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Physical activity and cardiac rehabilitation: a critical review of the literature
Coronary Health Care (1998) 2, 17%186 9 1998 Harcourt Brace & Co. Ltd
REVIEW ARTICLE
Physical activity and cardiac rehabilitation: a critical review of the literature J. Jolliffe, R. T a y l o r *
Senior Physiotherapist, Exeter Nuffield Hospital Exeter;, *Senior Lecturer, R&D Support Unit, Postgraduate Medical School, University of Exeter, Exeter, UK S U M M A R Y . Inadequate physical activity is one of the most prevalent risk factors for ill-health in western industrialized societies. In the secondary-care setting, cardiac rehabilitation offers an important potential means for enhancing the everyday physical activity of patients with cardiac disease. A critical review was undertaken to examine the effectiveness of cardiac rehabilitation in promoting long- to medium-term physical activity levels. A comprehensive literature search for studies was undertaken using bibliographic databases and published reference lists. Ten randomized controlled trials were identified that fulfilled the study inclusion criteria. These studies included a total of 13 objective assessments of physical activity outcome. It was found that in only 31% (i.e. 4 out of 13) of cases was there evidence of a statistically significant (P<0.05) improvement in physical activity outcome in the period (immediately to 9 years) following cardiac rehabilitation. These results suggest that there may be a need for cardiac rehabilitation programmes to place more emphasis towards to improving long-term physical activity levels of participants. However, the median methodological quality score for these trials of 2 (out of a possible score of 5) indicate the need for caution in the interpretation of the results. In particular, less than half of the studies gave evidence of using a validated physical activity selfreport questionnaire and only one of the studies attempted to measure physical activity directly. The results of this review indicate the need for future studies of cardiac rehabilitation to incorporate validated assessments of physical activity, such as standardized questionnaires, together with direct measures, such as activity or movement monitors.
This purpose of this review is examine the evidence regarding the impact of cardiac rehabilitation (CR) on medium- to long-term physical activity. In doing so, this paper will: (1) describe the concept of physical activity; (2) summarize the current recommendations of physical activity levels for health; (3) overview the current methods by which physical activity can be assessed; and (4) critically review the published evidence regarding the effectiveness of CR as a means of enhancing the physical activity levels of participants.
important differences between these terms. Physical activity can be regarded as 'comprising any body movement produced by the skeletal muscles that results in a substantial increase over the resting energy expenditure'. Therefore, it can be seen to include any activity that involves bodily movement, be that at work, home or during leisure time. It can account for 15-40% of a person's total energy expenditure (Bouchard et al. 1993). Physical fitness, however, is, 'a set of attributes which people can have, or can acquire, that relates to their ability to perform physical activity' (Health Education Authority 1995). Bouchard et al. (1993) define physical fitness even further by looking at performance-related fitness and health-related fitness. Performance-related fitness is that which is needed for optimal work or sport performance. It depends heavily on motor skills, cardiorespiratory power and muscular strength, power and endurance. Healthrelated fitness is an ability to perform daily activities with vigour and demonstrates traits and capabilities associated with low morbidity.
PHYSICAL ACTIVITY OR PHYSICAL FITNESS? The terms 'physical fitness' and 'physical activity' are often used interchangeably. However, there are
Correspondenceto: Dr R. S. Taylor,R&D Support Unit, PostgraduateMedicalSchool,Barrack Road,ExeterEX2 5DW, UK. Tel:+44(0)1392403050; Fax: +44(0) 1392403042; E-mail:[email protected] 179
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Physical activity and physical fitness are not the same, but do depend on each other to a greater or lesser extent. It is hard to become more active unless there is some degree of fitness, but it is hard to get fit unless you become more active! Catch 22.
PHYSICAL ACTIVITY AND H E A L T H Physical activity is seen to be the way forward in encouraging the population to become healthier. The Health Education Authority (Health Education Authority 1995) estimate a number of morbidity gains for the population of England and Wales if everyone adopted physical activity: 9 a 33% reduction in coronary heart disease (CHD) incidence; 9 a 25% reduction in strokes; 9 a 25% reduction in non-insulin dependent diabetes in the over 45s; 9 over a 50% reduction in hip fractures in the over 45s and identify the following health benefits associated with undertaking physical activity at recommended levels: 9 lowering of high blood pressure; 9 greater weight loss than dieting alone; 9 lower incidence of non-insulin-dependent diabetes; 9 better management of insulin-dependent diabetes; 9 higher bone-mass density and fewer osteoporotic fractures; 9 improved muscle strength and flexibility in older people; 9 less age-related deterioration in aerobic fitness; 9 reduction in mild anxiety and depression; 9 improved memory in older people; 9 improved self-esteem and confidence in performing daily tasks for elderly people.
R E C O M M E N D E D LEVELS OF ACTIVITY Recent work in the USA, Canada and the U K (Andersen et al. 1997; Bouchard et al. 1993; Colhoun & Prescott-Clarke 1996) have all concurred that the right levels of activity are three periods of 20 min of vigorous activity per week or five periods of 30 min of moderate intensity activity on most days of the week. The recommendation from the USA now is that people who want to become more active can accumulate 30 min of activity during the day (Andersen et al. 1997; N I H Consensus Panel on Physical Activity and Cardiovascular Health 1996). This recommendation is a long way from the traditional idea of having to reach 60-80% of maximal heart rate to achieve a benefit from activity. The idea that some activity is Coronary Health Care (1998) 2 (4), 179-186
better than none may be finding credence but the aim should still be to achieve sustained periods of activity at moderate or vigorous levels (Health Education Authority 1995). Moderate levels of activity are those with an energy cost of 5-7.5 kcal/min, e.g. long walks at a brisk or fast pace, heavy housework, working as a labourer, refuse-collector or sport or exercise such that an average person would not get sweaty or out of breath. Vigorous levels of activity are those with an energy cost of 7.5 kcal/min and over, e.g. sport or exercise that would make an average person sweaty or out of breath or heavy occupational work. Young & D i n a n (1994) point out that the older person has much in common with the athlete in that they are both working close to their limit. It must be remembered that many patients will feel as though they have worked vigorously at levels that might be seen as light or moderate to a younger, fitter person.
PREVALENCE OF PHYSICAL ACTIVITY The prevalence of physical activity has been measured by several comprehensive surveys over the last few years, the best known of which are probably the Allied Dunbar National Fitness Survey (ADNFS) and the Health Survey for England. These surveys and others of their type are admirably analysed by the HEA (1995). They summarize a combined analysis of the A D N F S and the HEA National Survey of Activity and Health (HEANSAH), giving a sample size of 6583 adults aged 16-74, which show a high prevalence of sedentary lifestyle among English adults. Extrapolations of these figures to a 1993 population show: 29% of men and 28% of women are categorized as sedentary, i.e. less than one session of 30 min continuous moderate activity per week, 35% of men and 48% women engage in moderate activity, but on an irregular basis, i.e. between one and five sessions per week, 36% of men and 24% of women are active at a moderate level or above on a regular basis, i.e. a minimum of 30 min of moderate activity on five or more days per week, and only 16% of men and 5% of women aged 16-64 participate regularly in vigorous activity, i.e. three sessions of at least 20 min of vigorous activity per week. If it is the level of physical activity, rather than physical fitness, that is seen as the gold standard for achieving a healthy population, how can this be ascertained in a cardiac population?
MEASURING PHYSICAL ACTIVITY Measuring physical activity can be undertaken in many different ways, all having advantages and disadvantages. Some of these methods are summarized in 9 1998 Harcourt Brace & Co. Ltd
Physical activity and cardiac rehabilitation Table
1 Physicalactivityassessmentprocedures
Calorimetry: direct heat exchange(insulatedchamber) indirect (respirometry) Physiologicmarkers: heart rate monitoring doubly labelledisotopewater VO2max Mechanicaland electronicmotion detectors: pedometer in-shoe step counters electronicmotion sensors accelerometers Behaviouralobservation Dietary energyintake (fooddiary) Occupational and leisuretime surveyinstruments: job classification global self assessment activitydiaries or records recall questionnaires quantitativehistories
Table 1. The most accurate forms of physical activity assessment are calorimetry and doubly labelled water, both of which can provide accurate measurements of average daily expenditure under controlled laboratory conditions (Bouchard et al. 1993; Montoye et al. 1996). However, these are expensive and only provide information regarding activity undertaken in the laboratory. Those measurements most suited to a clinical population in an outpatient or rehabilitation setting are the survey instruments or questionnaires. They all rely on co-operation and honesty from the subjects but provide a volume and detail of information relative to the cost and time invested. Picking the right questionnaire for your subject is not easy, as there are many to chose from. Lamb & Brodie (1990) and Montoye et al. (1996) review many of the commonly used physical activity questionnaires discussing the approaches needed and the advantages and limitations of this method of assessing physical activity. The advantages are the relative cost and feasibility for large populations. Specific activities can be identified, together with frequency and duration. The procedure does not seem to influence the subject's activity level as observation or diary-keeping may do and it can be possible to calculate total energy expenditure. However, the limitations of inaccurate recall, overestimation of time and intensity and the need to word self-administered questionnaires appropriately for the population it needs to reach, can confuse the results. The Stanford 7-day Recall Questionnaire (Blair et al. 1985) is an instrument for measuring habitual activity over a one-week period. It has been validated against several other instruments (Montoye et al. 1996). Hellman et al. (1997) has modified it for use with a cardiac population by adapting the intensity levels that are measured at moderate, hard and very hard activity. For example: moderate activity in the original questionnaire was estimated at 3-4.9 METS, 9 1998 Harcourt Brace & Co. Ltd
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whereas in the modified version it is estimated at 2-3.9 METS. This would seem to take account of the cardiac patients' different perceptions of moderate activity. The use of portable accelerometers, as opposed to step counters, has developed recently with the advent of sophisticated electronics. Montoye et al. (1996) review this subject, finding that most studies seem to be based on the Caltrac system. They conclude that the instrument should be waterproofed to register swimming and should be worn on the lower limb if cycling. If habitual activity is to be sampled, then various days must be sampled, including weekend days and, if average daily METs are needed, then 6 days of recordings should be averaged. The point is also made that increased energy expenditure when carrying or lifting will not be reflected. Measuring physical activity by a motion counter may have as many disadvantages as advantages (Montoye et al. 1996). Many of the validation procedures on these instruments are laboratory based, so still may not give reliable information regarding habitual activity. Some of the earlier motion counters have been tested against some of the more commonly used physical activity questionnaires and have shown a good agreement between the two (e.g. 7-day recall against Caltrac correlation coefficient -- 0.7), but this is by no means borne out by all studies. There needs to be far more investigation into the validity of physical activity questionnaires in a population with morbidity and into the role of activity motion counters in assessing that validity.
THE PROCESS OF CARDIAC REHABILITATION Over the last two to three decades, CR has become a fundamental and well-recognized component of the healthcare provision for cardiac patients in the majority of industrialized countries. In addition to its role of complementing the secondary preventive benefits of medical treatment for the cardiac patient, CR serves to optimize patient quality of life. This patient focus is emphasized in the World Health Organization's definition of successful CR the sum of activity required to ensure individuals the basic possible physical, mental and social conditions 'so that they may by their own efforts regain a normal as possible a place in the community' (World Health Organization Expert Committee 1993). At present, in the UK, although the precise content of the cardiac rehabilitative process may vary from one programme to another, virtually all programmes are based on exercise training. Many programmes also offer both risk-factor education and stress management. These comprehensive programmes are staffed by a multidisciplinary team, including nurses, physiotherapists, occupational therapists, clinical psychologists, dieticians and doctors. CR has traditionally been Coronary Health Care (1998) 2 (4), 179-186
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made available to patients suffering from angina, as well as following acute myocardial infarction (MI), coronary artery surgery and angioplasty. Although initially contraindicated as a group, there has been an increasing trend to offer exercise rehabilitation to patients with cardiac insufficiency.
THE EVIDENCE BASE FOR CARDIAC REHABILITATION
In the current climate of evidence-based healthcare and escalating healthcare costs, there is considerable pressure on all aspects of the NHS to 'prove their benefit'. In the case of CR, a substantial body of research has been published in recent years that provides an evidence base upon which it is possible to assess this question of benefit. Two independent reviews have each demonstrated that, by pooling the results of over 20 trials in which over 4000 patients have been randomized to exercise CR or conventional care, there is a 20-25% relative reduction in three-year all-cause mortality in patients receiving CR (O'Connor et al. 1989; Oldridge et al. 1988). This corresponds to having to only rehabilitate some 30-40 patients to save one life, a clinical benefit equivalent to that of beta-blockade. In addition to all-cause mortality, there is high-quality research evidence that demonstrates that the benefits of exercise-based CR extend to a number of other outcomes: 1. Enhancement in laboratory-based measures of physical fitness and exercise capacity: increase in maximal work capacity (DeBusk et al. 1979) and a slower heart rate and lower systolic blood pressure during submaximal exercise (Clausen 1975); 2. improvement in psychological well-being: reduction in anxiety and depression and improvements in mood-perceived well-being (Newton et al. 1991; Oldridge et al. 1988); 3. when combined with educational and behavioural strategies, improvements in coronary risk factors: reductions in atherogenic lipid profile and casual blood pressure (DeBusk et al. 1994; Ornish et al. 1983). Although these benefits are clearly substantial, they have been criticized by a number of commentators for failing to take adequate account of the primary goal of the CR process, i.e. returning patients to their optimal level of everyday function. As has been described earlier, routine physical activity is a central aspect of everyday wellbeing of patients. Although the relationship between physical activity and secondary prevention of CHD has not been firmly established, some of the potential benefits of activity have been described above. The desire to return to former leisure and social activities not only fits with CR goals, but might also be greater importance than increases in exercise capacity or Coronary Health Care (1998) 2 (4), 179-186
reductions in anxiety in demonstrating the true value of CR. Increased physical activity has been shown in epidemiological studies to be associated with a decreased risk of coronary artery disease (Paffenbarger et al. 1978). Enhancement of the everyday physical activity levels of participants is therefore an important piece in developing the 'evidence-based jigsaw' of CR. The authors are not aware of a comprehensive review to date that addresses this issue.
DOES CARDIAC REHABILITATION ENHANCE ROUTINE PHYSICAL ACTIVITY LEVELS? A literature search was undertaken to comprehensively identify and review studies undertaken to assess the impact of CR on physical activity. An initial group of studies was identified from a the US Cardiac Rehabilitation Guidelines. Additional studies were identified by a literature search of the MEDLINE, CINAHL and EMBASE databases searched for the period 1966-1996 using the key words: cardiac rehabilitation, physical activity and exercise habits. The bibliographies of the references obtained by these methods were also inspected. In addition, previous reviews, and major textbooks on CR were searched for references. Articles were selected for review if: (1) employed a randomized controlled design; (2) the intervention involved some form of exercise-based rehabilitation component; (3) the population included either post-MI, angina pectoris, post coronary artery bypass graft (CABG) and heart failure patients; and (4) assessment of patient physical activity level was undertaken. A total of ten studies were identified that fulfilled these criteria, the descriptions of which are shown in Table 2. Eight of the ten studies were performed in either the USA or Scandinavia with a high degree of similarity between studies in terms of both the CR (or intervention) and control groups. Cardiac programmes most commonly consisted of three months of hospital-based CR with 2-3 sessions per week of aerobic exercise training for 30-45 min duration per session, a level of exercise that fails within the recommendations for health discussed earlier and very much in line with that currently practised in the UK. In all studies, the control group received no formal exercise training input. Unlike much of the CR research literature, there was a good representation of female as well as male patients. However, most of the studies involved patients following acute MI and excluded older patients (70 years or older), the study of Carlsson and colleagues (1997) being the only study without an upper age limit. Although this age limitation could perhaps be seen as limiting the generalizability of these studies, it important to remember that, in many CR centres, older patients are either excluded or not referred for rehabilitation (Ades et al. 1992). 9 1998 Harcourt Brace & Co. Ltd
Physical activity and cardiac rehabilitation Table 2
183
Summary of study origin, size, and description of CR intervention
Duration and nature of intervention (Author's description)
Author
Country
Population 111
De Busk et al. 1979
USA
70 males, < 70 yrs 3-11 wks post MI
Bengtsson 1983
Sweden
110 males & females, < 65 yrs ~8 wks post MI
Erdman et al. 1986
Netherlands
80 males, < 65 yrs < 6 months post MI
Heath et al. 1987
USA
Hamalainen et al. 1989
Finland
37 males & females, Mean age: 59 yrs 1-2 wks post CABG 375 males & females, < 60 yrs 'few weeks' post MI
Gulanick et al. 1991
USA
Sivarajan et al. 1992
USA
Engblom et al. 1992
Finland
201 males & females, < 65 yrs 6-8 weeks post CABG
Todd & Ballantyne 1992
UK
40 males, < 60 yrs yrs Chronic stable angina [6]
12 months Exercise training (11 min/day)
Carlsson et al. 1997
Sweden
168 males & females, > 50 yrs 4 wks post MI
3 months Exercise training (2-3 sessions/wk, 40 min/session) + education programme [7]
40 males & females, < 79 yrs 4 wks post MI, CABG, angioplasty 258 males & females, < 70 yrs "-.4.5 days post MI
8 weeks (1) Gymnasium exercise training (3 sessions/wk, 30 min/session, 70-85% HRmax) (2) Home exercise training (7 sessions/wk as above) 3 months Exercise training (2 sessions/wk, 30 min/session, 90% HRmax) + counselling 6 months Hospital rehabilitation Exercise training (2 sessiondwk, 45 min/session) + counselling 3 months Home-based exercise training (5 sessions/wk, 30-40 min/session, 13-15 RPE [2]) 3 months Exercise training + education + psychological input [3]
5 weeks (1) Exercise training + teaching (3 sessions/wk, 30 min/session, 70-80% HRmax) (2) Teaching only 3 months (1) Exercise training (7 sessions/wk) (2) Exercise training (as above) + teaching-counselling [4] 3 weeks Exercise training (total of 21 hours, 70%HRmax) + relaxation training + group discussion sessions
Nature of control (Author's description) No exercise training
No exercise training
Home-based rehabilitation Usual care + brochure on physical fitness and jogging Routine follow-up care. No exercise testing or exercise follow-up.
Followed up by their own doctors and did not participate in any organized rehabilitation programme Routine care
Conventional medical and nursing management
Reference, hospitalbased treatment
[51 Same access to investigations and medical care. No exercise advice given. Usual care + 2-3 visits to G P
[1] Number of patients who met study inclusion/exclusion criteria and were randomized to either intervention or control. [2] Rate of perceived exertion. [3] Intensive input for 3 months although intervention follow-up continued for 3 years. [4] Eight l-hour sessions, which included education on anatomy and physiology of heart, medications, risk factors and emotional reactions to MI. [5] Also a 2-day informative course before surgery and 2-day refresher 8 months post CABG. [6] At least 6 months' duration and no previous MI. [7] A nurse-led programme of individual and group education for a total 9 hours input (1.5 hrs: smoking cessation; 5.5 hrs: dietary information; and 2 hrs: physical activity). Education on smoking cessation and diet al.so extended (orally and in writing) during follow-up year.
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184 Table 3
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Author
Physical activity outcome(s) (Author's description)
Instrument(s) and timing of assessment [11
Result(s) 121
De Busk et al. 1979
(1) Level of activity (2) Walking distance (1) Exercise habits (2) Leisure time exertion
Questionnaire Immediately post Questionnaire + Interview 10 months post Structured interview Immediately and 4.5 months post Questionnaire 3-5 months post Questionnaire Immediately, 2, 5, 9 years post Questionnaire Immediately post Questionnaire Immediately and 3 months post
(1) (2) (1) (2)
Bengtsson 1983 Erdman et al. 1986
Habitual exercise
Heath et al. 1987
Leisure time physical activity
Hamalainen et al. 1989
Participation in: Moderate and heavy exercise
Gulanick et al. 1991
Physical activity performance [3] (1) Walking distance (2) Physical activity level
Sivarajan et al. 1992
C > 1 I=C I=C I=C
I>C
I>C I=C I=C (1) I > C (immediately but not at 3 months)
(2) I = c Engblom et al. 1992
Exercise habits
Todd & Ballantyne 1992
Level of physical activity
Carlsson et al. 1997
Habitual physical activity
Questionnaire 5 and 11 months post Activity diary Immediately post Questionnaire 9 months post
I=C I=C I=C
[1] Timing relative to intervention period. [2] I = C: no statistically significant difference (i.e. P > 0.05) in physical activity between intervention and control groups; I > C: statistically greater physical activity in intervention group compared to control group; C > I: statistically greater physical activity in control group compared to experimental group. [3] Initiation or resumption of range of daily activities
Across the ten trials, there were a total of 13 separate assessments of physical activity, three studies addressing at the same time two differing activity outcomes (see Table 3). These physical assessments in the main involved general assessments of overall daily physical activity levels or exercise habits, although in some studies this assessment was restricted to assessment of leisure activity or walking habits. In only about 20% (i.e. 3 out of 14) of cases was there evidence of a statistically significant benefit in physical activity outcome in the CR group compared to control. Moreover, these beneficial effects were apparently only observed in the period immediately following CR and were not maintained in the long term (i.e. more than 6 months post rehabilitation) as evidenced by the study of Sivarajan et al. Of the remaining ten cases, nine reported no significant difference in physical activity outcome, while one study observed a statistically greater improvement in physical activity in the patients who received no exercise training compared to those in the exercise rehabilitation groups. The results of these studies appear to provide evidence that CR has a limited role in the enhancement of routine physical activity levels and shown also that such benefits in activity are more likely in the short term than the long term. However, there Coronary Health Care (1998) 2 (4), 179-186
remain a number of fundamental methodological weaknesses in these trials that may introduce biases to limit these conclusions. Perhaps of greatest concern is the self-report nature of the information, all studies assessing physical activity levels using questionnaires, diary, interview or some combination of the three. As was discussed in the previous section on the methodology of activity assessment, self-report methods are prone to assessment bias, particularly if individuals are required to recall their activity patterns for a period well in the past. Although it may be argued that such assessment bias may have been equally likely in both the intervention and control groups, given that physical activity was the main outcome of interest in this review, data-quality assurance is nonetheless important. The most obvious form of quality assurance is the use of standardized physical activity questionnaires with proven reliability and validity. Six of the trials used standardized instruments, including the three studies that demonstrated activity improvements with CR. Another means of dataquality assurance is the use of objective physical activity measures. Only one of the ten studies employed such methods. Todd & Ballantyne (1992) combined 24-hour heart rate recording with a patient activity diary. However, the results of this study are 9 1998 Harcourt Brace & Co. Ltd
Physical activity and cardiac rehabilitation ambiguous in terms of their contribution to an understanding of the role of effect of exercise rehabilitation on routine physical activity levels. An increase in activity would be expected to be reflected by an increase in 24-hour heart rate. However, that the authors failed to report a significant change in mean 24-hour heart rate with exercise rehabilitation probably indicates that an increase in heart rate was offset by a training bradycardia, an observation associated by a significant decrease in this group's nocturnal heart rate. Although a number of studies have described the utility of activity monitoring, such as accelerometers and pedometers, in various cardiac populations, we could find no randomized trials of CR that have employed these devices. Although this review was restricted to randomized controlled trials, in an attempt to minimize potential biases and confounding, the methodological quality of such trials cannot be assumed. Using a number of previously published methodology checklists, the methodological quality of the trials in this review was assessed on the bias of a number of criteria (see Table 4). The median quality score of these eleven trials was only 2 (out of a possible maximum score of 5), with three studies achieving a score less than this. Although certain of these quality criteria are less important than others, such as blinding of assessors to outcome when using patient self-report, a large dropout of patients during the trial and the failure to use standardized outcomes measures may have introduced considerable biases. It also important that trials recruit sufficient patients in order to have adequate power to detect a statistically significant change in outcome. Half of Table 4
185
the studies reviewed had fewer than 100 patients at the outset of the trial, and none of the ten studies reported any power calculation at their outset. Given that, in 6 out of the 14 assessments, an improvement, albeit statistically non-significant, was observed, it is quite possible that, with an increased sample size, these differences may have achieved statistical significance.
CONCLUSION Inadequate physical activity and a sedentary lifestyle are the most prevalent risk factors for ill-health in western industrialized societies. Current recommendations suggest that individuals need only accumulate 30 rain each day of moderate-intensity activity, such as walking. CR offers an important potential means for enhancing the everyday physical activity of patients with cardiac disease. However, although CR may increase physical activity in the short term, this review shows there is currently little evidence to support its efficacy in the medium to long term (i.e. 3-12 months after CR). These results suggest that there may be a need for CR programmes to place more emphasis towards to improving long-term physical activity levels of participants. Although all randomized trials, the limited experimental quality (i.e. lack of concealment of randomization procedure, inadequate blinding of assessors, failure to analyse the data by intention to treat, and substantial losses to follow-up) and the entirely self-report nature of physical activity data, using often unvalidated instruments, limits the validity of the results of this
Methodological quality o f C R trials.
Authors De Busk et al. 1979
Criterion 1
Criterion 2
•
x
Criterion 3
Criterion 4
Criterion 5
Total Score (/5)
,/
,/
r
3
./
x
1
./
~/
2
~"
J
3
./
x
2
./
J
3
~/
J
2
J
J
3
~/
x
1
,/
x
2
(90%) Bengtsson 1983
x
x
Erdman et al. 1986
x
x
Heath et al. 1987
x
x
Hamalainen et al. 1989
•
x
Gulanick et al. 1991
•
x
Sivarajan et al. al 1992
x
x
• (79%) x (71%) J (100%) J (98%) ./ (90%) x
(83%) Engblom et al. 1992
x
x
~/
(1OO%o) Todd & Ballantyne 1992
x
x
x
(78%) Carlsson et al. 1997
x
x
,/
(88%) Criterion 1: Adequate concealment (or description) o f randomization process. Criterion 2: Blinding of physical activity outcome assessment. Criterion 3: A t least 80% o f trial participants available at follow-up for physical activity assessment (percentage o f patients assessed based on baseline numbers). Criterion 4: Results analysed on the basis o f 'intention to treat'. Criterion 5: Standardized physical activity instrument used or citation of validation process given.
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review. There is therefore a need for future studies of CR to incorporate validated assessments of physical activity by use of standardized questionnaires backed up with objective measures (activity monitors). One of the review authors (JJ) is currently exploring this area by assessing the physical activity levels of cardiac patients 12 months following CR using both validated self-report questionnaires and accelerometry. ACKNOWLEDGEMENTS This review was undertaken while JJ was a postgraduate student on the MSc Health Care course at the Institute of General Practice, Postgraduate Medical School, University of Exeter, Exeter, UK. REFERENCES
Ades P, Wallmann ML, Plok DM, Coflesky JT 1992 Referral patterns and exercise response in the rehabilitation of female coronary patients aged > 62 years. American Journal of Cardiology 69:1422-1425 Andersen R, Blair S, Lawrence J, Cheskin M, Bartlett S 1997 Encouraging patients to become more physically active: the physician's role. Annals of Internal Medicine 127; 395-400 Bengtsson K 1983 Rehabilitation after myocardial infarction. Scandinavian Journal of Rehabilitation Medicine 15:1-9 Blair S, Haskell W, Ho P e t al. 1985 Assessment of habitual physical activity by seven-day recall in a community survey and controlled experiments. American Journal of Epidemiology 122(5): 794-804 Bouchard C, Shephard R J, Stephens T 1993 Physical activity, fitness and health. Consensus Statement. Human Kinetics, Leeds Carlsson R, Lindberg G, Westin L, Israelsson B 1997 Influence of coronary nursing management follow up on lifestyle after acute myocardial infarction. Heart 77:256-259 Clausen JP 1975 Circulatory adjustments to dynamic exercise and effect of physical training in patients with coronary artery disease. Progress in Cardiovascular Disease 18:459-495 Colhoun H, Prescott-Clarke P (eds) 1996 Health Survey for England 1994. HMSO, Norwich DeBusk RF, Houston N, Haskell W, Parker M, Fry G 1979 Exercise training soon after myocardial infarction. American Journal of Cardiology 44:1223-1229 DeBusk RF, Houston Miller N, Dennis CA et al. 1994 A case management system for coronary risk factor modification after acute myocardial infarction. Annals of Internal Medicine 120:72I~29 Engblom E, Heitanen EK, Hamalainen H, Kallio V, Inberg M, Knuts L-R 1992 Exercise habits and physical performance during comprehensive rehabilitation after coronary artery bypass surgery. European Heart Journal 13:1053 1059 Erdman RAM, Diuvenooreden H J, Verhage F, Kazemier M, Hugenholtz PG 1986 Predictability of beneficial effects in cardiac rehabilitation: a randomized clinical trial of psychosocial variables. Journal of Cardiopulmonary Rehabilitation 6:206-213 Gulanick M 1991 Is phase 2 cardiac rehabilitation necessary for early recovery of patients with cardiac disease? A randomized controlled study. Heart and Lung 20:9-15
Coronary Health Care (1998) 2 (4), 179-186
Hamalainen H, Luurila OL Kallio V, Knuts L-R, Arstila M, Hakkila J 1989 Long -term reduction in sudden death after a multifactorial intervention programme in patients with myocardial infarction: 10-year results of a controlled investigation. European Heart Journal 10:55-62 Health Education Authority 1995 Health Update. Physical Activity. HEA, London Health Education Authority and Sports Council 1992 Allied Dunbar National Fitness Survey. Main Findings. Sports Council and HEA, London Health Education Authority 1991 HEA National Survey of Activity and Health. Unpublished study conducted in 1991 Heath GW, Maloney PM, Fure CW 1987 Group exercise versus home exercise in coronary artery bypass patients: effects on physical activity habits. Journal of Cardiopulmonary Rehabilitation 7:190-195 Hellman EA, Williams M, Thalken L 1997 Construct validity of the modified 7-day activity interview used with older adults with cardiac problems. Rehabilitation Nursing Research 5: 126,133 Lamb KL, Brodie DA 1990 The assessment of physical activity by leisure time physical activity questionnaires. Sports Medicine 10:159-180 Montoye HL Kemper H, Saris W, Washburn R 1996 Measuring physical activity and energy expenditure. Human Kinetics, Leeds Newton M, Mutrie N, McArthur JD 1991 The effects of exercise in coronary rehabilitation programme. Scotish Medical Journal 36:38-41 NIH Consensus Panel on Physical Activity and Cardiovascular Health 1996 Journal of the American Medical Association 276; 241-246 O'Connor GT, Buring JE, Yusuf S et al. 1989 An overview of randomized trials of rehabilitation with exercise after myocardial infarction. Circulation 80:234-244 Oldridge NB, Guyatt GH, Fischer MS, Rimm AA 1988 Cardiac rehabilitation after myocardial infarction: combined experience of randomized clinical trials. Journal of the American Medical Association 260:945-910 Oldridge NB, Guyatt G, Jones N e t al. 1991 Effects on quality of life with comprehensive rehabilitation after acute myocardial infarction. American Journal of Cardiology 67: 1084-1089 Ornish D, Scherwitz LW, Doody RS et al. 1983 Effects of stress management and dietary changes on ischaemic heart disease. Journal of the American Medical Association 249: 54-59 Paffenbarger RS, Wing AL, Hyde RT 1978 Physical activity as an index of heart risk of college alumni. American Journal of Epidemiology 108:161-175 Sivarajan E, Bruce R, Lindskog BD, Almes M J, Belanger L, Green B 1992 Treadmill test responses to an early exercise program after myocardial infarction: a randomized study. Circulation 7:1420-1428 Todd IC, Ballantyne D 1992 Effect of exercise training on the total ischaemic burden: an assessment by 24 hour ambulatory monitoring. British Heart Journal 68:560-566 World Health Organization Expert Committee 1993 Rehabilitation after cardiovascular diseases, with special reference to developing countries. Technical report series no.831 Young A, Dinan S 1994 Fitness for older people. British Medical Journal 309:331 334
9 1998 Harcourt Brace & Co. Ltd
REVIEW ARTICLE
Physical activity and cardiac rehabilitation: a critical review of the literature J. Jolliffe, R. T a y l o r *
Senior Physiotherapist, Exeter Nuffield Hospital Exeter;, *Senior Lecturer, R&D Support Unit, Postgraduate Medical School, University of Exeter, Exeter, UK S U M M A R Y . Inadequate physical activity is one of the most prevalent risk factors for ill-health in western industrialized societies. In the secondary-care setting, cardiac rehabilitation offers an important potential means for enhancing the everyday physical activity of patients with cardiac disease. A critical review was undertaken to examine the effectiveness of cardiac rehabilitation in promoting long- to medium-term physical activity levels. A comprehensive literature search for studies was undertaken using bibliographic databases and published reference lists. Ten randomized controlled trials were identified that fulfilled the study inclusion criteria. These studies included a total of 13 objective assessments of physical activity outcome. It was found that in only 31% (i.e. 4 out of 13) of cases was there evidence of a statistically significant (P<0.05) improvement in physical activity outcome in the period (immediately to 9 years) following cardiac rehabilitation. These results suggest that there may be a need for cardiac rehabilitation programmes to place more emphasis towards to improving long-term physical activity levels of participants. However, the median methodological quality score for these trials of 2 (out of a possible score of 5) indicate the need for caution in the interpretation of the results. In particular, less than half of the studies gave evidence of using a validated physical activity selfreport questionnaire and only one of the studies attempted to measure physical activity directly. The results of this review indicate the need for future studies of cardiac rehabilitation to incorporate validated assessments of physical activity, such as standardized questionnaires, together with direct measures, such as activity or movement monitors.
This purpose of this review is examine the evidence regarding the impact of cardiac rehabilitation (CR) on medium- to long-term physical activity. In doing so, this paper will: (1) describe the concept of physical activity; (2) summarize the current recommendations of physical activity levels for health; (3) overview the current methods by which physical activity can be assessed; and (4) critically review the published evidence regarding the effectiveness of CR as a means of enhancing the physical activity levels of participants.
important differences between these terms. Physical activity can be regarded as 'comprising any body movement produced by the skeletal muscles that results in a substantial increase over the resting energy expenditure'. Therefore, it can be seen to include any activity that involves bodily movement, be that at work, home or during leisure time. It can account for 15-40% of a person's total energy expenditure (Bouchard et al. 1993). Physical fitness, however, is, 'a set of attributes which people can have, or can acquire, that relates to their ability to perform physical activity' (Health Education Authority 1995). Bouchard et al. (1993) define physical fitness even further by looking at performance-related fitness and health-related fitness. Performance-related fitness is that which is needed for optimal work or sport performance. It depends heavily on motor skills, cardiorespiratory power and muscular strength, power and endurance. Healthrelated fitness is an ability to perform daily activities with vigour and demonstrates traits and capabilities associated with low morbidity.
PHYSICAL ACTIVITY OR PHYSICAL FITNESS? The terms 'physical fitness' and 'physical activity' are often used interchangeably. However, there are
Correspondenceto: Dr R. S. Taylor,R&D Support Unit, PostgraduateMedicalSchool,Barrack Road,ExeterEX2 5DW, UK. Tel:+44(0)1392403050; Fax: +44(0) 1392403042; E-mail:[email protected] 179
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Physical activity and physical fitness are not the same, but do depend on each other to a greater or lesser extent. It is hard to become more active unless there is some degree of fitness, but it is hard to get fit unless you become more active! Catch 22.
PHYSICAL ACTIVITY AND H E A L T H Physical activity is seen to be the way forward in encouraging the population to become healthier. The Health Education Authority (Health Education Authority 1995) estimate a number of morbidity gains for the population of England and Wales if everyone adopted physical activity: 9 a 33% reduction in coronary heart disease (CHD) incidence; 9 a 25% reduction in strokes; 9 a 25% reduction in non-insulin dependent diabetes in the over 45s; 9 over a 50% reduction in hip fractures in the over 45s and identify the following health benefits associated with undertaking physical activity at recommended levels: 9 lowering of high blood pressure; 9 greater weight loss than dieting alone; 9 lower incidence of non-insulin-dependent diabetes; 9 better management of insulin-dependent diabetes; 9 higher bone-mass density and fewer osteoporotic fractures; 9 improved muscle strength and flexibility in older people; 9 less age-related deterioration in aerobic fitness; 9 reduction in mild anxiety and depression; 9 improved memory in older people; 9 improved self-esteem and confidence in performing daily tasks for elderly people.
R E C O M M E N D E D LEVELS OF ACTIVITY Recent work in the USA, Canada and the U K (Andersen et al. 1997; Bouchard et al. 1993; Colhoun & Prescott-Clarke 1996) have all concurred that the right levels of activity are three periods of 20 min of vigorous activity per week or five periods of 30 min of moderate intensity activity on most days of the week. The recommendation from the USA now is that people who want to become more active can accumulate 30 min of activity during the day (Andersen et al. 1997; N I H Consensus Panel on Physical Activity and Cardiovascular Health 1996). This recommendation is a long way from the traditional idea of having to reach 60-80% of maximal heart rate to achieve a benefit from activity. The idea that some activity is Coronary Health Care (1998) 2 (4), 179-186
better than none may be finding credence but the aim should still be to achieve sustained periods of activity at moderate or vigorous levels (Health Education Authority 1995). Moderate levels of activity are those with an energy cost of 5-7.5 kcal/min, e.g. long walks at a brisk or fast pace, heavy housework, working as a labourer, refuse-collector or sport or exercise such that an average person would not get sweaty or out of breath. Vigorous levels of activity are those with an energy cost of 7.5 kcal/min and over, e.g. sport or exercise that would make an average person sweaty or out of breath or heavy occupational work. Young & D i n a n (1994) point out that the older person has much in common with the athlete in that they are both working close to their limit. It must be remembered that many patients will feel as though they have worked vigorously at levels that might be seen as light or moderate to a younger, fitter person.
PREVALENCE OF PHYSICAL ACTIVITY The prevalence of physical activity has been measured by several comprehensive surveys over the last few years, the best known of which are probably the Allied Dunbar National Fitness Survey (ADNFS) and the Health Survey for England. These surveys and others of their type are admirably analysed by the HEA (1995). They summarize a combined analysis of the A D N F S and the HEA National Survey of Activity and Health (HEANSAH), giving a sample size of 6583 adults aged 16-74, which show a high prevalence of sedentary lifestyle among English adults. Extrapolations of these figures to a 1993 population show: 29% of men and 28% of women are categorized as sedentary, i.e. less than one session of 30 min continuous moderate activity per week, 35% of men and 48% women engage in moderate activity, but on an irregular basis, i.e. between one and five sessions per week, 36% of men and 24% of women are active at a moderate level or above on a regular basis, i.e. a minimum of 30 min of moderate activity on five or more days per week, and only 16% of men and 5% of women aged 16-64 participate regularly in vigorous activity, i.e. three sessions of at least 20 min of vigorous activity per week. If it is the level of physical activity, rather than physical fitness, that is seen as the gold standard for achieving a healthy population, how can this be ascertained in a cardiac population?
MEASURING PHYSICAL ACTIVITY Measuring physical activity can be undertaken in many different ways, all having advantages and disadvantages. Some of these methods are summarized in 9 1998 Harcourt Brace & Co. Ltd
Physical activity and cardiac rehabilitation Table
1 Physicalactivityassessmentprocedures
Calorimetry: direct heat exchange(insulatedchamber) indirect (respirometry) Physiologicmarkers: heart rate monitoring doubly labelledisotopewater VO2max Mechanicaland electronicmotion detectors: pedometer in-shoe step counters electronicmotion sensors accelerometers Behaviouralobservation Dietary energyintake (fooddiary) Occupational and leisuretime surveyinstruments: job classification global self assessment activitydiaries or records recall questionnaires quantitativehistories
Table 1. The most accurate forms of physical activity assessment are calorimetry and doubly labelled water, both of which can provide accurate measurements of average daily expenditure under controlled laboratory conditions (Bouchard et al. 1993; Montoye et al. 1996). However, these are expensive and only provide information regarding activity undertaken in the laboratory. Those measurements most suited to a clinical population in an outpatient or rehabilitation setting are the survey instruments or questionnaires. They all rely on co-operation and honesty from the subjects but provide a volume and detail of information relative to the cost and time invested. Picking the right questionnaire for your subject is not easy, as there are many to chose from. Lamb & Brodie (1990) and Montoye et al. (1996) review many of the commonly used physical activity questionnaires discussing the approaches needed and the advantages and limitations of this method of assessing physical activity. The advantages are the relative cost and feasibility for large populations. Specific activities can be identified, together with frequency and duration. The procedure does not seem to influence the subject's activity level as observation or diary-keeping may do and it can be possible to calculate total energy expenditure. However, the limitations of inaccurate recall, overestimation of time and intensity and the need to word self-administered questionnaires appropriately for the population it needs to reach, can confuse the results. The Stanford 7-day Recall Questionnaire (Blair et al. 1985) is an instrument for measuring habitual activity over a one-week period. It has been validated against several other instruments (Montoye et al. 1996). Hellman et al. (1997) has modified it for use with a cardiac population by adapting the intensity levels that are measured at moderate, hard and very hard activity. For example: moderate activity in the original questionnaire was estimated at 3-4.9 METS, 9 1998 Harcourt Brace & Co. Ltd
181
whereas in the modified version it is estimated at 2-3.9 METS. This would seem to take account of the cardiac patients' different perceptions of moderate activity. The use of portable accelerometers, as opposed to step counters, has developed recently with the advent of sophisticated electronics. Montoye et al. (1996) review this subject, finding that most studies seem to be based on the Caltrac system. They conclude that the instrument should be waterproofed to register swimming and should be worn on the lower limb if cycling. If habitual activity is to be sampled, then various days must be sampled, including weekend days and, if average daily METs are needed, then 6 days of recordings should be averaged. The point is also made that increased energy expenditure when carrying or lifting will not be reflected. Measuring physical activity by a motion counter may have as many disadvantages as advantages (Montoye et al. 1996). Many of the validation procedures on these instruments are laboratory based, so still may not give reliable information regarding habitual activity. Some of the earlier motion counters have been tested against some of the more commonly used physical activity questionnaires and have shown a good agreement between the two (e.g. 7-day recall against Caltrac correlation coefficient -- 0.7), but this is by no means borne out by all studies. There needs to be far more investigation into the validity of physical activity questionnaires in a population with morbidity and into the role of activity motion counters in assessing that validity.
THE PROCESS OF CARDIAC REHABILITATION Over the last two to three decades, CR has become a fundamental and well-recognized component of the healthcare provision for cardiac patients in the majority of industrialized countries. In addition to its role of complementing the secondary preventive benefits of medical treatment for the cardiac patient, CR serves to optimize patient quality of life. This patient focus is emphasized in the World Health Organization's definition of successful CR the sum of activity required to ensure individuals the basic possible physical, mental and social conditions 'so that they may by their own efforts regain a normal as possible a place in the community' (World Health Organization Expert Committee 1993). At present, in the UK, although the precise content of the cardiac rehabilitative process may vary from one programme to another, virtually all programmes are based on exercise training. Many programmes also offer both risk-factor education and stress management. These comprehensive programmes are staffed by a multidisciplinary team, including nurses, physiotherapists, occupational therapists, clinical psychologists, dieticians and doctors. CR has traditionally been Coronary Health Care (1998) 2 (4), 179-186
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made available to patients suffering from angina, as well as following acute myocardial infarction (MI), coronary artery surgery and angioplasty. Although initially contraindicated as a group, there has been an increasing trend to offer exercise rehabilitation to patients with cardiac insufficiency.
THE EVIDENCE BASE FOR CARDIAC REHABILITATION
In the current climate of evidence-based healthcare and escalating healthcare costs, there is considerable pressure on all aspects of the NHS to 'prove their benefit'. In the case of CR, a substantial body of research has been published in recent years that provides an evidence base upon which it is possible to assess this question of benefit. Two independent reviews have each demonstrated that, by pooling the results of over 20 trials in which over 4000 patients have been randomized to exercise CR or conventional care, there is a 20-25% relative reduction in three-year all-cause mortality in patients receiving CR (O'Connor et al. 1989; Oldridge et al. 1988). This corresponds to having to only rehabilitate some 30-40 patients to save one life, a clinical benefit equivalent to that of beta-blockade. In addition to all-cause mortality, there is high-quality research evidence that demonstrates that the benefits of exercise-based CR extend to a number of other outcomes: 1. Enhancement in laboratory-based measures of physical fitness and exercise capacity: increase in maximal work capacity (DeBusk et al. 1979) and a slower heart rate and lower systolic blood pressure during submaximal exercise (Clausen 1975); 2. improvement in psychological well-being: reduction in anxiety and depression and improvements in mood-perceived well-being (Newton et al. 1991; Oldridge et al. 1988); 3. when combined with educational and behavioural strategies, improvements in coronary risk factors: reductions in atherogenic lipid profile and casual blood pressure (DeBusk et al. 1994; Ornish et al. 1983). Although these benefits are clearly substantial, they have been criticized by a number of commentators for failing to take adequate account of the primary goal of the CR process, i.e. returning patients to their optimal level of everyday function. As has been described earlier, routine physical activity is a central aspect of everyday wellbeing of patients. Although the relationship between physical activity and secondary prevention of CHD has not been firmly established, some of the potential benefits of activity have been described above. The desire to return to former leisure and social activities not only fits with CR goals, but might also be greater importance than increases in exercise capacity or Coronary Health Care (1998) 2 (4), 179-186
reductions in anxiety in demonstrating the true value of CR. Increased physical activity has been shown in epidemiological studies to be associated with a decreased risk of coronary artery disease (Paffenbarger et al. 1978). Enhancement of the everyday physical activity levels of participants is therefore an important piece in developing the 'evidence-based jigsaw' of CR. The authors are not aware of a comprehensive review to date that addresses this issue.
DOES CARDIAC REHABILITATION ENHANCE ROUTINE PHYSICAL ACTIVITY LEVELS? A literature search was undertaken to comprehensively identify and review studies undertaken to assess the impact of CR on physical activity. An initial group of studies was identified from a the US Cardiac Rehabilitation Guidelines. Additional studies were identified by a literature search of the MEDLINE, CINAHL and EMBASE databases searched for the period 1966-1996 using the key words: cardiac rehabilitation, physical activity and exercise habits. The bibliographies of the references obtained by these methods were also inspected. In addition, previous reviews, and major textbooks on CR were searched for references. Articles were selected for review if: (1) employed a randomized controlled design; (2) the intervention involved some form of exercise-based rehabilitation component; (3) the population included either post-MI, angina pectoris, post coronary artery bypass graft (CABG) and heart failure patients; and (4) assessment of patient physical activity level was undertaken. A total of ten studies were identified that fulfilled these criteria, the descriptions of which are shown in Table 2. Eight of the ten studies were performed in either the USA or Scandinavia with a high degree of similarity between studies in terms of both the CR (or intervention) and control groups. Cardiac programmes most commonly consisted of three months of hospital-based CR with 2-3 sessions per week of aerobic exercise training for 30-45 min duration per session, a level of exercise that fails within the recommendations for health discussed earlier and very much in line with that currently practised in the UK. In all studies, the control group received no formal exercise training input. Unlike much of the CR research literature, there was a good representation of female as well as male patients. However, most of the studies involved patients following acute MI and excluded older patients (70 years or older), the study of Carlsson and colleagues (1997) being the only study without an upper age limit. Although this age limitation could perhaps be seen as limiting the generalizability of these studies, it important to remember that, in many CR centres, older patients are either excluded or not referred for rehabilitation (Ades et al. 1992). 9 1998 Harcourt Brace & Co. Ltd
Physical activity and cardiac rehabilitation Table 2
183
Summary of study origin, size, and description of CR intervention
Duration and nature of intervention (Author's description)
Author
Country
Population 111
De Busk et al. 1979
USA
70 males, < 70 yrs 3-11 wks post MI
Bengtsson 1983
Sweden
110 males & females, < 65 yrs ~8 wks post MI
Erdman et al. 1986
Netherlands
80 males, < 65 yrs < 6 months post MI
Heath et al. 1987
USA
Hamalainen et al. 1989
Finland
37 males & females, Mean age: 59 yrs 1-2 wks post CABG 375 males & females, < 60 yrs 'few weeks' post MI
Gulanick et al. 1991
USA
Sivarajan et al. 1992
USA
Engblom et al. 1992
Finland
201 males & females, < 65 yrs 6-8 weeks post CABG
Todd & Ballantyne 1992
UK
40 males, < 60 yrs yrs Chronic stable angina [6]
12 months Exercise training (11 min/day)
Carlsson et al. 1997
Sweden
168 males & females, > 50 yrs 4 wks post MI
3 months Exercise training (2-3 sessions/wk, 40 min/session) + education programme [7]
40 males & females, < 79 yrs 4 wks post MI, CABG, angioplasty 258 males & females, < 70 yrs "-.4.5 days post MI
8 weeks (1) Gymnasium exercise training (3 sessions/wk, 30 min/session, 70-85% HRmax) (2) Home exercise training (7 sessions/wk as above) 3 months Exercise training (2 sessions/wk, 30 min/session, 90% HRmax) + counselling 6 months Hospital rehabilitation Exercise training (2 sessiondwk, 45 min/session) + counselling 3 months Home-based exercise training (5 sessions/wk, 30-40 min/session, 13-15 RPE [2]) 3 months Exercise training + education + psychological input [3]
5 weeks (1) Exercise training + teaching (3 sessions/wk, 30 min/session, 70-80% HRmax) (2) Teaching only 3 months (1) Exercise training (7 sessions/wk) (2) Exercise training (as above) + teaching-counselling [4] 3 weeks Exercise training (total of 21 hours, 70%HRmax) + relaxation training + group discussion sessions
Nature of control (Author's description) No exercise training
No exercise training
Home-based rehabilitation Usual care + brochure on physical fitness and jogging Routine follow-up care. No exercise testing or exercise follow-up.
Followed up by their own doctors and did not participate in any organized rehabilitation programme Routine care
Conventional medical and nursing management
Reference, hospitalbased treatment
[51 Same access to investigations and medical care. No exercise advice given. Usual care + 2-3 visits to G P
[1] Number of patients who met study inclusion/exclusion criteria and were randomized to either intervention or control. [2] Rate of perceived exertion. [3] Intensive input for 3 months although intervention follow-up continued for 3 years. [4] Eight l-hour sessions, which included education on anatomy and physiology of heart, medications, risk factors and emotional reactions to MI. [5] Also a 2-day informative course before surgery and 2-day refresher 8 months post CABG. [6] At least 6 months' duration and no previous MI. [7] A nurse-led programme of individual and group education for a total 9 hours input (1.5 hrs: smoking cessation; 5.5 hrs: dietary information; and 2 hrs: physical activity). Education on smoking cessation and diet al.so extended (orally and in writing) during follow-up year.
9 1998 Harcourt Brace & Co. Lid
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184 Table 3
CoronaryHealth Care Method of physical activity assessment and results of CR trials
Author
Physical activity outcome(s) (Author's description)
Instrument(s) and timing of assessment [11
Result(s) 121
De Busk et al. 1979
(1) Level of activity (2) Walking distance (1) Exercise habits (2) Leisure time exertion
Questionnaire Immediately post Questionnaire + Interview 10 months post Structured interview Immediately and 4.5 months post Questionnaire 3-5 months post Questionnaire Immediately, 2, 5, 9 years post Questionnaire Immediately post Questionnaire Immediately and 3 months post
(1) (2) (1) (2)
Bengtsson 1983 Erdman et al. 1986
Habitual exercise
Heath et al. 1987
Leisure time physical activity
Hamalainen et al. 1989
Participation in: Moderate and heavy exercise
Gulanick et al. 1991
Physical activity performance [3] (1) Walking distance (2) Physical activity level
Sivarajan et al. 1992
C > 1 I=C I=C I=C
I>C
I>C I=C I=C (1) I > C (immediately but not at 3 months)
(2) I = c Engblom et al. 1992
Exercise habits
Todd & Ballantyne 1992
Level of physical activity
Carlsson et al. 1997
Habitual physical activity
Questionnaire 5 and 11 months post Activity diary Immediately post Questionnaire 9 months post
I=C I=C I=C
[1] Timing relative to intervention period. [2] I = C: no statistically significant difference (i.e. P > 0.05) in physical activity between intervention and control groups; I > C: statistically greater physical activity in intervention group compared to control group; C > I: statistically greater physical activity in control group compared to experimental group. [3] Initiation or resumption of range of daily activities
Across the ten trials, there were a total of 13 separate assessments of physical activity, three studies addressing at the same time two differing activity outcomes (see Table 3). These physical assessments in the main involved general assessments of overall daily physical activity levels or exercise habits, although in some studies this assessment was restricted to assessment of leisure activity or walking habits. In only about 20% (i.e. 3 out of 14) of cases was there evidence of a statistically significant benefit in physical activity outcome in the CR group compared to control. Moreover, these beneficial effects were apparently only observed in the period immediately following CR and were not maintained in the long term (i.e. more than 6 months post rehabilitation) as evidenced by the study of Sivarajan et al. Of the remaining ten cases, nine reported no significant difference in physical activity outcome, while one study observed a statistically greater improvement in physical activity in the patients who received no exercise training compared to those in the exercise rehabilitation groups. The results of these studies appear to provide evidence that CR has a limited role in the enhancement of routine physical activity levels and shown also that such benefits in activity are more likely in the short term than the long term. However, there Coronary Health Care (1998) 2 (4), 179-186
remain a number of fundamental methodological weaknesses in these trials that may introduce biases to limit these conclusions. Perhaps of greatest concern is the self-report nature of the information, all studies assessing physical activity levels using questionnaires, diary, interview or some combination of the three. As was discussed in the previous section on the methodology of activity assessment, self-report methods are prone to assessment bias, particularly if individuals are required to recall their activity patterns for a period well in the past. Although it may be argued that such assessment bias may have been equally likely in both the intervention and control groups, given that physical activity was the main outcome of interest in this review, data-quality assurance is nonetheless important. The most obvious form of quality assurance is the use of standardized physical activity questionnaires with proven reliability and validity. Six of the trials used standardized instruments, including the three studies that demonstrated activity improvements with CR. Another means of dataquality assurance is the use of objective physical activity measures. Only one of the ten studies employed such methods. Todd & Ballantyne (1992) combined 24-hour heart rate recording with a patient activity diary. However, the results of this study are 9 1998 Harcourt Brace & Co. Ltd
Physical activity and cardiac rehabilitation ambiguous in terms of their contribution to an understanding of the role of effect of exercise rehabilitation on routine physical activity levels. An increase in activity would be expected to be reflected by an increase in 24-hour heart rate. However, that the authors failed to report a significant change in mean 24-hour heart rate with exercise rehabilitation probably indicates that an increase in heart rate was offset by a training bradycardia, an observation associated by a significant decrease in this group's nocturnal heart rate. Although a number of studies have described the utility of activity monitoring, such as accelerometers and pedometers, in various cardiac populations, we could find no randomized trials of CR that have employed these devices. Although this review was restricted to randomized controlled trials, in an attempt to minimize potential biases and confounding, the methodological quality of such trials cannot be assumed. Using a number of previously published methodology checklists, the methodological quality of the trials in this review was assessed on the bias of a number of criteria (see Table 4). The median quality score of these eleven trials was only 2 (out of a possible maximum score of 5), with three studies achieving a score less than this. Although certain of these quality criteria are less important than others, such as blinding of assessors to outcome when using patient self-report, a large dropout of patients during the trial and the failure to use standardized outcomes measures may have introduced considerable biases. It also important that trials recruit sufficient patients in order to have adequate power to detect a statistically significant change in outcome. Half of Table 4
185
the studies reviewed had fewer than 100 patients at the outset of the trial, and none of the ten studies reported any power calculation at their outset. Given that, in 6 out of the 14 assessments, an improvement, albeit statistically non-significant, was observed, it is quite possible that, with an increased sample size, these differences may have achieved statistical significance.
CONCLUSION Inadequate physical activity and a sedentary lifestyle are the most prevalent risk factors for ill-health in western industrialized societies. Current recommendations suggest that individuals need only accumulate 30 rain each day of moderate-intensity activity, such as walking. CR offers an important potential means for enhancing the everyday physical activity of patients with cardiac disease. However, although CR may increase physical activity in the short term, this review shows there is currently little evidence to support its efficacy in the medium to long term (i.e. 3-12 months after CR). These results suggest that there may be a need for CR programmes to place more emphasis towards to improving long-term physical activity levels of participants. Although all randomized trials, the limited experimental quality (i.e. lack of concealment of randomization procedure, inadequate blinding of assessors, failure to analyse the data by intention to treat, and substantial losses to follow-up) and the entirely self-report nature of physical activity data, using often unvalidated instruments, limits the validity of the results of this
Methodological quality o f C R trials.
Authors De Busk et al. 1979
Criterion 1
Criterion 2
•
x
Criterion 3
Criterion 4
Criterion 5
Total Score (/5)
,/
,/
r
3
./
x
1
./
~/
2
~"
J
3
./
x
2
./
J
3
~/
J
2
J
J
3
~/
x
1
,/
x
2
(90%) Bengtsson 1983
x
x
Erdman et al. 1986
x
x
Heath et al. 1987
x
x
Hamalainen et al. 1989
•
x
Gulanick et al. 1991
•
x
Sivarajan et al. al 1992
x
x
• (79%) x (71%) J (100%) J (98%) ./ (90%) x
(83%) Engblom et al. 1992
x
x
~/
(1OO%o) Todd & Ballantyne 1992
x
x
x
(78%) Carlsson et al. 1997
x
x
,/
(88%) Criterion 1: Adequate concealment (or description) o f randomization process. Criterion 2: Blinding of physical activity outcome assessment. Criterion 3: A t least 80% o f trial participants available at follow-up for physical activity assessment (percentage o f patients assessed based on baseline numbers). Criterion 4: Results analysed on the basis o f 'intention to treat'. Criterion 5: Standardized physical activity instrument used or citation of validation process given.
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review. There is therefore a need for future studies of CR to incorporate validated assessments of physical activity by use of standardized questionnaires backed up with objective measures (activity monitors). One of the review authors (JJ) is currently exploring this area by assessing the physical activity levels of cardiac patients 12 months following CR using both validated self-report questionnaires and accelerometry. ACKNOWLEDGEMENTS This review was undertaken while JJ was a postgraduate student on the MSc Health Care course at the Institute of General Practice, Postgraduate Medical School, University of Exeter, Exeter, UK. REFERENCES
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