanisms by which RT improves mucociliary clearance in subjects with COPD, such as its impact on autonomic nervous system function and chronic inflammation.

3. Explore the effects of RT on other outcomes related to the mucociliary system, such as cough and sputum production.

4. Investigate whether there are differences in the effects of RT on mucociliary clearance based on the severity of COPD.

5. Compare the efficacy of different types of RT, such as conventional weight training versus resistance training using elastic tubing, on mucociliary clearance in subjects with COPD.

6. Evaluate the long-term effects of RT on other respiratory outcomes, such as lung function and exercise capacity, in subjects with COPD.