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In: Advances in Arterial Stiffness Research ISBN: 978-1-63485-838-0
Editor: Becky Chavez © 2016 Nova Science Publishers, Inc.
Chapter 7
HIGHER ARTERIAL STIFFNESS RELATED TO
BLOOD PRESSURE OVERRESPONSE TO ARM
AND LEG RESISTANCE EXERCISES IN
ELDERLY INDIVIDUALS
Takeshi Otsuki
1,*
and Takahiro Kotato
2
1
Faculty of Sport and Health Sciences,
Ryutsu Keizai University, Ryugasaki, Ibraki, Japan
2
Graduate School of Sport and Health Sciences,
Ryutsu Keizai University, Ryugasaki, Ibraki, Japan
ABSTRACT
Exaggerated elevation of systolic blood pressure (SBP) during
aerobic or resistance exercises is a marker for early cardiovascular
disease. Moreover, arterial stiffness is an essential characteristic of the
vascular system, directly affecting blood pressure. In addition, arterial
stiffness indirectly influences blood pressure, since stiffening of the aortic
arch and carotid arteries, which contain stretch-sensitive baroreceptors,
deteriorates the cardiovagal baroreceptor reflex sensitivity (BRS). We
hypothesized that aging-related increase in arterial stiffness and decrease
in cardiovagal BRS exaggerate the elevation of SBP and rate-pressure
product (RPP) during resistance exercise. To test this hypothesis, we
*
E-mail: takeshi.otsuki17@gmail.com.
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Takeshi Otsuki and Takahiro Kotato
138
investigated the blood pressure response to resistance training in 45
individuals aged between 45 and 76 years. The following were measured:
SBP and RPP during arm and leg resistance exercises, aortic pulse wave
velocity (PWV, a traditional index of central arterial stiffness), and
cardiovagal BRS. SBP and RPP during resistance exercises were
correlated with age, aortic PWV, and cardiovagal BRS. In particular,
stepwise regression analysis revealed that aortic PWV was an
independent predictor of SBP and RPP during exercise. We concluded
that elevations of SBP and RPP during arm and leg resistance exercises
are higher in elderly individuals than in middle-aged individuals. Higher
SBP and RPP elevations during resistance exercise may be associated
with increased arterial stiffness in elderly individuals.
Keywords: arterial stiffness, baroreceptor reflex sensitivity, cardiovagal
baroreceptor, rate-pressure product, systolic blood pressure
INTRODUCTION
Arterial stiffness, a substantial determinant of arterial compliance, is an
essential characteristic of the vascular system, directly affecting blood
pressure. Especially during exercise, the reduction in arterial compliance
causes the vascular load to transiently increase [1, 2]. In addition, arterial
stiffness indirectly influences blood pressure, since stiffening of the aortic arch
and carotid arteries, which contain stretch-sensitive baroreceptors, leads to
deterioration in the cardiovagal baroreceptor reflex sensitivity (BRS). In
middle-aged and elderly individuals with stiffened central arteries, higher
arterial stiffness and lower arterial compliance are related to exaggerated
increase in systolic blood pressure (SBP) [3], and in the product between SBP
and heart rate (rate-pressure product, RPP; a marker of cardiac load) [4] during
exercise on treadmill or cycle ergometer. Exaggerated SBP responses to
aerobic [5] and resistance [6] exercises are likely to be a risk factor for future
cardiovascular disease. As previous studies showed for aerobic exercises,
increased arterial stiffness in aged individuals may also exaggerate SBP and
RPP responses to resistance exercises. However, the influence of arterial
stiffness and cardiovagal BRS on SBP and RPP during resistance exercise
have not yet been elucidated.
We hypothesized that aging, by bringing about increased arterial stiffness
and decreased cardiovagal BRS, exaggerates the elevation of SBP and RPP
during resistance exercise. To test this hypothesis, we investigated the
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Higher Arterial Stiffness Related to Blood Pressure Overresponse …
139
following in individuals aged between 45 and 76 years: SBP and RPP during
arm and leg resistance exercises at 20%, 40%, and 60% one-repetition
maximum (1RM); aortic pulse wave velocity (PWV), which is a traditional
index of arterial stiffness; and cardiovagal BRS.
METHODS
Participants
Forty-five individuals (45–76 years of age) participated in this study
(Table 1). Although no subject had signs or symptoms of heart disease, five
subjects were taking antihypertensive medicine. Subjects were asked to refrain
from alcohol consumption and intense physical activity from the day before
testing and throughout the test, and refrain from caffeine consumption on the
day of the testing.
This study was approved by the Ethics Committee of Ryutsu Keizai
University, and conformed to the principles of the Helsinki Declaration. All
participants provided written informed consent prior to the beginning of the
study.
Resistance Exercise Protocol
After measurements of blood pressure and heart rate (HR) at rest, subjects
performed muscle stretching as warm-up exercise, followed by a cycling
exercise at 65% of their age-predicted maximal HR for 4 min. Next, an expert
instructor (Takahiro Kotato) assessed the 1RM for the one-hand arm curl
exercise. For that, subjects performed a single repetition of the exercise using
their dominant arm, with progressively increasing the weight load; the heaviest
weight that a subject could lift once, through a complete range of movement
(i.e., from a slightly flexed position to full flexion), was considered the 1RM
for that particular subject. Five minutes after the 1RM assessment, subjects
performed two sets of 10-repetitions of the one-hand arm curl exercise at 20%
1RM, under the instructions of the resistance exercise expert. One repetition
was performed for 8 s (3 s of concentric contraction, 1 s of maintaining full
flexion, 3 s of eccentric contraction, and 1 s of maintaining a slightly flexed
position), in agreement with the Exercise Guide 2006 presented the by
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Takeshi Otsuki and Takahiro Kotato
140
Ministry of Health, Labour and Welfare of Japan. The duration of one set was
80 s, and the inter-set recovery period was 100 s. Subjects were instructed not
to interrupt their respiration during the exercise. The 40% and 60% sessions
were conducted in a similar fashion, and the interval between sessions was 160
s.
After a rest period, subjects performed muscle stretching, followed by
double-leg leg press exercise, in a similar fashion to what was performed for
the arm curl exercise. For this exercise, the complete range of motion was
defined as starting from the position with a knee angle of 80° (considering
180° as full extension) to a slightly flexed position.
Blood Pressure and Heart Rate Measurements
Before the warm-up exercises, resting SBP and diastolic blood
pressure (DBP) were measured in quintuplicate, in a sitting position, using
an oscillometric blood pressure monitor (DINAMAP Pro Care 300; GE
Healthcare, Buckinghamshire, UK). Simultaneously with those measurements,
a three-lead ECG was recorded at 1,000 Hz to calculate the HR (LRR-03;
GMS, Tokyo, Japan).
SBP and DBP measurements were taken once during each exercise set,
starting at 20 s after the onset of the exercise activity, using the blood pressure
monitor. RR intervals (the intervals between two R peaks in the QRS complex
of the ECG) were averaged every 8 s (i.e., for every repetition), and the
maximal value among the averages was used as the HR of the respective set.
The arm curl exercise was performed with the dominant arm, and blood
pressure was measured on the nondominant arm. The mean value of the two
sets was calculated for the 20%, 40%, and 60% 1RM exercises.
Table 1. Subjects characteristics
Mean
±
SE
n (male/female)
45 (15/30)
Age, years
61.8
±
1.1
Body mass index, kg/m
2
22.3
±
0.5
HDL cholesterol, mg/dL
74
±
3
LDL cholesterol, mg/dL
128
±
4
Triglycerides, mg/dL
98
±
7
Glucose, mg/dL
96
±
3
Hemoglobin A1c, %
5.3
±
0.1
Insulin, μU/mL
4.3
±
0.3
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Aortic PWV Assessment
Aortic PWV was measured using applanation tonometry, with minor
modifications from what was described in our previous studies [7, 8]. Briefly,
in supine position, carotid and femoral artery pulse waves were obtained in
triplicate (BP-203RPE II; Omron Colin, Tokyo, Japan). Pulse wave transit
time was automatically determined by the device, as the delay between the
proximal and distal waveforms. The distance traveled by the pulse waves was
measured over the surface of the body. PWV was calculated as the distance
divided by the transit time.
Cardiovagal BRS Assessment
Spontaneous cardiovagal BRS was assessed according to previously
described methods [9-11]. Radial artery pressure waveforms were recorded in
a supine position by performing arterial applanation tonometry (Jentow;
Omron Colin), and sampled at 1,000 Hz using an analog-to-digital converter
(PowerLab 8/30; ADInstruments, Bella Vista, Australia) interfaced with a
personal computer equipped with data acquisition software (LabChart 7;
ADInstruments). Radial SBP was calculated from radial-artery waveforms
based on the assumption that radial-artery mean blood pressure (MBP) and
DBP were equal to the brachial values measured by oscillometry (BP-203RPE
II). ECG was sampled simultaneously with the recording of pressure
waveforms, at a sampling rate of 1,000 Hz, and the RR intervals were
calculated.
First, we identified sequences of three or more consecutive beats in which
the SBP progressively rose and the RR interval progressively lengthened, or in
which SBP progressively fell and the RR interval progressively shortened.
Next, linear regressions relating SBPs to the corresponding RR intervals for
each sequence were plotted, and the slopes were determined; only sequences
with linear R
2
values >0.85 were accepted. The slopes of the regression line
for the 5-min period spent in supine position were averaged to provide a
complete data set.
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Takeshi Otsuki and Takahiro Kotato
142
Blood Chemical Analysis
Blood samples were collected from the antecubital vein by performing
venipuncture, after overnight fasting. Serum concentrations of cholesterol,
triglycerides, and insulin, as well as plasma levels of glucose and hemoglobin
A1c, were determined as described in our previous study [12].
Statistical Analysis
Results are given as mean ± SE. Relationships between two variables were
investigated using Pearson’s correlation coefficient, and partial correlation
analysis. Stepwise regression analysis was used to determine significant and
independent correlations for SBP and RPP during exercise. Changes in blood
pressure, HR, RPP, and ratings of perceived exertion (RPE, Borg’s 6–20 scale)
during exercise were analyzed by repeated measures ANOVA. If a significant
F value was found, a post-hoc Fisher’s protected least significant differences
test was performed. P-values <0.05 were considered statistically significant.
RESULTS
All subjects completed the 20% and 40% 1RM exercise sessions.
However, with respect to the 60% 1RM session, one subject was not able to
complete all arm curl exercises, and four subjects were not able to complete all
leg press exercises. Blood pressure, HR, RPP, and RPE increased in an
exercise intensity-dependent manner; however, with respect to the leg press
exercises, there was no difference between DBP measured during the 40%
1RM session and DBP measured during the 60% 1RM session (Table 2).
Age was correlated with aortic PWV, SBP, and RPP at rest, as well as
with SBP and RPP during exercise (Table 3). The relationship between age
and cardiovagal BRS reached the threshold of statistical significance (P =
0.05). In the partial correlation analysis that adjusted for resting SBP, age was
correlated with SBP during exercise for both types of exercise and all
intensities, except for the 60% 1RM of the arm curl exercise. In addition, age
was correlated with RPP at 20%, 40%, and 60% 1RM of the arm curl exercise,
and with RPP at 20% 1RM of the leg press exercise, independently of resting
RPP.
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Aortic PWV was correlated with SBP and RPP at rest and during exercise
for both types of exercises (Table 4). The correlation with SBP and RPP
during exercise held true also in the partial correlation analysis that adjusted
for resting SBP or RPP.
Cardiovagal BRS was correlated with SBP and RPP during exercise for
both types of exercises, although the correlation with SBP at 60% 1RM of the
leg press exercise did not reach statistical significance (Table 5). In the partial
correlation analysis that adjusted for resting SBP or RPP, cardiovagal BRS
was correlated with SBP at 20% 1RM of the arm curl exercise, and with SBP
and RPP at 40% 1RM of the leg press exercise.
Aortic PWV was identified as an independent predictor of SBP and RPP
during arm curl (Tables 6 and 7) and leg press (Tables 8 and 9) exercises;
however, in the stepwise regression analysis, this relationship did not hold true
for SBP at 40% 1RM of the arm curl exercise and at 60% 1RM of the leg press
exercise. Age was associated with SBP independently of other factors only at
20% and 40% 1RM of the arm curl exercise, and at 40% 1RM of the leg press
exercise. Cardiovagal BRS was not identified as an independent predictor of
SBP or RPP during exercise.
DISCUSSION
To evaluate the influence of age-related arterial stiffness on the blood
pressure response to resistance training, the present study included middle-
aged and elderly adults that performed arm curl and leg press exercises at
intensities of 20%, 40%, and 60% 1RM. The following were measured: SBP
and RPP at rest and during exercise, aortic PWV, and cardiovagal BRS. We
found that SBP and RPP during resistance exercise were exaggerated in
elderly subjects. In addition, we demonstrated for the first time that the indices
of central arterial stiffness and cardiovagal BRS are correlated with SBP and
RPP during resistance exercise. In particular, the association of arterial
stiffness with SBP and RPP during exercise was independent of other factors.
Taken together, these results suggest that the age-related increase in arterial
stiffness is responsible for exaggerated SBP and RPP elevation during
resistance exercise.
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Takeshi Otsuki and Takahiro Kotato
144
Table 2. Blood pressure, heart rate, and ratings of perceived exertion at
rest and during resistance exercises
Rest
20%
40%
60%
Arm curl exercise (n
= 44)
SBP, mmHg
120
±
3
143
±
4
*
150
±
4
*†
167
±
4
*†‡
DBP, mmHg
72
±
2
84
±
2
*
90
±
2
*†
98
±
2
*†‡
Heart rate, bpm
71
±
2
78
±
1
*
82
±
1
*†
89
±
2
*†‡
RPP, bpm mmHg 10
-2
86
±
3
112
±
4
*
123
±
4
*†
149
±
5
*†‡
RPE (Borg’s 6–20
scale)
–
10.8
±
0.2
13.9
±
0.3
†
17.0
±
0.3
†‡
Leg press exercise (n
= 41)
SBP, mmHg
120
±
3
148
±
4
*
162
±
4
*†
175
±
4
*†‡
DBP, mmHg
72
±
2
83
±
2
*
95
±
3
*†
99
±
3
*†
Heart rate, bpm
71
±
2
81
±
2
*
92
±
2
*†
103
±
3
*†‡
RPP, bpm mmHg 10
-2
86
±
3
120
±
5
*
151
±
7
*†
184
±
9
*†‡
RPE (Borg’s 6–20
scale)
–
11.6
±
0.2
15.0
±
0.3
†
17.5
±
0.3
†‡
Values are means ± SEs. 20%, 20% one-repetition maximum (1RM); 40%, 40% 1RM; 60%, 60%
1RM; DBP, diastolic blood pressure; RPE, ratings of perceived exertion; RPP, rate-pressure
product; SBP, systolic blood pressure. *, P < 0.05 vs. rest; †, P < 0.05 vs. 20%; ‡, P < 0.05 vs.
40%.
Table 3. Relationships between age and systolic blood pressure and rate-
pressure product during resistance exercises
%1RM
n
Age
r
Partial r
Rest
PWV
–
45
0.583
***
–
BRS
–
45
0.293
–
SBP
–
45
0.489
**
–
RPP
–
45
0.341
*
–
Arm curl exercise
SBP
20%
45
0.626
***
0.481
**
40%
45
0.586
***
0.377
*
60%
44
0.547
***
0.297
RPP
20%
45
0.485
**
0.421
**
40%
45
0.456
**
0.338
*
60%
44
0.465
**
0.341
*
Leg press exercise
SBP
20%
45
0.623
***
0.445
**
40%
45
0.637
***
0.480
**
60%
41
0.538
***
0.361
*
RPP
20%
45
0.473
**
0.353
*
40%
45
0.399
*
0.283
60%
41
0.344
*
0.232
Systolic blood pressure (SBP) or rate-pressure product (RPP) at rest was included as a covariate in the
partial correlation analysis. 1RM, one-repetition maximum; BRS, baroreceptor reflex sensitivity;
PWV, pulse wave velocity. *, P < 0.05; **, P < 0.005; ***, P < 0.0005.
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Table 4. Relationships between arterial stiffness and systolic blood
pressure and rate-pressure product during resistance exercises
%1RM
n
Aortic pulse wave velocity
r
Partial r
Rest
SBP
–
45
0.575
***
–
RPP
–
45
0.657
***
–
Arm curl exercise
SBP
20%
45
0.694
***
0.490
**
40%
45
0.638
***
0.339
*
60%
44
0.614
***
0.308
*
RPP
20%
45
0.735
***
0.437
**
40%
45
0.711
***
0.379
*
60%
44
0.694
***
0.449
**
Leg press exercise
SBP
20%
45
0.701
***
0.499
***
SBP
40%
45
0.714
***
0.544
***
60%
41
0.562
***
0.361
*
RPP
20%
45
0.767
***
0.595
***
40%
45
0.714
***
0.595
***
60%
41
0.611
***
0.498
**
Systolic blood pressure (SBP) or rate-pressure product (RPP) at rest was included as a
covariate in the partial correlation analysis. 1RM, one-repetition maximum. *, P <
0.05; **, P < 0.005; ***, P < 0.0005.
Table 5. Relationships between cardiovagal baroreceptor reflex sensitivity
and systolic blood pressure and rate-pressure product
during resistance exercises
%1RM
n
Cardiovagal BRS
r
Partial r
Rest
SBP
–
45
-0.263
–
RPP
–
45
-0.363
*
–
Arm curl exercise
SBP
20%
45
-0.369
*
-0.308
*
40%
45
-0.357
*
-0.276
60%
44
-0.387
*
-0.292
RPP
20%
45
-0.390
*
-0.156
40%
45
-0.397
*
-0.177
60%
44
-0.367
*
-0.166
Leg press exercise
SBP
20%
45
-0.361
*
-0.256
40%
45
-0.432
**
-0.357
*
60%
41
-0.307
-0.191
RPP
20%
45
-0.412
**
-0.250
40%
45
-0.454
**
-0.317
*
60%
41
-0.399
*
-0.284
Systolic blood pressure (SBP) or rate-pressure product (RPP) at rest was included as a
covariate in the partial correlation analysis. 1RM, one-repetition maximum; BRS,
baroreceptor reflex sensitivity. *, P < 0.05; **, P < 0.005.
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Takeshi Otsuki and Takahiro Kotato
146
Table 6. Stepwise regression analysis to identify independent predictors of
systolic blood pressure during arm curl exercise
Systolic blood pressure during arm curl exercise
20% 1RM
40% 1RM
60% 1RM
n
45
45
44
R
2
0.862
0.842
0.767
P
< 0.0001
< 0.0001
< 0.0001
Age (years)
RC
0.590
0.794
[excluded]
SE
0.249
0.258
β
0.174
0.220
P
0.02
0.004
Pulse wave velocity
(m/s)
RC
0.020
[excluded]
0.031
SE
0.008
0.011
β
0.193
0.261
P
0.01
0.008
Cardiovagal BRS
(ms/mmHg)
RC
[excluded]
[excluded]
[excluded]
SE
β
P
Systolic blood
pressure at rest
(mmHg)
RC
0.953
1.095
0.992
SE
0.100
0.106
0.149
β
0.694
0.748
0.631
P
<0.001
<0.001
<0.001
Body mass index
(kg/m
2
)
RC
[excluded]
1.537
2.442
SE
0.532
0.714
β
0.182
0.266
P
0.006
0.001
Excluded variables
Sex (male = 0, female = 1), use of antihypertensive
medication (no = 0, yes = 1)
1RM, one-repetition maximum; BRS, baroreceptor reflex sensitivity; RC, regression
coefficient.
To date, several groups have investigated the effects of aging on blood
pressure response during resistance exercise [13-15]. Petrofsky and Laymon
have demonstrated that, in individuals aged between 20 and 65 years, age
was correlated with SBP and DBP elevations during isometric exercise
using finger flexors and quadriceps, at 40% maximal voluntary contraction
(MVC) [13]. Smolander et al. have shown that changes in MBP during
isometric contractions of finger flexors and quadriceps at 20–60% MVC was
greater in middle-aged individuals (54–59 years) than in young individuals
(23–29 years) [14]. These results are in agreement with the present findings,
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