(Stroke. 1995;26:101-105.)
© 1995 American Heart Association, Inc.
Articles |
From The Stroke Rehabilitation Research Program, University of Illinois at Chicago (K.P., L.F., T.T.), and the Departments of Medicine (L.T.B., J.P.S.) and Psychology and Social Sciences (M.L.), Rush Presbyterian St Luke's Medical Center, Chicago, Ill.
Correspondence to Dr K. Potempa, The Stroke Rehabilitation Research Program, University of Illinois at Chicago (m/c 802), 845 S Damen Ave, Chicago, IL 60612-7350.
| Abstract |
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Methods Forty-two subjects were randomly assigned to an exercise training group or to a control group. Treatments were given three times per week for 10 weeks in similar laboratory settings. Baseline and posttest measurements were made of maximal oxygen consumption, heart rate, workload, exercise time, resting and submaximal blood pressures, and sensorimotor function.
Results Only experimental subjects showed significant improvement in maximal oxygen consumption, workload, and exercise time. Improvement in sensorimotor function was significantly related to the improvement in aerobic capacity. After treatment, experimental subjects showed significantly lower systolic blood pressure at submaximal workloads during the graded exercise test.
Conclusions We conclude that hemiparetic stroke patients may improve their aerobic capacity and submaximal exercise systolic blood pressure response with training. Sensorimotor improvement is related to the improvement in aerobic capacity.
Key Words: blood pressure exercise rehabilitation
| Introduction |
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The purposes of this investigation were to (1) describe the responses of hemiparetic stroke patients to intense exercise and (2) determine the effect of aerobic training on cardiovascular and functional outcome measures.
| Subjects and Methods |
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Procedures
After a thorough explanation of the study, all subjects signed
informed consent forms that were approved by the institutional human
studies committee. Subjects underwent a complete history and physical
examination, chest radiograph, electrocardiogram, and laboratory blood
tests to screen for comorbid diseases. Subjects who met entry criteria
were randomly assigned to either the experimental group (a 10-week
aerobic exercise training program) or to the control group (a 10-week
program of passive range-of-motion exercise). Subjects received their
respective treatments three times per week, for 30 minutes each
session, for 10 weeks in similar laboratory environments. Baseline and
posttest measurements included resting heart rate, blood pressure, body
weight, maximal heart rate, oxygen consumption
(
O2), expiration per minute
(
E), carbon dioxide production
(
CO2), workload, exercise time, and
exercise blood pressure at submaximal workloads, as well as an
assessment of sensorimotor function using the Fugl-Meyer
Index.8
Graded Exercise Test Protocol
Exercise tests were performed in a humidity- and
temperature-controlled laboratory and at the same time of day for each
subject. Tests were conducted according to standard criteria of the
American College of Sports Medicine.9 Subjects were
acclimated to the testing procedures. The exercise protocol began with
seated rest on the bicycle ergometer for 2 minutes. Dynamic exercise
began at 10 W, and workloads increased by 10 W each minute until
maximal effort was achieved. Criteria for a maximal effort included
voluntary exhaustion (subjects could no longer continue pedaling) and a
respiratory exchange ratio (RER) greater than 1.15. An exercise test
was terminated and subjects were excluded from the study if there were
any untoward cardiac signs or symptoms that warranted stopping the test
for patient safety.9 At the point of voluntary exhaustion,
final measurements were made, and the subjects were given cool-down and
recovery periods. To document reliability of the exercise measurements,
a randomly selected subset of subjects was given two pretreatment
exercise tests separated by 48 hours. Subjects were maintained on all
drug prescriptions, including dosage, throughout the study.
Exercise Training Protocol
Subjects in the experimental group were exercised on an adapted
cycle ergometer for 30 minutes a session, three times per week, for 10
weeks. During the first 4 weeks of the program, the training load was
gradually increased from a workload representing 30% to 50% of
maximal effort to the highest level attainable by the subject. The
highest training load was then maintained for the final 6 weeks of
training.
Passive Range-of-Motion Protocol
Subjects in the control group were given passive exercise for
range of motion to body joints in a systematic procedure for 30
minutes, three times a week, for 10 weeks. Heart rate and blood
pressure were monitored as in the experimental aerobic training
group.
Measurements
Heart Rate
Heart rate was obtained from the RR interval on the
electrocardiogram. Resting heart rate was determined after the subject
sat for 20 minutes at rest in the laboratory before getting on the
ergometer for a graded exercise test. Maximal heart rate during the
graded exercise test was the average heart rate during the last 30
seconds of exercise.
Blood Pressure
Brachial artery blood pressure in the subject's unaffected arm
was measured using a calibrated mercury sphygmomanometer. Procedures
followed the American Heart Association Recommendations for Human Blood
Pressure Determination.10 The systolic blood pressure
(SBP) was determined at the first Korotkoff sound and the diastolic
blood pressure (DBP) at the fifth Korotkoff sound. Resting blood
pressure was determined after the subject sat for 20 minutes at rest in
the laboratory before getting on the ergometer for a graded exercise
test. Blood pressure during exercise was measured every 2 minutes
during the graded exercise test and at specified intervals during
training sessions.
Exercise Metabolic Parameters
O2,
CO2,
E,
and RER were continuously determined during graded exercise tests using
a breath-by-breath respiratory gas analysis assembly and
appropriate computerized software (Medical Graphics Cardiopulmonary
Exercise Stress Testing System, model 2001). Maximal values for
exercise parameters were the average values during the last 30 seconds
of exercise.
Workload
The electronically braked ergometer (Mijnhardt, model KEM-3)
features an automatic resistance adjustment to maintain the specified
workload within a wide range of cadence (50 to 70 rpm). Subjects
achieved the specified workload by maintaining the cadence between 50
to 70 rpm. The maximal workload for each graded exercise test was the
highest workload maintained for at least 30 seconds.
Exercise Time
Exercise time was the total amount of time in seconds of the
graded exercise test counted from the first downward stroke of the
ergometer pedal until the subject stopped pedaling.
Sensorimotor Function
Functional improvement was assessed with the Fugl-Meyer
Index,8 a 113-item observer-rated measure of sensorimotor
function. Total and subscale scores were used to determine functional
improvement with training. Previous work in our laboratory established
the
internal consistency reliability of the instrument as .96 for
the total scale and .75, .56, .51, and .96 for the sensation,
proprioception, balance, and motor subscales, respectively. The
intraclass correlation of interrater reliability was .99 for the total
instrument and .97, .94, .63, and .99 for the sensation,
proprioception, balance, and motor subscales,
respectively.11 The Fugl-Meyer Index was administered by
three registered physical and occupational therapists who were trained
in the procedure.
Data Analysis
This was a randomized, controlled clinical trial with a 2x2
experimental design to determine the impact of aerobic training on
physiological and functional outcomes in hemiparetic stroke patients. A
power analysis using data from our preliminary case work showed
that a sample size of 21 per cell will produce a power of .80 with an
effect size of .884 (standardized units) with an
of .05. The
preliminary case work also showed that we could expect this magnitude
of effect size for the principle variables in the study. Descriptive
statistics were used to characterize the sample and to display baseline
exercise responses. All data are presented as mean±SEM. Data were
subjected to a series of statistical analyses. First, treatment effects
were determined by a repeated-measures ANOVA of baseline and
posttreatment scores by treatment group. The differences between
baseline and posttest measurements were then computed as percentage
changes to describe how exercise training changed maximal
O2, workload, exercise time,
and Fugl-Meyer Index. These percentage changes were used in subsequent
ANOVA and ANCOVA of treatment outcomes. Two-way ANOVA was used to
determine the influence of lesion location (right or left hemisphere)
on treatment outcomes. A series of covariate analyses were performed to
determine the influence of age, pretreatment fitness level, training
workload, and pretreatment functional status on treatment outcomes.
Pearson correlations were performed to determine the magnitude and
significance of the relationship between improvement in aerobic fitness
and improvement in functional outcome.
To determine the effect of training on exercise blood pressure responses, SBP and DBP were measured at three submaximal workloads during exercise (0, 20, and 40 W). These three blood pressure readings were examined in a subset of subjects (n=25) who completed at least 40 W of exercise. For each of the three workloads, we measured the magnitude of change with treatment as the difference between pretest and posttest measures. These derived-change scores were subjected to repeated-measures ANOVA to determine differences in treatment effects by group.
Finally, a secondary analysis was performed to determine the relationships between the magnitude of pretreatment SBP and DBP response and the average percentage of drop in exercise blood pressure from before to after treatment. The pretreatment magnitude of blood pressure rise, or blood pressure response during exercise, was determined by the difference between blood pressure readings at 40 W (4 minutes) and blood pressure at the resting workload (0 minute). Pearson correlations were used to determine the relationship between the variables.
| Results |
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Reliability of Exercise Responses
Twenty-five subjects were given two baseline exercise tests from
which intraclass correlation coefficients and coefficients of
determination were derived.12 The intraclass correlation
coefficients for maximal
O2,
heart rate, workload, SBP, and DBP measured at 40 W of exercise were
.94, .97, .99, .83, and .72, respectively. The coefficients of
determination for these variables were .94, .97, .99, .85, and .74,
respectively.
Exercise Responses and Aerobic Training Effects
The baseline and posttreatment measurements are displayed in Table 2
. The improvement in maximal
O2 for exercise subjects ranged from
0% to 35.7%. Changes in resting measurements were not significant for
either group.
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The two-way ANOVAs for treatment group and lesion location were not
significant for
O2, workload,
or exercise time expressed as percent improvement. In the covariate
analyses, where percent improvement in
O2 was the dependent variable, the
training workload was the only significant covariate (F=5.97,
df=2, P=.022).
Mean values for baseline and posttreatment SBP and DBP were measured at
submaximal points during the graded exercise tests and are shown in the
Figure
. These blood pressure values include data on 25
subjects who exercised through at least 40 W on the graded exercise
test. Seventeen of the 25 subjects in this subgroup had diagnosed
hypertension, whereas the remaining 8 subjects were without
hypertension and were equally distributed between the experimental and
the control group. The ANOVA was significant for the SBP treatment
group by workload interaction (F=3.27, df=2,
P=.047). A similar pattern of change with treatment was
observed for DBP, but the DBP treatment group by workload interaction
was not quite significant (F=2.21, df=2,
P=.12).
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SBP response, measured in the baseline exercise test, was moderately correlated with the average drop in SBP from the baseline to the posttreatment exercise test across all three workloads measured (r=-.62, P=.04). The correlation for DBP was not significant.
Relationship Between Improvement in Aerobic Fitness and Improvement
in Sensorimotor Function
The ANOVA for between-group changes in Fugl-Meyer Index scores was
nonsignificant. The Pearson correlation of the improvement in
O2 and the improvement in the total
score of the Fugl-Meyer Index in the aerobic exercise treatment group
was significant (r=.56, P=.012). However, the
correlations for the four subscales of the Fugl-Meyer Index were not
significant.
| Discussion |
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O2,
CO2, and RER, as observed in
the present study, are not available in previous reports of intense
exercise in hemiparetic stroke patients. However, the absolute amount
of oxygen consumed per submaximal workload in these hemiparetic
subjects is greater than that observed in normal subjects of similar
age and body size.18 This oxygen increase confirms the
observations of Hoskins,4 who showed the increased energy
cost of submaximal aerobic exercise in hemiparetic subjects. The
increased energy cost of exercise may be related to the reduced
efficiency of motion and to the presence of
spasticity.18 19 The increased energy cost of spastic
muscle has been reported in subjects with spasticity due to multiple
sclerosis.19
Exercise training significantly increased mean maximal
O2, workload, and exercise
time. However, the improvement across subjects was not uniform. The
only variable among training workload, age, baseline level of fitness,
lesion location, and sensorimotor function that significantly predicted
treatment response was training workload. The percent improvements in
peak workload and exercise time are greater than those expected for the
percent improvement in maximal
O2.
This suggests that efficiency of motion is improving to a greater
extent than is aerobic capacity.
In a study of one-leg and two-leg exercise in hemiparetic subjects,
Landin and colleagues15 showed a reduced blood flow, an
augmented lactic acid production, and a decreased capacity to oxidize
free fatty acids in paretic muscle. Given that the purpose of our
investigation was to demonstrate the overall trainability of
hemiparetic subjects using a two-leg exercise protocol, our findings do
not explicate the physiological mechanisms that influence fatigue,
endurance, or trainability. We cannot be sure whether the increment in
O2 occurred as a result of central or
peripheral adaptation, or both. Furthermore, the ability of paretic
muscle to increase oxidative metabolism with exercise training is
unknown. This study does suggest, however, that the overall improvement
in aerobic capacity has implications for the submaximal effort that
hemiparetic patients engage in each day; these patients can carry out
their daily activities at a lower percentage of maximal
O2.
Exercise training significantly improved the exercise SBP across the three workloads examined. Although others have shown the value of exercise training in reducing resting blood pressure in hypertensive subjects,20 21 the results of this study demonstrate that exercise training attenuates SBP during moderate exercise in hemiparetic subjects. A pattern of attenuation was also observed for DBP at two of the three workloads; however, these changes were not statistically significant. This may be attributable to insufficient power of the study to detect small effects. The pretreatment SBP response correlated significantly with the percent improvement in the average exercise blood pressure; this correlation suggests that the improvement in SBP is greatest in subjects who had the highest baseline responses to exercise workload. This suggestion may be especially important because, for a given absolute workload, the magnitude of baseline blood pressure response in these hemiparetic subjects was greater than that observed in hypertensive subjects of similar ages.22 The elevations in blood pressure during exercise observed in this study may be comparable to those that occur during activities of daily life, and the influence of elevated blood pressure on the risk of future stroke is well documented.23 Many of the hemiparetic subjects studied were hypertensive and taking a variety of antihypertensive medications. The observed reductions in blood pressure with training are in addition to attenuations achieved with drug treatment alone, as observed in the baseline exercise test.
Our inability to detect changes in resting blood pressure may be related to the maximum effect of the antihypertensive drug treatment in the resting condition. Although others have observed a synergistic effect of exercise training and drug treatment on resting blood pressure in hypertensive subjects, this has not been a consistent finding.20 The reduction in resting blood pressure in hypertensive subjects after training has also been associated with low-intensity, rather than moderate- or high-intensity, training workloads.20 The relatively high training load in the present study may have contributed to the lack of change in resting blood pressure.
The ANOVA for between-group changes in sensorimotor function was
nonsignificant. However, because the improvement in
O2 was not uniform among subjects, it
was hypothesized that improvement in sensorimotor function might be
related to the magnitude of improvement in aerobic capacity. To test
this hypothesis, the data from the treatment group was subjected to a
Pearson correlation of the improvement in
O2 and the improvement in the total
score of the Fugl-Meyer Index; the result was significant. The moderate
and significant correlation between the Fugl-Meyer Index and the
improvement in aerobic capacity suggests that sensorimotor improvement
with training is related to the percent improvement in aerobic
capacity, or exercise intensity, rather than bicycle exercise per
se.
In summary, the results of this study demonstrate that moderately disabled, chronically hemiparetic stroke patients may improve their aerobic capacity with adequate exercise training. The subjects undergoing aerobic exercise also demonstrated improvement in functional workload and exercise time to a greater extent than expected for the increase in aerobic capacity. A subset of subjects in the aerobic exercise group also showed significant attenuation of exercise SBP with training. This result may have important implications for reduction of cardiovascular risk in patients who have clinically significant elevations of blood pressure during exercise. Finally, the improvement in aerobic capacity was significantly related to improvement in sensorimotor function, which indicates that exercise training functionally benefits those subjects able to train at an intensity high enough to increase aerobic capacity.
| Acknowledgments |
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Received June 24, 1994; revision received September 28, 1994; accepted October 14, 1994.
| References |
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