Key words: COPD; dyspnea; exercise; functional performance; health status; pulmonary rehabilitation

An Evaluation of Two Approaches to Exercise Conditioning in Pulmonary Rehabilitation* Edgar A. Normandin, PhD; Corliss McCusker, RN; MaryLou Connors, RN; Frederick Vale, RRT; Daniel Gerardi, MD, FCCP; and Richard L. ZuWallack, MD, FCCP Study objectives: To compare the effectiveness of two forms of exercise training in pulmonary rehabilitation. Design: A prospective, randomized, unblinded, 8-week trial. Setting: A hospital-based outpatient pulmonary rehabilitation program. Patients: Forty patients (20 patients in each group) with COPD who were referred for pulmonary rehabilitation. Interventions: We compared the short-term effectiveness of a high-intensity, lower-extremity endurance program with a low-intensity, multicomponent calisthenics program for the rehabilitation of patients with COPD. The high-intensity group trained predominately on the stationary bicycle and treadmill, with a goal of exercising at > 80% of maximal level determined from incremental testing for 30 min per session. The low-intensity group performed predominately classroom exercises for approximately 30 min per session. For both groups, twice-weekly sessions were held for 8 weeks. The primary outcome measure was health status, measured using the Chronic Respiratory Disease Questionnaire. Other outcomes included peak oxygen consumption on incremental treadmill exercise testing, exertional dyspnea, treadmill endurance time, the number of sit-to-stand repetitions and arm lifts in 1 min, overall dyspnea, and questionnaire-rated functional status. Measurements and results: Both groups showed significant postrehabilitation improvement in exercise variables, exertional and overall dyspnea, functional performance, and health status. Patients in the high-intensity group showed greater increases in treadmill endurance and greater reductions in exertional dyspnea, whereas those in the low-intensity group showed greater increases in armendurance testing. Both groups had similar improvements in overall dyspnea, functional performance, and health status. Conclusions: Despite differences in exercise performance, both high-intensity, lower-extremity endurance training and low-intensity calisthenics led to similar short-term improvements in questionnaire-rated dyspnea, functional performance, and health status. (CHEST 2002; 121:1085 1091) Key words: COPD; dyspnea; exercise; functional performance; health status; pulmonary rehabilitation Abbreviations: BDI baseline dyspnea index; CRQ Chronic Respiratory Disease Questionnaire; PFSS pulmonary functional status scale; TDI transitional dyspnea index; VAS visual analog scale; V e minute ventilation; V o 2 oxygen consumption From the Section of Pulmonary and Critical Care, Saint Francis Hospital and Medical Center, Hartford, CT. This study was funded in part by the Maximillian E. and Marion O. Hoffman Foundation, West Hartford, CT. Manuscript received April 16, 2001; revision accepted September 10, 2001. Correspondence to: Edgar Normandin, PhD, Section of Pulmonary and Critical Care, Saint Francis Hospital and Medical Center, 114 Woodland St, Hartford, CT 06105; e-mail: rzuwalla@stfranciscare.org Exercise training is a necessary component in the comprehensive pulmonary rehabilitation of individuals with COPD. 1,2 Although its short-term effectiveness has been substantiated in controlled studies, 3 8 the optimal type and intensity of exercise training in this patient population is debated. One approach uses standard exercise physiology principles and exercises patients to 70% of maximum on a treadmill or stationary bicycle for 20 to 30 min, two or three times weekly. Although they are often symptom limited, patients with COPD commonly achieve their anaerobic threshold with higher intensities of training. 3,9 Furthermore, a clear doseresponse effect of training in this population has been noted, with higher intensities of exercise pro- www.chestjournal.org CHEST / 121 / 4/ APRIL, 2002 1085

ducing greater increases in exercise performance. 3 Another approach is to use isolated training of peripheral muscles rather than whole-body conditioning, 5 because this type of exercise regimen might be better tolerated than whole-body conditioning at a high percentage of maximal cardiopulmonary workload. The effectiveness of this lower-level peripheral muscle conditioning has been clearly demonstrated, 5 with significant improvements established for upper-body and lower-body muscle endurance and treadmill endurance walk time. Lowintensity calisthenics training requires almost no equipment and might result in better long-term adherence to maintenance exercises at home. The purpose of this study was to compare the short-term effectiveness of high-intensity, predominately lower-extremity training with low-intensity calisthenics training in patients with COPD enrolled in an 8-week, comprehensive, outpatient, pulmonary rehabilitation program. Although multiple outcomes were evaluated, the principal measure we chose was health status, using the Chronic Respiratory Disease Questionnaire (CRQ). 10 Improvement in health status is a major goal of pulmonary rehabilitation, 1 and its use as an outcome measure in this investigation eliminates problems in interpreting exercise tests that would likely be influenced by the type of exercise training given in the rehabilitation sessions. Subjects Materials and Methods Patients who were referred to the Saint Francis Hospital and Medical Center Outpatient Pulmonary Rehabilitation Program and met the inclusion criteria below were randomized to either high-intensity training or low-intensity calisthenics training. Inclusion criteria included the following: (1) symptomatic COPD, (2) the ability to perform aerobic treadmill and stationary bicycle training and peripheral muscle training, (3) the absence of a significant comorbid disease that might interfere with the rehabilitation process or place the patient at undue risk for exercise training, and (4) no formal pulmonary rehabilitation within the past 12 months. Informed consent was obtained for all participants, and the study was approved by the Institutional Review Board of the medical center. Assessment Assessments were made before or during the first week of pulmonary rehabilitation and immediately after the 8-week program. These assessments included the following items. Incremental Exercise Testing: Maximal exercise tolerance was measured by a symptom-limited graded exercise test performed while the patient was breathing room air and using a treadmill. A modified Naughton protocol was used with 2-min stages of incremental exercise. All patients had at least one orientation session to treadmill walking before testing. Expired air was continuously analyzed by a MedGraphics cardiopulmonary diagnostic system (CPX-D, Breeze Ex v3.06; Medical Graphics Corporation; St. Paul, MN) to assess physiologic responses to exercise. Twelve-lead ECG (Quinton 500; Quinton; Bothell, WA) was used to monitor heart rate and detect possible arrhythmias or ischemic changes. BP was measured at the end of each 2-min stage of exercise. Pulse oximetry was used to measure arterial oxygen saturation. Variables analyzed included heart rate, respiratory rate, peak oxygen consumption (V o 2 ), minute ventilation (V e), and the V e/v o 2 ratio. In addition, the perceived level of breathlessness was measured at each minute of exercise using a visual analog scale (VAS). 11 This consisted of a vertical 300-mm line with the bottom end representing no breathlessness and the top end representing the greatest possible level of breathlessness. The distance, in millimeters, from the bottom was used to rate dyspnea. Measurements at rest and at approximately 50% and 80% of maximal exercise capacity were analyzed. Endurance Walk Testing: This test was performed on a treadmill on a separate day after incremental testing. A constant exercise level of approximately 85% of the initial maximum graded exercise test was chosen based on equations developed by the American College of Sports Medicine. 12 After a brief warm-up on the treadmill, patients were instructed to walk for as long as they could at this level. The duration of walking in minutes was recorded. Exercise was halted by the tester if the patient could walk no longer or reached a heart rate equal to the maximum heart rate achieved on the incremental test. The level of dyspnea was rated using a 10-point category scale during and at the end of testing. Sit-to-Stand Testing: The patient was seated in a standard chair without arms, then given instructions to stand up without using the arms, and then return to the seated position as many times as possible in a 1-min period. The exercise was first demonstrated by a staff member and then performed by the subject. The number of completed repetitions in 60 s was recorded. Rest periods within the 60 s were allowed. Dyspnea and muscle fatigue were rated using a 10-point category scale on completion of testing. Arm Lifts:The subject was instructed to stand and repetitively raise a wooden dowel, from a position resting against the thighs, up to eye level with the arms straight at the elbows, and the return to original position. Again, the maximum number of completed repetitions in 60 s was recorded. A 3-min version of this test was found to be responsive to pulmonary rehabilitation intervention. 13 We chose a 1-min version because of its simplicity and, in our experience, responsiveness to rehabilitation. Health Status (Health-Related Quality of Life): This was assessed using the CRQ, 10 a 20-item, investigator-administered questionnaire that was designed for patients with COPD. Each question is rated by the patient using a 7-point scale, with lower scores indicating greater impairment in health status. The instrument has four components (dyspnea, fatigue, emotional function, and mastery, ie, the feeling of control over the disease), as well as a total score. A 0.5-U per question change in this questionnaire resulting from therapy is thought to be clinically meaningful. 14 Thus, a 10-U change for the total score, a 2.5-U change for the dyspnea component, a 2-U change for the fatigue component, a 3.5-U change for the emotion component, and a 2-U change for the mastery component meet the clinically significant threshold. The investigator administering this test was blinded to the study intervention. The CRQ correlates with disease severity, 10 and has been demonstrated to improve after pulmonary rehabilitation. 15 Functional Performance: The pulmonary functional status scale (PFSS) 16 is a 56-item, self-administered questionnaire with functional (predominately activities of daily living) and emotional components. The former component includes subscores of selfcare, daily activities, household tasks, grocery shopping and meal preparation, transportation (mobility), and relationships. The 1086 Clinical Investigations

emotional component includes subscores of anxiety and depression. Higher scores indicate greater functional performance. Two uncontrolled studies have suggested that the PFSS is responsive to pulmonary rehabilitation intervention. 13,17 Questionnaire-Rated Dyspnea: Dyspnea associated with daily activities was measured using the baseline dyspnea index (BDI) and the transitional dyspnea indexes (TDI). 18 These are interviewer-administered questionnaires that assess dyspnea by determining the effect of this symptom on daily activities. The instrument takes approximately 3 to 4 min to complete. 19 The BDI has three scales, functional impairment, magnitude of task, and magnitude of effort; each is scored on a 0 (severe) to 4 (no impairment) scale. The three scales are summed to give the BDI focal score, which can range from zero (the most limitation from dyspnea) to 12 (no limitation from dyspnea). Changes in limitation in the areas of functional impairment, magnitude of task, and magnitude of effort are rated using the TDI. Each is scored on a 3 (major deterioration) to 0 (no change) to 3 (major improvement) scale. The focal TDI score, which sums the three scales, therefore can range from 9 (greatest increase in limitation caused by dyspnea) to 9 (greatest reduction in limitation caused by dyspnea). The BDI was administered at baseline, whereas the TDI was administered at the end of rehabilitation. The TDI has demonstrated responsiveness to pulmonary rehabilitation. 11,20 Pulmonary Rehabilitation Sessions: All patients participated in a comprehensive, multidisciplinary pulmonary rehabilitation program that included 16 3-h sessions during a period of 8 weeks. For patients who missed sessions, the duration of rehabilitation was extended past 8 weeks until the 16 sessions were completed. Rehabilitation sessions generally had between four patients and eight patients per group meeting twice weekly. Formal educational sessions, each lasting approximately 45 min, were given before exercise training. After the educational sessions, the two groups separated for exercise training. High-intensity, lowerextremity training was given in the exercise room, whereas low-intensity calisthenics training was given in an adjacent classroom. At least one rehabilitation staff member supervised each of the two concurrent exercise sessions. High-Intensity, Lower-Extremity Aerobic Endurance Conditioning: Patients randomized to this group received exercise training on a treadmill and stationary bicycle twice weekly for 8 weeks. The goal was to achieve 30 min of training per session, with the target exercise level set at approximately 80% of the maximum achieved on the baseline incremental exercise testing. 12 Although both treadmill and bicycle training were given to all patients, more time was usually spent on the former, which was preferred by most patients. Two-minute warm-up and cool-down periods were given, but were excluded from calculation of exercise duration. Similar to a previously reported protocol by Maltais and colleagues, 6 the attempt was to keep the exercise duration constant and adjust the intensity on an individual basis with the object of reaching target intensity. Target intensity, however, was not usually exceeded. Subjects were allowed one or two short rest periods, if desired. The exercise intensity was adjusted based on the subjects Borg-scale rated dyspnea and/or leg fatigue. Generally, the intensity was increased if the Borg rating was 4 (on a scale to 10) and decreased if it was 7 or if the heart rate approached the maximum observed in exercise testing. The duration of exercise and the time at target intensity were recorded for each session. Walking and stretching exercises at home to supplement the formal sessions were encouraged. Low-Intensity Peripheral Muscle Training: Patients randomized to this group received low-intensity muscle training twice weekly for 8 weeks. The exercise protocol was similar to the Hairmyres home exercise program described by Clark et al 5 ; however, the exercise program was lengthened and modified to closer resemble the ongoing exercise training program provided at this hospital. The exercises given at each session are listed in Table 1. Each exercise of 8 to 10 repetitions took 45 to 60 s to complete, for a total exercise time of approximately 30 min. With pacing for breathing and short rest breaks between several of the exercises, the exercise class duration was approximately 45 min. Data Analysis demographic and pulmonary function variables are given as means SD. Prerehabilitation-to-postrehabilitation changes in outcome variables were analyzed using a repeatedmeasures analyses of covariance (SAS GLM; SAS Institute; Cary, NC), with the particular outcome variable as the dependent variable, the treatment group as the independent variable, and the baseline value of the variable as a covariate. Changes in Table 1 Low-Intensity Peripheral Muscle Exercises Chair exercises 1 Head up and down (chin to chest) 2 Turn head to right and then left 3 Ear to shoulder (right and left) 4 Biceps curls (arms over side of chair with palms facing forward, bend elbow and raise hands up) 5 Shoulder circles (arms over side of chair, circle shoulders front and back) 6 More circles (hands on shoulders, circle front and back) 7 Arm stretch (arm straight up, then reach for center of back, right and left) 8 Wrist circles 9 Ankle circles (with leg extended) 10 Flex and point the toes (with leg extended) 11 Chest press Weights 1 Biceps curls (elbows in toward body, palms facing forward, raise arms up) 2 Wrist curls (with arms over the sides of a chair) 3 Triceps exercise (using both hands bring weight over head then to the back) 4 Shoulder exercise (arms over the side of a chair, with arms extended raise them up and down) 5 Arm exercise (arms in front extended, raise them up and down) 6 Arms beautiful (standing, elbows in, weights to shoulders, press back then bring back up to shoulders) Sticks River dance (raise sticks up, over to the side [rotating right and left], back up and down on lap for 2 min) Standing exercises 1 Circle torso over top of legs 2 Bend forward (back straight) then back 3 Crescent stretch (reach over head to side with right arm, then left) 4 Shoulder/chest stretch (clench hands in back, then bring shoulders back) 5 Clench hands in front, turn toward right then left 6 Calf raises 7 Quarter knee bends 8 Leg lifts to side 9 Lunge stretch (both heels on ground, front knee bent) 10 Reach for stars 11 March in place with fingertip taps (30 s) www.chestjournal.org CHEST / 121 / 4/ APRIL, 2002 1087

outcome variables are given as means SE. Statistical significance is given for both within-group changes from baseline and between-group changes from baseline. Stepwise forward logistic regression (SAS Stat version 6.7; SAS) was used to evaluate predictors of improvement in the CRQ total score. For this, changes in treadmill endurance time, the number of arm lifts, and the number of sit-to-stand repetitions were tested as predictor variables for a 10-U change in the CRQ. A change of 10 U of the CRQ is considered clinically meaningful. A p value of 0.05 was required to enter the model. Results Patients Of the initial 54 patients who entered the study and gave informed consent, 14 patients (7 patients in each group) did not complete the rehabilitation program. Three of the seven patients who dropped out in the high-intensity group did so because of prolonged exacerbations of respiratory disease, three patients withdrew consent, and one patient dropped out after the diagnosis of lung cancer. In the lowintensity group, four of the seven patients dropped out because of prolonged exacerbations of respiratory disease, one patient moved to another location, one patient dropped out after the diagnosis of lung cancer, and one patient was dropped because of poor attendance. characteristics of the 40 patients (20 patients per group) who completed rehabilitation are presented in Table 2. Both groups were Table 2 Patient Characteristics* Characteristics High-Intensity Endurance Low-Intensity Calisthenics Male/female gender, No. 11/9 10/10 Age, yr 69 7 67 9 FEV 1, % predicted 43 16 56 20 Body mass index, kg/m 2 27 6 27 6 Treadmill endurance time, min 7.6 6.6 6.4 4.5 Sit-to-stand repetitions, per min 15 4 16 5 Arm-lift repetitions, per min 34 13 33 9 Maximum heart rate, beats/min 124 19 115 19 Peak V o 2, L/min 0.89 0.47 0.98 0.43 Peak V co 2, L/min 0.88 0.56 0.87 0.42 Gas exchange ratio at peak exercise 0.97 0.10 0.90 0.07 V e/v o 2 at 80% peak V o 2 37 11 34 7 VAS dyspnea at 80% peak V o 2,mm 118 51 101 64 Oxygen saturation at peak exercise, % 89 6 87 7 BDI, U 6.5 1.6 6.0 1.9 CRQ total score, U 93 19 85 17 PFSS function, U 3.72 0.64 3.48 0.55 PFSS emotion, U 4.10 0.61 4.14 0.48 *Data are presented as mean SD unless otherwise indicated. prerehabilitation values are for selected demographic and severity variables; V co 2 carbon dioxide output. FEV 1 percent predicted was significantly lower in the high-intensity group (p 0.03), and the CRQ total score tended to be higher in this group (p 0.16). similar in most demographic and baseline outcome measures. However, the FEV 1 percent predicted in the high-intensity group was significantly lower than in the low-intensity group (p 0.03). Additionally, the CRQ total scores tended to be greater in the high-intensity group (p 0.16). There were no significant gender differences in the baseline outcome variables except for a higher peak V o 2 in men (p 0.03) and a trend for a greater number of arm-lift repetitions in men (p 0.08). None of the patients had previously received pulmonary rehabilitation. Exercise Variables The high-intensity group showed gradual increases in total exercise duration and duration of exercise at target range during the 8-week rehabilitation program (Fig 1). Table 3 lists the prerehabilitation-to-postrehabilitation changes in exercise variables for the two groups. The peak V o 2 in the high-intensity group increased by 0.11 L/min (p 0.02), whereas it did not significantly change in the low-intensity group. The between-group difference for the change in peak V o 2, however, was not significant (p 0.09). Likewise, V e/v o 2 at 50% and 80% of maximal exercise decreased in the highintensity group but not the low-intensity group, but the between-group differences were not significant. VAS dyspnea decreased by 26 mm and 45 mm at 50% and 80% of peak exercise, respectively, in the high-intensity group. This level of exertional dyspnea was significantly improved from baseline and was significantly greater than the 10-mm and 14-mm improvements in dyspnea at 50% and 80% of peak workloads in the lower intensity group, respectively (both, p 0.02). Treadmill endurance time increased significantly over the respective baselines in both groups. However, the increase of 8.4 1.3 min in the highintensity group was significantly greater than the 2.7 1.4-min increase in the low-intensity group (p 0.007). Both groups had significant increases in sit-to-stand repetitions and arm-lift repetitions after pulmonary rehabilitation. Whereas both groups had similar improvement in sit-to-stand testing, the lowintensity group had a significantly greater increase in the number of arm-lift repetitions than the highintensity group (12.2 2.0 repetitions vs 6.5 1.9 repetitions, p 0.04). Health Status Mean prerehabilitation total CRQ scores (Table 2) and component scores for the two groups were not significantly different, although the scores for the high-intensity group tended to be somewhat higher. 1088 Clinical Investigations

Figure 1. Total exercise and target-intensity training duration for the high-intensity group during the course of pulmonary rehabilitation. Wk week. As outlined in Table 4, both the high-intensity group and low-intensity group showed significant improvement in CRQ scores after rehabilitation, with the former increasing by 11.5 2.9 U and the latter by 18.8 2.9 U (both p 0.001 vs baseline). The two groups, however, did not significantly differ in this degree of improvement once differing baseline values were included in the linear model as covariates (p 0.09). The same was true for the four CRQ component scores, with both groups improving significantly from baseline, but no group difference in performance. Eight of 20 patients (40%) in the high-intensity group had clinically meaningful changes in the CRQ vs 14 of 20 patients (70%) in the low-intensity group (p 0.06). Functional Performance The PFSS function and emotion scores both showed significant improvement from baseline (Table 4), but there were no group differences in change for this outcome. However, for the emotion subscore, the improvement tended to be greater in the low-intensity group (5.8 U vs 3.1 U, p 0.13). Overall Dyspnea BDI levels were comparable at baseline. The TDI was significantly greater than 0 in both groups, indicating an overall decrease in dyspnea. TDI scores in the two groups, however, were not significantly different. Factors Related to Improvement in Health Status The baseline CRQ total score correlated significantly with baseline treadmill endurance time (r 0.45, p 0.008), the BDI score (r 0.49, p 0.001), and the PFSS function and emotion scores (r 0.48, p 0.006, and r 0.61, p 0.0002, respectively), but not with peak V o 2, or the number of arm-lift or sit-to-stand repetitions. In the high-intensity group, only improvement in treadmill endurance tended to predict a clinically meaningful (ie, 10 U) improvement in CRQ ( 2 3.3, p 0.07). In the low-intensity group, an increased number of arm lifts tended to predict a clinically meaningful improvement in CRQ ( 2 3.5, p 0.07). Table 3 Changes in Exercise Variables* Variables Higher Intensity Lower Intensity p Value High vs Low Peak V o 2, L/min 0.11 0.04 0.02 0.00 0.04 0.09 0.09 V e/v o 2 at 50% peak V o 2 3.69 1.00 0.001 1.10 1.00 0.28 0.08 V e/v o 2 at 80% peak V o 2 2.48 0.87 0.008 1.59 0.87 0.08 0.48 VAS dyspnea at 50% peak V o 2,mm 26 5 0.001 10 5 0.03 0.02 VAS dyspnea at 80% peak V o 2,mm 45 9 0.001 14 9 0.12 0.02 Treadmill endurance time, min 8.4 1.3 0.001 2.7 1.4 0.07 0.007 Arm-lift repetitions, per min 6.5 1.9 0.001 12.2 2.0 0.001 0.04 Sit-to-stand repetitions, per min 4.5 0.9 0.001 2.8 1.0 0.008 0.22 *Data are presented as mean SE of prerehabilitation to postrehabilitation changes in outcome variables. baseline refers to within-group statistical significance; p value high vs low refers to between-group statistical significance. www.chestjournal.org CHEST / 121 / 4/ APRIL, 2002 1089

Table 4 Changes in Questionnaire-Rated Variables Variables Higher Intensity Lower Intensity p Value Higher vs Lower CRQ total score, U 11.5 2.9 0.001 18.8 2.9 0.001 0.09 CRQ dyspnea, U 4.6 1.0 0.001 6.1 1.0 0.001 0.27 CRQ fatigue, U 2.8 0.7 0.001 3.9 1.0 0.001 0.35 CRQ emotion, U 3.1 1.2 0.02 5.8 1.2 0.001 0.13 CRQ mastery, U 2.7 0.6 0.001 3.4 0.6 0.001 0.43 PFSS function, U 2.8 0.7 0.001 3.9 0.7 0.001 0.35 PFSS emotion, U 3.1 1.2 0.01 5.8 1.2 0.001 0.13 TDI, U 2.9 0.5 0.001 3.2 0.5 0.001 0.69 *Data are presented as mean SE of prerehabilitation to postrehabilitation changes in outcome variables. baseline refers to within-group statistical significance; p value high vs low refers to between-group statistical significance. Discussion The purpose of this study was to compare two forms of exercise training, high-intensity, predominately lower-extremity endurance conditioning and low-intensity, calisthenics-type peripheral muscle training in the pulmonary rehabilitation of COPD. A recent statement of the American Thoracic Society and European Respiratory Society on skeletal muscle dysfunction in COPD stated that although there was no consensus on the optimal training intensity prescription for patients with COPD, based on the available literature, high-intensity training appears to be of advantage. 21 High-intensity exercise training near maximal workload follows sound physiologic principles and has established effectiveness in pulmonary rehabilitation. 3 However, low-intensity peripheral muscular conditioning is easier to perform, does not require special equipment, and also has proven effectiveness in pulmonary rehabilitation. 5 Not unexpectedly, our patients who trained at higher intensity using predominately their lower extremities showed greater improvement in outcome areas involving the lower extremities: peak V o 2 on the treadmill, longer treadmill endurance time, and reduced exertional dyspnea while on the treadmill. Similarly, those performing low-intensity calisthenics training (which emphasizes upper-extremities training) showed greater improvement in arm endurance testing. These findings undoubtedly reflect the specificity and dose effects of exercise training. 22 To our knowledge, this is the first study to evaluate the influence of dose and type of exercise on exercise performance, overall dyspnea, functional performance, and health status in patients with COPD. This is of considerable practical importance, because patients do not participate in pulmonary rehabilitation sessions to walk longer on treadmill in a laboratory setting, but to have fewer symptoms, function better in daily activities, and have less limitation from their lung disease. In our study, despite differences in exercise performance outcomes, both approaches to exercise training led to similar, significant improvements in overall dyspnea, functional performance, and health status. Furthermore, the improvement in the latter exceeded the estimated clinically meaningful change for the CRQ. 13 However, although we were able to demonstrate that twice-weekly, 30-min, low-intensity exercise sessions led to substantial improvements in health status, the study design did not address the optimal duration and frequency of this form of exercise training. As recommended by a recent American Thoracic Society Statement on pulmonary rehabilitation, 2 our pulmonary rehabilitation program has educational and psychosocial components that complement exercise training. The positive outcomes, however, were not likely primarily caused by the nonexercise components (such as education and psychosocial support), because previous studies have demonstrated that education alone does not lead to improvement in exercise ability, 4 dyspnea, 4 or health status, 23 and dyspnea management strategies without exercise are also not sufficient in these outcome areas. 24 Although exercise is considered a necessary component of pulmonary rehabilitation, the correlation between improvement in exercise tests and improvement in CRQ-measured health status is weak at best. 25 Similarly, after lung volume reduction surgery, improvement in Sickness Impact Profile scores correlated with reduction in air-trapping but not with improvement in the 6-min walk distance or total exercise time. 26 In our study, using stepwise logistic regression, improvement in treadmill endurance time in the high-intensity group and improvement in arm endurance in the low-intensity group tended to predict improvement in the CRQ, although neither relationship reached statistical significance (for both, p 0.07). This suggests that exercise-specific gains in each modality were related to their respective improvements in overall health-related quality of life. 1090 Clinical Investigations

A shortcoming of this study is that it evaluated only the short-term effectiveness of these interventions in pulmonary rehabilitation. It is intriguing to speculate that, because of the less-strenuous nature of the exercise training, long-term adherence (and hence outcome) might be improved in the low-intensity peripheral muscle group. A future study with longterm follow-up would be necessary to evaluate this. In summary, both high-intensity endurance conditioning involving the lower extremities and lowintensity calisthenics training involving the peripheral muscles led to significant short-term improvements in exercise ability. The former led to greater improvement in maximal exercise capacity, exertional dyspnea, and treadmill endurance. The latter led to greater improvement in arm endurance. Despite these differences in exercise performance, both approaches to exercise training resulted in significant and comparable improvements in overall dyspnea, functional performance, and health status. This suggests that, at least in the short-term, the approach to exercise training is of lesser importance in these important outcome measures. From a practical viewpoint, low-intensity calisthenics are easier to perform and might lead to better long-term adherence. Prolonged postrehabilitation follow-up studies would be useful to compare the long-term usefulness of these two approaches with exercise training. References 1 Ries AL, Carlin BW, Carrieri-Kohlman V, et al. Pulmonary rehabilitation: evidence-based guidelines. Chest 1997; 112: 1367 1397 2 Pulmonary rehabilitation: official statement of the American Thoracic Society. Am J Respir Crit Care Med 1999; 159: 1666 1682 3 Casaburi R, Patessio A, Ioli F, et al. Reductions in exercise lactic acidosis and ventilation as a result of exercise training in patients with obstructive lung disease. Am Rev Respir Dis 1991; 143:9 18 4 Ries AL, Kaplan RM, Limberg TM, et al. Effects of pulmonary rehabilitation on physiologic and psychosocial outcomes in patients with chronic obstructive pulmonary disease. Ann Intern Med 1995; 122:823 832 5 Clark CJ, Cochrane L, Mackay E. Low intensity peripheral muscle conditioning improves exercise tolerance and breathlessness in COPD. Eur Respir J 1996; 9:2590 2596 6 Maltais F, LeBlanc P, Jobin J, et al. Intensity of training and physiologic adaptation in patients with chronic obstructive pulmonary disease. Am J Respir Crit Care Med 1997; 155: 555 561 7O Donnell DE, McGuire M, Samis L, et al. General exercise training improves ventilatory and peripheral muscle strength and endurance in chronic airflow obstruction. Am J Respir Crit Care Med 1998; 157:1489 1497 8 Hernandez MT, Rubio TM, Ruiz FO, et al. 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Improvement in quality of life is unrelated to improvement in exercise endurance after outpatient pulmonary rehabilitation. J Cardiopulm Rehabil 1993; 13:51 54 26 Leyenson V, Furukawa S, Kuzma AM, et al. Correlation of changes in quality of life after lung volume reduction surgery with changes in lung function, exercise, and gas exchange. Chest 2000; 118:728 735 www.chestjournal.org CHEST / 121 / 4/ APRIL, 2002 1091