Download A comparison of the effects of strength and aerobic exercise training

European Heart Journal (1996) 17, 854-863
A comparison of the effects of strength and aerobic
exercise training on exercise capacity and lipids after
coronary artery bypass surgery
D. Wosornu*, D. Bedfordf and D. Ballantynet
* Department of Cardiology, Selly Oak Hospital, Birmingham B29 6JD, England; ^Department of Pathological
Biochemistry, Royal Infirmary, Glasgow; \Department of Cardiology, Victoria Infirmary, Glasgow G42 9TY,
Scotland
Background Coronary artery surgery improves symptoms
and prognosis in patients with angina. Aerobic exercise
rehabilitation improves exercise capacity and prognosis in
cardiac patients. Strength exercise training has not been
extensively studied.
Design We studied the effects of 6 months aerobic and
strength exercise training after coronary artery surgery in
81 men, mean age 57 years.
Results Treadmill time(s) increased by 130-3 (95% confidence interval 46-4 to 214-2) in the aerobic group; by 83-1
(0-9 to 165-3) in the strength group, and by 34-3 ( - 1 to
69-6) in the control group (P=004, control versus aerobic)
after 3 months; and by 196-4 (112-2 to 280-7) in the aerobic
group, by 122-7 (37-7 to 207-6) in the strength group and by
27 ( - 40-4 to 94-4) in the control group (P=0002, control
Introduction
Coronary artery surgery improves symptoms and quality of life in patients with angina. In certain subgroups
the operation can also prolong life'1"31. Exercise is of
value in primary 4 " 8 ', secondary'9""1 and tertiary1'21 prevention in cardiac disease. The effects of aerobic exercise
training have been extensively studied in patients with
coronary artery disease, including those who have
undergone coronary artery surgery19""'13"161. It has been
shown to improve prognosis'9"12'15'171 and to be of
benefit in increasing functional capacity'13'15'17"2'1, reducing inducible ischaemia'221 and in the modification of
risk factors'23"281. Strength or resistive exercise training
has not been subject to such extensive evaluation. A few
studies have been done in patients who have undergone
versus aerobic, and P=003 control versus strength) after 6
months. The level of fitness improved more in the strengthtrained group, and there was a minor reduction in body
weight and degree of fatness. There were no changes in
lipoprotein levels. Aerobic exercise training causes early
and sustained benefit in treadmill exercise capacity, while
the effects of strength exercise training are later in onset.
Exercise training alone did not influence lipid levels.
Conclusion Cardiac rehabilitation programmes should
be comprehensive, including advice on diet and other
risk factor modifications in addition to exercise sessions
involving aerobic and strength training elements.
(Eur Heart J 1996; 17: 854-863)
Key Words: Strength training, aerobic training, exercise
capacity, lipids.
prior aerobic exercise training, and it has been found to
improve endurance and strength'29"321. We compared the
effects of aerobic and strength exercise training after
coronary artery surgery in previously untrained men.
We assessed the effects on physique, exercise capacity,
myocardial function and perfusion, heart rate and
arrhythmias, lipoproteins and haemostatic factors. The
results of our findings on haemostatic factors are the
subject of a previous report'331. This is a report on
the effects on physique, treadmill exercise performance
and lipoprotein levels.
Patients and methods
The patients were 81 men referred from our hospital for
coronary artery bypass surgery. They were randomized
Revision submitted 4 September 1995, and accepted 23 October to three groups. Group 1 (n = 27) had no formal exercise
1995.
training, and were the control group. They were not
discouraged
from pursuing their usual leisure activities,
Correspondence Dzifa Wosornu. MD, Department of Cardiology,
e.g. golf. Group 2 (n = 27) had 6 months of graduated
Selly Oak Hospital, Birmingham B29 6JD, U.K.
0195-668X/96/060854 + 10 SI8.00/0
19% The European Society of Cardiology
Effects of training after coronary bypass surgery
855
Table 1 Patients' characteristics at baseline
Number
Age: years (SD)
Number of grafts
IMA grafts (number of patients)
Weeks post-surgery: median (range)
Control
Aerobic
Strength
27
56-6 (70)
3-2
22
12 (6-28)
27
56-5 (8-9)
30
17
12 (6-48)
27
59-2 (6-4)
3-3
16
12 (6-44)
Previous MI
Diabetes
Hypertension
11
1
1
17
1
4
15
1
1
Aspirin
Dipyridamole
Beta-blockers
Diuretics
ACE inhibitors
19
18
4
5
1
15
13
2
2
2
18
16
1
4
0
Current smokers
Previous smokers
Non-smokers
Employed
Off work
Retired
4
14
8
8
7
11
3
15
9
6
6
12
1
17
6
6
6
12
52 (40-63)
50 (41-58)
59 (55-64)
LVEF (%) mean (95% CI)
ACE = angiotensin-converting enzyme; LVEF = left ventricular ejection fraction.
supervised aerobic exercise training. Group 3 (n = 27)
had 6 months of graduated supervised strength exercise
training. Table 1 shows their details at baseline. Their
mean age was 57-4 years (SD 7-6), 56% had previous
infarcts, 60% were ex-smokers and 74% were not in
full-time employment. Medications were constant
throughout the study. There was no history of congestive heart failure. Left ventricular ejection fraction was
measured by radionuclide angiography. The patients
were assessed at baseline, at 3 months and at 6 months.
One patient in group 1 was lost to follow-up after 8
weeks. There were no drop-outs in group 2. Two
patients in group 3 dropped out after 2 weeks because of
problems with their surgical scars; another moved away
after 5 weeks.
Exercise programme
The programme was devised in conjunction with the
Department of Physical Therapy to include movements
involving all major muscle groups in exercises that are
simple to perform. The patients attended the same
location three times weekly for sessions of 12—40min.
They were supervised by a physician, a cardiac rehabilitation nurse and a physiotherapist. The aerobic exercises
were based on the Canadian Airforce XBX physical fitness programme. Exercises performed were arm
circling, arm raising, step-ups, trunk rotation, star or
stride jumps, crook-lying with trunk rotation and
bridging, hip abduction side lying, standing trunk curls,
trunk side flexion and running on the spot. Each patient
started at the same level: with 3 to 10 repetitions of each
exercise. The number of repetitions was increased over
time to intensify gradually the work performed. Each
patient had a chart of the exercises, and number of
repetitions was marked on this. After 7 to 10 days at
each level, the intensity was increased according to the
patient's progress and performance, as assessed jointly
by the physiotherapist, the physician and the patient.
Strength exercises were based on a universal Multigym
system, in which weights are connected by appropriately
placed pulley systems designed to allow movement of the
weights in specific directions. The exercises performed
were bench press, military press, biceps curl, upright
row, pull down, push down, pulley row, quadriceps curl,
hamstrings curl and sit-ups. Each was started with the
lightest weight of 2-5 kg, in three sets of 10 repetitions
with periods of rest (45 s) between each element. The
weight load was increased gradually, depending on the
individual's progress and symptoms. A description of all
the exercises is given in Appendix A. All the sessions
ended with a cool-down period of 5 min riding on a
stationary bicycle. By the end of the training period each
patient should have been exercising at his perceived level
of exertion. There was no heart rate or other cardiovascular monitoring. Perceived exertion is an acceptable
surrogate for heart rate monitoring. It was hoped
that, at the end of the programme, the patients would
continue unsupervised exercise in the community. To
decide on the level of that exercise, it was important for
them to learn to rely on their symptoms, rather than
their heart rate. The intensity of exercise training was
in keeping with recommendations of the American
Society of Sports Medicine1341, and the American Heart
Association1'31.
Eur Heart J, Vol. 17, June 1996
856 D. Wosornu et al.
Exercise tests
The exercise tests were done using a Marquette Case II
computerized treadmill system. Full 12-lead electrocardiographs, with automatic ST segment analysis are
printed every 3 min. The ST segments are measured
60 ms from the J-point, and values exceeding 01 mV are
considered positive for ischaemia. Heart rate, exercise
time, maximum ST segment depression, estimated workload in metabolic equivalents, percentage of target heart
rate reached are also recorded. A modified Balke protocol was used (Appendix B). This protocol was chosen
because it was used in the pre-surgery evaluations and
most of the patients were already familiar with it. In
addition, there is a gradual increase in work-load with
each stage, making it a physiologically sound means of
testing exercise capacity. All tests were carried out in the
morning after an overnight fast. The necessary blood
samples for lipoproteins and haemostatic factors were
taken prior to the exercise test. Each patient had four
exercise tests during the programme for the purposes of
exercise test data: two at baseline (average taken as
baseline performance) and one each at 3 and at 6
months. Blood pressure was measured manually at rest
and 2 min into each stage. The tests were symptomlimited, unless significant hypotension (a fall in systolic
blood pressure greater than 10 mmHg from the previous
reading), or ventricular tachycardia occurred. The following were recorded: resting heart rate, resting systolic
blood pressure, submaximal heart rate, submaximal
rate-pressure product, maximum rate-pressure product,
maximum heart rate, maximum treadmill time, maximum workload, maximum ST segment depression, percentage of target heart rate achieved, and heart rate at
5 min into recovery (FHR). Target heart fate is 220
minus age of patient. A recovery rate=(maximum heart
rate — FHR/5) and recovery rate ratio=maximum heart
rate - FHR/FHR were derived as further measures of
fitness.
Clinical examination
Patients had body weight, body mass index and skin fold
thickness measured. Body mass index is weight/height2.
Skin fold thickness was measured with Harpenden
calipers at four sites — biceps, triceps, scapula and
abdomen. The biceps and triceps measurements were
taken midway down the muscles, scapula measurement
was taken halfway down its medial aspect, and the
abdominal measurement was taken at the anterior
superior iliac spine. The sum of the four readings was
used as a measure of body fat, a well recognised means
of assessing body fat in nutritional and exercise training
studies1355.
Lipoprotein analysis
The assays were performed by technicians who were
not aware of the patients' groups. Total cholesterol and
Bat Heart J, Vol. 17, June 1996
triglyceride were assayed by enzymatic colorimetric tests
(Boehringer Mannheim). Lipoproteins were assayed by
beta-quantification. HDL subfraction 2 and 3 masses
were estimated by rate zonal ultracentrifugation with
ultraviolet scanning (Beckman Instruments). Apolipoprotein Al and B were measured by immunochemical
assay (Orion Diagnostica).
Statistical analysis
Results were analysed on an intention-to-treat basis,
using SPSS/PC + version 4 0 statistical data analysis
program. Descriptive statistics were done, followed by
tests of normality. Within- and between-group differences were assessed by analysis of variance (ANOVA)
with application of Scheffe test for normal data, and
Kruskal-Wallis test for non-normal data. When this
was significant (/><005), the analysis was taken further. Paired 't'-test or Wilcoxon test was done for
within-group data, and unpaired 't'-test or MannWhitney U test was done for between-group data.
Results are expressed as the mean with 95% confidence
interval.
Results
Records of the attendance and exercise work-out
were kept for each patient. Group 2 attended 64% and
group 3 attended 63% of their training sessions. There
were no deaths or cardiac arrests during the exercise
sessions.
Clinical examination
The results of weight, body mass index and skin fold
thickness are shown in Table 2. Group 1 was heavier
than the other two groups (P=0-07 at baseline). Weight
in groups 1 and 2 increased slightly over time, while that
in group 3 was relatively stable. At 3 months, group 1
gained 1 -3 kg, group 2 gained 0-9 kg, and group 3 lost
0-3 kg. The patients were overweight since their body
mass index exceeded 25. The pattern for body mass
index was similar to that of body weight. At 3 months,
group 1 increased body mass index by 0-4, group 2
increased by 0-3 and group 3 decreased by 0 1 . Skin fold
thickness was similar in all groups at baseline, and fell
with training in group 3 alone.
Exercise performance
Common symptoms limiting the exercise tests were
dyspnoea, fatigue, leg ache and chest pain. As would be
expected, 94% were cured of chest pain by coronary
artery surgery, with only five patients stopping the test
because of this symptom. This pattern did not change
during the training period. Exercise performance (Table
Effects of training after coronary bypass surgery
Table 2 Weight (kg), body mass index (kg. m
(mm) — mean (95% CI)
857
2
), skin fold thickness
Control
Aerobic
Strength
Weight
Baseline
3 months
6 months
80-5 (76-1 to 84-8)
81 8 (77-4 to 861)
81 6 (77-6 to 85-6)
76-3 (70-7 to 8 1 9 )
77-2 (71-6 to 82-8)
77-1 (71-4 to 82-8)
72-6 (68-5 to 76-6)
72-3 (68-2 to 76-4)*
72-7 (68-6 to 76-7)f
Body mass index
Baseline
3 months
6 months
27-5 (26-2 to 28-9)
27-9 (26-6 to 29-3)
27-9 (26-6 to 29-2)
26-9 (25-6 to 28-3)
27-2 (25-9 to 28-6)
27-2 (25 8 to 28-6)
25-8 (24-4- to 27 1)
25-7 (24-3 to 27)*
25-8 (24-5 to 27)
Skin fold thickness
Baseline
3 months
6 months
47-5 (41-5 to 53-4)
48-9 (43 to 54-8)
47-4 (42-3 to 52-5)
46-6 (40-6 to 52-6)
46-4 (40-5 to 52-2)
451 (393 to 50-9)
40-4 (36-8 to 44)
39-7 (36-8 to 42-6)J
38 (35 to 41)f
•ANOVA />=0-02; t/ J =003; J/>=0-04.
Table 3
Treadmill exercise performance and interval changes (s) — mean (95% CI)
Absolute values
Baseline
3 months
6 months
Interval changes
0-3 months
0-6 months
3-6 months
Control
Aerobic
Strength
P value
683-8 (558-6 to 809-1)
718-2 (585-3 to 851)
710-8 (575-6 to 846)
650-5 (549-7 to 751-3)
780-8 (673-2 to 888-4)
846-9 (746-5 to 947-3)
784-2 (657-8 to 910-5)
867-3 (743-6 to 991)
906-8 (785-3 to 1028-3)
ns
ns
0-03*
130-3 (46-4 to 214-2)
196-4 (112-2 to 280-7)
66-2 (13 to 119-3)
831 (0-9 to 165-3)
122-7 (37-7 to 207-6)
39-5 (5-6 to 73-5)
004f
0-002f
0-05t
34-3 ( - 1 to 69-6)
27 ( - 40-4 to 94-4)
- 7-3 ( - 60-6 to 45-9)
'Control versus strength; fcontrol versus aerobic.
3) improved in group 2 after 3 months, and was maintained at 6 months, in comparison with group 1. In
group 3, improvement in exercise performance did not
reach statistical significance until 6 months. The results
for estimated maximum workload (Table 4) in metabolic
equivalents (1 met = 3-5ml 0 2 m i n ~ ' ) follow a similar
pattern, but with more striking statistical differences.
There were no significant differences in resting heart
rate and systolic blood pressure, submaximum and
maximum heart rates, maximum ST segment depression, submaximum rate-pressure product, 5-min
heart rate, or percentage target heart rate between
the groups. Within group 3, resting heart rate fell
by 3 beats. min~', submaximum heart rate by
8 beats . min~', and submaximum rate-pressure product by 3946 beats . m i n ~ ' . mmHg~'. They also
achieved higher maximum rate-pressure product, recovery rate and recovery rate ratio compared to group 1
(Table 5). Group 3 may therefore have become fitter
than they had been prior to training.
Lipids and lipoprotein levels
Tables 6-8 show the results of the lipid and lipoprotein
analysis. The levels of total cholesterol, triglycerides and
their subfractions did not alter with either mode of
exercise training. There were no statistically significant
differences in any of the levels at any time.
Discussion
This study was carried out to compare the effects of
aerobic and strength exercise training in a group comprising only post-bypass patients. The results on exercise
capacity and safety should help to dispel the fears
surrounding strength training in cardiac patients.
The weight gain in the control group was not
accompanied by an increase in skin fold thickness, while
that in the aerobic group was associated with a small
drop in skin fold thickness. This is usually explained in
terms of a gain in muscle mass as a result of exercise
training and is supported by the pattern of lower skin
fold thickness in the strength group without much
change in body weight. A 10 mm increase in the sum of
four skin folds corresponds to a 5% increase in fatness1351. The changes in the strength group therefore
represent, at most, a 1% reduction in fatness.
Physical fitness and residual ischaemia were estimated by the parameters that were recorded. A resting
bradycardia and rapid recovery of heart rate after
Eur Heart J, Vol 17, June 1996
858 D. Wosornu et al.
Table 4 Estimated work-load and interval changes (mets) — mean (95% CI)
Control
Aerobic
Strength
P value
Absolute values
Baseline
3 months
6 months
7-5 (61 to 9)
7 8 (6-3 to 9 2)
7-8 (7-3 to 9 3)
7 (6-2 to 7-9)
8-4 (7-3 to 9-5)
9 (7-9 to 10-2)
8-6 (7-3 to 10)
9-3 (8 to 10-5)
10 (8-6 to 11-3)
ns
ns
003*
Interval changes
0-3 months
0-6 months
3-6 months
0-2 ( - 0-2 to 0-7)
0-2 ( - 0 - 5 to 1)
0 ( - 0-6 to 0 6)
1-4 (0-7 to 21)
2 (1-2 to 2-8)
0 6 (01 to 1-2)
0-6 ( - 0 - 2 to 1 5)
1-3 (0-4 to 2-3)
0-7 (0-3 to 1-2)
0009f
0-002|
0-05*
'Control versus strength; fcontrol versus aerobic.
Table 5 Maximum rate-pressure product (beats . min ' . mmHg '
ery rate (beats . min ~ '); recovery rate ratio — mean (95% CI)
Control
Aerobic
102); recov-
Strength
P value
Maximum rate-pressure product
Baseline
250-8 (227-3 to 274 3) 232 8 (211- 6 to 254 1) 256-5 (235-7 to 277-2)
3 months 252-1 (224-5 to 279-8) 234-3 (208- 2 to 260-3) 260-0 (238-2 to 281-9)
6 months 231-8 (209-4 to 254-2) 235 3 (210- 3 to 260-3) 265-7 (246-2 to 285-2)
ns
ns
002*
Recovery rate
Baseline
3 months
6 months
10 (8-9 to 11-3)
10 2 (8-9 to 116)
9 (7-3 to 10-7)
Recovery rate ratio
Baseline
3-3 (3 to 3-6)
3 months
3-4 (31 to 3-7)
6 months
3-2 (2-7 to 3-6)
10-5 (9-6 6o 11-4)
10-7 (9-5 to 11-9)
10-3 (8-6 to 12)
10-6 (9-6 to 11-6)
11 (9-9 to 12-2)
11-8 (10-6 to 13)
ns
ns
001*
3-6 (3-4 to 3-8)
3-6 (3-3 to 3-8)
3-4 (31 to 3-8)
3-4 (3-2 to 3-7)
3-4 (3 to 3-8)
3-7 (3-4 to 4)
ns
ns
0-03*
'Control versus strength.
Table 6
Total cholesterol and triglyceride levels (mmol. I ') — mean (95% CI)
Control
Aerobic
Strength
P value
Cholesterol
Baseline
3 months
6 months
6-5 (61 to 6-9)
6-4 (5-9 to 5-9)
6-2 (5-7 to 6-7)
6-2 (5-7 to 6-7)
61 (5 7 to 6-5)
6-2 (5-8 to 6-8)
6-6 (6-2 to 6-9)
6-3 (5-9 to 6-6)
6-4 (6-0 to 6-8)
ns
ns
ns
Triglycerides
Baseline
3 months
6 months
2-1 (1-7 to 2-5)
2-3 (1-8 to 2-9)
2-2 (1-7 to 2-7)
2-0 (1-6 to 2-4)
2-2 (1-8 to 2-6)
21 (1-7 to 2-5)
1-9 (1-6 to 2-4)
1-9 (1-6 to 2-2)
1-9 (1-6 to 2-3)
ns
ns
ns
exercise, low submaximal heart rate and rate-pressure
product indicate physical fitness. The maximum ratepressure product is an indicator of myocardial oxygen
demand at peak exercise, while maximum treadmill time
and work-load are indicators of fitness and disease
severity11819-361. ST segment depression is a measure of
ischaemia. In general, its absence in exercise testing is
said to imply a good prognosis. There are, however,
some doubts about the prognostic significance of ST
Eur Heart J, Vol. 17, June 1996
segment changes during exercise tests after coronary
artery surgery1 7]. In this study, there were no changes in
ST segment responses after exercise training.
Exercise training induces a training response
comprising a resting bradycardia, reduced heart rate and
rate-pressure product at submaximal exercise, increased
exercise duration, increased maximum oxygen consumption and cardiac output and a shorter recovery
time11719'2'1. There may also be an increase in the
Effects of training after coronary bypass surgery
859
Table 7 Low-, high- and very-low-density lipoprotein levels (mmol. I ') —mean
(95% CI)
Contro
Aerobic
Strength
P value
LDL
Baseline
3 months
6 months
4-4 (40 to 4-7)
4-3 (3-9 to 4-6)
4-0 (3-7 to 4-4)
4-1 (3-7 to 4-5)
4-0 (3-6 to 4-3)
4 0 (3-6 to 4-3)
4-4 (4-2 to 4-7)
4 3 (4-0 to 4-6)
4-3 (4-0 to 4-7)
ns
ns
ns
HDL
Baseline
3 months
6 months
1-2 (11 to 1-3)
11 (10 to 1-2)
1-1 (10 to 1-3)
•2 (1 1 to 1-3)
•2 (1 1 to 1-3)
•2 (11 to 1-3)
1 2 (11 to 1-3)
1-2 (10 to 1-3)
1-2 (11 to 1-4)
ns
ns
ns
VLDL
Baseline
3 months
6 months
1-0 (0-8 to 1-2)
11 (0-8 to 1-4)
10 (0-8 to 1-3)
•0
(0-7 to 1-4)
0 (0-8 to 1-3)
•0 (0-8 to 1-3)
0-9 (0-7 to 11)
0-9 (0-7 to 1-0)
0-9 (0-7 to 10)
ns
ns
ns
LDL = low-density lipoprotein.
HDL = high-density lipoprotein.
VLDL = very-low-density lipoprotein.
Table 8 HDL subfraction
2, HDL subfraction
3 ( m g % ) , apolipoprotein
Al and B (g.l
') — mean (95% CI)
Control
Aerobic
Strength
P value
HDL subfraction 2
Baseline
3 months
6 months
58-4 (46-9 to 69-9)
58-5 (47 1 to 69-9)
62-7 (49-2 to 76-1)
680 (52-4 to 83-4)
64 1 (51 9 to 76 4)
630 (49-7 to 76-2)
61-9 (48-7 to 75-1)
62-1 (47-8 to 76-4)
65-5 (50-8 to 80-2)
ns
ns
ns
HDL subfraction 3
Baseline
3 months
6 months
224-5 (203-3 to 245-6)
221-8 (202-8 to 240-8)
219-7 (202-0 to 237-4)
225-9 (200-5 to 251-3)
222-9 (207-7 to 238-2)
227-9 (207-9 to 247-9)
240-4 (222-3 to 258 4)
225-2 (200-2 to 250-2)
235-9 (212-8 to 259-0)
ns
ns
II (1-1 to 1-2)
ns
Apolipoprotein Al
Baseline
3 months
6 months
1-2 (1 1 to •2)
11 (1-1 to •2)
11 (1-0 to •2)
1-3 (1-1 to 1-4)
1-2 (1-0 to 1-4)
1-2 (11 to 1-3)
ns
11 (10 to 1-2)
11 (11 to 1-2)
Apolipoprotein B
Baseline
3 months
6 months
1-2 (11 to 1-4)
1-2 (11 to 1-3)
11 (1-0 to 1-3)
11 (10 to •3)
11 (10 to •2)
11 (10 to •3)
1-2 (1-1 to 1-3)
11 (1-0 to 1-2)
1-2 (11 to 1-3)
ns
ns
ns
exercise test work-load at which ischaemia occurs[22>381.
The exercise-trained groups in this study achieved these
to a varying extent.
The results support the view that exercise training improves exercise performance. Aerobic exercise
training in these patients caused early and sustained
improvement in treadmill performance, while the benefits of strength exercise training were of later onset.
However, there were no major differences in treadmill
performance between the two types of exercise training
at the end of the 6 months' training period. The improvements in exercise performance in the strength
group were associated with an increased level of fitness.
After 6 months, there was a 30% increase in treadmill
ns
ns
time in the aerobic group and a 16% increase in the
strength group, compared with an overall increase of
only 5% in the control group.
The use of the treadmill to assess those undergoing strength training may have underestimated their
achievements, as the effect of training tends to be very
specific1391. The strength-trained group did show significant improvements in exercise capacity on the treadmill.
This may partly be because their programme included
leg-strengthening exercises, the repetitive nature of
which could have improved their endurance. Specific
tests of strength, such as the one-repetition maximum,
may have shown up even greater benefits. One can
expect that these improvements in exercise capacity will
Eur Heart J, Vol. 17, June 1996
860 D. Wosornu et al.
be translated into major gains in the performance of
everyday activities, including those that involve lifting
and carrying.
Studies on exercise training after coronary
artery surgery
Previous studies have not addressed the effects of
strength training after coronary artery surgery. The
main results of this study are in keeping with studies on
aerobic training in which post-bypass patients have been
included. These patients are usually part of a group with
coronary artery disease. Their training has ranged from
3 times a week to daily sessions of 16-60 min, and from
6 weeks to 32 months. Cardiopulmonary exercise testing
was used in some studies. Post-bypass patients achieved
as much as post-infarction or angina patients'l6-4°l.
Maximum oxygen uptake increased, with no change in
resting heart rate or blood pressure, after 32 months of
daily aerobic exercise after coronary artery surgery14'1
Ninety per cent of the total improvement in functional
capacity had occurred by 4 months. In our exercisetrained groups, 67-69% of the total improvement had
occurred by 3 months. Other studies of aerobic exercise
training have also shown increases in maximum oxygen
uptake143'44'. In the PERFEXT study, post-bypass
patients formed a third of the group and they showed the
haemodynamic benefit (such as higher maximum oxygen
uptake) demonstrated in the other patients'161. All the
studies therefore show that aerobic exercise training
does improve exercise capacity after coronary artery
surgery, and support the results of the present study.
Studies involving strength training in cardiac
patients
Strength training and resistance exercises are usually
recommended in cardiac patients only after a period of
aerobic training has been completed145""*71. There are a
few reports on its effects in normal subjects and cardiac
patients, and most would recommend circuit weight
training as was used in this study130"3247'481. After 6
months of supplementary circuit training in 16 men
in cardiac rehabilitation, a significant improvement in
strength was observed, but there were no changes in
body weight or percentage fat[311. In our study, only the
strength-trained group showed a reduction in skin fold
thickness; their weight and body mass index remained
relatively stable. The aerobic-trained group gained
weight, as did the control group. Where direct comparisons have been made between aerobic and strength
training, the physiological responses to the latter have
been less alarming than anticipated'491. During circuit
weight training, percentage VO2 max was consistently
lower than that predicted for dynamic exercise, such as
running or cycling, for a given percentage of maximum
heart rate. Therefore, using heart rate to prescribe the
Eur Heart J, Vol. 17, June 1996
intensity of weight training exercise resulted in a lower
level of aerobic metabolism than during dynamic exercise150'. When circuit training was compared with treadmill exercise, there was less ischaemia, lower peak heart
rate and rate-pressure product, similar peak systolic
pressure, but higher diastolic pressure15'1. In that study,
as in ours, reliance was placed on symptomatic status to
judge the intensity of effort in the training sessions. In
another study, peak heart rate and rate-pressure product were similar, but peak systolic blood pressure was
higher during aerobic exercise than during circuit training. Treadmill time increased in both groups (as in this
study), but upper body strength increased only in the
circuit weight training group1521. Combined weight lifting and aerobic exercise training resulted in greater
improvements in both cycle ergometer performance and
one-repetition maximum than did aerobic training
alone153'. In our patients, the 5-min ride on a bicycle was
performed as a cool-down exercise by all the exercisetrained patients, and was a constant feature. The different interventions were those of strength-training using
universal Multigym equipment, and aerobic-training
based on the Canadian Airforce XBX physical fitness
programme.
Exercise training and lipid levels
The total cholesterol and low-density lipoprotein levels
were higher than is ideal for post-bypass patients, but is
in keeping with previous studies from Scotland'541. The
lack of effect of the exercise programmes may be linked
to their failure to cause a full training effect. Exercise
training has been found to have a variable and, at times,
transient effects of lipids. In a meta-analysis of 95 trials,
it was found that changes in body weight are relevant to
lipoprotein levels, with subjects who lose weight showing
more significant improvements in lipid levels'271. In postbypass patients, there were no changes in body weight,
cholesterol, low-density lipoprotein or apolipoprotein
B levels, triglycerides decreased and high-density lipoprotein increased after 2 months' aerobic training, but
by 1 year results were no different from the control
group'281. In some reports, improvements in lipid levels
have been found to correlate best with changes in VO2
max'55'561, while others have shown increases in highdensity lipoprotein with exercise training without
changes in diet, smoking or the achievement of a training effect'571. In a previous study from this institution,
aerobic exercise training for 6 months in 19 men postmyocardial infarction caused favourable changes in
lipoprotein levels, but there was no change in total
cholesterol levels and no relationship was found between
treadmill performance and lipid levels'241. Full cardiac
rehabilitation consisting of physical fitness, psychosocial
well-being and risk factor modification for 3 months
resulted in a fall in total cholesterol by 0-3 mmol. 1~',
but it remained high in those with initial values above
6-5 mmol. 1~ '; high and low-density lipoprotein did not
change1231. The level of total cholesterol in our patients
Effects of training after coronary bypass surgery
was about 6-5 mmol. 1 ', and was not altered by
exercise training.
The effects of strength training on lipids have
been assessed in dyslipidaemic patients, athletes, and a
few patients with coronary artery disease. Results are
varied. Some show no changes in lipid levels'58', but
there are some reports of beneficial effects of strength
training on lipid levels'59'601.
Limitations and strengths of the study
We were unable to perform cardiopulmonary exercise
testing. This would have improved the objectivity of the
assessment of exercise performance. It would have
helped to determine whether the significant improvements in treadmill time were secondary to increases in
leg strength or improved cardiovascular responses. It is
difficult to be certain of the extent to which motivation is
a factor in exercise performance without measuring
oxygen consumption and anaerobic threshold. Each
patient served as his own control. Assuming that the
patients' characters did not change during the study, the
'motivation factor' remained constant. We did not collect data on individual variation in progress with the
exercise programme. Haemodynamic and cardiac monitoring were not done during training. Some may consider this to be an important omission, but no adverse
events were recorded during training. It was not possible
to determine accurately the intensity of exercise training
without measures of haemodynamic responses. Assessments of upper or lower limb strength, e.g. using one
repetition maximum, were not included in the protocol
when the study was devised. We were therefore unable
to determine whether any of the groups had increases in
muscle strength after training.
The groups comprised only post-bypass patients,
randomized to different interventions, and there was a
control group. Although no formal dietary or risk factor
modification was done, such advice was available to all
patients and would have been the same. The sessions
and studies were supervised by the same personnel
throughout the programme.
Conclusions
Aerobic and strength exercise training result in significant improvements in treadmill exercise performance
after coronary artery surgery. Exercise training alone
did not cause clinically significant changes in lipoprotein
levels, body weight or percentage body fat. Cardiac
rehabilitation programmes should probably include
advice in dietary and risk factor modifications, and
psychosocial support in addition to aerobic and strength
exercise training.
We thank Miss Rita Smith and her staff for help with the
exercise tests, Miss Elizabeth Lightbody for help with the exercise
sessions and physiotherapy, and the technicians who processed the
samples for lipoprotein analysis.
861
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Appendix A
[39] Jones DA. Strength of skeletal muscle and the effects of
training. Br Med Bull 1992; 48: 592-604.
Aerobic exercise programme
[40] Adams WC, McHenry MM, Bemauer EM. Long term physiologic adaptations to exercise with special reference to performance and cardiorespiratory function in health and Arm circling. Stand with your feet slight apart. Abduct
disease. Am J Cardiol 1974; 33: 765-75.
arms and rotate at shoulders, forwards and backwards,
[41] Oldridge NB, Nagle FJ, Balke R, Corliss RJ, Kahn DR. starting with five in each direction.
Aortocoronary bypass surgery: effects of surgery and 32
months of physical conditioning on treadmill performance. Step-ups. Step up and down the 20 cm step at moderate
Arch Phys Med Rehabil 1978; 59: 268-75
pace, starting with 10 repetitions.
[42] Horgan JH, Teo KK, Murren KM, O'Riordan JM, Gallagher
T. The response to exercise training and vocational counsel- Trunk rotation. Stand with your feet slightly apart,
ling in post myocardial infarction and coronary artery bypass hands on hips. Rotate trunk to left and right, starting
surgery patients. Ir Med J 1980; 73. 463-9.
with five to each side.
Eur Heart J, Vol. 17, June 1996
Effects of training after coronary bypass surgery
Crook lying trunk rotation. Lie on your back, arms at
side, knees flexed. Rotate hips from side to side, starting
with five to each side.
Star Jumps. Stand with your feet together. Jump up
while abducting arms and legs fully, then return to
starting position. Start with three.
Side lying hip abduction. Lie on your right side, with
right arm stretched above head, left arm supporting
upper body at chest level, right knee flexed. Abduct left
leg fully, and return to starting position. Repeat on left
side, abducting right leg. Start with five on each side.
Standing trunk curls. Stand with your feet together,
arms at side. Bend knees with arms stretched forwards,
and lower your body towards the mat. Return to
starting position. Start with three.
Crook lying bridging. Lie on your back with knees
flexed. Raise hips while keeping feet and shoulders on
the mat, and return to starting position. Start with five.
Arm raising. Stand with your feet together, arms at
sides. Raise arms forward above head and return to
starting position. Start with five.
Trunk side flexion. Stand with your feet slightly apart.
Flex trunk to right, sliding the right hand down the right
leg, and repeat on the left side. Start with three on each
side.
Running on the spot. Raise your feet at least 10-20 cm
off mat while running on the spot for 1 min initially.
by pulling the bar up, until arms are fully flexed, and
return to start.
Upright row. Stand facing equipment. With your arms
extended, palms down, pull the bar up towards your
chin, and move elbows outwards at the same time to
raise the weights. Return to starting position.
Pull down. Sit on stool with equipment behind body.
Raise weights by pulling bar down towards shoulders,
and return to starting position.
Push down. Stand facing equipment. Bend your arms
with palms down and raise weights by pushing bar
downwards until arms are fully extended. Return to
starting position.
Pulley row. Sit on mat, legs fully stretched facing equipment. Reach for the bar and raise weights by pulling the
bar towards your body, and return to starting position.
Quadriceps curl. Sit on the edge of the bench. Hold
cushioned bar with flexed ankles and raise weights by
extending the knees. Return to starting position.
Hamstrings curl. Lie prone on the bench, with cushioned bar resting on back of ankles. Raise weights by
flexing knees. Return to starting position.
Sit ups. Lie supine on the mat, with legs stretched. Grip
fixed cushioned bar with ankles. Raise upper body, try
to touch your knees with your forehead and return to
starting position. Start with three repetitions.
Appendix B: exercise test protocol
Strength exercise programme
Bench press. Lie on your back on the bench, feet on the
floor, equipment behind head. Raise weights by pulling
bar towards your head, and return to starting position.
Military press. Kneel facing equipment. Raise weights
by pushing the bar from chest level to above your
head, fully extending your arms, and return to starting
position.
Biceps curl. Stand facing equipment. Bend your forearms, palms up, elbows tucked into sides. Raise weights
863
Stage
1
2
3
4
5
6
7
Speed
(k.p.h.)
Gradient
(min)
3
•6
9
12
15
18
21
3-2
4-8
4-8
4-8
4-8
4-8
7-2
0
4
8
12
16
20
20
Time
Mets
3
5
7
8
10
12
15
Eur Heart J, Vol. 17, June 19%