Locomotor Muscles in COPD: The Rationale for Rehabilitative Exercise Training

Effects of Combined Endurance and Resistance Eccentric Training on Muscle Function and Functional Performance in Patients With Chronic Obstructive Pulmonary Disease: Randomized Controlled Trial

OBJECTIVE

To evaluate the adherence to treatment and efficacy of an eccentric-based training (ECC) program on peripheral muscle function and functional exercise capacity in patients with chronic obstructive pulmonary disease (COPD).

DESIGN

Prospective, assessor-blinded, randomized controlled trial.

SETTING

The cardiopulmonary rehabilitation unit of a tertiary subacute referral center.

PARTICIPANTS

Thirty (N=30) stable inpatients (mean age 68±8 years; FEV1 44±18% of predicted) with COPD were included in the study.

INTERVENTIONS

Inpatients were randomly assigned to 4 weeks of a combined endurance and resistance ECC (n=15) or conventional training (CON; n=15).

MAIN OUTCOME MEASURES

Quadriceps peak torque (PT) was the primary outcome measure for muscle function. Rate of force development (RFD), muscle activation and quality (quadriceps PT/leg lean mass), 6-min walk distance (6MWD), 4-meter gait speed (4mGS), 10-meter gait speed, 5-repetition sit-to-stand (5STS), dyspnea rate, and mortality risk were the secondary outcomes. Evaluations were performed at baseline and repeated after 4 weeks and 3 months of follow-up.

RESULTS

Quadriceps PT, RFD, and muscle quality improved by 17±23% (P<.001), 19±24%, and 16±20% (both P<.05) within the ECC group. Besides, a significant between-group difference for RFD (56±94 Nm/s, P=.038) was found after training. Both groups showed clinically relevant improvements in 6MWD, 4mGS, dyspnea rate, and mortality risk, with no significant differences between groups.

CONCLUSION

Combined endurance and resistance ECC improved lower limbs muscle function compared with CON in inpatients with COPD. In contrast, ECC did not further improve functional performance, dyspnea, and mortality risk. ECC may be of particular benefit to effect on skeletal muscle function in patients with COPD.

Combined Exercise Training and Nutritional Interventions or Pharmacological Treatments to Improve Exercise Capacity and Body Composition in Chronic Obstructive Pulmonary Disease: A Narrative Review

Chronic obstructive pulmonary disease (COPD) is a chronic respiratory disease that is associated with significant morbidity, mortality, and healthcare costs. The burden of respiratory symptoms and airflow limitation can translate to reduced physical activity, in turn contributing to poor exercise capacity, muscle dysfunction, and body composition abnormalities. These extrapulmonary features of the disease are targeted during pulmonary rehabilitation, which provides patients with tailored therapies to improve the physical and emotional status. Patients with COPD can be divided into metabolic phenotypes, including cachectic, sarcopenic, normal weight, obese, and sarcopenic with hidden obesity. To date, there have been many studies performed investigating the individual effects of exercise training programs as well as nutritional and pharmacological treatments to improve exercise capacity and body composition in patients with COPD. However, little research is available investigating the combined effect of exercise training with nutritional or pharmacological treatments on these outcomes. Therefore, this review focuses on exploring the potential additional beneficial effects of combinations of exercise training and nutritional or pharmacological treatments to target exercise capacity and body composition in patients with COPD with different metabolic phenotypes.

Utility of Cardiopulmonary Exercise Testing in Chronic Obstructive Pulmonary Disease: A Review

Chronic obstructive pulmonary disease (COPD) is a disease defined by airflow obstruction with a high morbidity and mortality and significant economic burden. Although pulmonary function testing is the cornerstone in diagnosis of COPD, it cannot fully characterize disease severity or cause of dyspnea because of disease heterogeneity and variable related and comorbid conditions affecting cardiac, vascular, and musculoskeletal systems. Cardiopulmonary exercise testing (CPET) is a valuable tool for assessing physical function in a wide range of clinical conditions, including COPD. Familiarity with measurements made during CPET and its potential to aid in clinical decision-making related to COPD can thus be useful to clinicians caring for this population. This review highlights pulmonary and extrapulmonary impairments that can contribute to exercise limitation in COPD. Key elements of CPET are identified with an emphasis on measurements most relevant to COPD. Finally, clinical applications of CPET demonstrated to be of value in the COPD setting are identified. These include quantifying functional capacity, differentiating among potential causes of symptoms and limitation, prognostication and risk assessment for operative procedures, and guiding exercise prescription.

The Impact of Exercise Training and Supplemental Oxygen on Peripheral Muscles in Chronic Obstructive Pulmonary Disease: A Randomized Controlled Trial

OBJECTIVE

Exercise training is a cornerstone of the treatment of chronic obstructive pulmonary disease, whereas the related interindividual heterogeneity in skeletal muscle dysfunction and adaptations are not yet fully understood. We set out to investigate the effects of exercise training and supplemental oxygen on functional and structural peripheral muscle adaptation.

METHODS

In this prospective, randomized, controlled, double-blind study, 28 patients with nonhypoxemic chronic obstructive pulmonary disease (forced expiratory volume in 1 second, 45.92% ± 9.06%) performed 6 wk of combined endurance and strength training, three times a week while breathing either supplemental oxygen or medical air. The impact on exercise capacity, muscle strength, and quadriceps femoris muscle cross-sectional area (CSA) was assessed by maximal cardiopulmonary exercise testing, 10-repetition maximum strength test of knee extension, and magnetic resonance imaging, respectively.

RESULTS

After exercise training, patients demonstrated a significant increase in functional capacity, aerobic capacity, exercise tolerance, quadriceps muscle strength, and bilateral CSA. Supplemental oxygen affected significantly the training impact on peak work rate when compared with medical air (+0.20 ± 0.03 vs +0.12 ± 0.03 W·kg -1 , P = 0.047); a significant increase in CSA (+3.9 ± 1.3 cm 2 , P = 0.013) was only observed in the training group using oxygen. Supplemental oxygen and exercise-induced peripheral desaturation were identified as significant opposing determinants of muscle gain during this exercise training intervention, which led to different adaptations of CSA between the respective subgroups.

CONCLUSIONS

The heterogenous functional and structural muscle adaptations seem determined by supplemental oxygen and exercise-induced hypoxia. Indeed, supplemental oxygen may facilitate muscular training adaptations, particularly in limb muscle dysfunction, thereby contributing to the enhanced training responses on maximal aerobic and functional capacity.

Meta-analysis of the impact of physical activity on the recovery of physical function in COVID-19 patients

Background

The decrease in physical function resulting from COVID-19 infection exerts a substantial negative influence on the quality of life of individuals. Physical activity plays a crucial and irreplaceable role in hastening the elimination of adverse effects on the body caused by acute and chronic diseases. Nevertheless, there have been reports of unfavorable events following physical activity post-COVID-19 infection, sparking debate regarding the efficacy of physical activity as a rehabilitation method to enhance the physical function of COVID-19 patients.

Objective

The aim of this study is to investigate the impact of physical activity on promoting the restoration of physical function among individuals with COVID-19, and to offer guidance for the advancement and consideration of physical activity in the rehabilitation treatment of COVID-19 patients.

Methods

A search was conducted on the PubMed and Web of Science core collection databases, with the search period set from January 1, 2020, to February 6, 2023. The included literature was assessed for risk of bias and methodological quality according to the Cochrane Handbook for Systematic Reviews of Interventions, utilizing Review Manager 5.1 software. The outcome measures from the included studies were analyzed, and the quality of evidence for the outcome measures was graded using the GRADE classification criteria.

Results

The effect of physical activity intervention on improving the 6-Minute Walk Test score in COVID-19 patients was better than that of conventional treatment [WMD = 69.19(95%CI = 39.38, 98.99), I2 = 57%(p = 0.03)]. The effect of physical activity on improving the 30-Second Sit-to-Stand Test score was better than that of conventional treatment [WMD = 2.98(95%CI = 1.91, 4.04), I2 = 0%(p = 0.56)]. There was no significant difference between physical activity and conventional treatment in improving Grip strength in COVID-19 patients [WMD = 2.35(95%CI = -0.49, 5.20), I2 = 0%(p = 0.80)]. The effect of physical activity on improving the Timed Up and Go test score in COVID-19 patients was better than that of conventional treatment [WMD = -1.16(95%CI = -1.98, -0.34), I2 = 4%(p = 0.35)]. The effect of physical activity on improving Forced Vital Capacity in COVID-19 patients was better than that of conventional treatment [WMD = 0.14(95%CI = 0.08, 0.21), I2 = 0%(p = 0.45)]. The effect of physical activity on improving Forced Expiratory Volume in the first second in COVID-19 patients was better than that of conventional treatment [WMD = 0.08(95%CI = 0.02, 0.15), I2 = 52%(p = 0.10)].

Conclusions

Physical activity plays a crucial role in facilitating the recovery of exercise capacity and pulmonary function in COVID-19 patients, helping to expedite the restoration of overall physical health. It is crucial for COVID-19 patients to undergo an accurate assessment of their physical condition before engaging in any physical activity.

Role of nutrition in patients with coexisting chronic obstructive pulmonary disease and sarcopenia

Chronic obstructive pulmonary disease (COPD) is one of the most common chronic diseases in the elderly population and is characterized by persistent respiratory symptoms and airflow obstruction. During COPD progression, a variety of pulmonary and extrapulmonary complications develop, with sarcopenia being one of the most common extrapulmonary complications. Factors that contribute to the pathogenesis of coexisting COPD and sarcopenia include systemic inflammation, hypoxia, hypercapnia, oxidative stress, protein metabolic imbalance, and myocyte mitochondrial dysfunction. These factors, individually or in concert, affect muscle function, resulting in decreased muscle mass and strength. The occurrence of sarcopenia severely affects the quality of life of patients with COPD, resulting in increased readmission rates, longer hospital admission, and higher mortality. In recent years, studies have found that oral supplementation with protein, micronutrients, fat, or a combination of nutritional supplements can improve the muscle strength and physical performance of these patients; some studies have also elucidated the possible underlying mechanisms. This review aimed to elucidate the role of nutrition among patients with coexisting COPD and sarcopenia.

Improved clinical outcomes in response to a 12-week blended digital and community-based long-COVID-19 rehabilitation programme

Introduction

Two million people in the UK are experiencing long COVID (LC), which necessitates effective and scalable interventions to manage this condition. This study provides the first results from a scalable rehabilitation programme for participants presenting with LC.

Methods

601 adult participants with symptoms of LC completed the Nuffield Health COVID-19 Rehabilitation Programme between February 2021 and March 2022 and provided written informed consent for the inclusion of outcomes data in external publications. The 12-week programme included three exercise sessions per week consisting of aerobic and strength-based exercises, and stability and mobility activities. The first 6 weeks of the programme were conducted remotely, whereas the second 6 weeks incorporated face-to-face rehabilitation sessions in a community setting. A weekly telephone call with a rehabilitation specialist was also provided to support queries and advise on exercise selection, symptom management and emotional wellbeing.

Results

The 12-week rehabilitation programme significantly improved Dyspnea-12 (D-12), Duke Activity Status Index (DASI), World Health Orginaisation-5 (WHO-5) and EQ-5D-5L utility scores (all p < 0.001), with the 95% confidence intervals (CI) for the improvement in each of these outcomes exceeding the minimum clinically important difference (MCID) for each measure (mean change [CI]: D-12: -3.4 [-3.9, -2.9]; DASI: 9.2 [8.2, 10.1]; WHO-5: 20.3 [18.6, 22.0]; EQ-5D-5L utility: 0.11 [0.10, 0.13]). Significant improvements exceeding the MCID were also observed for sit-to-stand test results (4.1 [3.5, 4.6]). On completion of the rehabilitation programme, participants also reported significantly fewer GP consultations (p < 0.001), sick days (p = 0.003) and outpatient visits (p = 0.007) during the previous 3 months compared with baseline.

Discussion

The blended and community design of this rehabilitation model makes it scalable and meets the urgent need for an effective intervention to support patients experiencing LC. This rehabilitation model is well placed to support the NHS (and other healthcare systems worldwide) in its aim of controlling the impacts of COVID-19 and delivering on its long-term plan.

Clinical trial registration

https://www.isrctn.com/ISRCTN14707226, identifier 14707226.

Breathing Control Exercises Delivered in a Group Setting for Patients with Chronic Obstructive Pulmonary Disease: A Randomized Controlled Trial

Breathing control exercises are an important component of occupational therapy in patients with chronic obstructive pulmonary disease (COPD). Delivering these exercises in group settings may enhance their benefits. Therefore, this study assessed the effectiveness of breathing control exercises delivered in a group format to patients with severe COPD remitting from an acute pulmonary exacerbation. This randomized controlled trial of 6 weeks’ duration compared the addition of breathing exercise sessions delivered in a group setting to a standard exercise inpatient rehabilitation program (usual care) versus usual care alone. The standard exercise program consisted of endurance and strength training and therapeutic patient education. The intervention group received, in addition to usual care, 20 sessions of 30 min duration of breathing control exercises in a group setting. The primary outcome was quality of life (Saint George’s Respiratory Questionnaire). Secondary outcomes were the COPD assessment test, modified Borg scale, handgrip strength test, and five-time sit-to-stand test. Thirty-seven patients aged 69 ± 7 years were recruited. After the 6-week period, all outcomes significantly improved and exceeded the minimal clinically important difference in the intervention group only. Between-group changes were significant for each outcome. Conclusions: breathing control exercises in a group setting provide clinically relevant benefits in patients with severe COPD who are remitting from an acute pulmonary exacerbation.

Quantifying leg muscle deoxygenation during incremental cycling in hypoxemic patients with fibrotic interstitial lung disease

BACKGROUND

Hypoxaemia and cardiocirculatory abnormalities may impair muscle oxygen (O₂ ) delivery relative to O₂ requirements thereby increasing the rate of O₂ extraction during incremental exercise in fibrotic interstitial lung disease (f-ILD). Using changes in deoxyhaemoglobin concentration ([HHb]) by near-infrared spectroscopy (NIRS) as a proxy of O₂ extraction, we investigated whether a simplified (double-linear) approach, previously tested in heart failure, would provide useful estimates of muscle deoxygenation in f-ILD.

METHODS

A total of 25 patients (23 men, 72 ± 8 years; 20 with idiopathic pulmonary fibrosis, lung diffusing capacity for carbon monoxide = 44 ± 11% predicted) and 12 age- and sex-matched healthy controls performed incremental cycling to symptom limitation. Changes in vastus lateralis [HHb] assessed by NIRS were analysed in relation to work rate (WR) and O₂ uptake throughout the exercise.

RESULTS

Patients showed lower exercise capacity than controls (e.g., peak WR = 67 ± 18% vs. 105 ± 20% predicted, respectively; p < 0.001). The [HHb] response profile was typically S-shaped, presenting three distinct phases. Exacerbated muscle deoxygenation in patients versus controls was evidenced by: (i) a steeper mid-exercise [HHb]-WR slope (0.30 ± 0.22 vs. 0.11 ± 0.08 μmol/W; p = 0.008) (Phase 2), and (ii) a larger late-exercise increase in [HHb] (p = 0.002) (Phase 3). Steeper [HHb]-WR slope was associated with lower peak WR (r = -0.70) and greater leg discomfort (r = 0.77; p < 0.001) in f-ILD.

CONCLUSION

This practical approach to interpreting [HHb] during incremental exercise might prove useful to determine the severity of muscle deoxygenation and the potential effects of interventions thereof in hypoxemic patients with f-ILD.

The effect of a pressure ventilatory support on quadriceps endurance is maintained after exercise training in severe COPD patients. A longitudinal randomized, cross over study

Purpose: In severe chronic obstructive pulmonary disease (COPD) patients, the application of an inspiratory pressure support (IPS) during exercise increases exercise tolerance and the benefit of exercise training during pulmonary rehabilitation (PR). Moreover, it improves quadriceps endurance after a session of cycling exercise suggesting a reduced muscle fatigue. We looked for the persistence of this effect after PR and sought an association between the improved quadriceps endurance with IPS and the training load during PR.

Patients and methods: We studied 20 patients with severe COPD (6 in stage 3and 14 in stage 4 of GOLD) before and after PR. As part of a PR program, patients completed 16 cycling sessions over 6 weeks with the addition of IPS during exercise. As a surrogate of muscular fatigue, quadriceps endurance was measured at 70% of maximal strength in a control condition, after a constant work rate exercise test (CWR) with IPS (TlimQ IPS) or with a sham ventilation (TlimQsham), in a random order. These tests were repeated similarly at the end of PR.

Results: PR was associated with a significant increase in maximal power output, cycling endurance, quadriceps strength and endurance. Session training load (power output x duration of the session) increased by 142% during the course of the program. Before PR, CWR duration increases with IPS compared to sham ventilation (Δtime = +244s, p = 0.001). Compared to control condition, post-exercise TlimQ reduction was lower with IPS at isotime than at the end of CWR or than with sham ventilation (−9 ± 21%, −18 ± 16% and −23 ± 18%, respectively, p = 0.09, p &lt; 0.0001 and p &lt; 0.0001). After PR, the post-exercise decrease of TlimQ was reduced after IPS compared to sham (−9 ± 18% vs. −21 ± 17%, respectively, p = 0.004). No relationship was found between the prevention of quadriceps fatigue and the training load.

Conclusion: In severe COPD patients, the beneficial effect of a ventilator support on quadriceps endurance persisted after PR with IPS. However, it was not related to the increase in training load, and could not predict the training response to non-invasive ventilation during exercise.

Role of progression of training volume on intramuscular adaptations in patients with chronic obstructive pulmonary disease

Introduction: Quadriceps dysfunction is a common systemic manifestation of chronic obstructive pulmonary disease (COPD), for which treatment using resistance training is highly recommended. Even though training volume is suggested to be a key explanatory factor for intramuscular adaptation to resistance training in healthy older adults, knowledge is scarce on the role of progression of training volume for intramuscular adaptations in COPD.

Methods: This study was a sub-analysis of a parallel-group randomized controlled trial. Thirteen patients with severe to very severe COPD (median 66 yrs, forced expiratory volume in 1 s 44% predicted) performed 8 weeks of low-load resistance training. In a post hoc analysis, they were divided into two groups according to their training volume progression. Those in whom training volume continued to increase after the first 4 weeks of training outlined the continued progression group (n = 9), while those with limited increase (<5%) or even reduction in training volume after the initial 4 weeks composed the discontinued progression group (n = 4). Fiber-type distribution and oxidative muscle protein levels, i.e., citrate synthase (CS), hydroxyacyl-coenzyme A dehydrogenase (HADH), mitochondrial transcription factor A (TfAM) as well as quadriceps endurance measures (total work from elastic band and isokinetic knee extension tests), were assessed before and after the intervention period.

Results: The continued progression group sustained their training volume progression during weeks 5–8 compared to weeks 1–4 (median +25%), while the discontinued progression group did not (median -2%) (p = 0.007 between groups). Compared with baseline values, significant between-group differences in fiber type distribution and TfAM muscle protein levels (range ± 17–62%, p < 0.05) and in individual responses to change in Type I and Type IIa fiber type proportion, CS, HADH, and TfAM muscle protein levels outcomes (median 89 vs. 50%, p = 0.001) were seen in favor of the continued progression group. Moreover, only the continued progression group had a significant increase in HADH muscle protein levels (+24%, p = 0.004), elastic band (+56%, p = 0.004) and isokinetic (+7%, p = 0.004) quadriceps endurance, but the between-group differences did not reach statistical significance (range 14–29%, p = 0.330–1.000).

Discussion: The novel findings of the current study were that patients with COPD who had a continued progression of training volume across the 8-weeks intervention had an increased proportion of Type I fibers, and TfAM muscle protein levels and decreased proportion of Type II fibers compared to those that did not continue to progress their training volume after the initial weeks. Additionally, HADH muscle protein levels and quadriceps endurance measurements only improved in the continued progression group, although no significant between-group differences were seen. These findings highlight the importance of continued progression of training volume during resistive training to counteract quadriceps dysfunction within the COPD population. Still, considering the small sample size and the post hoc nature of our analyses, these results should be interpreted cautiously, and further research is necessary.

Impact of extrapulmonary comorbidities on physical activity in chronic obstructive pulmonary disease in Japan: A cross-sectional study

Physical activity, which can be affected by airflow limitation and extrapulmonary comorbidities, has been reported to be reduced in patients with chronic obstructive pulmonary disease, and reduced physical activity is associated with higher risks of exacerbation and mortality. The aim of the present study is to elucidate the comprehensive effect of extrapulmonary comorbidities on physical activity in Japanese patients with chronic obstructive pulmonary disease, of which evidence is lacking. We conducted a cross-sectional study with a series of tests, including lung function, physical activity, symptom scores, and parameters for comorbidities. Sixty outpatients with stable disease were enrolled, and the relationship between the parameters and physical activity was evaluated. Physical activity was assessed over 7 consecutive days using a triaxial accelerometer, which records total daily energy expenditure, step count, and walking time. Cardiovascular status was assessed via echocardiography, and pulmonary artery pressure was estimated using Doppler sonography. As to mental status, depression and anxiety were assessed using the Self-Rating Depression Scale and State-Trait Anxiety Inventory, respectively. Physical activity level was significantly correlated with step count, walking time, body mass index, lean body mass index, lung function, pulmonary artery pressure, depression, anxiety, and serum total cholesterol level. In a median regression model analysis, low lung function, low lean body mass index, depression, and low serum total cholesterol level were independently associated with decreased physical activity level. These findings suggest that physical inactivity is affected by multiple extrapulmonary factors, including skeletal muscle dysfunction, depressive symptoms, and nutritional state, in Japanese patients with chronic obstructive pulmonary disease.

What to stretch? - Isolated proprioceptive neuromuscular facilitation stretching of either quadriceps or triceps surae followed by post-stretching activities alters tissue stiffness and jump performance

To overcome a possible drop in performance following longer stretch durations (>60 s), post-stretching dynamic activities (PSA) can be applied. However, it is not clear if this is true for isolated proprioceptive neuromuscular facilitation (PNF) stretching of different muscle groups (e.g., triceps surae and quadriceps). Thus, 16 participants performed both interventions (triceps surae PNF + PSA; quadriceps PNF + PSA) in random order, separated by 48 h. Jump performance was assessed with a force plate, and tissue stiffness was assessed with a MyotonPro device. While no changes were detected in the countermovement jump performance, the PNF + PSA interventions resulted in a decrease in drop jump performance which led to a large magnitude of change following the triceps surae PNF + PSA and a small-to-medium magnitude of change following the quadriceps PNF + PSA. Moreover, in the triceps surae PNF + PSA intervention, a decrease in Achilles tendon stiffness was seen, while in the quadriceps PNF + PSA intervention, a decrease in the overall quadriceps muscle stiffness was seen. According to our results, we recommend that especially triceps surae stretching is avoided during warm-up (also when PSA is included) when the goal is to optimise explosive or reactive muscle contractions.

Different Responses to Pulmonary Rehabilitation in COPD Patients with Different Work Efficiencies

Background

Chronic obstructive pulmonary disease (COPD) often involves the cardiopulmonary dysfunction that deteriorates health-related quality of life (HRQL) and exercise capacity. Work efficiency (WE) indicates the efficiency of overall oxygen consumption (VO₂) during exercise. This study investigated whether different WEs have different effects on pulmonary rehabilitation (PR).

Methods

Forty-five patients with stable COPD were scheduled for PR. The PR programs consisted of twice-weekly sessions for three months. These patients were comprehensively evaluated by cardiopulmonary exercise testing and COPD assessment test (CAT) before and after PR. We compared these parameters between patients with a normal versus poor WE.

Results

Twenty-one patients had a normal WE and twenty-four patients had a poor WE (<8.6 mL/min/watt). Patients with a poor WE had earlier anaerobic metabolism, a poorer oxygen pulse, lower exercise capacity, more exertional dyspnea, and a poorer HRQL than those with a normal WE. PR improved exercise capacity, HRQL, anaerobic threshold, exertional dyspnea and leg fatigue in patients with either normal or poor WE. However, significant improvement of WE, oxygen pulse, respiratory frequency (Rf) during exercise, chest tightness, activity and sleepiness by CAT were noted only in patients with a poor WE. Among the patients with a poor WE, 29% patients had WE returned to normal after PR.

Conclusion

Patients with different WE had different responses to PR. PR improved exercise capacity and HRQL regardless of a normal or poor WE. However, WE, oxygen pulse, Rf during exercise, chest tightness, activity and sleepiness were only improved in patients with a poor WE.

The Exercising Brain: An Overlooked Factor Limiting the Tolerance to Physical Exertion in Major Cardiorespiratory Diseases?

“Exercise starts and ends in the brain”: this was the title of a review article authored by Dr. Bengt Kayser back in 2003. In this piece of work, the author highlights that pioneer studies have primarily focused on the cardiorespiratory-muscle axis to set the human limits to whole-body exercise tolerance. In some circumstances, however, exercise cessation may not be solely attributable to these players: the central nervous system is thought to hold a relevant role as the ultimate site of exercise termination. In fact, there has been a growing interest relative to the “brain” response to exercise in chronic cardiorespiratory diseases, and its potential implication in limiting the tolerance to physical exertion in patients. To reach these overarching goals, non-invasive techniques, such as near-infrared spectroscopy and transcranial magnetic stimulation, have been successfully applied to get insights into the underlying mechanisms of exercise limitation in clinical populations. This review provides an up-to-date outline of the rationale for the “brain” as the organ limiting the tolerance to physical exertion in patients with cardiorespiratory diseases. We first outline some key methodological aspects of neuromuscular function and cerebral hemodynamics assessment in response to different exercise paradigms. We then review the most prominent studies, which explored the influence of major cardiorespiratory diseases on these outcomes. After a balanced summary of existing evidence, we finalize by detailing the rationale for investigating the “brain” contribution to exercise limitation in hitherto unexplored cardiorespiratory diseases, an endeavor that might lead to innovative lines of applied physiological research.

Moderate Treadmill Training Induces Limited Effects on Quadriceps Muscle Hypertrophy in Mice Exposed to Cigarette Smoke Involving Metalloproteinase 2

Background

Long-term cigarette smoke (CS) induces substantive extrapulmonary effects, including musculoskeletal system disorders. Exercise training seems to protect long-term smokers against fiber atrophy in the locomotor muscles. Nevertheless, the extracellular matrix (ECM) changes in response to aerobic training remain largely unknown. Thus, we investigated the effects of moderate treadmill training on aerobic performance, cross-sectional area (CSA), fiber distribution, and metalloproteinase 2 (MMP-2) activity on quadriceps muscle in mice exposed to chronic CS.

Methods

Male mice were randomized into four groups: control or smoke (6 per group) and exercise or exercise+smoke (5 per group). Animals were exposed to 12 commercially filtered cigarettes per day (0.8 mg of nicotine, 10 mg of tar, and 10 mg of CO per cigarette). The CSA, fibers distribution, and MMP-2 activity by zymography were assessed after a period of treadmill training (50% of maximal exercise capacity for 60 min/day, 5 days/week) for 24 weeks.

Results

The CS exposure did not change CSA compared to the control group (p>0.05), but minor fibers in the frequency distribution (<1000 µm²) were observed. Long-term CS exposure attenuated CSA increases in exercise conditions (smoke+exercise vs exercise) while did not impair aerobic performance. Quadriceps CSA increased in mice nonsmoker submitted to aerobic training (p = 0.001). There was higher pro-MMP-2 activity in the smoke+exercise group when compared to the smoke group (p = 0.01). Regarding active MMP-2, the exercise showed higher values when compared to the control group (p = 0.001).

Conclusion

Moderate treadmill training for 24 weeks in mice exposed to CS did not modify CSA, despite inducing higher pro-MMP-2 activity in the quadriceps muscle, suggesting limited effects on ECM remodeling. Our findings may contribute to new insights into molecular mechanisms for CS conditions.

Effects of Home-Based Pulmonary Rehabilitation on Dyspnea, Exercise Capacity, Quality of Life and Impact of the Disease in COPD Patients: A Systematic Review

Conventional pulmonary rehabilitation programs are used as therapies for the treatment of chronic obstructive pulmonary disease (COPD). However, this modality presents barriers that make rehabilitation difficult. For this reason, home-based pulmonary rehabilitation (HBPR) has been used to overcome these barriers. The objective was to systematically compare a structured program with HBPR or a control group for participants with COPD. The primary outcome was an improvement in symptoms in the level of dyspnea and secondary outcomes were parameters in lung function, exercise capacity, health-related quality of life (HRQoL) and the impact of the disease on the individual. The Medline (via PubMed), Virtual Health Library and Cochrane Library databases were searched until May 10, 2021. Randomized controlled trials were included without restrictions on the year of publication or language. The risk of bias was evaluated using the Cochrane risk-of-bias tool for randomized trials (RoB). Our results showed that there was a significant decrease in the level of dyspnea, (MD: 5.46; 95% CI: 1.97 to 8.96), increased distance covered (MD: 61.75; 95% CI: 42, 94 to 80.56, significant improvement in HRQoL (MD: -11.30; 95% CI: -19.81 to -2.79) and reduction in the impact of the disease (DM: -4.71; 95% CI: -7.95 to -1.47). All results found were comparing the intervention group versus the control group. To conclude we found a reduction in the levels of dyspnea, an increase in the distance covered on the six-minute walk test, improving HRQoL and decreasing the impact of the disease in COPD patients in home-based pulmonary rehabilitation.Supplemental data for this article is available online at https://doi.org/10.1080/15412555.2021.2020234 .

Update on the Etiology, Assessment, and Management of COPD Cachexia: Considerations for the Clinician

Cachexia is a commonly observed but frequently neglected extra-pulmonary manifestation in patients with chronic obstructive pulmonary disease (COPD). Cachexia is a multifactorial syndrome characterized by severe loss of body weight, muscle, and fat, as well as increased protein catabolism. COPD cachexia places a high burden on patients (eg, increased mortality risk and disease burden, reduced exercise capacity and quality of life) and the healthcare system (eg, increased number, length, and cost of hospitalizations). The etiology of COPD cachexia involves a complex interplay of non-modifiable and modifiable factors (eg, smoking, hypoxemia, hypercapnia, physical inactivity, energy imbalance, and exacerbations). Addressing these modifiable factors is needed to prevent and treat COPD cachexia. Oral nutritional supplementation combined with exercise training should be the primary multimodal treatment approach. Adding a pharmacological agent might be considered in some, but not all, patients with COPD cachexia. Clinicians and researchers should use longitudinal measures (eg, weight loss, muscle mass loss) instead of cross-sectional measures (eg, low body mass index or fat-free mass index) where possible to evaluate patients with COPD cachexia. Lastly, in future research, more detailed phenotyping of cachectic patients to enable a better comparison of included patients between studies, prospective longitudinal studies, and more focus on the impact of exacerbations and the role of biomarkers in COPD cachexia, are highly recommended.

Does branched-chain amino acid supplementation improve pulmonary rehabilitation effect in COPD?

BACKGROUND

Muscle wasting is frequent in chronic obstructive lung disease (COPD) and associated with low branched-chain amino acids (BCAA). We hypothesized that BCAA supplementation could potentiate the effect of a pulmonary rehabilitation program (PRP) by inducing muscular change.

MATERIALS AND METHODS

Sixty COPD patients (GOLD 2-3) were involved in an ambulatory 4-week PRP either with BCAA oral daily supplementation or placebo daily supplementation in a randomized double-blind design. Maximal exercise test including quadriceps oxygenation measurements, functional exercise test, muscle strength, lung function tests, body composition, dyspnea and quality of life were assessed before and after PRP.

RESULTS

Fifty-four patients (64.9 ± 8.3 years) completed the protocol. In both groups, maximal exercise capacity, functional and muscle performances, quality of life and dyspnea were improved after 4-week PRP (p ≤ 0.01). Changes in muscle oxygenation during the maximal exercise and recovery period were not modified after 4-week PRP in BCAA group. Contrarily, in the placebo group the muscle oxygenation kinetic of recovery was slowed down after PRP.

CONCLUSION

This study demonstrated that a 4-week PRP with BCAA supplementation is not more beneficial than PRP alone for patients. A longer duration of supplementation or a more precise targeting of patients would need to be investigated to validate an effect on muscle recovery and to demonstrate other beneficial effects.

Practical Recommendations Relevant to the Use of Resistance Training for COVID-19 Survivors

The novel coronavirus disease (COVID-19) has emerged at the end of 2019 and caused a global pandemic. The disease predominantly affects the respiratory system; however, there is evidence that it is a multisystem disease that also impacts the cardiovascular system. Although the long-term consequences of COVID-19 are not well-known, evidence from similar diseases alerts for the possibility of long-term impaired physical function and reduced quality of life, especially in those requiring critical care. Therefore, rehabilitation strategies are needed to improve outcomes in COVID-19 survivors. Among the possible strategies, resistance training (RT) might be particularly interesting, since it has been shown to increase functional capacity both in acute and chronic respiratory conditions and in cardiac patients. The present article aims to propose evidence-based and practical suggestions for RT prescription for people who have been diagnosed with COVID-19 with a special focus on immune, respiratory, and cardiovascular systems. Based on the current literature, we present RT as a possible safe and feasible activity that can be time-efficient and easy to be implemented in different settings.

Towards Personalized Management of Sarcopenia in COPD

The awareness of the presence and consequences of sarcopenia has significantly increased over the past decade. Sarcopenia is defined as gradual loss of muscle mass and strength and ultimately loss of physical performance associated with aging and chronic disease. The prevalence of sarcopenia is higher in chronic obstructive pulmonary disease (COPD) compared to age-matched controls. Current literature suggests that next to physical inactivity, COPD-specific alterations in physiological processes contribute to accelerated development of sarcopenia. Sarcopenia in COPD can be assessed according to current guidelines, but during physical performance testing, ventilatory limitation should be considered. Treatment of muscle impairment can halt or even reverse sarcopenia, despite respiratory impairment. Exercise training and protein supplementation are currently at the basis of sarcopenia treatment. Furthermore, effective current and new interventions targeting the pulmonary system (eg, smoking cessation, bronchodilators and lung volume reduction surgery) may also facilitate muscle maintenance. Better understanding of disease-specific pathophysiological mechanisms involved in the accelerated development of sarcopenia in COPD will provide new leads to refine nutritional, exercise and physical activity interventions and develop pharmacological co-interventions.

The role of peripheral muscle fatigability on exercise intolerance in COPD

INTRODUCTION

Exercise limitation in chronic obstructive pulmonary disease (COPD) is multi-factorial; however, growing evidence indicates that muscle dysfunction may contribute in some patients.

AREAS COVERED

This work outlines current evidence for and against increased peripheral muscle fatigability in COPD through a comprehensive review of relevant literature available on PubMed/MEDLINE until May 2020. The authors first discuss key methodological issues relative to muscle fatigue assessment by non-volitional techniques, particularly magnetic stimulation. The authors then provide a detailed discussion of critical studies to have objectively measured skeletal muscle fatigue in individuals with COPD.

EXPERT OPINION

Current evidence indicates that localized (knee extension) and cycling exercise are associated with increased quadriceps fatigability in most COPD patients. Increased fatigability, however, has not been consistently found in response to walking, likely reflecting the tendency of 'central' respiratory constraints to overshadow potential functional impairments in the appendicular muscles in this form of exercise. Thus, addressing skeletal muscle abnormalities may be critical to translate improvements in lung mechanics (e.g., due to bronchodilator therapy) into better exercise tolerance. The positive effects of pulmonary rehabilitation on muscle fatigability are particularly encouraging and suggest a role for these measurements to test the efficacy of emerging adjunct training strategies focused on the peripheral muscles.

Heart, lungs, and muscle interplay in worsening activity-related breathlessness in advanced cardiopulmonary disease

PURPOSE OF REVIEW

Activity-related breathlessness is a key determinant of poor quality of life in patients with advanced cardiorespiratory disease. Accordingly, palliative care has assumed a prominent role in their care. The severity of breathlessness depends on a complex combination of negative cardiopulmonary interactions and increased afferent stimulation from systemic sources. We review recent data exposing the seeds and consequences of these abnormalities in combined heart failure and chronic obstructive pulmonary disease (COPD).

RECENT FINDINGS

The drive to breathe increases ('excessive breathing') secondary to an enlarged dead space and hypoxemia (largely COPD-related) and heightened afferent stimuli, for example, sympathetic overexcitation, muscle ergorreceptor activation, and anaerobic metabolism (largely heart failure-related). Increased ventilatory drive might not be fully translated into the expected lung-chest wall displacement because of the mechanical derangements brought by COPD ('inappropriate breathing'). The latter abnormalities, in turn, negatively affect the central hemodynamics which are already compromised by heart failure. Physical activity then decreases, worsening muscle atrophy and dysfunction.

SUMMARY

Beyond the imperative of optimal pharmacological treatment of each disease, strategies to lessen ventilation (e.g., walking aids, oxygen, opiates and anxiolytics, and cardiopulmonary rehabilitation) and improve mechanics (heliox, noninvasive ventilation, and inspiratory muscle training) might mitigate the burden of this devastating symptom in advanced heart failure-COPD.

Handgrip strength and its relation to isokinetic dynamometry in COPD

Abstract Introduction: Muscle dysfunction is one of the major changes found in chronic obstructive pulmonary disease (COPD) and associated with loss of functionality, morbidity and mortality. Objective: correlate two strength assessment methods: manual dynamometry for handgrip strength and isokinetic dynamometry for quadriceps strength in patients with COPD, and assess the body mass index, airflow obstruction, dyspnea, and exercise capacity (BODE), quality of life and muscle strength. Method: twenty-five patients with moderate to very severe COPD were evaluated by pulmonary function parameters, anthropometric variables, functional capacity, via the six-minute walk test, dyspnea, applying the modified Medical Research Council (mMRC) scale, BODE, quality of life, using the Saint George's Respiratory Questionnaire (SGRQ), handgrip strength with manual dynamometer and quadriceps force using an isokinetic dynamometer. Muscle strength was assessed with a manual portable dynamometer and isokinetic dynamometer. For statistical analysis, ANOVA with Bonferroni’s post-test, the chi-squared test and Pearson's correlation coefficient were used. Results: There was a strong correlation between the strength measurements and the two instruments (torque and quadriceps extension power with right handgrip strength: r = 0.74; p <0.001). The patients classified as very severe exhibited worse performance in the strength tests when compared to the moderate group, albeit with no statistically significant difference. Conclusion: In muscle strength measurements, a strong correlation was detected between the isokinetic dynamometer for quadriceps and the manual dynamometer for handgrip strength. These findings indicate that, in clinical practice, the manual dynamometer for handgrip strength could be used to assess peripheral muscle strength in patients with COPD.