Evaluation of an inspiratory muscle trainer in healthy humans

The influence of low resistance respiratory muscle training on pulmonary function and high intensity exercise performance

Background/objectives

Respiratory muscle training (RMT) was recognized as an effective means to improve respiratory muscle (RM) strength and enhance exercise performance. The purpose of this study was to examine the effect of low-intensity RMT on RM strength, pulmonary function, and performance.

Methods

Fourteen healthy active adults were assigned randomly to either a training or placebo group. The training group completed six weeks of RMT, which consisted of a first week, 1 set of 15 min/d, 5 d/wk at 10-25% of maximal inspiratory pressure (PImax), and the remaining 5 weeks, 2 sets of 15 min/d, 5 d/wk, at 30% PImax. The placebo group followed the same protocol but with almost no additional ventilatory resistance. Measurement of RM strength and endurance, spirometry, and endurance exercise performance were obtained before and after the RMT program.

Results

In the training group, PImax (+14%) and maximal expiratory pressure (PEmax, +27%), forced vital capacity (FVC, +3.6%), maximal oxygen uptake (VO2max, +11%), and time to exhaustion (Tlim90%, +25%) increased significantly from baseline values (P < 0.05). No significant changes were observed in the placebo group. Also, no significant interaction in maximum voluntary ventilation (MVV12), minute ventilation (VE), and respiratory rate (RR) were detected.

Conclusions

These data suggest that low-intensity RMT is an effective tool to improve RM strength, pulmonary elastic properties and endurance exercise performance.

Respiratory muscle training induces additional stress and training load in well-trained triathletes-randomized controlled trial

Background: Respiratory muscle training (RMT) has been investigated in the context of improved athletic performance and pulmonary function. However, psychophysiological costs of RMT remain understudied. Voluntary isocapnic hyperpnoea (VIH) and inspiratory pressure threshold loading (IPTL) are widely applied RMT methods. The main purposes of this study were to assess whether RMT induces additional load on well-trained triathletes and determine differences in RMT-induced load between sexes and applied methods. Materials and Methods: 16 well-trained triathletes (n = 16, 56% males) underwent 6 weeks of VIH or IPTL program with progressive overload. Blood markers, subjective measures, cardiac indices, near-infrared spectroscopy indices, inspiratory muscle fatigue, and RMT-induced training load were monitored pre-, in and post-sessions. We used multiple ANOVA to investigate effects of sex, training method, and time on measured parameters. Results: There were significant interactions for acid-base balance (p = 0.04 for sex, p < 0.001 for method), partial carbon dioxide pressure (p = 0.03 for sex, p < 0.001 for method), bicarbonate (p = 0.01 for method), lactate (p < 0.001 for method), RMT-induced training load (p = 0.001 for method for single session, p = 0.03 for method per week), average heart rate (p = 0.03 for sex), maximum heart rate (p = 0.02 for sex), intercostales muscle oxygenation (p = 0.007 for testing week), and intercostales muscle oxygenation recovery (p = 0.003 for testing week and p = 0.007 for method). Conclusion: We found that RMT induced additional load in well-trained triathletes. Elicited changes in monitored variables depend on sex and training method. VIH significantly increased subjective training load measures. IPTL was associated with disbalance in blood gasometry, increase in lactate, and reports of headaches and dizziness. Both methods should be applied with consideration in high-performance settings.

Maximal respiratory pressures: Measurements at functional residual capacity in individuals with different health conditions using a digital manometer

BACKGROUND

Measuring maximal respiratory pressure is a widely used method of investigating the strength of inspiratory and expiratory muscles.

OBJECTIVES

To compare inspiratory pressures obtained at functional residual capacity (FRC) with measures at residual volume (RV), and expiratory pressures obtained at FRC with measures at total lung capacity (TLC) in individuals with different health conditions: post-COVID-19, COPD, idiopathic pulmonary fibrosis (IPF), heart failure (CHF), and stroke; and to compare the mean differences between measurements at FRC and RV/TLC among the groups.

METHODS

Inspiratory and expiratory pressures were obtained randomly at different lung volumes. Mixed factorial analysis of covariance with repeated measures was used to compare measurements at different lung volumes within and among groups.

RESULTS

Seventy-five individuals were included in the final analyses (15 individuals with each health condition). Maximal inspiratory pressures at FRC were lower than RV [mean difference (95% CI): 11.3 (5.8, 16.8); 8.4 (2.3, 14.5); 11.1 (5.5, 16.7); 12.8 (7.1, 18.4); 8.0 (2.6, 13.4) for COVID-19, COPD, IPF, CHF, and stroke, respectively] and maximal expiratory pressures at FRC were lower than TLC [mean difference (95% CI): 51.9 (37.4, 55.5); 60.9 (44.2, 77.7); 62.9 (48.1, 77.8); 58.0 (43.9, 73.8); 57.2 (42.9, 71.6) for COVID-19, COPD, IPF, CHF, and stroke, respectively]. All mean differences were similar among groups.

CONCLUSION

Although inspiratory and expiratory pressures at FRC were lower than measures obtained at RV/TLC for the five groups of health conditions, the mean differences between measurements at different lung volumes were similar among groups, which raises the discussion about the influence of the viscoelastic properties of the lungs on maximal respiratory pressure.

The Effects of Respiratory Muscle Training on Resting-State Brain Activity and Thoracic Mobility in Healthy Subjects: A Randomized Controlled Trial

BACKGROUND

Although inspiratory muscle training (IMT) is an effective intervention for improving breath perception, brain mechanisms have not been studied yet.

PURPOSE

To examine the effects of IMT on insula and default mode network (DMN) using resting-state functional MRI (RS-fMRI).

STUDY TYPE

Prospective.

POPULATION

A total of 26 healthy participants were randomly assigned to two groups as IMT group (n = 14) and sham IMT groups (n = 12).

FIELD STRENGTH/SEQUENCE

A 3-T, three-dimensional T2* gradient-echo echo planar imaging sequence for RS-fMRI was obtained.

ASSESSMENT

The intervention group received IMT at 60% and sham group received at 15% of maximal inspiratory pressure (MIP) for 8 weeks. Pulmonary and respiratory muscle function, and breathing patterns were measured. Groups underwent RS-fMRI before and after the treatment.

STATISTICAL TESTS

Statistical tests were two-tailed P < 0.05 was considered statistically significant. Student's t test was used to compare the groups. One-sample t-test for each group was used to reveal pattern of functional connectivity. A statistical threshold of P < 0.001 uncorrected value was set at voxel level. We used False discovery rate (FDR)-corrected P < 0.05 cluster level.

RESULTS

The IMT group showed more prominent alterations in insula and DMN connectivity than sham group. The MIP was significantly different after IMT. Respiratory rate (P = 0.344), inspiratory time (P = 0.222), expiratory time (P = 1.000), and inspiratory time/total breath time (P = 0.572) of respiratory patterns showed no significant change after IMT. All DMN components showed decreased, while insula showed increased activation significantly.

DATA CONCLUSION

Differences in brain activity and connectivity may reflect improved ventilatory perception with IMT with a possible role in regulating breathing pattern by processing interoceptive signals.

EVIDENCE LEVEL

2 TECHNICAL EFFICACY: Stage 4.

Effects on Respiratory Pressures, Spirometry Biomarkers, and Sports Performance after Inspiratory Muscle Training in a Physically Active Population by Powerbreath®: A Systematic Review and Meta-Analysis

Sports performance in athletes can be limited by respiratory factors, so it is understandable to propose that inspiratory muscle training (IMT) can improve respiratory function and exercise performance. Power-Breathe^® (PwB) is a sectorized respiratory muscle training tool that uses a resistive load to train IMT. There is currently a growing interest in respiratory muscle training, so we set out to systematically assess the effects of IMT with PwB on respiratory parameters and athletic performance in physically active, healthy adults. Based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline, the Cochrane and PEDro scales to assess methodological quality, effect size using the Rosenthal formula, and the Cochrane tool for estimation of risk of bias, studies searchable in Medline, Web of Science, and Cochrane. In addition, for the performance of the meta-analysis, the documentation and quantification of the heterogeneity in each meta-analysis were directed through the Cochran's Q test and the I2 statistic; in addition, a publication bias analysis was performed using funnel plots. Of the total of 241 studies identified in the search, 11 studies for the systematic review and nine for the meta-analysis met the exclusion and/or inclusion criteria. IMT, with PwB, showed significant improvements in maximal inspiratory pressure (MIP) and substantial improvements in forced vital capacity (FVC) in the meta-analysis results. Also, sports performance was significantly increased by IMT with PwB. In conclusion, the use of PwB is an IMT tool that improves respiratory and sports performance.

Inspiratory Muscle Training in Obstructive Sleep Apnea Associating Diabetic Peripheral Neuropathy: A Randomized Control Study

Objective

This work is aimed at assessing the effects of inspiratory muscle training on lung functions, inspiratory muscle strength, and aerobic capacity in diabetic peripheral neuropathy (DPN) patients with obstructive sleep apnea (OSA).

Methods

A randomized control study was performed on 55 patients diagnosed with DPN and OSA. They were assigned to the training group (IMT, n = 28) and placebo training group (P-IMT, n = 27). Inspiratory muscle strength, lung functions, and aerobic capacity were evaluated before and after 12 weeks postintervention. An electronic inspiratory muscle trainer was conducted, 30 min a session, three times a week for 12 consecutive weeks.

Results

From seventy-four patients, 55 have completed the study program. A significant improvement was observed in inspiratory muscle strength (p < 0.05) in the IMT group while no changes were observed in the P-IMT group (p > 0.05). No changes were observed in the lung function in the two groups (p > 0.05). Also, VO₂max and VCO₂max changed significantly after training in the IMT group (p < 0.05) while no changes were observed in the P-IMT group (p > 0.05). Other cardiopulmonary exercise tests did not show any significant change in both groups (p > 0.05).

Conclusions

Based on the outcomes of the study, it was found that inspiratory muscle training improves inspiratory muscle strength and aerobic capacity without a notable effect on lung functions for diabetic patients suffering from DPN and OSA.

Effect of Inspiratory Muscle Training on Performance of Handball Athletes

Inspiratory muscle training (IMT) is a strategy that has been used to improve performance in different sports modalities. This study investigated the effects of an IMT program on respiratory muscle strength and resistance as well as aerobic physical performance (PP) of handball athletes. Nineteen 20 ± 3 year-old male athletes were allocated into an experimental (EG, n = 10) or a placebo group (PG, n = 9). Their respiratory muscle strength was evaluated by measuring the maximum inspiratory and expiratory pressures (MIP and MEP), muscular respiratory resistance by maximum voluntary ventilation (MVV) and aerobic PP by the cardiopulmonary exercise test. The study was designed to evaluate the effects of a 12-week IMT program with five sessions a week. A significant difference was observed in the pre and post IMT values of the MIP (170 ± 34 to 262 ± 33 cmH2O) and MEP (177 ± 36 to 218 ± 37 cmH2O) in the EG, and MIP (173 ± 45 to 213 ± 21 cmH2O) in the PG, with a large effect size for the MIP, when the groups were compared. MVV showed a significant increase (162 ± 24 to 173 ± 30 L) in the EG, with a small effect size. There was a significant difference in maximum oxygen uptake (54 ± 8 to 60 ± 7 ml/kg/min) in aerobic PP. Oxygen uptake at the respiratory compensation point (RCP) (46 ± 6 to 50 ± 5 ml/kg/min), with a moderate effect size for both variables, was observed in the EG after IMT. We concluded that IMT provided a significant increase in respiratory muscle strength and resistance, contributing to increased aerobic PP in the EG, which suggests that IMT could be incorporated in handball players' training.

Safety and efficacy of inspiratory muscle training for preventing adverse outcomes in patients at risk of prolonged hospitalisation

Background

The early institution of inspiratory muscle training on hospitalised patients with no established respiratory deficits could prevent in-hospital adverse outcomes that are directly or indirectly associated to the loss of respiratory muscle mass inherent to a prolonged hospital stay. The objective of the clinical trial is to assess the impact of inspiratory muscle training on hospital inpatient complications.

Methods

This is a double-blind randomised controlled trial. Subjects in the intervention group underwent an inspiratory muscle training loaded with 50% maximum inspiratory pressure twice daily for 4 weeks from study enrolment. Patients were randomly assigned to an inspiratory muscle training group or a sham inspiratory muscle training group. All patients received conventional physiotherapy interventions. Baseline and post-intervention respiratory and peripheral muscle strength, functionality (performance of activities of daily living), length of hospital stay, and death were evaluated. Clinical outcomes were assessed until hospital discharge. This study was approved by the Institutional Hospital Ethics Committee (03/2014).

Results

Thirty-one patients assigned to the inspiratory muscle training group and 34 to the sham inspiratory muscle training group were analysed. Patients in the inspiratory muscle training group had a shorter mean length of hospital stay (35.3 ± 2.7 vs. 41.8 ± 3.5 days, p < 0.01) and a lower risk of endotracheal intubation (relative risk (RR) = 0.36; 95% confidence interval (CI) 0.27–0.97; p = 0.03) as well as muscle weakness (RR = 0.36; 95% CI 0.19–0.98; p = 0.02) and mortality (RR = 0.23; 95% CI 0.2–0.94; p = 0.04). The risk of adverse events did not differ significantly between groups.

Conclusion

Inspiratory muscle training was a protective factor against endotracheal intubation, muscle weakness, and mortality.

Trial registration

ClinicalTrials.gov, ID: NCT02459444. Registered on 19 May 2015.

Activation of respiratory muscles during respiratory muscle training

It is unknown which respiratory muscles are mainly activated by respiratory muscle training. This study evaluated Inspiratory Pressure Threshold Loading (IPTL), Inspiratory Flow Resistive Loading (IFRL) and Voluntary Isocapnic Hyperpnea (VIH) with regard to electromyographic (EMG) activation of the sternocleidomastoid muscle (SCM), parasternal muscles (PARA) and the diaphragm (DIA) in randomized order. Surface EMG were analyzed at the end of each training session and normalized using the peak EMG recorded during maximum inspiratory maneuvers (Sniff nasal pressure: SnPna, maximal inspiratory mouth occlusion pressure: PImax). 41 healthy participants were included. Maximal activation was achieved for SCM by SnPna; the PImax activated predominantly PARA and DIA. Activations of SCM and PARA were higher in IPTL and VIH than for IFRL (p<0.05). DIA was higher applying IPTL compared to IFRL or VIH (p<0.05). IPTL, IFRL and VIH differ in activation of inspiratory respiratory muscles. Whereas all methods mainly stimulate accessory respiratory muscles, diaphragm activation was predominant in IPTL.

Use of Powerbreathe® in inspiratory muscle training for athletes: systematic review

Abstract Introduction: Inspiratory muscle training (IMT) has been used as part of athletic training. It is beneficial due to an increase in respiratory capacity, and can be related to the optimization of exercise tolerance. There are a growing number of publications on the subject, however the methodological rigor of these publications is still unknown. Objective: To perform a systematic literature review in order to analyze the effects of Powerbreathe® on inspiratory muscle training by athletes. Methods: Original scientific studies published in English, from 2000 to 2015, were included. Their typology was classified. The literature search was performed in the Lilacs, Medline, Pubmed, and Scielo databases using the following keywords: inspiratory muscle training, athletes, and Sports medicine (in English), treinamento muscular inspiratório, atleta, medicina esportiva (in Portuguese). Results: Inspiratory muscle training with specific linear resistance has been used in some athletic training, and its results are promising. However, its application is still recent and generally supported by experiments with limited population and which do not properly define the confounding factors for the results. Conclusion: The state of the art suggests that IMT is useful as a respiratory therapy supporting the training of athletes for some specific sports. However, there is a scarcity of studies of high methodological quality, thus requiring further experiments on the subject.

Determinants of inspiratory muscle strength in healthy humans

We investigated (1) the relationship between the baseline and inspiratory muscle training (IMT) induced increase in maximal inspiratory pressure (P(I,max)) and (2) the relative contributions of the inspiratory chest wall muscles and the diaphragm (P(oes)/P(di)) to P(I,max) prior to and following-IMT. Experiment 1: P(I,max) was assessed during a Müeller manoeuvre before and after 4-wk IMT (n=30). Experiment 2: P(I,max) and the relative contribution of the inspiratory chest wall muscles to the diaphragm (P(oes)/P(di)) were assessed during a Müeller manoeuvre before and after 4-wk IMT (n=20). Experiment 1: P(I,max) increased 19% (P<0.01) post-IMT and was correlated with baseline P(I,max) (r=-0.373, P<0.05). Experiment 2: baseline P(I,max) was correlated with P(oe)/P(di) (r=0.582, P<0.05) and after IMT PI,max increased 22% and Poe/Pdi increased 5% (P<0.05). In conclusion, baseline P(I,max) and the contribution of the chest wall inspiratory muscles relative to the diaphragm affect, in part, baseline and IMT-induced P(I,max). Great care should be taken when designing future IMT studies to ensure parity in the between-subject baseline P(I,max).

[Inspiratory muscles strength training in recreational athletes]

INTRODUCTION

Respiratory muscles strength and endurance influence athletic performance. Besides conventional spirometry, sniff test, inspiratory and expiratory maximal pressures can directly assess respiratory muscle strength. Respiratory muscles can be train through a device offering inspiratory and expiratory resistance.

METHODS

Nineteen subjects aged 18 to 30 years and practicing leisure sport trained inspiratory muscles on Powerbreathe(®) for eight weeks. Resistance was set at 85% of maximal inspiratory pressure determined during a preliminary session. Evaluation was made trough voluntary and non-invasive methods on Macro 5000(®) (PI max, PE max and sniff test).

RESULTS

An increase of 21.77% of the maximum inspiratory pressure, 17% of the maximum expiratory pressure and 18% of the sniff test are recorded after eight weeks of training.

CONCLUSIONS

A specific training of inspiratory muscles (Powerbreathe(®) Sports performance) increases the power of these muscles (voluntary and non-invasive tests).

Pre-operative inspiratory muscle training preserves postoperative inspiratory muscle strength following major abdominal surgery - a randomised pilot study

INTRODUCTION

The aim of this pilot study was to assess the effect of pre-operative inspiratory muscle training (IMT) on respiratory variables in patients undergoing major abdominal surgery.

PATIENTS AND METHODS

Respiratory muscle strength (maximum inspiratory [MIP] and expiratory [MEP] mouth pressure) and pulmonary functions were measured at least 2 weeks before surgery in 80 patients awaiting major abdominal surgery. Patients were then allocated randomly to one of four groups (Group A, control; Group B, deep breathing exercises; Group C, incentive spirometry; Group D, specific IMT). Patients in groups B, C and D were asked to train twice daily, each session lasting 15 min, for at least 2 weeks up to the day before surgery. Outcome measurements were made immediately pre-operatively and postoperatively.

RESULTS

In groups A, B and C, MIP did not increase from baseline to pre-operative assessments. In group D, MIP increased from 51.5 cmH(2)O (median) pre-training to 68.5 cmH(2)O (median) post-training pre-operatively (P < 0.01). Postoperatively, groups A, B and C showed a fall in MIP from baseline (P < 0.01, P < 0.01) and P = 0.06, respectively). No such significant reduction in postoperative MIP was seen in group D (P = 0.36).

CONCLUSIONS

Pre-operative specific IMT improves MIP pre-operatively and preserves it postoperatively. Further studies are required to establish if this is associated with reduced pulmonary complications.

Chest wall volume changes during inspiratory loaded breathing

We assessed the effect of inspiratory loaded breathing (ILB) on respiratory muscle strength and investigated the extent to which respiratory muscle fatigue is associated with chest wall volume changes during ILB. Twelve healthy subjects performed ILB at 76 ± 11% of maximal inspiratory mouth pressure (MIP) for 1h. MIP and breathing pattern during 3 min of normocapnic hyperpnea (NH) were measured before and after ILB. Breathing pattern and chest wall volume changes were assessed by optoelectronic plethysmography. After ILB, six subjects decreased MIP significantly (-16 ± 10%; p < 0.05), while the other six subjects did not (0 ± 7%, p = 0.916). Only subjects with decreased MIP after ILB lowered end-expiratory rib cage volume (volume at which inspiration is initiated) below resting values during ILB. During NH after ILB, tidal volume was smaller in subjects with decreased MIP (-19 ± 16%, p < 0.05), while it remained unchanged in the other group (-3 ± 11%, p = 0.463). These results suggest that respiratory muscle fatigue depends on the lung volume from which inspiratory efforts are made during ILB.

Isocapnic hyperpnea training improves performance in competitive male runners

The effects of voluntary isocapnic hyperpnea (VIH) training (10 h over 4 weeks, 30 min/day) on ventilatory system and running performance were studied in 15 male competitive runners, 8 of whom trained twice weekly for 3 more months. Control subjects (n = 7) performed sham-VIH. Vital capacity (VC), FEV1, maximum voluntary ventilation (MVV), maximal inspiratory and expiratory mouth pressures, VO2max, 4-mile run time, treadmill run time to exhaustion at 80% VO2max, serum lactate, total ventilation (V(E)), oxygen consumption (VO2) oxygen saturation and cardiac output were measured before and after 4 weeks of VIH. Respiratory parameters and 4-mile run time were measured monthly during the 3-month maintenance period. There were no significant changes in post-VIH VC and FEV1 but MVV improved significantly (+10%). Maximal inspiratory and expiratory mouth pressures, arterial oxygen saturation and cardiac output did not change post-VIH. Respiratory and running performances were better 7- versus 1 day after VIH. Seven days post-VIH, respiratory endurance (+208%) and treadmill run time (+50%) increased significantly accompanied by significant reductions in respiratory frequency (-6%), V(E) (-7%), VO2 (-6%) and lactate (-18%) during the treadmill run. Post-VIH 4-mile run time did not improve in the control group whereas it improved in the experimental group (-4%) and remained improved over a 3 month period of reduced VIH frequency. The improvements cannot be ascribed to improved blood oxygen delivery to muscle or to psychological factors.

The influence of inspiratory and expiratory muscle training upon rowing performance

We investigated the effect of 4 week of inspiratory (IMT) or expiratory muscle training (EMT), as well as the effect of a subsequent 6 week period of combined IMT/EMT on rowing performance in club-level oarsmen. Seventeen male rowers were allocated to either an IMT (n = 10) or EMT (n = 7) group. The groups underwent a 4 week IMT or EMT program; after interim testing, both groups subsequently performed a 6 week program of combined IMT/EMT. Exercise performance and physiological responses to exercise were measured at 4 and 10 week during an incremental rowing ergometer 'step-test' and a 6 min all-out (6MAO) effort. Pressure threshold respiratory muscle training was undertaken at the 30 repetition maximum load (approximately 50% of the peak inspiratory and expiratory mouth pressure, P (Imax) or P (Emax), respectively). P (Imax) increased during the IMT phase of the training in the IMT group (26%, P < 0.001) and was accompanied by an improvement in mean power during the 6MAO (2.7%, P = 0.015). Despite an increase in P (Emax) by the end of the intervention (31%, P = 0.03), the EMT group showed no significant changes in any performance parameters during either the 'step-test' or 6MAO. There were no significant changes in breathing pattern or the metabolic response to the 6MAO test in either group, but the IMT group showed a small decrease in HR (2-5%, P = 0.001). We conclude that there were no significant additional changes following combined IMT/EMT. IMT improved rowing performance, but EMT and subsequent combined IMT/EMT did not.

Muscle metabolism and exercise tolerance in COPD

This article explores the hypothesis that dyspnea in patients with COPD arises from an imbalance between the load placed on the respiratory muscle pump and its capacity. Evidence to support this concept is presented, and possible therapeutic approaches are discussed.