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(Chest. 2000;117:1291-1299.)
© 2000 American College of Chest Physicians

Habitual Activities and Peak Aerobic Capacity in Patients With Asymptomatic and Symptomatic Left Ventricular Dysfunction*

Use of a New Physical Activity Scoring System

Alessandro Mezzani, MD; Ugo Corrà, MD; Claudio Baroffio, MD; Enzo Bosimini, MD and Pantaleo Giannuzzi, MD

* From the Salvatore Maugeri Foundation, Veruno Rehabilitation Center, Division of Cardiology, Veruno (NO), Italy.

Correspondence to: Alessandro Mezzani, MD, Via Nuova Intra-Premeno, 114 28811 Arizzano (VB), Italy; e-mail: amezzani{at}fsm.it


   Abstract
TOP
 Abstract
Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 Appendix 1
 References
 
Background: A reduced level of daily activities is thought to be an important determinant of aerobic exercise intolerance in patients with chronic heart failure chronic heart failure; however, few data exist about the relationship between habitual physical activity level and peak aerobic capacity in patients at different clinical stages of left ventricular dysfunction.

Study objectives: The purposes of this study were as follow: (1) to validate a simple interviewer-administered scoring system for evaluation of habitual physical activity level of patients with chronic heart failure and asymptomatic left ventricular dysfunction (ALVD); (2) to determine the relationship between habitual physical activity level and peak aerobic capacity in chronic heart failure and ALVD patients; and (3) to compare habitual activity levels among different New York Heart Association (NYHA) classes in these populations.

Setting: Cardiology division at a tertiary-care hospital.

Study population: We studied 167 consecutive patients with chronic heart failure (NYHA class I to III), 40 patients with ALVD, and 52 healthy subjects (HS).

Measurements and results: Habitual physical activity level was evaluated by means of an interview-based activity scoring system considering leisure time and occupational activities and also recent deconditioning events (eg, hospital admissions); a final activity score (AS) ranging from 0.8 to 5 was obtained. All patients and HS performed a symptom-limited cardiopulmonary exercise test up to a respiratory exchange ratio of >= 1.1. AS was an independent predictor of peak oxygen consumption (O2) in all groups, with a significantly higher O2 vs AS relationship slope in the ALVD and HS groups than in the chronic heart failure group. Moreover, AS was found to be significantly lower in chronic heart failure than in ALVD patients and HS (1.6 ± 0.6 vs 2.2 ± 0.7 vs 3.5 ± 1.1, respectively; p < 0.0001), as was peak O2 (14.7 ± 3.7 mL/kg/min vs 20 ± 4 mL/kg/min vs 33.1 ± 10 mL/kg/min, respectively; p < 0.0001), but the latter differences were canceled after adjusting for AS values. Significant AS and peak O2 reductions were observed in chronic heart failure patients with NYHA class progression from I to III.

Conclusions: Habitual physical activity level is progressively decreased with worsening of heart failure symptoms and is related to peak aerobic capacity in both chronic heart failure and ALVD patients. However, this relationship appears to be weak in patients with chronic heart failure, whereas daily activity is a strong independent predictor of peak aerobic capacity both in ALVD patients and HS. This may be related to the intervention of factors other than skeletal muscle deconditioning in the exercise pathophysiology of chronic heart failure patients.

Key Words: asymptomatic left ventricular dysfunction • chronic heart failure • daily physical activity • peak aerobic capacity


   Introduction
TOP
 Abstract
 Introduction
Materials and Methods
 Results
 Discussion
 Conclusion
 Appendix 1
 References
 
Habitual physical activity level is one of the most important determinants of peak aerobic capacity in healthy men and women across a broad range of ages.1 2 3 4 5 6 Deconditioning events, eg, prolonged bed rest, negatively affect peak aerobic capacity in normal individuals7 ; conversely, the effects of deconditioning can be reversed by aerobic exercise training.8 Because both habitual physical activity level and peak aerobic capacity are usually reduced in patients with chronic heart failure chronic heart failure,9 10 11 12 13 14 deconditioning has been proposed as one of the major determinants of aerobic power impairment in this population.15 16 17 18 19 This hypothesis assumes the existence of a symptom-induced self-limitation of habitual physical activities in patients with previously asymptomatic left ventricular dysfunction (ALVD), and is supported by the effectiveness of aerobic exercise training in chronic heart failure patients19 20 21 22 23 and by the finding of similar skeletal muscle metabolic abnormalities in chronic heart failure patients and normal sedentary subjects,18 even though the latter finding has been challenged by recent data.24 However, little data exist about the relationship linking habitual physical activity level and peak aerobic capacity in patients with chronic heart failure,9 10 25 and, more importantly, it is not clear whether any difference exists in habitual physical activity at different functional and symptomatic stages of left ventricular dysfunction (LVD).

To clarify these issues, we validated a new habitual physical activity level scoring system and applied it to ALVD and chronic heart failure patients and to a group of healthy control subjects (HS). The activity scores (ASs) obtained were then analyzed for between-group differences and correlation to peak oxygen consumption (O2).


   Materials and Methods
TOP
 Abstract
 Introduction
 Materials and Methods
Results
 Discussion
 Conclusion
 Appendix 1
 References
 
Study Population
Three hundred four ambulatory patients referred to our institution between January 1996 and July 1997 for cardiopulmonary exercise testing were considered prospectively for the study. Inclusion criteria were as follows: (1) echocardiographic left ventricular ejection fraction <= 45%; (2) cardiopulmonary exercise test stopped for fatigue or dyspnea and with a peak respiratory exchange ratio (RER) >= 1.1; and (3) absence of severe COPD, symptomatic peripheral vascular disease, diabetes with severe end-organ damage, or orthopedic limitations. According to these criteria, 207 patients were selected; of these, 167 had a history of unequivocal chronic heart failure clinical episodes, and 40 had a history of ALVD (Table 1 ). Among the excluded patients, 20 patients (6.5%) had an ejection fraction > 45%, 46 patients (15%) stopped exercising because of causes different from fatigue or dyspnea, 20 patients (6.5%) stopped exercising because of fatigue or dyspnea but with an RER < 1.1, and 11 patients (3.5%) had a concomitant severe noncardiac disease. Fifty-two HS were used as a control group (Table 1) . Recruitment criteria for HS were as follows: (1) no history of cardiac or noncardiac disease, and (2) normal resting ECG. Twenty-two HS were medium-level cycling amateurs on a regular training program (three to four sessions a week, 2 h/session). All patients and HS were included in the study after their informed, written consent was obtained.


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  		Table 1. Demographic and Clinical Characteristics*

 
Anthropometric Evaluation
Three skinfold thicknesses were measured in all patients according to standard procedures26 by means of a Lafayette caliper. Measurements were performed immediately before conducting exercise testing procedures. The skinfold sites used for women were triceps, suprailiac, and thigh; chest, abdomen, and thigh skinfold sites were used for men. Body density was calculated using the Jackson-Pollock prediction equations for white adults, and percent body fat was determined by the Siri formula.27

Activity Scoring System
Before exercise testing, patients’ level of weekly physical activity was scored by an interviewer. Patients were asked to describe their habitual weekly leisure time and occupational activities during the previous 6 months; activity intensity was then classified by the interviewer as low, moderate, heavy, or very heavy (see Appendix). These intensities corresponded to activities involving an energy consumption of approximately <= 2 metabolic equivalents (METs), > 2 <= 4 METs, > 4 <= 6 METs, and > 6 METs, respectively.28 To be classified at the moderate, heavy, or very heavy level, patients had to have performed one or more of the listed activities corresponding to that level for at least 4 h/wk. Five different levels of weekly physical activity intensity were thus identified, corresponding to the AS 1 to 5 . Because deconditioning events (ie, hospitalizations) are frequent in patients with LVD,29 the occurrence of hospital admissions during the 4 months preceding the exercise test was evaluated. Inasmuch as a bed rest of 10 to 15 days can decrease peak aerobic capacity by about 10 to 20%,7 the final AS was arbitrarily reduced by 20% if a hospital admission had taken place during the month preceding the test, or by 10% if hospitalization(s) had occurred between 30 and 120 days before the test (for the full scoring system, see Appendix).

Objectivity of the scoring system was determined by two independent interviewers in 50 patients and in 20 HS, and reliability was assessed by a test-retest design in 48 patients and 20 HS.

Cardiopulmonary Exercise Testing
All patients underwent an incremental cardiopulmonary exercise test on a bicycle ergometer (Ergo-metrics 800S; Sensormedics; Yorba Linda, CA) >= 2 h after a light meal was consumed. To stabilize gas measurements, patients were asked to remain still on the ergometer for 3 min before exercising. After a 2-min warm-up period at 0 W workload, a ramp protocol of 10 W/min was started and continued until exhaustion. Pedaling rate was kept constant at 55 to 65 revolutions/min. A 12-lead ECG was monitored continuously during the test (MAX-1; Marquette Electronics; Milwaukee, WI), and cuff BP was manually recorded every minute. Respiratory gas exchange measurements were obtained breath-by-breath using a computerized metabolic cart (Vmax29; Sensormedics). Before each test, O2 and CO2 analyzers and flow mass sensor were calibrated using available precision gas mixtures and a 3-L syringe, respectively. Peak O2 per kilogram was recorded as the mean value of O2 during the last 30 s of the test and expressed in milliliters per kilogram per minute.

Statistics
Intergroup differences among clinical, demographic, and peak exercise variables were compared using unpaired t test, one-way analysis of variance with Fisher’s protected least significant difference post hoc multiple comparison test, or {chi}2 procedure with Fisher’s Exact Test when appropriate. The relationship between peak O2 per kilogram as a dependent variable and age, body fat, and AS was evaluated using simple and stepwise multiple linear regression analysis; a predicted residual sum of squares method30 was used for cross-validation and calculation of standard error of the estimate of the obtained multiple regression models. Analysis of covariance (ANCOVA) was performed to determine whether differences in peak O2 per kilogram among groups were maintained after adjusting for AS.

The level of statistical significance was set at a two-tailed p value <= 0.05. All calculations were performed using the SuperANOVA 1.11 and StatView 4.02 statistical packages (Abacus Concepts; Berkeley, CA).


   Results
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
Discussion
 Conclusion
 Appendix 1
 References
 
Demographic and Clinical Characteristics
ALVD, chronic heart failure, and HS groups did not differ as to age, weight, body fat, and lean body mass, but significantly fewer women were present in the ALVD and HS groups than in the chronic heart failure group (Table 1) . Chronic heart failure patients showed a more depressed left ventricular systolic function than did the ALVD ones, as indicated by a significantly lower mean left ventricular ejection fraction, whereas mean left ventricular end-diastolic volumes did not differ between the two groups. All the ALVD patients were in New York Heart Association (NYHA) class I, whereas most of the chronic heart failure patients were in NYHA classes II and III (92% altogether). The cause of LVD was ischemic heart disease in most patients, with a significantly lower prevalence of idiopathic cardiomyopathy in the ALVD group.

The percentage of patients taking ß-blockers and angiotensin-converting enzyme inhibitors did not differ between the asymptomatic and symptomatic groups, but diuretics and digoxin were administered significantly more in chronic heart failure than ALVD patients.

Addition to the study group of the 20 patients (16 chronic heart failure and 4 ALVD) who stopped exercising because of fatigue or dyspnea but with an RER < 1.1 did not significantly affect any of the evaluated variables, leaving all statistical calculations unmodified.

Activity Scoring System Objectivity and Reliability
AS was determined by two independent interviewers in 50 patients and in 20 HS; the intraclass correlation coefficients between the two sets of measurements were 0.98 and 0.96, respectively, indicating a low interobserver variability. Reliability was assessed by a test-retest design in 48 patients and 20 HS; the habitual physical activity level was scored twice by the same interviewer 15 days apart, with intraclass correlation coefficients between the two determinations of 0.97 and 0.95, respectively.

Exercise Testing
HS and ALVD patients exercised longer than chronic heart failure patients (1,384 ± 117 s and 677 ± 167 s vs 524 ± 172 s, respectively; p < 0.0001 for all comparisons; mean ± SD), reaching significantly higher mean values of peak O2 per kilogram (33.1 ± 10 mL/kg/min and 20 ± 4 mL/kg/min vs 14.7 ± 3.7 mL/kg/min, respectively; p < 0.0001 for all comparisons) and peak work rate (231 ± 53 W and 113 ± 28 W vs 87 ± 29 W, respectively; p < 0.0001 for all comparisons).

A significant decrease of mean peak aerobic capacity was observed in the chronic heart failure group with NYHA class progression (18.7 ± 3.5 mL/kg/min vs 15.5 ± 3.7 mL/kg/min vs 12.9 ± 3.2 mL/kg/min in NYHA class I, II, and III, respectively; Fig 1 ), whereas ALVD patients showed values of peak O2 per kilogram similar to those of the chronic heart failure NYHA class I group (Fig 1) .



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  		Figure 1. Comparison of mean AS (top) and peak aerobic capacity (peak O2 per kilogram) values (bottom) between HS and patients with ALVD or chronic heart failure (CHF) in different NYHA classes. Worsening of symptoms was associated with a significant decrease of both AS and peak aerobic capacity. *p < 0.02; **p < 0.0002; ***p < 0.0001; {dagger}p < 0.03; {dagger}{dagger}p < 0.002.

 
Given the existence of significant differences in sex and cause of LVD among HS and asymptomatic and symptomatic patients, comparisons were repeated after excluding from calculations women and patients with idiopathic cardiomyopathy. Significant differences in peak O2 per kilogram were not modified by this procedure.

Mean peak RER did not differ among the three groups.

Simple and Multiple Regression Analysis
In the chronic heart failure group, AS was a univariate, significant, but modest, predictor of peak O2 per kilogram (r = 0.48, p < 0.0001; Fig 2 and Table 2 ), whereas age showed a poor, although significant, relationship to peak O2 per kilogram, and percent body fat did not (Table 2) . The multiple regression model (r = 0.53; standard error of the estimate, 4.1 mL/kg/min) indicated AS was the strongest independent predictor of peak O2 (determination coefficient, 23%), with a minor contribution of age (relative increase of determination coefficient, 3%) to dependent variable prediction.



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  		Figure 2. Peak aerobic capacity (peak O2 per kilogram) vs AS correlation in ALVD and chronic heart failure patients. See Figure 1 legend for abbreviations.

 

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  		Table 2. Simple Regression Statistics vs Peak O2 per kilogram as a Dependent Variable

 
In the ALVD group, AS showed a good correlation to peak O2 per kilogram (r = 0.69, p < 0.0001; Fig 2 and Table 2 ). Body fat was significantly, albeit modestly, correlated to peak O2 per kilogram (r = 0.41, p = 0.009), whereas, in these patients, age was not (Table 2) . Multiple stepwise linear regression analysis showed that AS was the only independent predictor of peak O2 per kilogram in the ALVD group (r = 0.69; standard error of the estimate, 3.2 mL/kg/min), accounting for 47% of the dependent variable variance.

In the HS group, AS was strongly correlated to peak O2 (r = 0.83, p < 0.0001; Fig 3 and Table 2 ), but not to age or body fat (Table 2) . By multiple regression analysis, AS accounted for most (70%) of the peak O2 variance.



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  		Figure 3. Peak aerobic capacity (peak O2 per kilogram) vs AS correlation in HS.

 
AS Differences Among Groups
No patient in the ALVD and chronic heart failure groups showed an AS of > 4. AS was found to differ significantly among the three groups, with HS showing the higher AS mean value and chronic heart failure patients the lower one (Table 1) . Moreover, and in analogy with peak aerobic capacity, AS showed a significant decrease with symptom progression in chronic heart failure patients (2.1 ± 0.5 vs 1.7 ± 0.5 vs 1.3 ± 0.5 in NYHA class I, II, and III, respectively; Fig 1 ), whereas ALVD patients had AS values comparable to those of the chronic heart failure NYHA class I group (Fig 1) .

To further explore the relationship between level of habitual physical activity and peak aerobic capacity, ANCOVA was performed to compare peak O2 per kilogram values in the HS, ALVD, and chronic heart failure groups with AS used as a covariate. The AS effect was found to be significant (p < 0.0001), and AS-adjusted peak O2 per kilogram means did not differ among HS, ALVD, and chronic heart failure groups (F statistic, 2.5; p = 0.08; adjusted means, 21.3 ± 6 mL/kg/min vs 16.6 ± 3.6 mL/kg/min vs 14.8 ± 3.5 mL/kg/min, respectively), showing that differences in peak O2 per kilogram were mainly accounted for by differences in AS (Fig 4 ). Regressor x factor interaction analysis showed that AS vs peak O2 per kilogram slopes were significantly higher in HS and ALVD patients than in the chronic heart failure group (7.9 mL/kg/min and 4.3 mL/kg/min vs 3.2 mL/kg/min, respectively; p < 0.0001), indicating a stronger correlation of habitual physical activity level to peak aerobic capacity in normal subjects and asymptomatic patients than in symptomatic ones.



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  		Figure 4. Comparison of peak aerobic capacity (peak O2) values among HS, ALVD patients, and chronic heart failure patients after an ANCOVA procedure using AS as a covariate. Baseline peak aerobic capacity differences (top) were abolished after adjusting for AS (bottom). ANOVA = analysis of variance; see Figure 1 legend for other abbreviation.

 

   Discussion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
Conclusion
 Appendix 1
 References
 
This study validates a new interviewer-administered habitual physical activity scoring system and provides evidence that aerobic exercise tolerance is related to habitual physical activity level in both asymptomatic and symptomatic patients with LVD, and that progression of heart failure symptoms is associated with a progressive decrease of patients’ habitual activities.

Habitual physical activity level or energy expenditure has been evaluated in patients with chronic heart failure by means of limb movement sensors,9 10 shoe-mounted pedometers,11 doubly labeled water technique,12 and Duke Activity Status Index.25 However, with the exception of the latter, these techniques cannot be applied to a large number of patients; moreover, all of them explore only a several-day period, which is unlikely to significantly reflect the individual’s conditioning level. The activity scoring system we developed proved to be simple to administer and evaluated a period of 6 months, also taking into consideration deconditioning events, which are known to be frequent in patients with chronic heart failure. Objectivity and short-term reliability of the scoring system proved to be highly acceptable in our populations. Peak aerobic performance was considered as the reference measurement to assess the validity of the system; this choice may be questionable, inasmuch as some authors have found peak O2 to scarcely reflect daily physical activity of chronic heart failure patients as measured by limb movement sensors.9 10 However, the range of chronic heart failure patients’ physical activities is usually narrow, rendering detection of significant correlations very difficult, and it is acknowledged that an alternative test against which an interview-based system estimating habitual physical activity could be reliably validated is not currently available.31

Our data showed a mean AS 28% lower in chronic heart failure patients compared with asymptomatic ones; this finding was associated with a 26% lower mean peak O2 per kilogram in the symptomatic than in the asymptomatic group, which is in accordance with previous results.13 32 AS was the only independent predictor of peak O2 per kilogram even among other factors known to affect peak aerobic capacity in chronic heart failure patients, such as age and percent body fat,33 accounting for 23% of the multiple regression model variability. Moreover, AS values were inversely related to patients’ NYHA class, which seems to indicate an increasing limitation of daily physical activity with disease progression. After adjusting peak O2 per kilogram mean values for AS, the difference in peak aerobic capacity between chronic heart failure and both ALVD patients and HS was no longer significant. Overall, even though a cause and effect relationship between AS and peak O2 per kilogram cannot be assumed, these findings add further to the evidence indicating a role of deconditioning in peak aerobic capacity impairment during the natural history of LVD. However, it must be noted that the observed differences in mean AS among asymptomatic and symptomatic patients and HS were not associated with different mean lean body mass values; according to previously reported data,34 this result suggests that the impaired aerobic exercise performance of chronic heart failure patients might have been mainly caused by qualitative rather than quantitative skeletal muscle changes.

In ALVD patients, our findings indicated a significantly stronger AS vs peak O2 per kilogram relationship (Table 2) than in chronic heart failure ones. These data are in good agreement with those of HS (Table 2) , in whom AS was the only independent predictor of peak O2 per kilogram, suggesting a normal-appearing behavior of patients with ALVD.

It is worth noting that the amount of scatter in the AS vs peak O2 per kilogram relationship was relevant not only in asymptomatic and symptomatic patients (Fig 2) but also in HS (Fig 3) ; this may be related to the contribution of factors other than deconditioning to exercise intolerance in these populations.15 16 17 35 36

Limitations of Study
The scoring system we adopted is a rough estimate of the habitual physical activity level. Evidence exists that strenuous activities are recalled more accurately than moderate or mild ones,31 which are obviously more represented in a population of patients with LVD; a more accurate activity scoring system may have yielded a more precise evaluation, especially in the chronic heart failure group. However, deconditioning is not the only determinant of peak aerobic capacity in patients with LVD. Moreover, the clinical applicability of more complex (to the point of exhaustive) activity scoring systems remains questionable.31 A second limitation is that, given the cross-sectional design of this study, definitive conclusions could not be drawn about the effect of the level of physical conditioning on aerobic exercise capacity at different moments of disease progression in the individual patient. A longitudinal study considering the different determinants of peak aerobic capacity before, at the moment of, and after the onset of symptoms would provide an opportunity to clarify this issue. Finally, the degree of muscle atrophy was not specifically evaluated in our study. This may be of importance, inasmuch as the presence of cachectic patients in our population may have influenced peak aerobic capacity values.37 However, mean lean body mass was comparable in the three study groups, thus ruling out a major effect of muscle mass loss on the results of this study.


   Conclusion
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
Appendix 1
 References
 
Our data indicate that habitual physical activity, as described by a new interviewer-administered scoring system, is related to aerobic performance in both ALVD and chronic heart failure patients and that daily activities progressively decrease with worsening of heart failure symptoms, thus supporting the hypothesis that the level of physical conditioning does play a role in determining peak aerobic capacity during the natural history of LVD. This seems to be true especially in ALVD patients, who exhibit a response to conditioning stimuli similar to that of HS, ie, a rather predictable peak aerobic capacity on the basis of the individual’s physical activity level. On the other hand, the aerobic capacity of patients with chronic heart failure appears to be less sensitive to differences in level of physical conditioning, probably because of the existence of other factors besides deconditioning as determinants of exercise intolerance in the presence of more homogeneous and limited physical activity habits. These findings point out the need of more-accurate means for a better definition of the relative contribution of skeletal muscle deconditioning to aerobic exercise impairment at different clinical stages of LVD.


   Appendix 1
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 Appendix 1
References
 
Criteria for Activity Intensity Definition
Low-intensity occupation:
sitting in office; walking slowly in work area.

Low-intensity leisure time activity (or sedentary lifestyle if no occupation):
sitting reading a book or watching television; slowly walking around household; dressing-undressing; driving car or motor scooter.

Moderate-intensity occupation (at least 4 h/wk):
carpentry, general workshop; painting indoors; electrical work; plumbing; farming, feeding small animals; walking in work area at moderate to brisk speed, or walking in work area at slow to moderate speed carrying < 25-lb weight, or walking 2 to 4 miles/h on level ground; driving heavy truck, bus.

Moderate-intensity leisure time activity (at least 4 h/wk):
bicycling, stationary, < 50 W; bicycling < 10 miles/h; dancing, ballroom, slow; fishing; gardening, raking lawn, mowing lawn with motor-powered mower, sacking grass and leaves, pruning trees; playing golf; walking 2 to 4 miles/h on level ground, or walking the dog.

Heavy-intensity occupation (at least 4 h/wk):
carpentry outdoors, eg, installing rain gutters; painting outdoors; farming, shoveling grain; truck driving, loading and unloading truck; using heavy power tools, pneumatic jackhammer, drills, etc; walking carrying < 25-lb weight upstairs/uphill.

Heavy-intensity leisure time activity (at least 4 h/wk):
bicycling, stationary, 50 to 125 W; bicycling 10 to 11.9 miles/h; dancing, ballroom, fast; hunting; gardening, eg, mowing lawn with hand mower, chopping wood, digging; playing tennis, doubles; downhill skiing, light to moderate effort; walking carrying < 25-lb weight upstairs/uphill.

Very heavy-intensity occupation (at least 4 h/wk):
carpentry, sawing hardwood; farming, forking straw bales; coal mining, shoveling coal; forestry, general; horse racing, galloping; using heavy tools (not power) such as shovel, pick, tunnel bar, spade; walking carrying 25 to 50-lb weight upstairs/uphill.

Very heavy-intensity leisure time activity (at least 4 h/wk):
bicycling, stationary, > 125 < 175 W; bicycling 12 to 13.9 miles/h; dancing, aerobic, high impact; jogging, general; playing tennis, singles; cross-country skiing, light to moderate effort; downhill skiing, vigorous effort; swimming laps, freestyle, light to moderate effort; rock or mountain climbing; walking carrying 25- to 50-lb weight upstairs/uphill.

Activity Score (previous 6 months)
Low-intensity occupation and leisure time activity (or no occupation with sedentary lifestyle)

With hospital admission during the 30 days preceding the test: 0.8

With hospital admission 30 to 120 days before the test: 0.9

With no hospital admissions during the 120 days preceding the test: 1.0

Low-intensity occupation with moderate-intensity leisure time activity (or vice versa)

With hospital admission during the 30 days preceding the test: 1.6

With hospital admission 30 to 120 days before the test: 1.8

With no hospital admissions during the 120 days preceding the test: 2.0

Moderate-intensity occupation and leisure time activity

With hospital admission during the 30 days preceding the test: 2.4

With hospital admission 30 to 120 days before the test: 2.7

With no hospital admissions during the 120 days preceding the test: 3.0

Heavy-intensity occupation or leisure time activity

With hospital admission during the 30 days preceding the test: 3.2

With hospital admission 30 to 120 days before the test: 3.6

With no hospital admissions during the 120 days preceding the test: 4.0

Very heavy-intensity occupation or leisure time activity

With hospital admission during the 30 days preceding the test: 4.0

With hospital admission 30 to 120 days before the test: 4.5

With no hospital admissions during the 120 days preceding the test: 5.0


   Acknowledgements
 
The authors thank Rosemary Allpress for her careful revision of the English manuscript.


   Footnotes
 
Abbreviations: ALVD = asymptomatic left ventricular dysfunction; ANCOVA = analysis of covariance; AS = activity score; HS = healthy control subjects; LVD = left ventricular dysfunction; MET = metabolic equivalent; NYHA = New York Heart Association; RER = respiratory exchange ratio; O2 = oxygen consumption

Received for publication December 7, 1998. Accepted for publication November 17, 1999.


   References
TOP
 Abstract
 Introduction
 Materials and Methods
 Results
 Discussion
 Conclusion
 Appendix 1
 References
 

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