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RESEARCH ARTICLE
Comparative effectiveness of aerobic,
resistance, and combined training on
cardiovascular disease risk factors: A
randomized controlled trial
Elizabeth C. Schroeder
1
, Warren D. Franke
2
, Rick L. SharpID
2
, Duck-chul LeeID
2
*
1Department of Kinesiology and Nutrition, University of Illinois, Chicago, IL, United States of America,
2Department of Kinesiology, Iowa State University, Ames, IA, United States of America
*dclee@iastate.edu
Abstract
Although exercise has well-documented health benefits on cardiovascular disease (CVD),
the benefit of combination exercise on CVD risk factors in individuals with elevated risk has
not been fully elucidated. We compared the effects of aerobic, resistance, and a combina-
tion of both aerobic and resistance training on CVD risk factors including peripheral and cen-
tral BP, cardiorespiratory fitness (CRF), muscular strength, body composition, blood
glucose and lipids. Sixty-nine adults (58±7 years) with an elevated blood pressure or hyper-
tension, overweight/obesity, and sedentary lifestyle were randomized to one of the three
8-week exercise programs or a non-exercise control group. Participants in all three exercise
groups had an equal total exercise time, 3 days/week (aerobic: 60 minutes/session vs. resis-
tance: 60 minutes/session vs. combination: aerobic 30 minutes/session plus resistance
30 minutes/session). Combined training provided significant reductions in peripheral (-4
mmHg) and central diastolic BP (-4 mmHg), increase in CRF (4.9 ml/kg/min), increase in
upper (4 kg) and lower (11 kg) body strength, and increase in lean body mass (0.8 kg)
(p <0.05). Aerobic training only increased CRF (7.7 ml/kg/min), and reduced body weight
(-1.0 kg) and fat mass (-0.9 kg) (p <0.05). Resistance training only increased lower body
strength (13 kg) and reduced waist circumference (-1.7 cm) (p <0.05). However, neither aer-
obic or resistance training alone showed significant reductions in BP (p>0.05). Furthermore,
a composite score of CVD risk factors indicated a greater reduction with combination train-
ing compared to the control group. In conclusion, among individuals at an increased risk for
CVD, as little as 8-weeks of combined training may provide more comprehensive CVD ben-
efits compared to time-matched aerobic or resistance training alone.
Introduction
Hypertension, or elevated blood pressure, leads to increased risk of cardiovascular disease
(CVD) and is the number one leading risk factor for mortality [1]. However, hypertension is
also one of the most significant modifiable risk factors in the prevention of cardiovascular
PLOS ONE | https://doi.org/10.1371/journal.pone.0210292 January 7, 2019 1 / 14
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OPEN ACCESS
Citation: Schroeder EC, Franke WD, Sharp RL, Lee
D-c (2019) Comparative effectiveness of aerobic,
resistance, and combined training on
cardiovascular disease risk factors: A randomized
controlled trial. PLoS ONE 14(1): e0210292.
https://doi.org/10.1371/journal.pone.0210292
Editor: Stephen L. Atkin, Weill Cornell Medical
College Qatar, QATAR
Received: November 15, 2018
Accepted: December 18, 2018
Published: January 7, 2019
Copyright: ©2019 Schroeder et al. This is an open
access article distributed under the terms of the
Creative Commons Attribution License, which
permits unrestricted use, distribution, and
reproduction in any medium, provided the original
author and source are credited.
Data Availability Statement: All relevant data are
within the manuscript and its Supporting
Information files.
Funding: This work was supported by the Iowa
State University College of Human Sciences seed
grant (DL). DL’s research activity was supported by
the National Institutes of Health (HL133069). There
was no additional external funding received for this
study. The funders had no role in study design,
data collection and analysis, decision to publish, or
preparation of the manuscript.
disease [2]. With a prevalence of hypertension in the US population around 29% [3] and its
predicted continual increase [4], it is a critical health concern to reduce hypertension and
improve cardiovascular disease risk. Although pharmacological interventions are often relied
on to reduce blood pressure, lifestyle modification is the first line of therapy suggested by sev-
eral governing bodies [5–7].
Lifestyle modifications often emphasize improvements in diet and exercise habits. The
American College of Sports Medicine (ACSM), the American Heart Association, and others
[8] have all provided professional exercise recommendations for adults with hypertension.
However, most of these recommendations focus on aerobic exercise prescription [8]. The
health benefits of aerobic exercise are well established [9–11], but less data exist in regards to
the health benefits of resistance exercise, especially on cardiovascular health in individuals
with elevated blood pressure [12]. Indeed, recent reviews and meta-analyses have established
that aerobic and resistance exercise can both have a significant blood pressure lowering effect
of approximately 3–4 mmHg in both systolic and diastolic blood pressure [13–16]. This small
decrease has shown to be highly clinically relevant as it is estimated to reduce cardiac morbid-
ity by 5%, stroke by 8–14%, and all-cause mortality by 4% in the average population.[13] Most
earlier exercise studies on blood pressure and other CVD risk factors, however, have focused
more on either aerobic or resistance training alone.
Recent studies have begun using a combination of aerobic and resistance exercise to deter-
mine if additive benefits exist in which an ~3 mmHg reduction in blood pressure has been
observed [17]. Although a similar reduction in blood pressure compared to either aerobic or
resistance training alone, both aerobic and resistance exercise provide independent, modality
specific benefits toward cardiovascular disease risk factors. In general, aerobic exercise induces
greater improvements in cardiorespiratory fitness and cardio-metabolic variables, whereas
resistance exercise mainly effects muscular strength and has positive effects on body composi-
tion, such as muscle mass and bone density.
The combination of aerobic and resistance exercise could have an additive effect and fur-
ther decrease the risk of CVD risk factors, however, there is a vast breadth of populations and
co-morbidities included in studies on combination training, various exercise prescriptions
and timing, and few with the sole focus on blood pressure reduction [17]. Additionally, many
of the combined exercise training studies do not have an aerobic- or resistance-only group or
are not a well-controlled randomized trials [15]. Therefore, it is unclear whether the additional
benefits of combination exercise is simply due to extra exercise time rather than the indepen-
dent additive benefits from each aerobic and resistance exercise. Further, data on well-con-
trolled exercise interventions in middle-aged individuals with a heightened cardiovascular
disease risk profile without overt disease are still scarce.
The purpose of this study was to compare the effects of time-matched aerobic training only,
resistance training only, and combined aerobic and resistance training on blood pressure and
CVD risk factors compared to a non-exercising control group. We conducted an 8-week ran-
domized controlled trial in middle-aged adults with an elevated blood pressure or hyperten-
sion, overweight or obesity, and sedentary lifestyle. We hypothesized the combined aerobic
and resistance training would elicit greater improvement in blood pressure and CVD risk fac-
tors compared with either training only group.
Methods
Participants
This study consisted of 69 adults, 45 to 74 years of age, who had an elevated blood pressure or
hypertension (systolic/diastolic blood pressure of 120-149/80-99 without taking anti-
Exercise training and cardiovascular disease risk factors
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Competing interests: The authors have declared
that no competing interests exist.
hypertensive medications), overweight or obesity (body mass index [BMI] of 25–40 kg/m
2
),
and sedentary lifestyle (not meeting the aerobic and resistance exercise guidelines over the last
3 months [18]). Participants were free of any serious medical conditions (unstable coronary
heart disease, decompensated heart failure, severe pulmonary hypertension) that would not
allow safe participation in exercise according to ACSM and American Heart Association
[19,20]. Other exclusion criteria included individuals who smoked; pregnant women or
women anticipating pregnancy; and those who planned on being away for more than 2 weeks
during the intervention period. The Iowa State University Institutional Review Board (IRB)
approved this study (IRB ID: 14–330; August 8
th
, 2014) and each participant signed an
informed consent document prior to participation. The protocol was registered with Clinical-
Trials.gov (ID: NCT03734146; https://clinicaltrials.gov/ct2/show/NCT03734146?id=
NCT03734146&rank=1) following completion of the study, as it was considered an internally
funded pilot study. The authors confirm that all ongoing and related trials for this intervention
are registered.
Study design
Study recruitment was completed between August and October 2014. To enhance adherence,
participants were screened by phone prior to enrollment (by ECS) in an orientation session.
After determining that study criteria were met, participants attended two education sessions to
minimize dropout. Participants were then randomly assigned by a study statistician to one of
four parallel groups in a 1:1:1:1 ratio: 1) no-training control, 2) aerobic training only, 3) resis-
tance training only, or 4) combination of both aerobic and resistance training. Group alloca-
tion was based on age, sex, BMI, and baseline blood pressure and completed using a
computer-generated randomization. Participants were not aware of their group allocation
until baseline measures were completed. This was a single-center, parallel-group, superiority
study conducted at Iowa State University in Ames, Iowa, United States from August to Decem-
ber 2014.
Outcome measures were assessed at baseline (August to October 2014) and following the
8-week intervention (October to December 2014). Participants arrived to the laboratory for
baseline and 8-week follow-up measures having refrained from physical activity for at least 24
hours. All pre- and post-intervention measures were conducted in the same laboratory at the
same time of day in an identical sequence at each time point by investigators blinded to group
allocation. Measures occurred over two days. On the first visit, participants arrived to the lab
following an overnight fast (>12 hours) for assessment of blood pressure, heart rate, body
composition, lipid profile, and glucose. Participants were then familiarized with the treadmill
and strength tests. On the second visit, participants completed assessments of cardiorespira-
tory fitness and muscular strength. A 3-day diet record was kept for the next 3-days. Partici-
pants additionally wore a pedometer throughout the entire study duration to monitor outside
physical activity levels.
Full details of the trial protocol can be found in the supporting information (S1 Protocol)
available with the full text of this article at http://journals.plos.org/plosone/.
Assessments
Peripheral and central blood pressure and resting heart rate were measured using the Sphyg-
mocor XCEL (AtCor Medical, Itasca, IL, USA) automated oscillometric device. A brachial
blood pressure cuff was placed on the participant’s left arm over the brachial artery in a seated
position. The brachial pressure was measured 3 times by the device, with a two-minute rest
period between each measurement. Immediately following each blood pressure, the brachial
Exercise training and cardiovascular disease risk factors
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volume displacement waveform was obtained by inflating the cuff to a sub-diastolic pressure.
A generalized transfer function was used to estimate central blood pressure [21]. The first
reading was discarded and the device reported the average of the last 2 readings for all
measurements.
BMI (kg/m
2
) was calculated using measured body weight and height. Waist circumference
was measured at the level of the umbilicus (cm). Body composition was assessed via multi-fre-
quency bioelectrical impedance analysis (BIA) with 8 tactile electrodes (InBody 720, Biospace
Co, Ltd, Seoul, Korea), in which variables of body fat percentage, fat mass, and fat free mass
were obtained.
Cardiorespiratory fitness was assessed using a submaximal treadmill exercise test following
the modified Balke and Ware protocol [22]. All participants reached 70% of their heart rate
reserve (equivalent to 85% of age-predicted maximal heart rate) prior to ending the submaxi-
mal test. Cardiorespiratory fitness was estimated using the following formula from the Ameri-
can College of Sports Medicine: 3.5 + (0.1 x speed) + (1.8 x speed x grade) [19].
Maximal contractile strength was assessed with a seated chest and leg press (TechnoGym
Wellness System, Gambettola, Italy) 1 repetition maximum (RM) following standard proce-
dures [19]. Participants warmed up with light resistance and weight was added at 5–10 kg (or
5–10% of body weight) increments for upper body and 15–20 kg (or 10–20% of body weight)
increments for lower body until a maximum load was reached. A 2 minute resting period was
allowed between each attempt. An absolute 1 RM was determined when the participant suc-
cessfully lifted the weight through the entire range of motion but could no longer increase the
load. For one participant who exceeded the maximum amount of weight on the leg press, the 1
RM was estimated using a training load chart [23].
A 5-mL venous blood draw from a superficial arm vein was obtained to assess lipid profile
(total cholesterol, low- and high-density lipoprotein cholesterol, and triglycerides) and glucose.
Samples were collected in a serum separation tube and centrifuged for 15 minutes following a
30-minute clotting time. Serum samples were analyzed offsite by LabCorp (Des Moines, IA).
Exercise intervention
All exercise groups completed 8 weeks of supervised training with equal training time, exercis-
ing 3 days per week for 60 minutes per session. The non-exercise control group did not exer-
cise during the intervention.
The aerobic only group utilized the treadmill or cycle ergometer. Starting at 40% of their
heart rate reserve, participants were progressed to approximately 70% of their heart rate
reserve (equivalent to 85% of the age-predicted heart rate maximum). Participants could
choose to exercise at a higher intensity but not to exceed 80% of their heart rate reserve. A
heart rate monitor was worn during all exercise sessions.
The resistance only group performed 12 exercises: chest press, shoulder press, pull-down,
lower-back extension, abdominal crunch, torso rotation, biceps curl, triceps extension, leg
press, quadriceps extension, leg curl, and hip abduction. The program started with 2 sets of
18–20 maximal repetitions and progressed to 3 sets of 10–14 maximal repetitions with a rest of
1–2 minutes between sets. In this program, participants achieved exhaustion in each set, indi-
cating the lower the repetition, the higher the intensity. Total weight lifted in each exercise ses-
sion was automatically monitored and stored by a computer-controlled exercise intervention
system (TechnoGym Wellness System).
The combination group completed 30 minutes of aerobic exercise and 30 minutes of resis-
tance exercise per session. Participants followed the same intensity and protocol as the afore-
mentioned individual groups, but the resistance training was reduced to 8 exercises instead of
Exercise training and cardiovascular disease risk factors
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12 (excluding shoulder press, arm curl, arm extension, and leg extension) and 2 sets instead of
3. Order was not specified, although a majority of participants completed aerobic exercise
prior to resistance. All participants were asked to refrain from any moderate or vigorous physi-
cal activity outside the intervention, and reported daily steps using an accelerometer
(OMRON HJ-321, OMRON Healthcare, Hoofddorp, Netherlands) during the entire interven-
tion period.
Dietary counseling
All study groups received the same dietary counseling by a registered dietician based on the
Dietary Approaches to Stop Hypertension (DASH) Diet [24] to minimize dietary variability
among groups [25]. The focus of this counseling was on changing the quality of the diet with-
out changing the total energy intake to avoid weight loss. A 3-day food diary was obtained dur-
ing the first and eighth week of the intervention and analyzed using The Food Processor Diet
and Nutrition Analysis Software (ESHA, Salem, Oregon).
Data analysis
A composite risk factor score was derived by summing the standardized residuals (Z-scores) of
the change value from baseline to follow-up for 5 well-established CVD risk factors, also
recently identified by the American Heart Association [26]: mean arterial pressure, total cho-
lesterol, lower body strength, cardiorespiratory fitness, and body fat percentage [10,27,28].
Lower body strength and cardiorespiratory fitness were reverse coded (multiplied by -1) prior
to entry in the equation, due to increases in strength and fitness seen as beneficial. A lower
score is indicative of a better CVD risk factor profile following the intervention. We also
explored other composite risk factor scores based on different combinations of CVD risk fac-
tors. This was a pilot study funded internally by the institution (Iowa State University), thus
power and sample size were not officially calculated, but determined by the amount of the
awarded research fund, scope of the project, and recommendations by the expert project appli-
cation review committee.
All data were checked for normality and transformed when necessary. Descriptive statistics
were calculated for each variable and presented as mean (standard deviation, SD). The primary
outcome variables were peripheral and central systolic and diastolic blood pressure. Secondary
outcomes included BMI, weight, waist circumference, body composition, cardiorespiratory fit-
ness, muscular strength, and fasting lipids and glucose. Analyses were performed on an inten-
tion-to-treat basis using the last observation carried forward method and included all
randomly allocated persons at baseline. A linear-mixed effects model was used to assess the
change in all outcome variables with repeated measures for time, group, and time-by-group
interaction, adjusted for age, sex, and the baseline value of each outcome variable. A covariance
structure was determined the best fit with the lowest values for the information criteria after
evaluation of different structures. A Bonferroni correction was applied to correct for multiple
comparisons between groups. Data are presented as least-squares adjusted means with stan-
dard error (SE) or mean change with 95% confidence intervals (CI). Statistical analyses were
performed using the SAS software (SAS Institute, Cary, NC). All p-values are 2-sided, with sig-
nificance set a priori at p <0.05.
Results
Fig 1 shows the flow of participants from recruitment to follow-up. Of the 69 individuals ran-
domized, 66 (96%) completed the 8-week intervention. Mean exercise attendance was 96% in
all groups except resistance training (92%). On average, aerobic exercise participants
Exercise training and cardiovascular disease risk factors
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completed 100 ±6% of the prescribed exercise amount in minutes, with a mean exercise inten-
sity greater than what was prescribed (119 ±13%) based on the heart rate measured during
each exercise session throughout the intervention. Resistance training participants completed
100 ±2% of prescribed sets, and exercised at the weight prescribed 99 ±11% of the time. Based
on pedometer counts, lifestyle physical activity outside the intervention did not change signifi-
cantly over time (5689 ±2005, 5429 ±1883, 5404 ±2125, 5664 ±2285, 5466 ±1896,
5535 ±2116, 5191 ±1893, and 5095 ±2039 steps/day from week 1 to week 8, respectively;
p = 0.69) and no difference was observed across groups (p>0.05). Also, no significant changes
were noted in total calorie, fat, carbohydrate, protein, or sodium intake (p>0.05). No adverse
events occurred in any of the intervention groups.
At baseline, participants were 58 ±7 years old, 61% women, and had a body mass index of
32.4 ±5.2 kg/m
2
. Baseline resting systolic blood pressure was 131 ±13 and diastolic blood
pressure was 81 ±9 mmHg (Table 1).
Table 2 presents the data on the primary outcome variables. Following 8 weeks of exercise,
the combination group reduced peripheral and central diastolic blood pressure -4 mmHg
[95% CI: -6, -1] and -4 mmHg [95% CI: -7, -2], respectively. No significant improvements
were observed in peripheral or central systolic blood pressure in any group. However, the aero-
bic and combination groups both showed a reduction in resting heart rate of -2 bpm [95% CI:
-5, 1], which were significantly different from the control group (p<0.02).
Secondary outcomes of body composition, fitness, strength, and lipid profile are summa-
rized in Table 3. Aerobic training yielded the greatest benefit in body composition with reduc-
tions in BMI (-0.3 kg/m
2
[95% CI: -0.7, 0.0]), weight (-1.0 kg [95% CI: -1.9, -0.1]) and fat mass
(-0.9 kg [95% CI: -1.5, -0.2]). The resistance training group decreased waist circumference by
-1.7 cm [95% CI: -3.3, -0.1] while the combination group increased both lean body mass (0.8
kg [95% CI: 0.1, 1.5]) and weight (0.9 kg [95% CI: 0.00, 1.8]). Improvements in both cardiore-
spiratory fitness and muscular strength were seen in the combined training group, with
expected training benefits in aerobic and resistance training only. Cardiorespiratory fitness
was increased in the aerobic training group and combination group by 7.7 ml/kg/min [95%
CI: 3.9, 11.5] and 4.9 ml/kg/min [95% CI: 1.1, 8.7], respectively. However, no significant
changes were observed in either the resistance or control group. Lower body muscular strength
increased significantly in both the resistance (13 kg [95% CI: 4, 23]) and combination training
groups (11 kg [95% CI: 2, 20]) in comparison with the control group. Upper body muscular
strength increased in all exercise groups. Minimal changes occurred in fasting glucose and the
lipid profile following training. The resistance training group reduced triglycerides (-26 mg/dL
[95% CI: -47, -5]), as did the control group (-22 mg/dL [95% CI: -43, -1]).
Following the exercise intervention, the composite cardiovascular disease risk score indi-
cated a slight reduction, although not significant, in the aerobic (-0.34 [95% CI: -1.46, 0.77]),
resistance (-0.10 [95% CI: -1.25, 1.06]), and combination (-0.78 [95% CI: -1.89, 0.34]) training
groups and increase in the control group (0.95 [95% CI: -0.20, 2.10]). In comparison, the
reduction for the combination group was different from the control group (p = 0.04). We
found similar results in other composite risk factor scores based on different CVD risk factors.
Discussion
A specific goal of this study was to ensure that the total exercise time was consistent across
exercise groups to be more applicable to the general population and help determine the effec-
tiveness of each intervention style. The primary finding of this study was that only combined
training provided significant changes in blood pressure, with reductions in diastolic pressure.
Although participants in the aerobic and resistance training groups did receive benefit from
Exercise training and cardiovascular disease risk factors
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exercise training in other aspects of cardiovascular health (i.e. body composition), the com-
bined group experienced more cumulative benefits across all cardiovascular outcomes as indi-
cated by the composite score. Despite aerobic exercise having the most well-known health
benefits, this study supports the 2008 Physical Activity Guidelines recommendation of
Fig 1. Participant flow chart.
https://doi.org/10.1371/journal.pone.0210292.g001
Table 1. Baseline participant characteristics
a
.
All Aerobic Resistance Combination Control
N 69 17 17 18 17
Age, years 58 (7) 58 (7) 57 (9) 58 (7) 58 (6)
Women, n (%) 42 (61%) 10 (59%) 10 (59%) 11 (61%) 11 (65%)
Post-Menopausal, n (%) 35 (83%) 9 (90%) 7 (70%) 9 (82%) 10 (91%)
Race/ethnicity
White, n (%) 64 (93%) 16 (94%) 16 (94%) 16 (89%) 16 (94%)
Non-White, n (%) 5 (7%) 1 (6%) 1 (6%) 2 (11%) 1 (6%)
Body Composition
BMI, kg/m
2
32.4 (5.2) 32.5 (5.9) 33.1 (5.9) 31.9 (5.5) 32.4 (3.7)
Weight, kg 94.5 (19.0) 97.1 (20.7) 95.8 (21.2) 93.6 (18.9) 91.4 (16.0)
Waist Circumference, cm 105 (13) 103 (14) 106 (17) 104 (13) 106 (10)
Lean Body Mass, kg 56.9 (13.2) 59.2 (13.4) 58.2 (13.9) 55.9 (14.0) 54.2 (12.0)
Fat Mass, kg 38.3 (11.4) 38.6 (13.0) 38.3 (12.6) 38.5 (12.5) 37.8 (7.3)
Body Fat Percentage, % 40.1 (8.1) 39.1 (8.6) 39.5 (8.0) 40.6 (10.0) 41.4 (5.7)
Resting Hemodynamics
Resting Heart Rate, bpm 69 (9) 67 (10) 70 (10) 66 (7) 72 (10)
Peripheral SBP, mmHg 131 (13) 131 (10) 131 (14) 131 (16) 129 (12)
Peripheral DBP, mmHg 81 (9) 81 (10) 81 (11) 81 (10) 80 (8)
Central SBP, mmHg 120 (11) 120 (10) 122 (11) 121 (13) 119 (12)
Central DBP, mmHg 82 (9) 82 (10) 82 (11) 82 (9) 82 (7)
VO
2
max, ml/kg/min 30.6 (9.3) 31.1 (9.5) 29.9 (8.9) 31.4 (11.4) 29.9 (7.6)
Lower Body 1 RM, kg 123 (47)�122 (44) 136 (56) 111 (43) 123 (44)�
Upper Body 1 RM, kg 44 (21) 46 (23) 45 (21) 42 (20) 45 (23)
Fasting Blood Lipids and Glucose
Glucose, mg/dL 98 (8)�97 (8) 102 (8)�98 (8) 96 (6)
Triglycerides, mg/dL 162 (73) 151 (68) 167 (93) 146 (67) 184 (60)
HDL Cholesterol, mg/dL 53 (13)�55 (13) 49 (12) 52 (15)�54 (13)
LDL Cholesterol, mg/dL 130 (32)�134 (28) 121 (33)�130 (37) 133 (28)
Total Cholesterol, mg/dL 214 (37) 219 (26) 200 (33) 215 (47) 223 (36)
Diet (n = 64) (n = 15) (n = 15) (n = 18) (n = 16)
Total Intake, kcal 1882 (473) 1966 (582) 1857 (484) 1842 (465) 1871 (387)
Fat, g 73 (21) 75 (20) 68 (20) 69 (22) 78 (22)
Protein, g 79 (22) 77 (21) 80 (24) 80 (26) 79 (16)
Carbohydrates, g 229 (76) 250 (101) 230 (66) 228 (67) 210 (66)
Sodium, mg 2952 (1024) 2928 (1036) 2821 (1073) 2959 (1132) 3091 (916)
BMI: body mass index; DBP: diastolic blood pressure; HDL: high-density lipoprotein cholesterol; LDL: low-density lipoprotein cholesterol; RM: repetition maximum;
SBP: systolic blood pressure
a
:Data presented as mean (SD) for continuous variables or number of participants (%) for categorical variables
�: Missing one data point
https://doi.org/10.1371/journal.pone.0210292.t001
Exercise training and cardiovascular disease risk factors
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combination training and suggests individuals may receive greater and more complete CVD
health benefits by performing both aerobic and resistance exercise.
Our training intervention was effective as we observed training-induced adaptations com-
monly reported after aerobic and resistance training: aerobic training led to significant
increases in cardiorespiratory fitness and resistance training led to significant increases in
muscular strength. Both aerobic and combination training had significant increases in cardio-
respiratory fitness in this study, and the aerobic group had a larger increase in cardiorespira-
tory fitness than the combination group, although not statistically significant (effect
size = 0.34). However, it is important to note that only the combined training group experi-
enced significant benefits in both cardiorespiratory fitness and muscular strength in this study.
While each exercise intervention elicited the expected changes in fitness and strength, the pri-
mary outcome of this study focused on blood pressure and CVD risk factors.
Our exercise intervention did not result in systolic blood pressure reductions. Meta-analy-
ses and earlier studies have reported decreases in systolic blood pressure following aerobic or
resistance exercise training alone or in combination [17,29–32]. This contradiction may reflect
that most exercise interventions that elicit reductions in blood pressure have been at least 12
weeks long [30,33–35]. This could indicate that an 8-week intervention is not long enough to
Table 2. Baseline, follow-up, and changes in resting hemodynamics�.
Mean (SE) Mean (95% CI)
Intervention
Group
n Baseline Value Follow-up Value Within-Group Changes Between-Group Comparison vs. Control
Group
P-Value vs. Control Group
Peripheral Systolic Blood Pressure
Aerobic 17 131 (3) 131 (3) 0 (-4, 4) 1 (-5, 7) 0.72
Resistance 17 131 (3) 130 (3) -1 (-5, 3) 0 (-6, 5) 0.95
Combination 18 131 (3) 131 (3) 0 (-4, 4) 1 (-5, 6) 0.74
Control 17 129 (3) 129 (3) -1 (-5, 3) -
Peripheral Diastolic Blood Pressure
Aerobic 17 81 (2) 79 (2) -2 (-4, 0) -2 (-6, 1) 0.20
Resistance 17 80 (2) 80 (2) 0 (-2, 3) 0 (-4, 3) 0.91
Combination 18 81 (2) 77 (2) -4 (-6, -1) -4 (-7, 0) 0.04
Control 17 80 (2) 80 (2) 0 (-2, 3) -
Central Systolic Blood Pressure
Aerobic 17 120 (3) 119 (3) -1 (-4, 3) 0 (-4, 5) 0.88
Resistance 17 122 (3) 119 (3) -2 (-6, 1) -1 (-6, 4) 0.62
Combination 18 121 (3) 120 (3) -1 (-4, 3) 0 (-4, 5) 0.88
Control 17 119 (3) 118 (3) -1 (-4, 3) -
Central Diastolic Blood Pressure
Aerobic 17 82 (2) 79 (2) -2 (-5, 0) -2 (-5, 2) 0.39
Resistance 17 81 (2) 81 (2) 0 (-3, 2) 1 (-3, 4) 0.66
Combination 18 82 (2) 78 (2) -4 (-7, -2) -3 (-7, 0) 0.05
Control 17 82 (2) 81 (2) -1 (-3, 2) -
Resting Heart Rate
Aerobic 17 67 (2) 65 (2) -2 (-5, 1) -5 (-9, -1) 0.01
Resistance 17 69 (2) 72 (2) 2 (-1, 5) 0 (-4, 4) 0.82
Combination 18 66 (2) 64 (2) -2 (-5, 1) -5 (-9, 1) 0.02
Control 17 73 (2) 74 (2) 2 (-1, 5) -
�All values adjusted for age, sex, and baseline value of each hemodynamic outcome measure.
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Exercise training and cardiovascular disease risk factors
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detect the expected blood pressure responses to exercise in this specific population. Addition-
ally, participants qualified for the study based on orientation screening blood pressures, how-
ever, during the baseline visit 15 participants had a blood pressure <120/80. With normal
baseline blood pressure, reductions with exercise are less likely to be detected [17] and could
be another potential explanation to our results, although these participants were equally spread
throughout each intervention group. Despite no changes in systolic blood pressure, significant
reductions in diastolic blood pressure were seen with combination training.
Despite minimal changes in blood pressure, these data contribute to a growing body of lit-
erature. A recent meta-analysis was performed on randomized controlled trials looking at
resistance training only in pre- and hypertensive individuals [12]. Only 5 studies were avail-
able, in which 4 had a population over the age of 60 years. Although many trials have been per-
formed with aerobic training in this population, this stresses the importance of performing
well-controlled resistance and combination exercise interventions in a middle-aged population
with elevated risk factors without overt disease.
Exercise in conjunction with changes in body composition have previously shown benefits
for blood pressure reduction and other CVD risk factors [36]. In regards to body composition,
the aerobic training group had the most significant improvements with reductions in BMI,
weight, fat mass, and body fat percentage. A recent meta-analysis of randomized controlled tri-
als comparing aerobic, resistance, and combination training found aerobic training resulted in
greater fat mass reductions than resistance training [37]. Although not significant, all training
groups had a reduction in body fat percentage, which lends support to exercise training as an
Table 3. Changes in body composition, cardiorespiratory fitness, muscular strength, blood glucose and lipids�.
Characteristics Aerobic Resistance Combination Control
Body Composition
BMI, kg/m
2
-0.3 (-0.7, 0.0)
e
-0.1 (-0.5, 0.2) 0.2 (-0.1, 0.6) 0.0 (-0.3, 0.4)
Weight, kg -1.0 (-1.9, -0.1)
e
-0.2 (-1.1, 0.7) 0.9 (0.0, 1.8) 0.1 (-0.8, 1.0)
Waist Circumference, cm 0.4 (-1.2, 2.0) -1.7 (-3.3, -0.1)
ce
0.9 (-0.7, 2.5) 0.5 (-1.2, 2.1)
Lean Body Mass, kg -0.3 (-1.0, 0.5) 0.1 (-0.6, 0.9) 0.8 (0.1, 1.5)
bc
-0.2 (-0.9, 0.6)
Fat Mass, kg -0.9 (-1.5, -0.2)
b
-0.3 (-1.0, 0.3) -0.1 (-0.7, 0.5) 0.2 (-0.5, 0.8)
Body Fat, % -0.5 (-1.1, 0.0) -0.2 (-0.8, 0.4) -0.5 (-1.0, 0.1)
b
0.2 (-0.4, 0.8)
Cardiorespiratory Fitness and Muscular Strength
VO
2
max, ml/kg/min 7.7 (3.9, 11.5)
bd
1.5 (-2.4, 5.4) 4.9 (1.1, 8.7) 1.9 (-1.8, 5.8)
Lower Body 1 RM, kg -1 (-10, 8) 13 (4, 23)
c
11 (2, 20)
c
2 (-7, 12)
Upper Body 1 RM, kg 4 (2, 6) 4 (2, 6) 4 (3, 6) 2 (0, 4)
Blood Glucose and Lipids
Glucose, mg/dL 0 (3, 3) -1 (-4, 2) -2 (-4, 1) 2 (-1, 5)
Triglycerides, mg/dL -11 (-32, 10) -26 (-47, -5) 3 (-17, 24) -22 (-43, -1)
HDL Cholesterol, mg/dL 0 (-2, 2) 0 (-2, 3) -2 (-4, 0) -2 (-4, 1)
LDL Cholesterol, mg/dL -1 (-9, 6) -1 (-9, 7) 2 (-6, 9) 3 (-4, 11)
Total Cholesterol, mg/dL -4 (-12, 5) -6 (-15, 2) -3 (-11, 5) -3 (-11, 6)
BMI, body mass index; HDL, high-density lipoprotein; LDL, low-density lipoprotein; RM, repetition maximum�All data presented as mean (95% confidence interval)
and adjusted for age, sex, and baseline value of each outcome measure
a
Different from all other groups, p<0.05
b
Different from control group, p<0.05
c
Different from aerobic training group, p<0.05
d
Different from resistance training group, p<0.05
e
Different from combination training group, p<0.05
https://doi.org/10.1371/journal.pone.0210292.t003
Exercise training and cardiovascular disease risk factors
PLOS ONE | https://doi.org/10.1371/journal.pone.0210292 January 7, 2019 10 / 14
effective intervention for healthy weight management. Combination training increased weight
slightly but elicited beneficial changes in body composition (increase in lean body mass). Over-
all, training-induced changes in fasting blood lipids and glucose were small and did not vary
between training and control groups. It was not surprising that fasted lipids and glucose were
unaltered by exercise training considering all groups were within normal ranges at baseline.
The primary outcome of our paper was blood pressure reduction, however, the study of a
single CVD risk factor does not fully elucidate the cumulative benefit of exercise on multiple
aspects of CVD risk studied, such as blood pressure, body composition, fitness, strength, and
metabolism. Furthermore, individuals who do not show improvement in one CVD risk factor
may show improvements in other CVD risk factors. One way to assess overall risk is to create
a composite score using the sum of standardized scores [38,39]. Our composite score sug-
gested that combination training elicits greater overall improvements in CVD risk factors than
the control group. This provides support for the prescription of combination training for the
greatest overall benefits from exercise training in middle-aged adults with elevated CVD risk.
Strengths of this study include the randomization that ensured participants were compara-
ble at baseline in major confounding factors (e.g., age, sex), orientation sessions to minimize
potential drop-out that led to high attendance and adherence, intention-to-treat analysis to
include all participants randomized at baseline, and participants at high risk for developing
CVD. Additionally, unlike previous studies [25,40], all exercise sessions had equal training
time with objective verification of the amount and intensity of exercise being completed.
Objective measurement of all exercises in this study eliminated the possibility of over- or
under-reporting. Furthermore, the exercise prescriptions were well tolerated by sedentary,
overweight/obese individuals, making them easily obtainable by a more general population.
Lastly, participants wore a pedometer throughout the intervention period to minimize the
uncertainty about changes in physical activity outside the intervention, commonly seen in
other studies.
A randomized clinical trial is not without its limitations. One limitation comes from cardio-
respiratory fitness being estimated using a submaximal treadmill test instead of a maximal
effort. Although these values may be overestimated at baseline and with the change following
training, the consistency in measurement technique still allows for a comparison to be made
between groups and with training. Our control group was also not a true non-treatment group
since they received the lifestyle educational session and information regarding diet prior to
starting. Furthermore, although the reported steps and diet did not change significantly
throughout the study, volunteers for an exercise intervention tend to be a motivated group.
Thus, subtle lifestyle changes that could not be accounted for in this study may have contrib-
uted to our findings.
Conclusion
Among individuals at high risk of developing CVD with an elevated blood pressure or hyper-
tension, a combination of aerobic and resistance exercise training resulted in improved dia-
stolic blood pressure, increased lean body mass, and increased strength and cardiorespiratory
fitness, even though the exercise intervention was only 8 weeks long. Moreover, these data sug-
gest that combination training may be of better value than either aerobic or resistance training
alone, as it appeared to have the most beneficial effect on the composite of CVD risk factors.
However, further studies with a larger sample size and longer intervention is clearly warranted
on the overall cardiovascular benefits of different types and combinations of exercise. Cumula-
tively our data suggest that concurrent aerobic and resistance training may be a more potent
Exercise training and cardiovascular disease risk factors
PLOS ONE | https://doi.org/10.1371/journal.pone.0210292 January 7, 2019 11 / 14
means to improve CVD risk factor burden among at-risk middle-aged adults than aerobic or
resistance exercise alone.
Supporting information
S1 CONSORT Checklist.
(DOC)
S1 Protocol. Institutional Review Board approved protocol.
(PDF)
Author Contributions
Conceptualization: Duck-chul Lee.
Formal analysis: Elizabeth C. Schroeder.
Funding acquisition: Duck-chul Lee.
Investigation: Elizabeth C. Schroeder, Duck-chul Lee.
Methodology: Duck-chul Lee.
Project administration: Duck-chul Lee.
Supervision: Warren D. Franke, Rick L. Sharp, Duck-chul Lee.
Writing – original draft: Elizabeth C. Schroeder.
Writing – review & editing: Warren D. Franke, Rick L. Sharp, Duck-chul Lee.
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