International Journal of Clinical Medicine, 2013, 4, 532-538
Published Online December 2013 (
Open Access IJCM
Association of Body Composition and Aerobic Fitness on
Heart Rate Variability and Recovery in Young-Adult
Black Men
Michael R. Esco1, Robert L. Herron2, Stephen J. Carter2, Andrew A. Flatt1
1Human Performance Laboratory, Department of Physical Education and Exercise Science, Auburn University at Montgomery,
Montgomery, USA; 2Exercise Physiology Laboratory, Department of Kinesiology, The University of Alabama, Tuscaloosa, USA.
Received September 19th, 2013; revised October 17th, 2013; accepted November 12th, 2013
Copyright © 2013 Michael R. Esco et al. This is an open access article distributed under the Creative Commons Attribution License,
which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Background: The primary purpose of this investigation was to determine the differences in resting heart rate variability
and heart rate recovery between norm-referenced aerobic fitness groupings, independent of body composition, in Black
men. Additionally, we sought to clarify the independent relationships that heart rate variability and heart rate recovery
displayed with maximal aerobic fitness and selected body composition measures. Methods: Body mass index, waist
circumference, and the sum of skinfold thickness were determined in forty Black men (23 ± 3 years). Each subject as-
sumed a supine position while heart rate variability was analyzed for 5-minute and recorded as normalized high-fre-
quency power and normalized low-frequency power to normalized high frequency ratio. A graded exercise treadmill
protocol was performed to attain maximal aerobic fitness. Heart rate recovery was recorded at 1- and 2-minute of a
cool-down period. Heart rate variability and heart rate recovery were compared across two groups whose maximal
aerobic fitness was either below or above the normative mean value for the age group of men. Results: The results in-
dicated that heart rate variability was higher in the group whose maximal aerobic fitness was above the normative mean
value compared with the lower fit group (p < 0.05), but the differences disappeared when adjusting for body composi-
tion (p > 0.05). Regression analysis revealed that the sum of skinfolds accounted for the variation in normalized high
frequency power (R2 = 0.20, p < 0.05) and normalized low-frequency power to normalized high frequency ratio (R2 =
0.30, p < 0.05), while waist circumference accounted for the variation in heart rate recovery at 2-minute (R2 = 0.20, p <
0.05). Conclusion: The results suggest that heart rate variability and heart rate recovery hold independent relationships
to body composition but not aerobic fitness in young-adult, Black men.
Keywords: Skinfold Thickness; Waist Circumference; Cardiovascular; Autonomic
1. Introduction
Heart rate variability (HRV) and heart rate recovery
(HRR) are two non-invasive measures of cardiovascular-
autonomic modulation [1-4]. HRV represents the auto-
nomic controlled beat-to-beat oscillations that occur in
heart rate, while HRR describes the parasympathetic-
mediated decline in heart rate immediately following
exercise [2,3]. The clinical importance of both markers
stands in their ability to independently predict untoward
cardiac events and early development of cardiovascular
disease [2,4].
Recent evidence has suggested that HRV and HRR
may reflect improved measures of physical fitness through
lifestyle modification, yet the extent of this relationship
remains unclear [5-7]. While several studies have indi-
cated a possible link concerning aerobic fitness and body
composition to HRV and HRR, much of the research
emphasizes the relative importance of aerobic fitness. As
a result, more research is needed to clarify the associa-
tion of body composition with HRV and HRR [5,8-10].
Among the many factors contributing to disease states,
the influence of race may be an important variable often
overlooked. Accordingly, Blacks experience a greater pre-
valence of cardiovascular mortality compared with Whites
[11,12]. Blacks also tend to be less physically active and
have lower levels of aerobic fitness [12-14]. Research
has indicated the existence of biological differences re-
Association of Body Composition and Aerobic Fitness on Heart Rate
Variability and Recovery in Young-Adult Black Men
garding body composition between races [15]. Despite
the apparent health disparities between racial groups,
some investigators have shown greater HRV at rest and
faster HRR following exercise in Blacks compared with
Whites. However, the findings remain equivocal as oth-
ers have presented conflicting data [16-19]. As such, the
inconsistency of these results has led to speculations that
the relationship between physical fitness and cardiac-
autonomic control may be race-dependent.
Furthermore, Esco et al. [10] showed that cardiovas-
cular autonomic modulation is significantly related to
maximal aerobic fitness and body composition. However,
of the independent variables analyzed in the study, the
sum of skinfold thickness appeared to have the strongest
independent relationship with HRV and HRR, compared
with other body composition parameters and maximal
aerobic fitness [10]. Unfortunately, the study analyzed
mostly white men [10]. Therefore, race-specific study in
this area involving only Black men is needed. The results
of such investigation could have important implications
related to lifestyle interventions designed to reduce the
risk of cardiovascular disease in this at-risk and under-
studied group.
The primary purpose of this investigation was to de-
termine if differences in HRV and HRR would be re-
flected by norm-referenced aerobic fitness groupings, in-
dependent of body composition in young-adult Black
men. Additionally, we sought to clarify the independent
relationships that HRV and HRR display with VO2max
and selected body composition measures (e.g. body mass
index [BMI], waist circumference [WC], and the sum of
skinfold thickness [SF]) within the group.
2. Materials and Methods
2.1. Study Sample
Forty young-adult Black men participated in the study
(age = 23 ± 3 years, height = 180.0 ± 9.3 cm, weight =
82.8 ± 11.2 kg). Prior to study involvement, all subjects
completed a health history questionnaire and were as-
sessed to determine if they met inclusion criteria. All
approved subjects were apparently healthy, free from
cardiopulmonary, metabolic, and/or orthopedic impair-
ments. At the time of data collection, all subjects were
not taking any prescription or over-the-counter medica-
tions, each displaying normal blood pressure (i.e. <140/
90 mmHg). Subjects were non-smokers with normal
electrocardiogram (ECG) readings, between the ages of
19 and 29 years, and self-reported race as Non-Hispanic/
Black over three generations. Written informed consent
was obtained from each subject prior to study involve-
ment. All research procedures were approved by the In-
stitutional Review Board for Human Participants.
2.2. Procedures
All data were collected during a single visit to the labo-
ratory. For convenience, each subject selected a 2-hour
time slot on any day to complete the experimental pro-
cedures: from 7:00 AM and 9:00 AM, or from 9:00 AM
and 11:00 AM. Subjects were instructed to avoid strenu-
ous exercise for 24-h prior to the test, consumption of
alcohol or sympathomimetic agents 12 hours before the
test. Additionally, subjects were required not to eat at
least 10-h prior to data collection.
Height was measured with a wall-mounted stadiometer
(SECA, Seca Instruments Ltd,Hamburg, Germany) and
body weight was measured with a digital scale (TANITA
BWB-800A, Tanita Corp, Tokyo, Japan) while the sub-
jects stood erect without shoes. Body mass index (BMI)
was determined as weight in kilograms divided by height
in meters squared (kg·m2). Waist circumference was
measured with a Gulick spring loaded handle (Mabis,
Tokyo, Japan) in accordance with current American Col-
lege of Sports Medicine (ACSM) recommendations [20].
Calibrated skinfold calipers (Harpenden; Baty Interna-
tional, West Sussex, United Kingdom) were used to
measure the skinfold thickness from seven sites including:
pectoralis major, triceps, mid-axillary region, subscapu-
laris, suprailliac crest, abdomen, and thigh. The sum total
of all measurements was recorded to the nearest 0.5 mm.
Additionally, all measurements followed ACSM guide-
lines [20].
Before the maximal exercise test, each subject was in-
structed to lay supine for a 10minutes on an athletic
training table in a dimly lit climate controlled laboratory.
Room temperature and humidity were maintained at ap-
proximately 22.2˚C and 50%, respectively. During this
time, heart rate was assessed via ECG with the electrodes
placed across the subject’s chest in a modified Lead II
arrangement. The electrode leads were connected to a
Biopac MP100 data acquisition system (Goletta, CA,
USA). All variables were stored for offline analysis. The
ECG recordings were visually inspected and any ectopic/
non-sinus beats were removed and replaced by the adja-
cent normal cycle. If three or more ectopic beats were
found within any ECG segment, the reading was ex-
cluded from analysis. The last 5 minute period of the
ECG recording was used for HRV analysis.
The frequency domain analysis of HRV involved
transforming the ECG into a power spectrum via fast
Fourier transformation with a Hanning window by spe-
cialized HRV software (Nevrokard version 11.0.2, Izola,
Slovenia). The areas under the high frequency (0.15 -
0.40 Hz) and low frequency (0.04 - 0.14 Hz) components
of the power spectrum were normalized. Normalized
high frequency (HFnu) was recorded to represent para-
sympathetic influence. Normalized low frequency to
Open Access IJCM
Association of Body Composition and Aerobic Fitness on Heart Rate
Variability and Recovery in Young-Adult Black Men
HFnu ratio (LF:HF) was recorded to represent sym-
pathovagal balance. All HRV analyses were carried out
in accordance with written established HRV guidelines
All subjects completed a maximal graded exercise test
using the Bruce protocol on a treadmill (Full Vision, Inc.,
Carrollton, TX). The concentration of expired oxygen and
carbon dioxide gases were collected at the mouth with a
pneumotach and analyzed using a calibrated Parvo Med-
ics True One® 2400 metabolic cart (Sandy, UT). Maximal
oxygen uptake was determined if two of the following
criteria occurred: a plateau in VO2 (within ± 2 ml·kg1·min1)
despite an increasing work rate; respiratory exchange ratio
>1.15; heart rate within 10 beats of age predicted (220
age) maximum or volitional fatigue. Once VO2max was
achieved, intensity was reduced to a speed of 1.5 mph at
2% grade. HRR was determined as the difference between
HRmax and the heart rate recorded at 1- (HRR1) and
2-minute (HRR2) into recovery.
2.3. Statistical Analysis
Means and standard deviations were determined for all
descriptive variables. The sample size was categorized
into 2 groups based on whether they were below (AFG1,
n = 20) or above (AFG2, n = 20) the value that corre-
sponded to the referenced 50th percentile for VO2max for
college-age men: i.e., 43.9 ml·kg1·min 1 [20].
One-way analysis of variance (ANOVA) procedures
were used to compare HRV (i.e., HFnu and LF:HF) and
HRR (i.e., HRR1 and HRR2) between AFG1 and AFG2.
Follow-up analysis of covariance (ANCOVA) proce-
dures were performed to control for the potential con-
founders of BMI, WC, and SF.
Zero-order correlations were also used to determine
the relationship between the studied variables. To clarify
the influence of VO2max (as a continuous variable), BMI,
WC, and SF on the variation in HFnu, LF:HF, HRR1,
and HRR2, stepwise multiple regression procedures were
used. The level of significance for all statistical tests was
set at p < 0.05 (SPSS/PASW version 18.0, Somers, NY).
3. Results
All participants successfully completed the testing pro-
cedures. Descriptive statistics for the complete sample
are presented in Table 1. Mean values and significant
group differences for VO2max, BMI, WC, SF, HFnu,
LF:HF, HRR1, and HRR2 are also displayed in Tab le 1.
The one-way ANOVA procedures revealed significantly
lower HFnu and significantly higher LF:HF values in
AGF1 compared to AGF2 (p < 0.05, Ta ble 1 ). However,
the one-way ANCOVA procedures showed that the dif-
ferences in HFnu and LF:HF were not present when con-
trolling for BMI (p = 0.22, p = 0.18, respectively), WC (p
= 0.12, p = 0.11, respectively, Table 1), and SF (p = 0.51,
p = 0.58, respectively, Table 1).
Pearson product-moment correlations between all of
the studied variables are shown in Table 2. VO2max did
not correlate with any HRV or HRR parameter (p > 0.05).
BMI and SF were the only anthropometric variables to
significantly correlate with either HFnu or LF:HF (p <
0.05). Significant correlations were not found between
any independent variable and HRR1 (p > 0.05). Only
BMI and WC provided significant correlations with
HRR2 (p < 0.05).
The stepwise regression procedures showed that SF
was the only variable to significantly account for the
Table 1. Means and standard deviations of the studied
variables within each group separately and the entire sam-
AFG1 (n = 20)AFG2 (n = 20) ALL (n = 40)
VO2max 39.13 ± 3.15 50.53 ± 3.88* 44.83 ± 6.75
BMI 26.48 ± 3.70 24.57 ± 2.37 25.55 ± 3.23
WC 73.07 ± 23.1358.80 ± 25.47* 66.12 ± 25.04
SF 82.20 ± 27.3356.65 ± 20.72* 69.75 ± 27.28
HFnu 47.53 ± 6.56 52.25 ± 7.61*† 49.90 ± 7.41
LF:HF 0.83 ± 0.24 0.65 ± 0.27*† 0.74 ± 0.26
HRR1 21.60 ± 6.00 21.60 ± 6.58 21.60 ± 6.22
HRR2 44.45 ± 8.17 43.10 ± 10.26 43.77 ± 9.18
AFG1 = group of subjects with VO2max values below the 50th percentile
normative value for age; AFG2 = group of subjects with VO2max values
above the 50th percentile normative value for age; BMI = body mass index;
WC = waist circumference; SF = sum of skinfold thickness; VO2max =
maximal oxygen consumption; HFnu = normalized high frequency (HF)
power; LF:HF = low frequency power to HF power ratio; HRR1 = heart rate
recovery at 1-minute post-exercise; HRR2 = heart rate recovery at 2-minute
post-exercise. *Significantly different from AFG1 (p < 0.05). The effect for
SFG disappeared when controlling for BMI and SF (each separately).
Table 2. Zero-order correlation coefficients (r) showing the
relationship between the var iables.
HFnu 0.27 0.40 0.22 0.46
LF:HF 0.25 0.45 0.29 0.54
HRR1 0.08 0.13 0.09 0.12
HRR2 0.03 0.37 0.44 0.29
VO2max = maximal oxygen consumption, BMI = body mass index, WC =
waist circumference, SF = sum of skinfold thickness from 7-site, HRR1 =
1-minute heart rate recovery, HRR2 = 2-minute heart rate recovery, HFnu =
Normalized high frequency of heart rate variability, LF:HF = low frequency
to high frequency ratio. Significantly related, p < 0.01.
Open Access IJCM
Association of Body Composition and Aerobic Fitness on Heart Rate
Variability and Recovery in Young-Adult Black Men
variation of HFnu (R2 = 0.21, p < 0.05) and LF:HF (R2 =
0.30, p < 0.05). VO2max, BMI, or WC did not contribute
to the variation in HFnu (p > 0.05) or LF:HF (p > 0.05)
and were not included in the models. Stepwise regression
also revealed that WC was the only variable to signifi-
cantly account for the variation in HRR2 (R2 = 0.20).
VO2max, BMI, or SF did not significantly contribute to the
variation in HFnu (p > 0.05) and were not included in the
4. Discussion
The chronic effects of impaired cardiac-autonomic con-
trol exhibited as either lower HRV or delayed HRR can
indicate the development of heart disease, hypertension,
dyslipidemia, and type 2 diabetes [21,22]. These health
conditions are prevalent at earlier ages in Blacks com-
pared with other races [23-25]. Due to the discrepancies
between races in cardiovascular disease risk factors,
autonomic control and physical fitness [24,26,27] race-
specific studies are needed.
The purpose of this study was to determine whether
referenced aerobic fitness groupings would reflect dif-
ferences in HRV and HRR, independent of selected an-
thropometric markers of body composition, and if the
selected physical fitness parameters (i.e., VO2max, BMI,
WC, and SF] were each significantly associated with the
cardiac-autonomic variables in Black men.
According to the American College of Sports Medi-
cine [20], the 50th percentile for VO2max for the age
group of the current sample is 43.9 ml·kg1·min1. The
two groups were separated below (i.e., AFG1) and above
(i.e., AFG2) this value. Though statistical significance
was not found in HRR between groups, AFG1 had sig-
nificantly lower HFnu and higher LF:HF compared to
AFG2 indicating a less favorable autonomic balance in
AFG1. However, the group differences in the HRV pa-
rameters were not present when markers of body compo-
sition were controlled for. In addition, BMI and SF were
the only variables to be significantly related to HFnu and
LF:HF. Alternatively, BMI and WC were the only vari-
ables to significantly correlate to HRR2. The stepwise
regression procedures demonstrated that SF accounted
for 21% and 30% of the variation in HFnu and LF:HF,
respectively, and that WC accounted for 20% of the va-
riation in HRR2. Therefore, SF seems to be the strongest
predictor of resting HRV, while WC is the strongest pre-
dictor of HRR in Black men. When analyzed as a con-
tinuous variable, the stepwise regression procedures ex-
cluded VO2max as it did not significant relate to any HRV
or HRR parameter.
Previous investigations assessing the influence of
aerobic fitness on cardiovascular-autonomic control have
shown equivocal findings. Researchers suggest that train-
ing-induced bradycardia experienced by endurance ath-
letes is caused by the increased parasympathetic tone
[28]. However, others had claimed that this phenomenon
was due to intrinsic, rather than extrinsic factors [29].
Still, some studies have suggested that there may [5,30]
or may not [31,32] be an independent association be-
tween increases in aerobic fitness and enhanced HRR or
HRV. Furthermore, there does not appear to be a signifi-
cant difference in HRV and HRR between aerobically-
trained and anaerobically-trained athletes [33,34]. As
such, it seems reasonable to propose that other compo-
nents of physical fitness may play a role in enhancing
cardiovascular-autonomic control rather than just in-
creased VO2max.
Body composition is a parameter of physical fitness
that appears to be independently linked to autonomic
activity. Increased adiposity is thought to contribute to
heightened sympathetic nervous activity at rest, while
blunting metabo- and baro-reflex sensitivity during and
following exercise [24,35,36]. Studies have shown that
WC, BMI, and body fat percentage are each negatively
associated with HRV and HRR [9,10,37]. Similar to the
current study, Esco and colleagues [10] showed that SF
explained the greatest variation of HRV and HRR when
analyzed via stepwise regression. However, separating
independent variables from their study, including VO2max,
did not add statistical significance to either model. Inter-
estingly though, the sample consisted of mostly White
men [10].
The novelty of the current investigation highlights the
relationship between selected markers of physical fitness
and cardiovascular-autonomic modulation in Black men.
We believe that this is an important area of research due
to the higher prevalence of cardiac-related disorders in
Blacks, and due to the discrepancies in physical fitness
and cardiovascular autonomic control between races [13,
14,16,18,19]. Similar to other studies [10,18], it appears
that the difference in HRV across groups based on
VO2max in Black men may be due to the fitter subjects
having a healthier body composition profile.
Significant HRR differences were not found between
AGF1 and AGF2. The post-exercise autonomic marker,
HRR2, was significantly and independently related to
WC, but not SF or VO2max. This result is at odds with
previous research conducted by Esco et al. [10] who
showed HRR to be significantly related to SF, but not
WC in mainly White men. Conversely, Gutin et al. [18]
showed that WC had a negative influence on sympa-
thetic-to-parasympathetic balance in Black adolescents,
but not compared to their White counterparts. Interest-
ingly, some studies suggest a higher HRV profile and
faster HRR post-exercise in Blacks compared to Whites,
Open Access IJCM
Association of Body Composition and Aerobic Fitness on Heart Rate
Variability and Recovery in Young-Adult Black Men
despite Blacks having lower levels of cardiovascular fit-
ness and higher rates of obesity [18,38,39]. One way to
interpret these paradoxical findings is that the relation-
ship between body composition, aerobic fitness and car-
diac-autonomic control is race-specific. Nevertheless, the
current findings strengthen the usefulness of simple body
composition measures in predicting cardiovascular dis-
ease risk factors in Black men at any level of aerobic
The age of the current sample should be considered
when interpreting the results, as only apparently healthy,
young adult Black men were analyzed. Aging has been
shown to affect cardiovascular-autonomic control and
physical fitness. More specifically, Blacks have been
shown having a more favorable autonomic profile in
younger years of age [18]. However, these patterns may
become confounded with aging due to the influence and
higher prevalence of obesity or markers of inflammation
in Blacks [18,40,41]. Accordingly, similar investigations
that include older aged subjects and other ethnic/racial
groups are needed to better understand this relationship.
In conclusion, this study provided a direct comparison
of HRV and HRR in young Black men with differing
levels of aerobic fitness. The results of the investigation
suggested higher HRV with a higher level of aerobic
fitness in Black men primarily because of the fitter group
having a superior body composition profile compared to
the lower fit group. Skinfold thickness was the greatest
predictor of resting HRV. Heart rate recovery did not
differ from high fit and low fit groups, but was signifi-
cantly related to WC. The results of this study under-
score the importance of body composition when explain-
ing the relationship between physical fitness and cardio-
vascular-autonomic control in young Black men. Ac-
cording to these results, lifestyle interventions should be
designed to improve aerobic fitness and body composi-
tion to fully enhance cardiovascular-autonomic function
to mitigate risk for an acute cardiac event. Additional
research is needed to further define the relationship be-
tween physical fitness and cardiovascular-autonomic mo-
dulation, thus aiding clinicians to provide appropriate
lifestyle modifications to lower at-risk populations for
cardiovascular disease.
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