Effect of respiratory muscle endurance training in patients with COPD undergoing pulmonary rehabilitation

BACKGROUND: Respiratory muscle endurance training (hyperpnea training) has been shown to have beneficial effects in patients with COPD. STUDY OBJECTIVES: The purpose of this study was to determine whether hyperpnea training, when added to an endurance exercise training program, would lead to additional benefits compared with endurance training alone in patients with COPD. SETTING AND PARTICIPANTS: Patients with COPD entering an 8-week outpatient pulmonary rehabilitation program. Fifteen patients (mean [+/- SE] FEV1, 45 +/- 6% predicted) were randomized to combined therapy, and 14 patients (mean FEV1, 44 +/- 4% predicted) were randomized to endurance training. METHODS: Peak exercise capacity, exercise endurance time during constant workload cycle exercise, 6-min walk distance, quality of life as measured by the chronic respiratory questionnaire, respiratory muscle strength and endurance, and quadriceps fatigability were measured before and after endurance or combined training. RESULTS: After rehabilitation, peak exercise capacity, exercise endurance time, 6-min walk distance, and quality of life all increased in both groups, but there was no significant difference in the extent of improvement between groups. Mean respiratory muscle endurance increased to a significantly greater extent in the combined therapy group (17.5 +/- 2.7 vs 8.5 +/- 2.5 min, respectively; p = 0.02). Respiratory muscle strength was significantly increased, and quadriceps fatigability was significantly reduced after rehabilitation in the combined therapy group but not in the endurance training group, but the difference between groups did not reach statistical significance. CONCLUSION: The endurance of the respiratory muscles can be improved by specific training beyond that achieved by endurance training alone in patients with COPD. However, this improvement did not translate into additional improvement in quality of life or exercise performance.     

Aerobic and strength training in patients with chronic obstructive pulmonary disease

The purpose of this study was to evaluate whether strength training is a useful addition to aerobic training in patients with chronic obstructive pulmonary disease (COPD). Forty-five patients with moderate to severe COPD were randomized to 12 wk of aerobic training alone (AERO) or combined with strength training (AERO + ST). The AERO regimen consisted of three weekly 30-min exercise sessions on a calibrated ergocycle, and the ST regimen included three series of eight to 10 repetitions of four weight lifting exercises. Measurements of peripheral muscle strength, thigh muscle cross-sectional area (MCSA) by computed tomographic scanning, maximal exercise capacity, 6-min walking distance (6MWD), and quality of life with the chronic respiratory questionnaire were obtained at baseline and after training. Thirty-six patients completed the program and constituted the study group. The strength of the quadriceps femoris increased significantly in both groups (p < 0.05), but the improvement was greater in the AERO + ST group (20 +/- 12% versus 8 +/- 10% [mean +/- SD] in the AERO group, p < 0.005). The thigh MCSA and strength of the pectoralis major muscle increased in the AERO + ST group by 8 +/- 13% and 15 +/- 9%, respectively (p < 0.001), but not in the AERO group (3 +/- 6% and 2 +/- 10%, respectively, p > 0.05). These changes were significantly different in the two study groups (p < 0.01). The increase in strength of the latissimus dorsi muscle after training was modest and of similar magnitude for both groups. The changes in peak exercise work rate, 6MWD, and quality of life were comparable in the two groups. In conclusion, the addition of strength training to aerobic training in patients with COPD is associated with significantly greater increases in muscle strength and mass, but does not provide additional improvement in exercise capacity or quality of life.     

Specific expiratory muscle training in COPD

BACKGROUND: There are several reports showing that expiratory muscle strength and endurance can be impaired in patients with COPD. This muscle weakness may have clinically relevant implications. Expiratory muscle training tended to improve cough and to reduce the sensation of respiratory effort during exercise in patients other than those with COPD. METHODS: Twenty-six patients with COPD (FEV(1) 38% predicted) were recruited for the study. The patients were randomized into two groups: group 1, 13 patients were assigned to receive specific expiratory muscle training (SEMT) daily, six times a week, each session consisting of 1/2 h of training, for 3 months; and group 2, 13 patients were assigned to be a control group and received training with very low load. Spirometry, respiratory muscle strength and endurance, 6-min walk test, Mahler baseline dyspnea index (before), and the transitional dyspnea index (after) were measured before and after training. RESULTS: The training-induced changes were significantly greater in the SEMT group than in the control group for the following variables: expiratory muscle strength (from 86 +/- 4.1 to 104 +/- 4.9 cm H(2)O, p < 0.005; mean difference from the control group, 24%; 95% confidence interval, 18 to 32%), expiratory muscle endurance (from 57 +/- 2.9% to 76 +/- 4.0%, p < 0.001; mean difference from the control group, 29%; 95% confidence interval, 21 to 39%), and in the distance walked in 6 min (from 262 +/- 38 to 312 +/- 47 m, p < 0.05; mean difference from the control group, 14%; 95% confidence interval, 9 to 20%). There was also a small but not significant increase (from 5.1 +/- 0.9 to 5.6 +/- 0.7, p = 0.14) in the dyspnea index. CONCLUSIONS: The expiratory muscles can be specifically trained with improvement of both strength and endurance in patients with COPD. This improvement is associated with increase in exercise performance and no significant change in the sensation of dyspnea in daily activities.     

Exercise capacity and quadriceps muscle metabolism following training in subjects with COPD

The aim of the study was to determine whether 16 sessions of exercise training, completed twice weekly, alters exercise capacity, quadriceps muscle metabolism, cross-sectional area (CSA) and strength in subjects with chronic obstructive pulmonary disease (COPD). We studied (a) 10 COPD subjects (mean age+/-sem = 71+/-2 years; FEV1 = 0.99+/-0.1 L) before and after 16 sessions of exercise training, and (b) 10 healthy subjects (age = 68+/-3 years). The COPD subjects underwent an incremental peak exercise test using a cycle ergometer and a 6-min walk test: both improved following exercise training (P < 0.05). Magnetic resonance spectroscopy measurements, in quadriceps muscle, of post-exercise phosphocreatinine (PCr) recovery kinetics were used to assess mitochondrial function in vivo: in the COPD subjects pre-training this was 19+/-8% lower than in healthy subjects (P = 0.03), but a 38+/-12% increase was seen in the COPD subjects following training (P = 0.003). Magnetic resonance imaging was used to assess quadriceps CSA: after training in the COPD subjects this showed a 7+/-2% increase (P = 0.03). Quadriceps strength, measured by the best of five maximum voluntary contractions, also showed a 32+/-11% increase in the COPD subjects (P = 0.007). Sixteen sessions of exercise training, performed twice weekly, increased exercise capacity as well as quadriceps mitochondrial capacity, CSA and strength in the subjects with COPD.     

Skeletal muscle strength and endurance in patients with mild COPD and the effects of weight training.

This study poses two questions: 1) is there an abnormality in isokinetic skeletal muscle strength and endurance in mild chronic obstructive pulmonary disease (COPD)? and 2) what is the effect of a randomized, controlled, 12 week hospital outpatient weight training programme in terms of skeletal muscle function and exercise tolerance? Upper and lower limb isokinetic maximum and sustained muscle function were compared in 43 COPD patients (age 49+/-11 yrs), mean forced expiratory volume in one second (FEV1) 77+/-23% pred and 52 healthy, sedentary subjects (age 51 (10) yrs), mean FEV1 109+/-16% pred. The 43 COPD patients were randomly allocated into training (n=26) and control (n=17) groups. Isokinetic and isotonic muscle function, whole body endurance, maximal exercise capacity and lung function were measured. The COPD patients had reduced isokinetic muscle function (with the exception of sustained upper limb strength) as compared with healthy sedentary subjects. Muscle function improved after weight training in the COPD patients. Whole body endurance during treadmill walking also improved with no change in maximal oxygen consumption. A deficit in skeletal muscle function can be identified in patients with mild chronic obstructive pulmonary disease which cannot be explained by factors such as hypoxaemia and malnutrition. Intervention with weight training is effective in countering this deficit which the authors conclude is probably due to muscle deconditioning.     

Contractile leg fatigue after cycle exercise: a factor limiting exercise in patients with chronic obstructive pulmonary disease

We evaluated whether contractile fatigue of the quadriceps occurs after cycling exercise in patients with chronic obstructive pulmonary disease (COPD) and whether it could contribute to exercise limitation. Eighteen COPD patients performed two constant work-rate cycling exercises up to exhaustion. These tests were preceded by nebulization of placebo or 500 microg of ipratropium bromide. Muscle fatigue was defined as a postexercise reduction in quadriceps twitch force of more than 15% of the resting value. There was an increase in endurance time postipratropium compared with placebo nebulization (440 +/- 244 seconds vs. 322 +/- 188 seconds, p = 0.06). Nine patients developed contractile fatigue after placebo exercise. In these patients, ipratropium did not increase the endurance time (394 +/- 220 seconds with placebo vs. 400 +/- 119 seconds with ipratropium) despite an 11% improvement in FEV1. In the nine patients who did not fatigue after placebo exercise, endurance time increased from 249 +/- 124 seconds with placebo to 479 +/- 298 seconds with ipratropium (p < 0.05). There was a significant correlation between the improvement in endurance time with ipratropium and quadriceps twitch force at 10 minutes after placebo exercise (r = 0.59, p = 0.01). The occurrence of contractile fatigue during exercise may explain why bronchodilation fails to improve exercise tolerance in some COPD patients.     

Evidence of local exercise-induced systemic oxidative stress in chronic obstructive pulmonary disease patients.

Chronic inactivity may not be the sole factor involved in the myopathy of chronic obstructive pulmonary disease (COPD) patients. One hypothesis is that exercise-induced oxidative stress that leads to muscle alterations may also be involved. This study investigated whether exercise localised to a peripheral muscle group would induce oxidative stress in COPD patients. Eleven COPD patients (FEV1 1.15+/-0.4 L (mean+/-SD)) and 12 healthy age-matched subjects with a similar low quantity of physical activity performed endurance exercise localised to a peripheral muscle group, the quadriceps of the dominant leg. The authors measured plasma levels of thiobarbituric reactive substances (TBARs) as an index of oxidative stress, the release in superoxide anion (O2*-) by stimulated phagocytes as an oxidant, and blood vitamin E as one antioxidant. Quadriceps endurance was significantly lower in the COPD patients compared with healthy subjects (136+/-16 s versus 385+/-69 s (mean+/-SEM), respectively). A significant increase in TBARs 6 h after quadriceps exercise was only found in the COPD patients. In addition, significantly higher O2*- release and lower blood vitamin E levels were found in COPD patients than in controls at rest. This blood vitamin E level was significantly correlated with the resting level of plasma TBARs in the COPD patients. This study mainly showed that quadriceps exercise induced systemic oxidative stress in chronic obstructive pulmonary disease patients and that vitamin E levels were decreased in these patients at rest. The exact relevance of these findings to chronic obstructive pulmonary disease myopathy needs to be elucidated.     

Feasibility of high-intensity,interval-based respiratory muscle training in COPD

BACKGROUND: Specific respiratory muscle training can improve respiratory muscle function in patients with COPD, but the magnitude of improvement appears dependent on the magnitude of the training load. High training loads are difficult to achieve using conventional, constant loading techniques, but may be possible using interval-based training techniques. METHODS: To assess the feasibility of high-intensity respiratory muscle training, nine subjects with moderate-to-severe COPD (FEV(1) 34 +/- 12% predicted [mean +/- SD]) completed 8 weeks of interval-based respiratory muscle training combined with a general exercise program. This involved three 20-min sessions per week, each session comprising seven 2-min bouts of breathing against a constant inspiratory threshold load, each bout separated by 1 min of unloaded recovery. Inspiratory load was progressively incremented. Respiratory muscle strength (maximum inspiratory pressure generated against an occluded airway [PImax]) and endurance (maximum pressure generated against a progressively increasing inspiratory threshold load [Pthmax]) were measured before and immediately after the 8-week training period. RESULTS: By the third training session (week 1), subjects breathed against a threshold that required generation of pressures equivalent to 68 +/- 5% of the pretraining PImax. By week 8, this had increased to 95 +/- 12% of the pretraining PImax. On completion of training, PImax had increased by 32 +/- 27% (p < 0.05), Pthmax had increased by 56 +/- 33% (p < 0.05), and Pthmax/PImax had increased by 20 +/- 20% (p < 0.05). CONCLUSIONS: This study has demonstrated that high-intensity, interval-based respiratory muscle training is feasible in patients with moderate-to-severe COPD, resulting in significant improvements in respiratory muscle strength and endurance when performed three times a week for 8 weeks.     

The contribution of peripheral muscle function to shuttle walking performance in patients with chronic obstructive pulmonary disease

PURPOSE: The contribution of muscle strength and mass to incremental and endurance walking performance in chronic obstructive pulmonary disease (COPD) is unknown. This study analyzes the relationship between field incremental and endurance walking performance and indices of peripheral muscle mass and strength. METHODS: Eighty-five stable COPD patients (53 males; mean [SD] age = 67 [9] years; mean [SD] forced expiratory volume in 1 second [FEV1] = 35 [14] [% predicted]) were studied prior to participation in pulmonary rehabilitation. Isometric quadriceps and handgrip strength were measured. Total body and lower limb lean muscle mass were estimated using dual energy x-ray absorptiometry. Exercise performance was measured using the incremental shuttle walk test (ISWT) and the endurance (ESWT) shuttle walk test. RESULTS: ISWT was related to muscle strength (r = 0.467, P 相似文献   

Improvement in quadriceps strength and dyspnea in daily tasks after 1 month of electrical stimulation in severely deconditioned and malnourished COPD

STUDY OBJECTIVES: Low body weight in COPD patients is associated with worsening dyspnea, reduced leg strength, and poor prognosis. Classical rehabilitation strategies are then limited by reduced exercise tolerance. Thus, we proposed to evaluate whether electrostimulation (ES) was a beneficial technique in the rehabilitation programs for severely deconditioned COPD patients after an acute exacerbation. DESIGN: Randomized, controlled study. SETTING: Pulmonary rehabilitation center. PATIENTS: Seventeen patients with severe COPD (mean [ +/- SD] FEV(1), 30 +/- 3% predicted) and low body mass index (BMI) [18 +/- 2.5 kg/m(2)]. METHODS: Patients were randomly assigned either to usual rehabilitation (UR) alone or to a UR-plus-ES program for 4 weeks. Quadriceps muscle strength, total muscle mass (MM), exercise capacity, and health-related quality of life were measured before and after rehabilitation. RESULTS: The training with ES plus UR induced a significant twofold improvement in the mean number of maximal voluntary contraction (MVC) compared to UR alone (97 +/- 71 vs 36 +/- 34 contractions, respectively; p = 0.03) and resulted in a more significant improvement in dyspnea when performing daily tasks (decrease in the dyspnea domain score of the 28-item Maugeri Foundation Respiratory Failure questionnaire, -1.7 +/- 1.0 vs -0.2 +/- 1.2 points, respectively; p = 0.05). There was also a significant increase in walking distance (63 +/- 40 m; p = 0.01) and BMI (0.6 +/- 0.5 kg/m(2); p = 0.02) after training in the ES + UR group. A significant relationship was found between changes in MVC and changes in MM after training in the ES + UR group (r = 0.94; p = 0.03). CONCLUSIONS: The combination of ES and UR was associated with greater improvement in quadriceps strength and dyspnea during the performance of daily tasks than UR alone in severely disabled COPD patients with low BMI. In this population, ES has been revealed as a useful procedure, complementing the usual pulmonary rehabilitation.     

Reduced muscle redox capacity after endurance training in patients with chronic obstructive pulmonary disease.

The present study was undertaken to test whether endurance training in patients with COPD, along with enhancement of muscle bioenergetics, decreases muscle redox capacity as a result of recurrent episodes of cell hypoxia induced by high intensity exercise sessions. Seventeen patients with COPD (FEV(1), 38 +/- 4% pred; PaO2), 69 +/- 2.7 mm Hg; PaCO2, 42 +/- 1.7 mm Hg) and five age-matched control subjects (C) were studied pretraining and post-training. Reduced (GSH) and oxidized (GSSG) glutathione, lipid peroxidation, and gamma-glutamyl cysteine synthase heavy subunit chain mRNA expression (gammaGCS-HS mRNA) were measured in the vastus lateralis. Pretraining redox status at rest and after moderate (40% Wpeak) constant-work rate exercise were similar between groups. After training (DeltaWpeak, 27 +/- 7% and 37 +/- 18%, COPD and C, respectively) (p < 0.05 each), GSSG levels increased only in patients with COPD (from 0.7 +/- 0.08 to 1.0 +/- 0.15 nmol/ mg protein, p < 0.05) with maintenance of GSH levels, whereas GSH markedly increased in C (from 4.6 +/- 1.03 to 8.7 +/- 0.41 nmol/ mg protein, p < 0.01). Post-training gammaGCS-HS mRNA levels increased after submaximal exercise in patients with COPD. No evidence of lipid peroxidation was observed. We conclude that although endurance training increased muscle redox potential in healthy subjects, patients with COPD showed a reduced ability to adapt to endurance training reflected in lower capacity to synthesize GSH.     

Exercise-induced quadriceps oxidative stress and peripheral muscle dysfunction in patients with chronic obstructive pulmonary disease

Exercise-induced muscle oxidative stress may be involved in the myopathy associated with chronic obstructive pulmonary disease (COPD). This study was designed to look at whether local exercise induces muscle oxidative stress and whether this oxidative stress may be associated with the reduced muscle endurance in patients with COPD. Quadriceps endurance was measured in 12 patients with COPD (FEV1 = 0.96 +/- 0.14 SEM) and 10 healthy sedentary subjects by repeated knee extensions of the dominant leg. Biopsies of the vastus lateralis muscle were obtained before and 48 hours after exercise. Muscle oxidative stress was measured by lipid peroxidation and oxidized proteins. Muscle antioxidant was evaluated by peroxidase glutathion activity. Quadriceps endurance was significantly reduced in patients with COPD when compared with the healthy control subjects (p < 0.01). Forty-eight hours postexercise, only patients with COPD had a significant increase in muscle lipid peroxidation (p < 0.05) and oxidized proteins (p < 0.05), whereas increased peroxidase glutathion activity was only observed in control subjects (p < 0.05). Both increases in muscle lipid peroxidation and oxidized proteins were significantly and inversely correlated with quadriceps endurance capacity in COPD (p < 0.05). In summary, local exercise induced muscle oxidative stress in patients with COPD, whereas it failed to raise antioxidant activity. In these individuals, muscle oxidative stress was associated with a reduced quadriceps endurance.     

Comparison of specific expiratory, inspiratory, and combined muscle training programs in COPD

BACKGROUND: Respiratory muscle weakness may contribute to dyspnea and exercise limitation in patients with significant COPD. In an attempt to reduce the severity of breathlessness and to improve exercise tolerance, inspiratory muscle training has been applied in many COPD patients. On the other hand, there is a paucity of data related to expiratory muscle performance and training in COPD. METHODS: Thirty-two patients with significant COPD (ie, mean FEV(1), 37% of predicted) were recruited for the study. The patients were randomized into four groups: eight patients were assigned to receive specific expiratory muscle training (SEMT); eight patients received specific inspiratory muscle training (SIMT); eight patients received SEMT and SIMT (ie, the SEMT + SIMT group); and eight patients who were assigned to a control group received training with very low load. All patients trained daily, six times a week, with each session consisting of one half hour of training, for 3 months. Spirometry, respiratory muscle strength and endurance, 6-min walk test distance, the perception of dyspnea, and the Mahler baseline dyspnea index (BDI) were measured before and following training. RESULTS: Training caused a statistically significant specific increase in the expiratory muscle strength and endurance (in the SEMT and SEMT + SIMT groups) and in the inspiratory muscle strength and endurance (in the SIMT and SEMT + SIMT groups). There was significant increase in the distance walked in 6 min in the SEMT, SIMT, and SEMT + SIMT groups. However, the increase in the SIMT and SEMT + SIMT groups was significantly greater than that in the SEMT group. There was a statistically significant increase in the BDI, and a decrease in the mean Borg score during breathing against resistance in the SIMT and SEMT + SIMT groups, with no changes in the SEMT and control groups. CONCLUSIONS: The inspiratory and expiratory muscles can be specifically trained with improvement of both muscle strength and endurance. The improvement in the inspiratory muscle performance is associated with an increase in the 6-min walk test distance and the sensation of dyspnea. There is no additional benefit gained by combining SIMT with SEMT, compared to using SIMT alone.     

The effects of 1 year of specific inspiratory muscle training in patients with COPD

AIM: We assessed the long-term benefits of inspiratory muscle training (IMT) on inspiratory muscle strength, exercise capacity, the perception of dyspnea, quality of life, primary care use, and hospitalizations in patients with significant COPD. PATIENTS: Forty-two consecutive COPD patients with FEV(1) < 50% of predicted were randomized into a group that received IMT for 1 year, and a control group that received training with a very low load. RESULTS: There was a statistically significant increase in inspiratory muscle strength (at the end of the third month of training) as assessed by maximal inspiratory pressure (from 71 +/- 4.9 to 90 +/- 5.1 cm H(2)O [+/- SEM], p < 0.005) and 6-min walk distance (at the end of the third month of training; from 256 +/- 41 to 312 +/- 54 m; p < 0.005), a decrease in the mean Borg score during breathing against resistance (at the end of the ninth month of training), improvement in the health-related quality-of-life scores (at the end of the sixth month of training) in the training group but not in the control group. At the end of the training year, these changes were maintained; in addition, a decrease in primary health-care use and hospitalization days was observed. CONCLUSIONS: Our study shows that during IMT in patients with significant COPD, there is an increase in exercise capacity, improvement in quality of life, and decrease in dyspnea. Our study also provides evidence that long-term IMT can decrease the use of health services and hospitalization days.     

Applicability of a threshold loading device for inspiratory muscle testing and training in patients with COPD

We evaluated application of a Pth device for testing inspiratory muscle endurance among patients with severe but stable COPD. Endurance time in five patients was reproducible. Magnitude of variability was +/- 1.26 minutes with a range of +/- 0.19 to +/- 2.28 minutes. Eleven inpatients completed inspiratory muscle training twice daily for four weeks in addition to their usual program of respiratory rehabilitation. The mean age of our experimental cohort was 65 years; FEV1, 33 +/- 12 percent predicted; and Dsb, 42 +/- 7 percent predicted. Baseline measurements showed no significant differences in pulmonary function, exercise tolerance, inspiratory muscle strength or inspiratory muscle endurance between control and study groups. Following training, the study group significantly improved inspiratory muscle endurance as evidenced by an increase in endurance time while breathing against the same absolute external Pth load used during baseline assessments. There were no associated changes in lung mechanics, muscle strength or exercise tolerance.     

Effect of pulmonary rehabilitation on quadriceps fatiguability during exercise

We have recently shown that patients with chronic obstructive pulmonary disease (COPD) develop contractile fatigue of their quadriceps muscle following endurance exercise. Pulmonary rehabilitation can produce physiological adaptations in patients with COPD. We hypothesized that if pulmonary rehabilitation induces physiological adaptations in the exercising muscle, it should become more fatigue resistant. Twenty one patients with COPD, mean age 69.9 +/- 1.9 yr, FEV(1) 45 +/- 4% predicted, participated in an 8-wk outpatient, supervised pulmonary rehabilitation exercise program. Quadriceps contractile fatigue was detected by a fall in quadriceps twitch force postexercise. Twitch force was measured during magnetic stimulation of the femoral nerve. Because potentiated twitches may be more sensitive at detecting fatigue, both unpotentiated (TwQu) and potentiated (TwQp) twitches were obtained before and 10, 30, and 60 min after constant load cycle exercise. Prerehabilitation, during constant load exercise, patients exercised at 37 +/- 4 W for 11.2 +/- 1.8 min. Prerehabilitation, TwQu fell significantly postexercise down to a minimum value of 82.5 +/- 3.1% of the baseline preexercise value (p < 0.001). Similarly, prerehabilitation, TwQp fell significantly postexercise down to a minimum value of 73.9 +/- 3.9% of baseline (p < 0.001). Postrehabilitation, for the same intensity and duration of exercise, TwQu was not significantly different from baseline at any time postexercise. Postrehabilitation, TwQp fell significantly postexercise but the fall in TwQp with exercise was significantly less postrehabilitation compared with prerehabilitation (p < 0.001). In conclusion, pulmonary rehabilitation resulted in increased fatigue resistance of the quadriceps muscle in patients with COPD.     

Exercise training in COPD: how to distinguish responders from nonresponders

PURPOSE: Pulmonary rehabilitation programs consistently have improved exercise capacity, quality of life, and symptoms over the past decade. Although training has been shown to be an essential component of the rehabilitation program, individual patients do not always benefit to the same extent. The present study was designed to investigate which patients were achieving significant benefit of exercise training. METHODS: Forty-nine stable outpatients with moderate to severe COPD (FEV1 37 (15)%pred) were evaluated before and after 12 weeks of exercise training (3 times per week). Responders in exercise capacity were defined as having 15% increase in maximal workload and/or 25% increase in walking distance, while responders in quality of life showed an improvement of at least 10 points on the chronic respiratory disease questionnaire. With multivariate discriminant analysis, responders were distinguished from nonresponders based upon their initial characteristics. RESULTS: Thirty-two patients were responders in terms of improved exercise capacity. Ventilatory reserve (VE/MVV), inspiratory muscle strength (Plmax), and peripheral muscle strength (handgrip force and quadriceps force) were significant predictors of the training response (P < 0.05) (accuracy 80% P < 0.001). Although the explained variance was modest, patients that were clearly ventilatory limited and had normal skeletal muscle strength were not likely to benefit from exercise training in terms of exercise capacity. No physiologic variables predicted whether a patient would increase quality of life after exercise training. CONCLUSION: Patients with reduced exercise capacity who experience less ventilatory limitation to exercise and more reduced respiratory and peripheral muscle strength are more likely to improve with exercise training. Improvements in quality of life after exercise training were significant but remained unpredictable with variables included in the present trial.     

Cycle ergometer and inspiratory muscle training in chronic obstructive pulmonary disease.

In patients with chronic obstructive pulmonary disease (COPD) the intensity of aerobic training is limited by dyspnea. Improving strength of the inspiratory muscles could enhance aerobic exercise training by reducing exercise-related dyspnea. We examined effects of home-based inspiratory muscle training (IMT) and cycle ergometry training (CET) in 53 patients with moderate to severe COPD (FEV(1)% pred, 50 +/- 17 [mean +/- SD]). Patients were randomly assigned to 4 mo of training in one of four groups: IMT, CET, CET + IMT, or health education (ED). Patients were encouraged to train to the limits of their dyspnea. Inspiratory muscle strength and endurance increased in IMT and CET + IMT groups compared with CET and ED groups (p < 0. 01). Peak oxygen uptake increased and heart rate, minute ventilation, dyspnea, and leg fatigue decreased at submaximal work rates in the CET and CET + IMT groups compared with the IMT and ED groups (p < 0. 01). There were no differences between the CET and CET + IMT groups. Home-based CET produced a physiological training effect and reduced exercise-related symptoms while IMT increased respiratory muscle strength and endurance. The combination of CET and IMT did not produce additional benefits in exercise performance and exercise-related symptoms. This is the first study to demonstrate a physiological training effect with home-based exercise training.     

Walking versus cycling: sensitivity to bronchodilation in chronic obstructive pulmonary disease

RATIONALE: There is no consensus regarding which exercise test to use to evaluate the functional impact of bronchodilators in patients with chronic obstructive pulmonary disease. OBJECTIVE AND METHODS: Bronchodilator-induced changes in endurance time were evaluated during cycling and walking in 17 patients with chronic obstructive pulmonary disease who completed two cycle endurance tests and two endurance shuttle walks at 80% of peak capacity. Each endurance test was preceded by the nebulization of a placebo or 500 microg of ipratropium bromide using a randomized, double-blind, crossover design. Quadriceps twitch force was measured with magnetic stimulation of the femoral nerve before and after each endurance test. RESULTS: Cycling endurance time did not improve significantly after bronchodilation despite a significant increase in FEV1 (delta endurance time ipratropium bromide - placebo: 51 +/- 255 s, p = 0.42). A similar change in FEV1 was associated with a significant improvement in walking endurance time (delta endurance time ipratropium bromide - placebo: 164 +/- 177 s, p < 0.01). A 22 +/- 17% fall in quadriceps twitch force was observed after cycling, whereas no significant change was seen after walking. CONCLUSION: The endurance shuttle walk is a sensitive test to detect changes in exercise tolerance after bronchodilation. Differences in the occurrence of quadriceps muscle fatigue may explain, in part, the different responsiveness to change between cycling and walking.     

Inspiratory muscle training in patients with chronic obstructive pulmonary disease

To investigate the effects of inspiratory muscle resistive loading training (IMT) on exercise performance in chronic obstructive pulmonary disease (COPD), 13 patients undergoing standard pulmonary rehabilitation were divided into control (n = 6) and experimental (n = 7) groups. Prior to training, we measured inspiratory muscle strength and endurance, resting pulmonary function, and exercise performance on a bicycle ergometer (a progressive test and an endurance test at two thirds of maximal work load). We then determined their resistive loads for training by measuring their 10-min maximal sustainable resistance. Training by patients in the experimental group involved inspiring against a predetermined resistive load. The control subjects breathed through a sham training tube, so that studies were performed in double-blind fashion. The training consisted of 15-min sessions twice daily for 4 wk. The IMT dramatically improved inspiratory muscle endurance--represented as either sustainable inspiratory pressure (SIP) or endurance time at 60% of maximal inspiratory mouth pressure (Pimmax) at functional residual capacity. The SIP of the trained group increased from 29 +/- 11 to 46 +/- 11% of Pimmax (p less than 0.005). Training slightly increased inspiratory muscle strength (p less than 0.05), as determined by Pimmax. In contrast, resting pulmonary function and performance of both progressive and constant-load exercise remained unchanged. We conclude that 4-wk IMT in a pulmonary rehabilitation setting improves inspiratory muscle endurance in patients with COPD without changing pulmonary function or exercise performance.