We read with interest the recent multicentre UK study by Sandercock
and colleagues1 quantifying prescribed exercise volume and changes in
cardiorespiratory fitness (CRF) involving 950 patients across four UK
outpatient cardiac rehabilitation (CR) centres routinely performing CRF
testing pre- and post-CR and with clinical practice consistent with
professional body guidelines. The authors characterise low volume exercise
training programmes across the four rehabilitation centres - with patients
receiving a modal value of 8 exercise sessions (range 6-16). This appears
in stark contrast to the international studies outlined in the author's
earlier systematic review and evidence-based guidelines2.
Although CRF improvements varied by rehabilitation centre and testing
protocol (treadmill test protocol was a significant source of the between-
trial heterogeneity), the overall improvement in CRF (0.52 METS) was only
one third the mean estimate reported in their earlier meta-analysis (1.55
METs)2. The authors indicated that if representative of UK services, these
low training volumes and small increases in CRF may partially explain the
reported inefficacy of UK CR to reduce patient mortality and morbidity, as
outlined by the RAMIT group3.
We agree with the assertion that lower exercise training volumes may
be partly responsible for the lower than expected CRF values reported in
the UK centres evaluated. Indeed, the CRF improvements within UK centres
reported by Sandercock and colleagues1 are not consistent with data
observed in our community-based CR investigations (Heartwatch, Leeds
Leisure Services) using submaximal (85% age-predicted maximum heart rate)
exercise testing protocols to evaluate short (3 month) and longer-term (15
month) community-based exercise training in a large, representative sample
of patients with cardiovascular disease. We hereby report unpublished
observations of 139 patients (79% males; mean age 62 (8) years); BMI 28
(4) kg*m-2; 62% on beta-blockers) who undertook 3 months of structured
exercise-based community CR (undertaking a minimum of 2 circuit training
sessions per week). Pre and post-CR exercise testing at the Heartwatch
Centre was conducted on a Marquette treadmill using a specifically
designed 2-minute stage incremental walking protocol4. The oxygen
consumption at stages 5 and 6 (10 to 12 minutes duration) of the protocol
was an estimated 25 to 29 ml?kg-1?min-1. Patients were encouraged to
exercise up to 85% of age-predicted maximum heart rate (220?age) or a
"very hard" rating of perceived exertion (RPE 17) using the Borg scale.
Following 3 months exercise training, surrogate CRF variables including
exercise duration (10.1 ? 2.5 min v 11.5 ? 2.7 min; P=0.0001)
significantly improved. These improvements in submaximal CRF are
consistent with our earlier reported observations5 among 154 non-diabetic
CVD patients (89% male; aged 60 ?9 years; body mass index [BMI], 27?4 kg?m
-2) who completed a further 12 months of exercise training. Self-reported
exercise training compliance rates at 15 months, reported on clinical
reassessment was 2.9 ?0.9 sessions per week. Exercise test results showed
that submaximal treadmill duration increased from 10.1 to 12.2 minutes.
These short and longer term improvements in CRF to graded walking
represented an additional 2-minute stage of the incremental walking
protocol4, corresponding to a 1.0 MET improvement in CRF.
We also feel that the methods used to estimate exercise training
volumes and the impact this may have on exercise prescription may also be
contributory factors in many UK-based CR programmes. The prescription of
an appropriate exercise dose should be predicated on a clear appreciation
of patient requirements and their physical characteristics including the
degree of cardiac dysfunction and level of skeletal muscle wastage.
Exercise intensity thresholds should be high enough to be effective but
should be titrated within appropriate safety margins. Therefore, CRF
should be assessed as accurately possible in cardiac populations. In the
UK, there has arguably been a historical over-reliance on exercise
prescription derived from indirect, submaximal assessments of exercise
capacity, such as the incremental shuttle walk test (ISWT) and/or 6-minute
walk tests (6-MWT) in patients undertaking CR. This observation was
clearly evident in the recent publication by Dr Sandercock and colleagues1
who reported the use of these assessment modalities in four audited
centres (treadmill and cycle ergometry were also used in two centres).
Many UK centres will then use performance from submaximal tests to inform
exercise training prescription relying solely on using predicted heart
rate training zones and/or ratings of perceived exertion. Clearly,
submaximal exercise test protocols do not rigorously evaluate the
integrity of the cardiorespiratory system (a primary purpose of the
exercise test). Therefore, it is possible that patient effort may be more
variable in submaximal, self-paced tests such as the 6-MWT. Consequently,
the widespread practice of submaximal exercise testing in the UK may be
one of the reasons why CR programmes appear to be less effective.
In Europe and North America there is a much greater focus on "gold
standard" techniques, including maximal exercise testing with metabolic
gas exchange (cardiopulmonary exercise testing) which provide the
preferred method for assessing CRF and prescribing exercise training in
CR. Exercise prescription may be fine-tuned on the ventilatory anaerobic
threshold or respiratory compensation point. There is overwhelming
evidence indicating the superior prognostic value of ventilatory markers
including peak oxygen uptake, VE/VCO2 slope, and exertional oscillatory
ventilation, amongst others, especially in lower functional capacity
groups such as chronic heart failure6. Ventilatory markers are rarely
assessed and are seldom considered during exercise prescription in the
majority of CR programmes in the UK.
Under certain circumstances, there may be a requirement to assess
individual responses to exercise with submaximal testing protocols. For
example, if the assessment of exercise capacity is undertaken outside a
hospital setting (sporting or community centre); if a medical doctor is
not available to supervise the maximal test; or when a large number of
patients require assessment over a short time frame. If maximal exercise
testing is to become more pervasive in the UK there will be a requirement
for an initial capital outlay on equipment (though existing testing
systems may be under-utilised in many Trusts around the country), and
there will be a need for specialist staff training and on-going consumable
costs. However, we should not lose perspective over the major objectives
of CR, the Cinderella of cardiology services, and bear in mind the
apparent under-prescription of exercise that seems to be common practice
in UK centres. UK-based CR should not be run on a shoe-string budget. It
has been long-established that increasing CRF reduces mortality and
morbidity in secondary prevention settings7. There is a pressing need to
adopt a more evidence-based approach to exercise prescription in patients
undertaking CR in the UK.
Dr Lee Ingle & Professor Sean Carroll
Department of Sport, Health & Exercise Science
University of Hull
Kingston-upon-Hull HU6 7RX
United Kingdom
References:
1. Sandercock GR, Cardoso F, Almodhy M, Pepera G. Cardiorespiratory
fitness changes in patients receiving comprehensive outpatient cardiac
rehabilitation in the UK: a multicentre study. Heart. 2012 Nov 24. [Epub
ahead of print].
2. Sandercock G, Hurtado V, Cardoso F. Changes in cardiorespiratory
fitness in cardiac rehabilitation patients: A meta-analysis. Int J
Cardiol. 2011; [Epub ahead of print].
3. West RR, Jones DA, Henderson AH. Rehabilitation after myocardial
infarction trial (RAMIT): multi-centre randomised controlled trial of
comprehensive cardiac rehabilitation in patients following acute
myocardial infarction. Heart 2012; 98(8):637-44.
4. Lehmann G, Schmid S, Ammer R, Sch?mig A, Alt E. Evaluation of a
new treadmill exercise protocol. Chest1997;112(1):98-106.
5. Carroll S, Tsakirides C, Hobkirk J, Moxon JW, Moxon JW, Dudfield
M, Ingle L. Differential improvements in lipid profiles and Framingham
recurrent risk score in patients with and without diabetes mellitus
undergoing long-term cardiac rehabilitation. Arch Phys Med Rehabil
2011;92(9):1382-7.
6. Arena R, Myers J, Williams MA, et al. Assessment of functional
capacity in clinical and research settings: A scientific statement from
the American Heart Association Committee on Exercise, Rehabilitation, and
Prevention of the Council on Clinical Cardiology and the Council on
Cardiovascular Nursing Circulation. 2007;116: 329-343.
7. Vanhees L, Fagard R, Thijs L, Amery A. Prognostic value of
training-induced change in peak exercise capacity in patients with
myocardial infarcts and patients with coronary bypass surgery. Am J
Cardiol 1995; 15; 76(14):1014-9.
Conflict of Interest:
None declared
We read with interest the recent multicentre UK study by Sandercock and colleagues1 quantifying prescribed exercise volume and changes in cardiorespiratory fitness (CRF) involving 950 patients across four UK outpatient cardiac rehabilitation (CR) centres routinely performing CRF testing pre- and post-CR and with clinical practice consistent with professional body guidelines. The authors characterise low volume exercise training programmes across the four rehabilitation centres - with patients receiving a modal value of 8 exercise sessions (range 6-16). This appears in stark contrast to the international studies outlined in the author's earlier systematic review and evidence-based guidelines2. Although CRF improvements varied by rehabilitation centre and testing protocol (treadmill test protocol was a significant source of the between- trial heterogeneity), the overall improvement in CRF (0.52 METS) was only one third the mean estimate reported in their earlier meta-analysis (1.55 METs)2. The authors indicated that if representative of UK services, these low training volumes and small increases in CRF may partially explain the reported inefficacy of UK CR to reduce patient mortality and morbidity, as outlined by the RAMIT group3.
We agree with the assertion that lower exercise training volumes may be partly responsible for the lower than expected CRF values reported in the UK centres evaluated. Indeed, the CRF improvements within UK centres reported by Sandercock and colleagues1 are not consistent with data observed in our community-based CR investigations (Heartwatch, Leeds Leisure Services) using submaximal (85% age-predicted maximum heart rate) exercise testing protocols to evaluate short (3 month) and longer-term (15 month) community-based exercise training in a large, representative sample of patients with cardiovascular disease. We hereby report unpublished observations of 139 patients (79% males; mean age 62 (8) years); BMI 28 (4) kg*m-2; 62% on beta-blockers) who undertook 3 months of structured exercise-based community CR (undertaking a minimum of 2 circuit training sessions per week). Pre and post-CR exercise testing at the Heartwatch Centre was conducted on a Marquette treadmill using a specifically designed 2-minute stage incremental walking protocol4. The oxygen consumption at stages 5 and 6 (10 to 12 minutes duration) of the protocol was an estimated 25 to 29 ml?kg-1?min-1. Patients were encouraged to exercise up to 85% of age-predicted maximum heart rate (220?age) or a "very hard" rating of perceived exertion (RPE 17) using the Borg scale. Following 3 months exercise training, surrogate CRF variables including exercise duration (10.1 ? 2.5 min v 11.5 ? 2.7 min; P=0.0001) significantly improved. These improvements in submaximal CRF are consistent with our earlier reported observations5 among 154 non-diabetic CVD patients (89% male; aged 60 ?9 years; body mass index [BMI], 27?4 kg?m -2) who completed a further 12 months of exercise training. Self-reported exercise training compliance rates at 15 months, reported on clinical reassessment was 2.9 ?0.9 sessions per week. Exercise test results showed that submaximal treadmill duration increased from 10.1 to 12.2 minutes. These short and longer term improvements in CRF to graded walking represented an additional 2-minute stage of the incremental walking protocol4, corresponding to a 1.0 MET improvement in CRF.
We also feel that the methods used to estimate exercise training volumes and the impact this may have on exercise prescription may also be contributory factors in many UK-based CR programmes. The prescription of an appropriate exercise dose should be predicated on a clear appreciation of patient requirements and their physical characteristics including the degree of cardiac dysfunction and level of skeletal muscle wastage. Exercise intensity thresholds should be high enough to be effective but should be titrated within appropriate safety margins. Therefore, CRF should be assessed as accurately possible in cardiac populations. In the UK, there has arguably been a historical over-reliance on exercise prescription derived from indirect, submaximal assessments of exercise capacity, such as the incremental shuttle walk test (ISWT) and/or 6-minute walk tests (6-MWT) in patients undertaking CR. This observation was clearly evident in the recent publication by Dr Sandercock and colleagues1 who reported the use of these assessment modalities in four audited centres (treadmill and cycle ergometry were also used in two centres). Many UK centres will then use performance from submaximal tests to inform exercise training prescription relying solely on using predicted heart rate training zones and/or ratings of perceived exertion. Clearly, submaximal exercise test protocols do not rigorously evaluate the integrity of the cardiorespiratory system (a primary purpose of the exercise test). Therefore, it is possible that patient effort may be more variable in submaximal, self-paced tests such as the 6-MWT. Consequently, the widespread practice of submaximal exercise testing in the UK may be one of the reasons why CR programmes appear to be less effective.
In Europe and North America there is a much greater focus on "gold standard" techniques, including maximal exercise testing with metabolic gas exchange (cardiopulmonary exercise testing) which provide the preferred method for assessing CRF and prescribing exercise training in CR. Exercise prescription may be fine-tuned on the ventilatory anaerobic threshold or respiratory compensation point. There is overwhelming evidence indicating the superior prognostic value of ventilatory markers including peak oxygen uptake, VE/VCO2 slope, and exertional oscillatory ventilation, amongst others, especially in lower functional capacity groups such as chronic heart failure6. Ventilatory markers are rarely assessed and are seldom considered during exercise prescription in the majority of CR programmes in the UK.
Under certain circumstances, there may be a requirement to assess individual responses to exercise with submaximal testing protocols. For example, if the assessment of exercise capacity is undertaken outside a hospital setting (sporting or community centre); if a medical doctor is not available to supervise the maximal test; or when a large number of patients require assessment over a short time frame. If maximal exercise testing is to become more pervasive in the UK there will be a requirement for an initial capital outlay on equipment (though existing testing systems may be under-utilised in many Trusts around the country), and there will be a need for specialist staff training and on-going consumable costs. However, we should not lose perspective over the major objectives of CR, the Cinderella of cardiology services, and bear in mind the apparent under-prescription of exercise that seems to be common practice in UK centres. UK-based CR should not be run on a shoe-string budget. It has been long-established that increasing CRF reduces mortality and morbidity in secondary prevention settings7. There is a pressing need to adopt a more evidence-based approach to exercise prescription in patients undertaking CR in the UK.
Dr Lee Ingle & Professor Sean Carroll Department of Sport, Health & Exercise Science University of Hull Kingston-upon-Hull HU6 7RX United Kingdom
References:
1. Sandercock GR, Cardoso F, Almodhy M, Pepera G. Cardiorespiratory fitness changes in patients receiving comprehensive outpatient cardiac rehabilitation in the UK: a multicentre study. Heart. 2012 Nov 24. [Epub ahead of print].
2. Sandercock G, Hurtado V, Cardoso F. Changes in cardiorespiratory fitness in cardiac rehabilitation patients: A meta-analysis. Int J Cardiol. 2011; [Epub ahead of print].
3. West RR, Jones DA, Henderson AH. Rehabilitation after myocardial infarction trial (RAMIT): multi-centre randomised controlled trial of comprehensive cardiac rehabilitation in patients following acute myocardial infarction. Heart 2012; 98(8):637-44.
4. Lehmann G, Schmid S, Ammer R, Sch?mig A, Alt E. Evaluation of a new treadmill exercise protocol. Chest1997;112(1):98-106.
5. Carroll S, Tsakirides C, Hobkirk J, Moxon JW, Moxon JW, Dudfield M, Ingle L. Differential improvements in lipid profiles and Framingham recurrent risk score in patients with and without diabetes mellitus undergoing long-term cardiac rehabilitation. Arch Phys Med Rehabil 2011;92(9):1382-7.
6. Arena R, Myers J, Williams MA, et al. Assessment of functional capacity in clinical and research settings: A scientific statement from the American Heart Association Committee on Exercise, Rehabilitation, and Prevention of the Council on Clinical Cardiology and the Council on Cardiovascular Nursing Circulation. 2007;116: 329-343.
7. Vanhees L, Fagard R, Thijs L, Amery A. Prognostic value of training-induced change in peak exercise capacity in patients with myocardial infarcts and patients with coronary bypass surgery. Am J Cardiol 1995; 15; 76(14):1014-9.
Conflict of Interest:
None declared