Respiratory muscle endurance training in obese patients

Obesity and the Importance of Breathing

Obesity is a complex and non-communicable disease with a pandemic entity. Currently, multiple causes can lead to obesity, and it is not always easy to create a direct relationship between physical inactivity, poor quality of nutrients consumed, and calculation of excess calories. Among the associated comorbidities, obesity creates a dysfunctional environment of respiratory rhythms at the central and peripheral levels, with functional, morphological, and phenotypic alteration of the diaphragm muscle. This pathological adaptation of breathing is one of the most important causes of the dysregulation of the autonomic system, which will negatively affect the progression of comorbidities and chronic non-physiological adaptations in obese persons. Introducing a physical activity program involving diaphragm training could be a very valid strategy to restore the systemic autonomic response, delaying or avoiding the onset of pathologies in excess fat. This brief narrative review focuses on the importance of breathing in obese subjects.

A Randomized Trial of Inspiratory Training in Children and Adolescents With Obesity

Introduction: Children with obesity suffer excess dyspnea that contributes to sedentariness. Developing innovative strategies to increase exercise tolerance and participation in children with obesity is a high priority. Because inspiratory training (IT) has reduced dyspnea, we sought to assess IT in children with obesity. Methods: We conducted a 6-week randomized IT trial involving 8- to 17-year-olds with obesity. Participants were randomized 1:1 to either high [75% of maximal inspiratory pressure (MIP)] or low resistance control (15% of MIP) three times weekly. Assessments included adherence, patient satisfaction, and changes in inspiratory strength and endurance, dyspnea scores and total activity level. Results: Among 27 randomized, 24 (89%) completed the intervention. Total session adherence was 72% which did not differ between treatment groups. IT was safe, and more than 90% felt IT benefitted breathing and general health. IT led to a mean improvement (95% CI) in inspiratory strength measured by MIP of 10.0 cm H2O (-3.5, 23.6; paired t-test, p = 0.139) and inspiratory endurance of 8.9 (1.0, 16.8; paired t-test, p = 0.028); however, there was no significant difference between high- and low-treatment groups. IT led to significant reductions in dyspnea with daily activity (p < 0.001) and in prospectively reported dyspnea during exercise (p = 0.024). Among the high- versus low-treatment group, we noted a trend for reduced dyspnea with daily activity (p = 0.071) and increased daily steps (865 vs. -51, p = 0.079). Discussion: IT is safe and feasible for children with obesity and holds promise for reducing dyspnea and improving healthy activity in children with obesity. Breathe-Fit trial NCT05412134.

The molecular mechanism of obesity: The science behind natural exercise yoga and healthy diets in the treatment of obesity

The review centers on the scientific evidence underlying obesity, providing a detailed examination of the role of perilipin in this condition. It explores potential causes of obesity and delves into therapeutic approaches involving exercise, yoga, and herbal treatments. The paper discusses natural sources that can contribute to combating obesity and underscores the importance of exercise in a scientific context for overcoming obesity. Additionally, it includes information on herbal ingredients that aid in reducing obesity. The review also examines the impact of exercise type and intensity at various time intervals on muscle development. It elucidates triglyceride hydrolysis through different enzymes and the deposition of fatty acids in adipose tissue. The mechanisms by which alpha/beta hydrolase domain-containing protein 5 (ABHD5) and hormone-sensitive lipase (HSL) target and activate their functions are detailed. The inflammatory response in obesity is explored, encompassing inflammatory markers, lipid storage diseases, and their classification with molecular mechanisms. Furthermore, the hormonal regulation of lipolysis is elaborated upon in the review.

Determination of the minimal important difference for inspiratory muscle strength in people with severe and very severe COPD

OBJECTIVE

Inspiratory muscle training is recommended for people with chronic obstructive pulmonary disease (COPD) with inspiratory muscle weakness. Clinical interpretation of changes in inspiratory muscle strength could be helped by the determination of cut-off values. The aim of this study was to estimate the minimal important difference for inspiratory muscle strength assessed with maximal inspiratory pressure (MIP) in people with COPD.

DESIGN

Post hoc analysis of a randomized controlled trial (EMI2 study) including people with severe to very severe COPD undergoing a pulmonary rehabilitation program was conducted. The determination of the minimal important difference was realized using both anchor-based and distribution-based methods.

SETTING

The study includes patients admitted to the rehabilitation program unit of the Centre Hospitalier des Pays de Morlaix (Morlaix, France) between March 5, 2014 and September 8, 2016.

PARTICIPANTS

Seventy-three people with severe to very severe COPD (age 62.2  ±  8.0 years, forced expiratory volume in 1 s 36.4  ±  9.5% of theoretical) were analyzed.

INTERVENTION

Patients followed a standardized pulmonary rehabilitation program 5 days a week for 4 weeks. The program included aerobic training, ground-based outdoor walking training, and strengthening of lower and upper limb muscles.

MAIN MEASURES

At the end of the pulmonary rehabilitation program, MIP improved by 14.8  ±  14.9 cmH2O (p < 0.05). Regarding the anchor-based method, only the modified Medical Research Council was selected as an appropriate anchor. The receiver operating characteristic curve analysis reported a minimal important difference of 13.5 cmH2O (sensibility: 75% specificity: 67.5%). Using distribution-based methods, the estimate of minimal important difference was 7.9 cmH2O (standard error of measurement method) and 10.9 cmH2O (size effect method).

RESULTS

The estimations proposed by this study ranged from 7.9 to 13.5 cmH2O.

CONCLUSIONS

The measurement of minimal important difference is a simple tool for assessing the changes of inspiratory muscle strength during a pulmonary rehabilitation program. We propose a minimal important difference of 13.5 cmH2O for the improvement of MIP. Further studies are needed to confirm this estimation.ClinicalTrials.gov identifier: NCT02074813.

Inspiratory Muscle Rehabilitation Training in Pediatrics: What Is the Evidence?

Pulmonary rehabilitation is typically used for reducing respiratory symptoms and improving fitness and quality of life for patients with chronic lung disease. However, it is rarely prescribed and may be underused in pediatric conditions. Pulmonary rehabilitation can include inspiratory muscle training that improves the strength and endurance of the respiratory muscles. The purpose of this narrative review is to summarize the current literature related to inspiratory muscle rehabilitation training (IMRT) in healthy and diseased pediatric populations. This review highlights the different methods of IMRT and their effects on respiratory musculature in children. Available literature demonstrates that IMRT can improve respiratory muscle strength and endurance, perceived dyspnea and exertion, maximum voluntary ventilation, and exercise performance in the pediatric population. These mechanistic changes help explain improvements in symptomology and clinical outcomes with IMRT and highlight our evolving understanding of the role of IMRT in pediatric patients. There remains considerable heterogeneity in the literature related to the type of training utilized, training protocols, duration of the training, use of control versus placebo, and reported outcome measures. There is a need to test and refine different IMRT protocols, conduct larger randomized controlled trials, and include patient-centered clinical outcomes to help improve the evidence base and support the use of IMRT in patient care.

Effect of Threshold Inspiratory Muscle Training on Functional Fitness and Respiratory Muscle Strength Compared to Incentive Spirometry in Children and Adolescents With Obesity: A Randomized Controlled Trial

BACKGROUND

To determine the effect of threshold inspiratory muscle training (IMT) on functional fitness and respiratory muscle strength (RMS) compared to incentive spirometry (IS) in children/adolescents with obesity.

METHODS

A total of 60 obese children/adolescents aged 8-15 years were randomized into the threshold IMT group (n = 20), the IS group (n = 20), or the control group (n = 20). The IMT group performed 30 inspiratory breaths with the intensity set at 40% of baseline maximal inspiratory pressure (MIP) twice daily for 8 weeks; the IS group performed 30 breaths with sustained maximum inspiration twice daily for 8 weeks; and, the control group was assigned no training device for 8 weeks. Six-min walk test (6-MWT), RMS, and spirometry were compared between baseline and 8 weeks.

RESULTS

Six-MWT distance (528.5 ± 36.2 vs. 561.5 ± 35.2 m, p = 0.002) and MIP (121.2 ± 26.8 vs. 135.3 ± 32.1%Predicted, p = 0.03) were significantly improved after 8 weeks of IMT training. There was no significant difference in any evaluated pulmonary function parameters between baseline and 8 weeks in the IS or control groups; however, 6-MWT distance demonstrated a trend toward significant improvement in the IS group (526.9 ± 59.1 vs.549.0 ± 50.6 m, p = 0.10). No significant difference among groups was found for any variable relative to change from baseline to post-training.

CONCLUSION

Eight weeks of threshold IMT training significantly improved both inspiratory muscle strength (MIP) and functional fitness (6-MWT) in children/adolescents with obesity. Eight weeks of IS training yielded a trend toward significantly improved functional fitness.

Is there a role of pulmonary rehabilitation in extrapulmonary diseases frequently encountered in the practice of physical medicine and rehabilitation?

There is a group of diseases such as low back pain, osteoporosis, fibromyalgia and obesity for which pulmonary rehabilitation can be applied. Although these diseases do not directly impact the lungs, respiratory dysfunction occurs through various mechanisms during the disease process and complicates the underlying primary disease. Respiratory dysfunction and spirometric abnormalities have been observed from the early stages of these diseases, even without obvious signs and symptoms. These patients should be carefully evaluated for pulmonary problems as a sedentary lifestyle may hide the presence of respiratory symptoms. Once pulmonary problems have been detected, pulmonary rehabilitation should be added to the routine treatment of the primary disease.

Acute Cardiopulmonary and Muscle Oxygenation Responses to Normocapnic Hyperpnea Exercise in COPD

PURPOSE

This study aimed to investigate cardiorespiratory responses and intercostal muscle oxygenation during normocapnic hyperpnea exercise in chronic obstructive pulmonary disease (COPD).

METHODS

Twenty-two patients with COPD performed a cardiopulmonary cycling exercise test to assess peak oxygen consumption (V˙O2peak) and minute ventilation (V˙Epeak). They also performed a normocapnic hyperpnea exercise alone, at 50%-60% of V˙Epeak to exhaustion, using a respiratory device (Spirotiger) connected to a gas analyzer to monitor V˙O2, V˙E, and end-tidal CO2 partial pressure. Cardiac output, and intercostal and vastus lateralis muscle oxygenation were continuously measured during exercise using finger photoplethysmography and near-infrared spectroscopy, respectively. Arterial blood gases (arterial PCO2) and inspiratory capacity were obtained at rest and at the end of hyperpnea exercise.

RESULTS

The hyperpnea exercise lasted 576 ± 277 s at a V˙E of 34.5 ± 12.1 L·min-1 (58% ± 6% of V˙Epeak), a respiratory rate of 22 ± 4 breaths per minute, and a tidal volume of 1.43 ± 0.43 L. From rest to the end of hyperpnea exercise, V˙O2 increased by 0.35 ± 0.16 L·min-1 (P < 0.001), whereas end-tidal CO2 partial pressure and arterial PCO2 decreased by ~2 mm Hg (P = 0.031) and ~5 mm Hg (P = 0.002, n = 13), respectively. Moreover, inspiratory capacity fell from 2.44 ± 0.84 L at rest to 1.96 ± 0.59 L (P = 0.002). During the same period, heart rate and cardiac output increased from 69 ± 12 bpm and 4.94 ± 1.15 L·min-1 at rest to 87 ± 17 bpm (P = 0.002) and 5.92 ± 1.58 L·min-1 (P = 0.007), respectively. During hyperpnea exercise, intercostal deoxyhemoglobin and total hemoglobin increased by 14.26% ± 13.72% (P = 0.001) and 8.69% ± 12.49% (P = 0.003) compared with their resting value. However, during the same period, vastus lateralis oxygenation remained stable (P > 0.05).

CONCLUSIONS

In patients with COPD, normocapnic hyperpnea exercise provided a potent cardiorespiratory physiological stimulus, including dynamic hyperinflation, and increased intercostal deoxyhemoglobin consistent with enhanced requirement for muscle O2 extraction.

12-Week Inspiratory Muscle Training Improves Respiratory Muscle Strength in Adult Patients with Stable Asthma: A Randomized Controlled Trial

This study aims to investigate and compare the effects of conventional breathing exercises and an inspiratory muscle training intervention on clinical symptoms in asthma patients. Sixty asthma patients (40–65 years old) were randomly assigned to either the conventional breathing exercises (BTE) or inspiratory muscle training (IMT) group for a 12-week intervention period. Outcome measurements were performed before and after the intervention, including the spirometry data, maximal inspiratory and expiratory pressures (PImax and PEmax), asthma control test, asthma control questionnaire, six-minute walk test, and three-day physical activity log, were recorded. PImax expressed as % of predicted value controlled for age and gender in healthy subjects (% predicted) increased by 16.92% (82.45% to 99.38%, p < 0.05) in the BTE group and by 29.84% (71.19% to 101.03%, p < 0.05) in the IMT group. Except for forced vital capacity, which was reduced in the BTE group, all other measured variables improved in both groups, and no statistically significant between-group differences were found. IMT appears to be more effective than breathing exercise intervention in promoting improvements in respiratory muscle strength. IMT may act as an alternative to conventional breathing exercises for middle-aged and elderly asthma patients.

Methodology and reliability of respiratory muscle assessment

The optimal method for respiratory muscle endurance (RME) assessment remains unclear. This study assessed the test-retest reliability of two RME-test methodologies. Fifteen healthy adults attended the laboratory on four occasions, separated by 5 ± 2 days, and completed each test in a random, "one on two" order. They performed spirometry testing, maximal respiratory pressure assessment and two different RME tests: an inspiratory resistive breathing (IRB) and an isocapnic hyperpnea endurance (IHE) test. Typical error, expressed as coefficient of variation, for IRB maximal inspiratory pressure (MIP) and IHE maximal ventilation were 12.21 (8.85-19.67) % and 10.73 (7.78-17.29) %, respectively. Intraclass correlation coefficients for the same parameters were 0.83 (0.46-0.94) and 0.80 (0.41-0.93), respectively. No correlations were found between RME parameters derived from the IHE and IRB tests (all p > 0.05). Significant positive correlations were found between both IRB and IHE outcomes and spirometry parameters, MIP and maximal expiratory pressure (p < 0.05). Given these results, IRB and IHE appear to be suitable for RME testing in healthy people, although they may reflect different physiological mechanisms (respiratory mechanics and respiratory muscle capacity for IHE test vs. inspiratory muscle capacity for IRB test). Future studies are therefore warranted that compare IRB and IHE tests in clinical settings.

AIRWAY POSITIVE PRESSURE VS. EXERCISES WITH INSPIRATORY LOADING FOCUSED ON PULMONARY AND RESPIRATORY MUSCULAR FUNCTIONS IN THE POSTOPERATIVE PERIOD OF BARIATRIC SURGERY

BACKGROUND

Bariatric surgery can trigger postoperative pulmonary complications due to factors inherent to the procedure, mainly due to diaphragmatic dysfunction.

AIM

To evaluate and compare the effects of two levels of positive pressure and exercises with inspiratory load on lung function, inspiratory muscle strength and respiratory muscle resistance, and the prevalence of atelectasis after gastroplasty.

METHODS

Clinical, randomized and blind trial, with subjects submitted to bariatric surgery, allocated to two groups: positive pressure group, who received positive pressure at two levels during one hour and conventional respiratory physiotherapy and inspiratory load group, who performed exercises with load linear inspiratory pressure, six sets of 15 repetitions, in addition to conventional respiratory physiotherapy, both of which were applied twice in the immediate postoperative period and three times a day on the first postoperative day. Spirometry was performed for pulmonary function analysis, nasal inspiratory pressure for inspiratory muscle strength and incremental test of respiratory muscle resistance for sustained maximal inspiratory pressure, both preoperatively and on hospital discharge on the second postoperative day.

RESULTS

There was no significant difference (p> 0.05) in the expiratory reserve volume and in the tidal volume in the pre and postoperative periods when compared intra and intergroup. There was no significant difference (p>0.05) in the nasal inspiratory pressure and the maximal inspiratory pressure maintained in the inspiratory load group in the intragroup evaluation, but with a significant difference (p<0.05) compared to the positive pressure group. The prevalence of atelectasis was 5% in both groups with no significant difference (p>0.05) between them.

CONCLUSION

Both groups, associated with conventional respiratory physiotherapy, preserved expiratory reserve volume and tidal volume and had a low atelectasis rate. The inspiratory loading group still maintained inspiratory muscle strength and resistance of respiratory muscles.

Ventilatory support or respiratory muscle training as adjuncts to exercise in obese CPAP-treated patients with obstructive sleep apnoea: a randomised controlled trial

BACKGROUND

Obstructive sleep apnoea (OSA) and obesity are interdependent chronic diseases sharing reduced exercise tolerance and high cardiovascular risk.

INTERVENTION

A 3-month intervention with innovative training modalities would further improve functional capacity and cardiovascular health than usual cycle exercise training in already continuous positive airway pressure (CPAP)-treated obese patients with OSA.

METHODS

Fifty three patients (35

MEASUREMENTS AND MAIN RESULTS

All training modalities increased 6 min walking distance without differences between groups (P=0.97). ERGO+NIV and ERGO+RMT led to significantly higher improvement in VO2peak compared with ERGO (3.1 (95% CI 1.6 to 4.6) vs 2.3 (0.8 to 3.7) vs 0.5(-1.0 to 1.9) mL/min/kg, respectively, P=0.04) and ERGO+NIV significantly reduced self-measured blood pressure compared with ERGO+RMT and ERGO (systolic: -9.5 (95% CI -14.1 to -4.9) vs -13 (-5.8 to 3.1) vs -0.7 (-5.1 to 3.8) mm Hg, respectively, P=0.01). Waist and neck circumferences were reduced after ERGO+NIV compared with ERGO+RMT and ERGO (P=0.01).

CONCLUSIONS

Combining RMT or NIV with cycling exercise training failed to provide further improvement in functional capacity as compared with cycling exercise training alone. However, the combination of NIV and exercise training demonstrated superiority for improving cardiometabolic risk factors in obese CPAP-treated patients with OAS.

TRIAL REGISTRATION NUMBER

Results, NCT01155271.

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Key Words

• pulmonary rehabilitation
• respiratory muscles
• sleep apnoea

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Affiliation(s)

Isabelle Vivodtzev HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France Physical Medicine and Rehabilitation, Spaulding Rehabilitation Hospital, Harvard Medical School, Cambridge, Massachusetts, USA
Renaud Tamisier HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France
Marilie Croteau Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Quebec, QC, Canada
Jean-Christian Borel HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France
Angélique Grangier HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France
Bernard Wuyam HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France
Patrick Lévy HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France
Caroline Minville Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Quebec, QC, Canada
Frédéric Sériès Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Quebec, QC, Canada
François Maltais Centre de Recherche, Institut Universitaire de Cardiologie et de Pneumologie de Québec, Université Laval, Quebec, QC, Canada
Jean-Louis Pépin HP2 Laboratory, Centre Hospitalier Universitaire Grenoble Alpes, INSERM U1042, Grenoble Alps University, Grenoble, France

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Efficacy of inspiratory muscle training as a practical and minimally intrusive technique to aid functional fitness among adults with obesity

OBJECTIVE

To examine the efficacy of inspiratory muscle training (IMT) as a non-intrusive and practical intervention to stimulate improved functional fitness in adults with obesity. As excess adiposity of the chest impedes the mechanics of breathing, targeted re-training of the inspiratory muscles may ameliorate sensations of breathlessness, improve physical performance and lead to greater engagement in physical activity.

METHODS

Sixty seven adults (BMI=36±6.5) were randomized into either an experimental (EXP: n=35) or placebo (PLA: n=32) group with both groups undertaking a 4-week IMT intervention, comprising daily use of a inspiratory resistance device set to 55% (EXP), or 10% (PLA) of maximum inspiratory effort.

RESULTS

Inspiratory muscle strength was significantly improved in EXP (19.1 cmH₂0 gain; P<0.01) but did not change in PLA. Additionally, the post training walking distance covered was significantly extended for EXP (P<0.01), but not for PLA. Bivariate analysis demonstrated a positive association between the change (%) of performance in the walking test and BMI (r=0.78; P<0.01) for EXP.

CONCLUSION

The findings from this study suggest IMT provides a practical, self-administered intervention for use in a home setting. This could be a useful strategy to improve the functional fitness of obese adults and perhaps lead to better preparedness for engagement in physical activity initiatives.

Respiratory muscle endurance, oxygen saturation index in vastus lateralis and performance during heavy exercise

The purpose of this study was to investigate the relationships between respiratory muscle endurance, tissue oxygen saturation index dynamics of leg muscle (TSI) and the time to exhaustion (TTE) during high intensity exercise. Eleven males performed a respiratory muscle endurance test, a maximal incremental running field test (8 km h(-1)+0.5 km h(-1) each 60s) and a high-intensity constant speed field test at 90% VO2max. The TSI in vastus lateralis was monitored with near-infrared spectroscopy. The TSI remained steady between 20 and 80% of TTE. Between 80 and 100% of TTE (7.5 ± 6.1%, p<0.05), a significant drop in TSI concomitant with a minute ventilation increase (16 ± 10 l min(-1)) was observed. Moreover, the increase of ventilation was correlated to the drop in TSI (r=0.70, p<0.05). Additionally, respiratory muscle endurance was significantly correlated to TSI time plateau (20-80% TTE) (r=0.83, p<0.05) and to TTE (r=0.95, p<0.001). The results of the present study show that the tissue oxygen saturation plateau might be affected by ventilatory work and that respiratory muscle endurance could be considered as a determinant of performance during heavy exercise.

Current knowledge and impressions of speech-language pathologists of the swallow of persons who are obese

PURPOSE

The overall goal of this study was to provide insight on the topic of dysphagia in the obese population. More specifically, the purpose of this study was to obtain preliminary descriptive data on the knowledge and impressions of speech-language pathologists (SLPs) working in the field of dysphagia on the swallow of persons who are obese.

METHODS

One hundred seventy-seven SLPs responded to a web-based survey that was posted on two popular listserves that serve the dysphagia community.

RESULTS

Descriptive results showed that nearly all SLPs have assessed and treated patients who are obese for dysphagia, that there is little consensus as to how the obese swallow compares to the normal swallow, and that there is a consensus that dysphagia observed in the obese population is most likely related to other concomitant disorders.

CONCLUSIONS

Results provide preliminary insight into the knowledge and impressions of SLPs working with dysphagia and highlight the need for future research to determine (1) if there is an increased incidence of dysphagia in the obese population, and (2) if obesity itself constitutes a risk factor for dysphagia or if any dysphagia observed in this population is related to other comorbidities.

Evaluation of cardiorespiratory fitness and respiratory muscle function in the obese population

Cardiorespiratory fitness (CRF) is one of the most important health metrics in apparently healthy individuals, those at increased risk for cardiovascular (CV) disease and virtually all patient populations. In addition to CRF, a host of other variables obtained from aerobic exercise testing provides clinically valuable information. Individuals classified as obese (i.e. a body mass index ≥30 kg/m(2)) have varying degrees of CV, pulmonary and skeletal muscle dysfunction that impact CRF and other key aerobic exercise testing variables. Moreover, there is now evidence indicating inspiratory and expiratory respiratory muscle function, even in the absence of interstitial lung disease, is potentially compromised as a result of obesity. When obesity-induced respiratory muscle dysfunction is present, it has the potential to contribute to the limitations in CRF. The current review will discuss aerobic exercise testing and the assessment of respiratory muscle function in the obese population.

Impact loading and locomotor-respiratory coordination significantly influence breathing dynamics in running humans

Locomotor-respiratory coupling (LRC), phase-locking between breathing and stepping rhythms, occurs in many vertebrates. When quadrupedal mammals gallop, 1∶1 stride per breath coupling is necessitated by pronounced mechanical interactions between locomotion and ventilation. Humans show more flexibility in breathing patterns during locomotion, using LRC ratios of 2∶1, 2.5∶1, 3∶1, or 4∶1 and sometimes no coupling. Previous studies provide conflicting evidence on the mechanical significance of LRC in running humans. Some studies suggest LRC improves breathing efficiency, but others suggest LRC is mechanically insignificant because ‘step-driven flows’ (ventilatory flows attributable to step-induced forces) contribute a negligible fraction of tidal volume. Yet, although step-driven flows are brief, they cause large fluctuations in ventilatory flow. Here we test the hypothesis that running humans use LRC to minimize antagonistic effects of step-driven flows on breathing. We measured locomotor-ventilatory dynamics in 14 subjects running at a self-selected speed (2.6±0.1 ms⁻¹) and compared breathing dynamics in their naturally ‘preferred’ and ‘avoided’ entrainment patterns. Step-driven flows occurred at 1-2X step frequency with peak magnitudes of 0.97±0.45 Ls⁻¹ (mean ±S.D). Step-driven flows varied depending on ventilatory state (high versus low lung volume), suggesting state-dependent changes in compliance and damping of thoraco-abdominal tissues. Subjects naturally preferred LRC patterns that minimized antagonistic interactions and aligned ventilatory transitions with assistive phases of the step. Ventilatory transitions initiated in ‘preferred’ phases within the step cycle occurred 2x faster than those in ‘avoided’ phases. We hypothesize that humans coordinate breathing and locomotion to minimize antagonistic loading of respiratory muscles, reduce work of breathing and minimize rate of fatigue. Future work could address the potential consequences of locomotor-ventilatory interactions for elite endurance athletes and individuals who are overweight or obese, populations in which respiratory muscle fatigue can be limiting.

Four weeks of inspiratory muscle training improves self-paced walking performance in overweight and obese adults: a randomised controlled trial

Objective. To examine whether a programme of inspiratory muscle training (IMT) improves accumulative distance of self-paced walking in overweight and obese adults. Methods. A total of 15 overweight and obese adults were randomized into experimental (EXP: n = 8) and placebo (PLA: n = 7) groups. Lung function, inspiratory muscle performance, 6-minute walking test, and predicted [Formula: see text]O(2) max were assessed prior to and following the 4-week IMT intervention. Both groups performed 30 inspiratory breaths, twice daily using a proprietary inspiratory resistance device set to 55% of baseline maximal effort (EXP), or performing the same inspiratory training procedure at the minimum resistive setting (PLA). Results. Lung function was unchanged in both groups after-training; however inspiratory muscle strength was significantly improved in EXP (19 ± 25.2 cm H(2)O gain; P < 0.01) but did not significantly change in PLA. Additionally, the posttraining distance covered in the 6-minute walking test was significantly extended for EXP (62.5 ± 37.7 m gain; P < 0.01), but not for PLA. A positive association was observed between the change (%) of performance gain in the 6-minute walking test and body mass index (r = 0.736; P < 0.05) for EXP. Conclusion. The present study suggests that IMT provides a practical, minimally intrusive intervention to significantly augment both inspiratory muscle performance and walking distance covered by overweight and obese adults in a clinically relevant 6-minute walk test. This indicates that IMT may provide a useful priming (preparatory) strategy prior to entry in a physical training programme for overweight and obese adults.

Noninvasive ventilation in mild obesity hypoventilation syndrome: a randomized controlled trial

OBJECTIVE

Open studies suggest that treatment of obesity hypoventilation syndrome (OHS) by noninvasive ventilation (NIV) restores sleep quality and daytime vigilance and reduces cardiovascular morbidity. However, to our knowledge no randomized controlled trial (RCT) comparing NIV to conservative measures is available in the field. The goal of this study was to assess in patients with OHS, during an RCT, effects of 1-month NIV compared with lifestyle counseling on blood gas measurements, sleep quality, vigilance, and cardiovascular, metabolic, and inflammatory parameters.

METHODS

Thirty-five patients in whom OHS was newly diagnosed were randomized either to the NIV group or the control group represented by lifestyle counseling. Assessments included blood gas levels, subjective daytime sleepiness, metabolic parameters, inflammatory (hsCRP, leptin, regulated upon activation normal T-cell express and secreted [RANTES], monocyte chemoattractant protein-1, IL-6, IL-8, tumor necrosis factor-α, resistin) and antiinflammatory (adiponectin, IL-1-RA) cytokines, sleep studies, endothelial function (reactive hyperemia measured by peripheral arterial tonometry [RH-PAT]), and arterial stiffness.

RESULTS

Despite randomization, NIV group patients (n = 18) were older (58 ± 11 years vs 54 ± 6 years) with a higher baseline Paco(2) (47.9 ± 4.2 mm Hg vs 45.2 ± 3 mm Hg). In intention-to-treat analysis, compared with control group, NIV treatment significantly reduced daytime Paco(2) (difference between treatments: -3.5 mm Hg; 95% CI, -6.2 to -0.8) and apnea-hypopnea index (-40.3/h; 95% CI, -62.4 to -18.2). Sleep architecture was restored, although nonrespiratory microarousals increased (+9.4/h of sleep; 95% CI, 1.9-16.9), and daytime sleepiness was not completely normalized. Despite a dramatic improvement in sleep hypoxemia, glucidic and lipidic metabolism parameters as well as cytokine profiles did not vary significantly. Accordingly, neither RH-PAT (+0.02; 95% CI, -0.24 to 0.29) nor arterial stiffness (+0.22 m/s; 95% CI, -1.47 to 1.92) improved.

CONCLUSIONS

One month of NIV treatment, although improving sleep and blood gas measurements dramatically, did not change inflammatory, metabolic, and cardiovascular markers.

TRIAL REGISTRY

ClinicalTrials.gov; No.: NCT00603096; URL: www.clinicaltrials.gov.

Força muscular respiratória de mulheres obesas mórbidas e eutróficas

A obesidade mórbida é uma condição clínica que afeta a capacidade funcional, sendo a musculatura respiratória igualmente comprometida. Objetivou-se avaliar a força muscular inspiratória e expiratória de mulheres obesas mórbidas (MO) e eutróficas (ME). Estudo transversal com amostra composta por 21 mulheres (14 MO e 7 ME), pareadas pela idade e altura. A avaliação da força muscular inspiratória e expiratória foi realizada por meio da verificação das pressões inspiratória e expiratória por manovacuometria. Quando comparadas as pressões respiratórias estáticas máximas obtidas com os valores preditos para ME e MO, constata-se que as do primeiro grupo apresentam valores de P Imáx=119,14±1,9 cmH2O (152% do predito) e P Emáx=141,1±10,2 cmH2O (98,5% do predito) dentro dos limites de normalidade ou acima, enquanto no grupo de obesas mórbidas os valores de P Imáx=66±18,7 cmH2O (84,3% do predito) e P Emáx=78,4±14,2 cmH2O (54,3% do predito) foram inferiores aos preditos. Comparando-se as pressões respiratórias estáticas máximas obtidas de MO com ME, observa-se diferença significativa tanto para os valores de P Imáx (66±18,7 versus 119±1,9 cmH2O) como P Emáx (78,4±14,2 versus 141,14±10,20) com significância estatística de 0,001. Conclui-se que a força muscular respiratória é marcadamente diminuída em MO, quando comparadas a ME.