Asthma is a pathological condition comprising of a variety of symptoms which affect the ability to function in daily life. Due to the high prevalence of asthma and associated healthcare costs, it is important to identify low-cost alternatives to traditional pharmacotherapy. One of these low cost alternatives is the use of inspiratory muscle training (IMT), which is a technique aimed at increasing the strength and endurance of the diaphragm and accessory muscles of respiration. IMT typically consists of taking voluntary inspirations against a resistive load across the entire range of vital capacity while at rest. In healthy individuals, the most notable benefits of IMT are an increase in diaphragm thickness and strength, a decrease in exertional dyspnea, and a decrease in the oxygen cost of breathing. Due to the presence of expiratory flow limitation in asthma and exercise-induced bronchoconstriction, dynamic lung hyperinflation is common. As a result of varying operational lung volumes, due in part to hyperinflation, the respiratory muscles may operate far from the optimal portion of the length-tension curve, and thus may be forced to operate against a low pulmonary compliance. Therefore, the ability of these muscles to generate tension is reduced, and for any given level of ventilation, the work of breathing is increased as compared to non-asthmatics. Evidence that IMT is an effective treatment for asthma is inconclusive, due to limited data and a wide variation in study methodologies. However, IMT has been shown to decrease dyspnea, increase inspiratory muscle strength, and improve exercise capacity in asthmatic individuals. In order to develop more concrete recommendations regarding IMT as an effective low-cost adjunct in addition to traditional asthma treatments, we recommend that a standard treatment protocol be developed and tested in a placebo-controlled clinical trial with a large representative sample.
KEYWORDS: Respiratory muscles; asthma treatment; exercise tolerance; lung hyperinflation; pulmonary function
PMID: 27094568 DOI: 10.1080/00913847.2016.1176546

RATIONALE: The relationship of functional parameters such as lung mechanics, chest kinematics, metabolism and peripheral and respiratory muscle function with the level of exercise tolerance remains a controversial subject. While it has been previously shown that pulmonary rehabilitation is capable of improving exercise tolerance in patients afflicted by COPD, as expressed by values of 6-minute walking test (6MWT), the degree of contribution to this change by each of the aforementioned parameters remains unclear.
AIMS: To investigate the correlation between changes in exercise capacity and other functional markers following pulmonary rehabilitation in COPD and to determine which parameters are more closely related to improvements of exercise tolerance.
MATERIALS AND METHODS: Three hundred and twenty-seven patients with COPD (with average, 95% CI for forced expiratory volume in the first second [FEV1]: 45% [25%-83%] predicted, age: 64 [48-80] years, and BMI: 27 [13.5-40.4] kg/m2) participated in this study. Thirty percent of the patients had pulmonary hypertension as comorbidity. Patients underwent a pulmonary rehabilitation program with 20-30 minutes sessions two to three times per day for 4 weeks. The program was composed of chest wall-stretching, controlled breathing exercises, and a personalized training schedule for cycling and treadmill use. Measurements of 6MWT, lung function, chest wall expansion, grip strength, maximal inspiratory pressure, and breath holding time were taken. The Body mass index, airflow Obstruction, Dyspnea and Exercise capacity (BODE-index), body mass index [BMI], FEV1, 6MWT, modified Medical Research Dyspnea Scale score, and an alternative scale score (for BMI, FEV1, 6MWT, and COPD Assessment Test) were calculated.
RESULTS: Rehabilitation resulted in a generalized improvement in 6MWT among patients (average: 360 [95% CI: 178-543 m] vs average: 420 [95% CI: 238-601 m], p<0.05). Improvements in exercise tolerance were found to be most closely associated with changes in composite BODE-index (R2=-0.6), Alternative Scale (R2=-0.56), dyspnea score (modified Medical Research Dyspnea Scale R2=-0.54), and health status (COPD Assessment Test R2=-0.4, p<0.05). In addition, improvements in exercise tolerance were found to moderately correlate with improvements in inspiratory vital capacity (IVC, R2=0.34, p<0.05). Post-rehabilitation changes in IVC displayed a connection with grip strength (R2=0.6) and chest expansion (R2=0.48).
CONCLUSION: Enhancements in exercise tolerance had correlation with changes in IVC, BODE-index, and the new Alternative Scale. However, comprehensive assessment needs to include considerations of chest kinematics and peripheral and respiratory muscle function as well.
PMID: 29535512 PMCID: PMC5836697 DOI: 10.2147/COPD.S153525

PURPOSE: The aim of our study was to assess the long-term effects of specific inspiratory muscle training (IMT) in patients with neuromuscular disorders (NMDs) who have various degrees of respiratory impairment.
PATIENTS AND METHODS: Twenty-seven patients with NMDs (Duchenne's muscular dystrophy, 18 patients; spinal muscular atrophy, 9 patients) underwent 24 months of IMT. Patients were divided into three groups according to their vital capacity (VC) values. VC was measured as the parameter for the respiratory system involvement of the disease. Maximal inspiratory pressure (PImax) was assessed as the parameter for respiratory muscle strength, and the results of the 12-s maximum voluntary ventilation test (12sMVV) were assessed as the parameter for respiratory muscle endurance. Pulmonary and inspiratory muscle function parameters were assessed 6 months before training, at the beginning of training, and then every 3 months.
RESULTS: The PImax values improved in group A (VC, 27 to 50% predicted) from 51.45 to 87.00 cm H(2)O, in group B (VC, 51 to 70% predicted) from 59.38 to 94.4 cm H(2)O, and in group C (VC, 71 to 96% predicted) from 71.25 to 99.00 cm H(2)O. The 12sMVV values improved in group A from 52.69 to 69.50 L/min, in group B from 53.18 to 62.40 L/min, and in group C from 59.48 to 70.5 L/min. For all three groups, there was a significant improvement of PImax (p < 0.007) and 12sMVV (p < 0.015) until the 10th month when a plateau phase was reached with no decline in the following month until the end of training.
CONCLUSION: With IMT, respiratory muscle function can be improved in the long term of up to 2 years.
PMID: 11555507 DOI: 10.1378/chest.120.3.765

Respiratory impairment, due to respiratory muscle weakness, is a major cause of morbidity and mortality in patients with amyotrophic lateral sclerosis/motor neuron disease (ALS/MND). Threshold loading may strengthen the inspiratory muscles and thereby improve patient prognosis. A phase II, double-blind, randomized-controlled trial was undertaken to determine whether a 12-week inspiratory muscle training programme attenuated the decline in respiratory function and inspiratory muscle strength in patients with ALS/MND. Nine patients were randomized to inspiratory muscle training and 10 to sham training. Primary endpoints were respiratory function (forced vital capacity, vital capacity), lung volumes and inspiratory muscle strength. Patients were assessed before, during and immediately after a 12-week training period, and at eight weeks follow-up. While improvements in inspiratory muscle strength were observed in both treatment arms, there was a non-significant increase in maximum inspiratory pressure of 6.1% in the experimental group compared to controls (standard error of mean, 6.93%; 95% confidence interval -8.58 -20.79; p=0.39). The gains in inspiratory muscle strength were partially reversed during a period of training cessation. In conclusion, inspiratory muscle training may potentially strengthen the inspiratory muscles and slow the decline in respiratory function in patients with ALS/MND.
PMID: 19922129 DOI: 10.3109/17482960903082218

PURPOSE: We have shown that individuals with recurrent nonspecific low back pain (LBP) and healthy individuals breathing against an inspiratory load decrease their reliance on back proprioceptive signals in upright standing. Because individuals with LBP show greater susceptibility to diaphragm fatigue, it is reasonable to hypothesize that LBP, diaphragm dysfunction, and proprioceptive use may be interrelated. The purpose of this study was to investigate whether inspiratory muscle training (IMT) affects proprioceptive use during postural control in individuals with LBP.
METHODS: Twenty-eight individuals with LBP were assigned randomly into a high-intensity IMT group (high IMT) and low-intensity IMT group (low IMT). The use of proprioception in upright standing was evaluated by measuring center of pressure displacement during local muscle vibration (ankle, back, and ankle-back). Secondary outcomes were inspiratory muscle strength, severity of LBP, and disability.
RESULTS: After high IMT, individuals showed smaller responses to ankle muscle vibration, larger responses to back muscle vibration, higher inspiratory muscle strength, and reduced LBP severity (P < 0.05). These changes were not seen after low IMT (P > 0.05). No changes in disability were observed in either group (P > 0.05).
CONCLUSIONS: After 8 wk of high IMT, individuals with LBP showed an increased reliance on back proprioceptive signals during postural control and improved inspiratory muscle strength and severity of LBP, not seen after low IMT. Hence, IMT may facilitate the proprioceptive involvement of the trunk in postural control in individuals with LBP and thus might be a useful rehabilitation tool for these patients.
PMID: 24870567 DOI: 10.1249/MSS.0000000000000385