***TASK*** the task is to summarize an input biomedical literature in six sentences 
    ***INPUT*** the input is a biomedical literature 
    ***OUTPUT*** the output is the summary of an input biomedical literature in six sentences 
    ***DOCUMENTATION*** 
    ***EXAMPLES*** 
    Input: Introduction Patients with chronic obstructive pulmonary disease ( COPD ) exhibit aerobic function , autonomic nervous system , and mucociliary clearance alterations . These parameters can be attenuated by aerobic training , which can be applied with continuous or interval efforts . However , the possible effects of aerobic training , using progressively both continuous and interval sessions ( ie , linear periodization ) , require further investigation . Aim To analyze the effects of 12-week aerobic training using continuous and interval sessions on autonomic modulation , mucociliary clearance , and aerobic function in patients with COPD . Methods Sixteen patients with COPD were divided into an aerobic ( continuous and interval ) training group ( AT ) ( n=10 ) and a control group ( CG ) ( n=6 ) . An incremental test ( initial speed of 2.0 km·h−1 , constant slope of 3 % , and increments of 0.5 km·h−1 every 2 minutes ) was performed . The training group underwent training for 4 weeks at 60 % of the peak velocity reached in the incremental test ( vVO2peak ) ( 50 minutes of continuous effort ) , followed by 4 weeks of sessions at 75 % of vVO2peak ( 30 minutes of continuous effort ) , and 4 weeks of interval training ( 5 × 3-minute effort at vVO2peak , separated by 1 minute of passive recovery ) . Intensities were adjusted through an incremental test performed at the end of each period . Results The AT presented an increase in the high frequency index ( ms2 ) ( P=0.04 ) , peak oxygen uptake ( VO2peak ) ( P=0.01 ) , vVO2peak ( P=0.04 ) , and anaerobic threshold ( P=0.02 ) . No significant changes were observed in the CG ( P>0.21 ) group . Neither of the groups presented changes in mucociliary clearance after 12 weeks ( AT : P=0.94 and CG : P=0.69 ) . Conclusion Twelve weeks of aerobic training ( continuous and interval sessions ) positively influenced the autonomic modulation and aerobic parameters in patients with COPD .  However , mucociliary clearance was not affected by aerobic training In the GRADE approach , r and omized trials start as high- quality evidence and observational studies as low- quality evidence , but both can be rated down if most of the relevant evidence comes from studies that suffer from a high risk of bias . Well-established limitations of r and omized trials include failure to conceal allocation , failure to blind , loss to follow-up , and failure to appropriately consider the intention-to-treat principle . More recently recognized limitations include stopping early for apparent benefit and selective reporting of outcomes according to the results . Key limitations of observational studies include use of inappropriate controls and failure to adequately adjust for prognostic imbalance . Risk of bias may vary across outcomes ( e.g. , loss to follow-up may be far less for all-cause mortality than for quality of life ) , a consideration that many systematic review s ignore . In deciding whether to rate down for risk of bias -- whether for r and omized trials or observational studies -- authors should not take an approach that averages across studies . Rather , for any individual outcome , when there are some studies with a high risk , and some with a low risk of bias , they should consider including only the studies with a lower risk of bias Abstract Objective : The aim of this study was to investigate the effects of moderate continuous training ( MCT ) and high intensity aerobic interval training ( AIT ) on systolic ventricular function and aerobic capacity in COPD patients . Methods : Seventeen patients with COPD ( 64 ± 8 years , 12 men ) with FEV1 of 52.8 ± 11 % of predicted , were r and omly assigned to isocaloric programs of MCT at 70 % of max heart rate ( HR ) for 47 minutes ) or AIT ( ∼90 % of max HR for 4 × 4 minutes ) three times per week for 10 weeks . Baseline cardiac function was compared with 17 age- and sex-matched healthy individuals . Peak oxygen uptake ( VO2-peak ) and left ( LV ) and right ventricular ( RV ) function examined by echocardiography , were measured at baseline and after 10 weeks of training . Results : At baseline , the COPD patients had reduced systolic function compared to healthy controls ( p < 0.05 ) . After the training , AIT and MCT  increased VO2-peak by 8 % and 9 % and work economy by 7 % and 10 % , respectively ( all p < 0.05 ) . LV and RV systolic function both improved ( p < 0.05 ) , with no difference between the groups after the two modes of exercise training . Stroke volume increased by 17 % and 20 % , LV systolic tissue Doppler velocity ( S ’ ) by 18 % and 17 % and RV S ’ by 15 % after AIT and MCT , respectively ( p < 0.05 ) . Conclusion : Systolic cardiac function is reduced in COPD . Both AIT and MCT  improved systolic cardiac function . In contrast to other patient groups studied , higher exercise intensity does not seem to have additional effects on cardiac function or aerobic capacity in COPD patients Objectives Chronic obstructive pulmonary disease ( COPD ) is associated with cardiac autonomic nervous system dysregulation . This study evaluates the effects of interval hypoxic training on cardiovascular and respiratory control in patients with mild COPD . Methods In 18 eucapnic normoxic mild COPD patients ( age 51.7 ± 2.4 years , mean ± SEM ) , r and omly assigned to either training or placebo group , and 14 age-matched healthy controls ( 47.7 ± 2.8 years ) , we monitored end-tidal carbon dioxide , airway flow , arterial oxygen saturation , electrocardiogram , and continuous noninvasive blood pressure at rest , during progressive hypercapnic hyperoxia and isocapnic hypoxia to compare baroreflex sensitivity to hypoxia and hypercapnia before and after 3 weeks of hypoxic training . In double-blind fashion , both groups received 15 sessions of passive intermittent hypoxia ( training group ) or normoxia ( placebo group ) . For the hypoxia group , each session consisted of three to five hypoxic ( 15–12 % oxygen ) periods ( 3–5 min ) with 3-min normoxic intervals . The placebo group inhaled normoxic air . Results Before training , COPD patients  showed depressed baroreflex sensitivity , as compared with healthy individuals , without evident chemoreflex abnormalities . After training , in contrast to placebo group , the training group showed increased ( P < 0.05 ) baroreflex sensitivity up to normal levels and selectively increased hypercapnic ventilatory response ( P < 0.05 ) , without changes in hypoxic ventilatory response . Conclusion Eucapnic normoxic mild COPD patients already showed signs of cardiovascular autonomic abnormalities at baseline , which normalized with hypoxic training . If confirmed in more severe patients , interval hypoxic training may be a therapeutic strategy to rebalance early autonomic dysfunction in COPD patients BACKGROUND The chronic obstructive pulmonary disease ( COPD ) is associated with the strength and resistance decreasing in addition to the dysfunction on autonomic nervous system ( ANS ) . The aerobic training isolated or in association with the resistance training showed evidence of beneficial effects on an autonomic modulation of COPD ; however , there are no studies addressing the effect of isolated resistance training . AIMS This study aims at investigating the influence of resistance training on an autonomic modulation through heart rate variability ( HRV ) , functional capacity and muscle strength in individuals with COPD . DESIGN Clinical series study . SETTING Out patients . POPULATION The study involved 13 individuals with COPD . METHODS The experimental protocol was composed by an initial and final evaluation that consisted in autonomic evaluations ( HRV ) , cardiopulmonary functional capacity evaluation ( 6-minute walk test ) and strength evaluation ( dynamometry )  in addition by the resistance training performed by 24 sessions lasted 60 minutes each one and on a frequency of three times a week . The intensity was determined initially with 60 % of one maximum repetition and was progressively increased in each five sessions until 80 % . RESULTS The HRV temporal and spectral indexes analysis demonstrates improvement of autonomic modulation , with significant statistical increases to sympathetic and parasympathetic components of ANS representing by SDNN , LF and HF . In addition , it was observed significant statistical increases to shoulder abduction and knee flexion strength and functional capacity . CONCLUSION The exclusive resistance training performed was able to positively influence the autonomic modulation ; in addition it promoted benefits on cardiorespiratory functional capacity and strength benefits in individuals with COPD . CLINICAL REHABILITATION IMPACT This study could contribute to clinical and professionals research ers that act with COPD , even though the resistance component of pulmonary rehabilitation presents consensual benefits on several healthy indicators parameters . There is no evidence about the effects on HRV before . Moreover , this study showed , on clinical practice , the HRV uses as an ANS activity on sinus node evaluation and highlights further importance on scientific context Background : Pulmonary rehabilitation ( PR ) has emerged as a recommended st and ard of care in symptomatic COPD . Objectives : We now studied whether PR may affect cardiovascular response to exercise in these patients . Methods : Twenty-seven patients ( 9 females aged 69 ± 8 years ) with moderate-to-severe airflow obstruction admitted to a 9-week PR course performed a pre-to-post evaluation of lung function test and symptom-limited cardiopulmonary exercise test ( CPET ) .  Oxygen uptake ( VO2 ) , tidal volume ( VT ) , dyspnea and leg fatigue scores were measured during CPET  . Cardiovas-cular response was assessed by means of oxygen pulse ( O2Pulse ) , the oxygen uptake efficiency slope and heart rate recovery at the 1st min . Results : A significant increase in peak VO2 and in all cardiovascular parameters ( p < 0.05 ) was found following PR when compared to baseline . Leg fatigue ( p < 0.05 ) , but not dyspnea , was significantly reduced after PR . When assessed at metabolic and ventilatory iso levels [ % VCO2max and % minute ventilation ( VEmax ) ] , O2Pulse and VT were significantly higher ( p < 0.05 ) at submaximal exercise ( 75 and 50 % of VCO2max and VEmax ) after PR when compared to baseline . VT percent changes at 75 % VCO2max and 75 % VEmax after PR significantly correlated with corresponding changes in O2Pulse ( p < 0.01 ) . Conclusions : In COPD patients , a PR training program  improved the cardiovascular response during exercise at submaximal exercise independent of the external workload . This change was associated with an enhanced ventilatory function during exercise BACKGROUND Current literature lacks solid evidence on the improvement of heart rate variability ( HRV ) after exercise training in patients with COPD . OBJECTIVES We aim ed to investigate changes in HRV after two exercise training programs in patients with COPD and to investigate the determinants of these eventual changes . METHODS Forty patients with COPD ( FEV(1 ) 39 ± 13%pred ) were r and omized into high ( n = 20 ) or low ( n = 20 ) intensity exercise training ( 3-month duration ) , and had their HRV assessed by the head-up tilt test before and after either protocol s. Baseline spirometry , level of daily physical activity , exercise capacity , body composition , functional status , health-related quality of life and muscle force were also assessed to investigate the determinants of improvement in HRV after the training program . RESULTS There was a significant improvement in HRV only after the high-intensity protocol ( pre versus post ; SDNN 29 ± 15 ms versus 36 ± 19 ms ; rMSSD 22 ± 14 ms versus 28 ± 22 ms ; p < 0.05 for both ) . Higher values of biceps brachialis strength , time spent walking in daily life and SDNN at baseline were determinants of improvement in HRV after the training program . CONCLUSIONS High-intensity exercise training  improves HRV at rest and during orthostatic stimulus in patients with COPD . Better baseline total HRV , muscle force and daily physical activity level are predictors of HRV improvements after the training program BACKGROUND AND OBJECTIVES The present pilot study was undertaken to evaluate the efficacy of an aerobic exercise training ( AET ) program alone or combined with an antihypertensive agent ( irbesartan ) to reduce blood pressure ( BP ) and enhance heart rate variability ( HRV ) in chronic obstructive pulmonary disease patients . METHODS Twenty-one patients were r and omly assigned to a double-blind treatment with exercise and placebo ( n=11 ) or exercise and irbesartan ( n=10 ) . Subjects underwent 24 h  BP monitoring  and 24 h  electrocardiographic recording  before and after the 12-week AET . HRV was investigated using three indexes from the power spectral analysis and three indexes calculated from the time domain . The AET program consisted of exercising on a calibrated ergocycle for 30 min three times per week . Five patients in the placebo group were excluded during follow-up because they were not compliant . RESULTS There was no change in 24 h systolic and diastolic BP before ( 130+/-14 mmHg and 70+/-3 mmHg , respectively ) and after ( 128+/-8 mmHg and 70+/-8 mmHg , respectively ) exercise training in the placebo group , whereas in the irbesartan group systolic and diastolic B 
    Output:
    
Evidence synthesis of studies with high method ological quality revealed that a high quality evidence level supported a significant increase for time-domain heart rate variability ( HRV ) analyses and the heart rate recovery ( HRR ) following AET .
The review also found that frequency domain HRV analyses were not significantly affected by AET .
CONCLUSION Aerobic exercise training demonstrated beneficial but limited effects on the AF in COPD .
Presently , it is not clear whether these effects are sustained in the long term .