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Journal of Exercise Physiologyonline
February 2014
Volume 17 Number 1
Editor-in-Chief
Official Research Journal of
Tommy
the American
Boone, PhD,
Society
MBA
of
Review
Board
Exercise
Physiologists
Todd Astorino, PhD
Julien Baker,
ISSN 1097-9751
PhD
Steve Brock, PhD
Lance Dalleck, PhD
Eric Goulet, PhD
Robert Gotshall, PhD
Alexander Hutchison, PhD
M. Knight-Maloney, PhD
Len Kravitz, PhD
James Laskin, PhD
Yit Aun Lim, PhD
Lonnie Lowery, PhD
Derek Marks, PhD
Cristine Mermier, PhD
Robert Robergs, PhD
Chantal Vella, PhD
Dale Wagner, PhD
Frank Wyatt, PhD
Ben Zhou, PhD
Official Research Journal
of the American Society of
Exercise Physiologists
ISSN 1097-9751
JEPonline
Effects of Abdominal Exercises in the Blood Pressure
and Autonomic Indexes in Healthy Young Adults
Raphael M. Cunha1, Raphael G. Parente1, Paulo J.D.C. Jaime1,
Mayara C.C. Souza1, Ademar A. Soares Júnior1, Tiago P. Oliveira2,
Daniel Umpierre3
¹Exercise Physiology Laboratory (LAFEX /ESEFFEGO) UEG/Brazil,
²Laboratory of Motor Assessment (LAM / UFJF) – UFJF/Brazil,
³Exercise Pathophysiology Research Laboratory – UFRGS/Brazil
ABSTRACT
Cunha RM, Parente RG, Jaime PJDC, Souza MCC, Júnior AAS,
Oliveira TP, Umpierre D. Effects of Abdominal Exercises in the Blood
Pressure and Autonomic Indexes in Healthy Young Adults. JEPonline
2014;17(1):40-49. The purpose of the present study was to compare
the blood pressure (BP) as well as the autonomic responses during
different types of abdominal exercises in 30 subjects (age 18 to 25 yrs
of age) who performed an exercise session consisting of 3 types of
abdominal exercises (straight partial sit-up - SPSU, oblique partial situp – OPSU, and lying hip flexion - LHF), 3 sets, 15 to 20 repetitions,
and a control session with the identical experimental procedures but
without exercise. Brachial BP was measured before, during, and after
intervention at 5, 10, and 20 min. Heart rate variability (HRV) was
assessed at baseline, during abdominal exercises, and in the postintervention periods. Compared with baseline, systolic BP increased
immediately after the SPSU, OPSU, and LHF exercises (P<0.001).
Systolic BP and diastolic BP were not altered during the control
session. In both sessions, BP was not affected in the post-intervention
periods. In comparison with the control session, systolic BP increased
7.6%, 5.8%, and 7.6% after the SPSU, OPSU, and LHF exercises,
respectively (P<0.001). Diastolic BP did not differ between sessions.
After the LHF exercise, HRV was significantly decreased (P<0.05)
when compared to the control session. In healthy subjects, abdominal
exercises at low-to-moderate intensities induced small increases in
BP, which was accompanied by a discrete decrease in HRV.
Key Words: Abdominal Muscles, Blood Pressure, Heart Rate
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INTRODUCTION
Several studies have described the influence of aerobic and resistance exercises on blood pressure
(BP) and autonomic responses (8,9,20,26,28,35). A typical aerobic exercise session, such as 45 min
of cycling at 70% of the maximal heart rate, increases the systolic blood pressure while maintains or
reduces the diastolic blood pressure (14). Underlying the commonly observed increases in heart rate
(HR), the cardiac autonomic responses are also affected by showing significant vagal withdrawal and
up-regulated sympathetic outflow at the sinus node (27).
On the other hand, resistance exercises present mixed muscular efforts that are characterized not
only by the dynamic component of muscle contractions that are similar to the aerobic stimulus, but
also by an isometric component that is especially active whenever heavy loads are used. Depending
on the level of this component, the increase in vascular resistance may be more pronounced, which
may exacerbate the increase in blood pressure during exercise (15,30). Additionally, Heffernan et al.
(11) found greater autonomic distress induced by resistance exercises. They reported greater values
in HR and smaller values in heart rate variability (HRV) after a resistance exercise session that
consisted of 3 sets of 10 repetitions of 10 resistance exercises compared to a 30-min aerobic session
on a cycle ergometer.
While strong abdominal muscles contribute to the support and posture of the body, weak abdominal
muscles are associated with low back pain (34). Given that a large percent of the population has
weak abdominal muscles, it is common to exercise these muscles in exercise programs for both
healthy and clinical settings (12,23,32,33). Previous studies (2,6) have indicated that abdominal
exercises increase blood pressure, which is dramatically increased when the Valsalva maneuver is
performed (6). Considering that patients with cardiovascular diseases such as hypertension and
chronic heart failure experience impairments in autonomic balance (18,22), it would be clinically
useful to determine the cardiac autonomic behavior during commonly used abdominal exercises (1).
Thus, the purpose of the present study was to compare the BP as well as the autonomic responses
during 3 types of different types of abdominal exercises in healthy subjects.
METHODS
Subjects
Thirty subjects (18 to 25 yrs of age) who were not engaged in regular exercise programs were
recruited in this study. None of the subjects had high blood pressure or overt cardiovascular disease.
Exclusion criteria consisted of a body mass index ≥30 kg·m-2, diabetes mellitus, cardiac, renal or
hepatic diseases, orthopedic limitations or any other limitations to perform exercises. The study
protocol was approved by the Institutional Review Board of the General Hospital of Goiania
(Registration Number, 070/11), which conforms to the provisions of the Declaration of Helsinki. All
subjects read and signed the informed consent before participation in the study.
Procedures
This study included 3 visits to the Exercise Physiology Laboratory. On the first day, body mass, body
fat, and height measurements were determined and, then, the subjects were familiarized with the
proper abdominal exercise techniques. On different days, the subjects performed two experimental
protocols in a randomized order that carried out at the same time of the day following a 2-hr fast. The
subjects were requested to not drink alcohol throughout their participation in the phases of the study.
42
Both the exercise session (ES) and the control session (CS) took place in a controlled temperature
environment (22 to 24°C) at least 48 hrs apart. The ES consisted of 3 abdominal exercises performed
on the floor in the supine position without the use of external devices. The 3 exercises consisted of:
(a) straight partial sit-up (SPSU) (6); (b) oblique partial sit-up (OPSU) (6); and (c) lying hip flexion
(LHF) (started out lying on the back with knees and hips flexed at ~90º, flexing the hips to leave the
floor slightly).
The ES consisted of abdominal exercises that are usually prescribed in rehabilitation and conditioning
programs. Abdominal exercises 1 and 3 consisted of 3 sets of 15 repetitions. Movement 2 consisted
of 3 sets of 20 repetitions (with 10 repetitions for each side). One-min intervals were allowed between
the sets and the exercises. The subjects were asked to breathe continuously to avoid the Valsalva
maneuver. In the CS, the subjects were lying down as during the ES but they did not perform the
exercises.
Measurements
An automatic BP device (Omron 705CP®, Omron Healthcare, USA) was used to measure BP, which
were based on the Seventh Report of the Joint National Committee on Prevention, Detection,
Evaluation, and Treatment of High Blood Pressure (5). Baseline (resting) BP was measured after 10
min seated in a chair. Exercise BP was measured after each of the 3 exercises while lying on a
mattress on the floor at 5, 10, and 20 min. Recovery BP was measured while seated in a chair.
Heart rate (HR) was continuously recorded using a HR monitor (Polar, RS 800 CX®, USA). In order
to analyze HR and heart rate variability (HRV), data containing the time series of RR-interval (RRi)
were exported to Matlab software (MathWorks, EUA). Initially, a third-order median filter operation
was applied on RRi time series, where each discrepant value was replaced with the median of the
value as well as the preceding and following values. The first and last values were not filtered by the
median. Then, the filtered signal was divided according to each phase of the protocol (i.e., baseline,
SPSU, OPSU, LHF, and 5-10, 10-15, and 15-20 min of recovery). For each window, the mean HR
and the root mean square of successive differences in RR intervals (RMSSD) were calculated. Since
the HR data were not stationary during the whole experimental sessions, we chose not to perform
HRV analysis in the frequency domain (31).
Statistical Analyses
Values are expressed as mean ± standard error (SE). Data distribution was assessed by the Shapiro
Wilk test. To compare hemodynamic responses during the exercise sessions, a two-way repeated
measures analysis of variance (time and session) was used with the Newman–Keuls method to
identify significant differences. A two-tailed P value of less than 0.05 was considered as statistically
significant.
RESULTS
Although 30 subjects were initially included in the study, 11 did not complete the protocol. For these
subjects, lack of time was indicated as the primary reason for dropping out of the study. The results
therefore represent the data from the remaining 19 subjects (13 women and 6 men). As shown in
Table 1, values for BMI and blood pressure were within the normal range for clinical purposes.
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Table 1. Subject Characteristics.
Variables
Results
Age (yrs)
20.9 ± 2.3
Weight (kg)
60.2 ± 8.8
Height (m)
1.67 ± 0.09
BMI (kg·m-2)
21.5 ± 2.1
Body Fat (%)
21.8 ± 8.6
SBP at Rest (mmHg)
108 ± 10.5
DBP at Rest (mmHg)
67 ± 6.4
Values expressed as mean ± standard error.
In comparison with the ES baseline SBP of 110 mmHg, it increased 5.5%, 4.2%, and 7.3% after the
SPSU, OPSU, and LHF abdominal exercises, respectively (P<0.001). During the recovery, the SBP
responses were not significantly different from the ES baseline. In the CS, SBP did not differ
significantly throughout the protocols when compared with baseline values. After the CS intervention,
the SBP responses were not significantly different from the baseline. In comparison with the CS, SBP
increased 7.6%, 5.8%, 7.6% during the SPSU, OPSU, and LHF exercises, respectively (P<0.001).
Additionally, SBP was similar between both sessions at the post-intervention time points (recovery)
(Figure 1). For the DBP responses, ES did not differ from CS throughout the protocols (Figure 2).
Figure 1. Systolic Blood Pressure Responses throughout the
Exercise and Control Session.
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Figure 2. Diastolic Blood Pressure Responses throughout the
Exercise and Control Session.
Compared with baseline, the subjects’ HR responses were not significantly increased during the
SPSU and OPSU exercises. However, the LHF exercise resulted in a significant increase of 6.7% in
HR the baseline (P = 0.03). During the recovery phase of the ES exercise, the HR values were similar
to the baseline at 5 min. When compared to the CS, HR during the ES was significantly increased
during the 3 abdominal exercises. During the recovery, HR was not significantly different between the
sessions (Figure 3).
Figure 3. Heart Rate Responses throughout the Exercise and
Control Session.
Figure 4 shows the RMSSD index during the experimental sessions. The RMSSD values of SPSU
and OPSU exercises did not differ significantly from the baseline values or between sessions.
However, during the LHF exercise, the RMSSD was significantly decreased compared with baseline
and to the CS. During the recovery period, the RMSSD values were similar to baseline and also
between sessions.
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Figure 4. Heart Rate Variability Responses throughout the Exercise
and Control Session.
DISCUSSION
The present study indicates that common types of abdominal exercises performed at low-to-moderate
intensity resulted in relatively small increases in SBP, HR, and the RMSSD index. Although the
subjects’ SBP response increased significantly during the exercises, the response was expected
given the increased hemodynamic demand caused by the exercise. During the recovery, the values
returned to baseline values. The DBP did not change throughout the different conditions of the study.
Although previous studies have assessed blood pressure (13,15,24) and autonomic responses
(10,11) during acute and chronic resistance training, there are only a few studies (2,6,25) that have
assessed the cardiovascular responses during specific resistance exercises used for conditioning and
rehabilitation purposes (2,6,25). Our data show that the increase in SBP was small, and it did not
differ across the abdominal exercise type. This finding is in agreement with a previous study (6) with
normotensive adults who performed 3 abdominal exercises with and without breath holding. Finnoff
and colleagues (6) did not present SBP differences in abdominal exercises carried out without breath
holding. This was also the case with Rao and Bellare (25) who reported on 21 females following
muscular exercises for abdominal wall strengthening with similar increases in SBP after two different
abdominal exercises. In contrast, Boone and Johns (2) evaluated the BP response after inversion
abdominal exercise. They reported a significantly greater increase in BP, but comparison to the
present study is made difficult by the specific methodology and position of the inverted subjects.
In disagreement with the previous studies (2,6,25), the present study did not observed significant
changes in DBP values throughout the abdominal exercises. It is likely that two possible mechanisms
are responsible for unexpected response in DBP during the abdominal exercises. First, the isometric
component, which depends on exercise intensity, was insufficient to promote a significant increase in
DBP. The second and more likely mechanism responsible for the DBP response is the fact that the
measurements were performed immediately after each abdominal exercise. A rebound vasodilatation
after each exercise cannot be ruled out (4).
46
Studies (17,26) have shown that a single resistance exercise session may reduce postexercise blood
pressure in normotensive and hypertensive individuals. Since the abdominal exercises did not result
in a significant decrease in blood pressure after the 3-exercise protocols, it is possible that either a
minimum amount of resistance exercises or a routine including different muscle groups is needed to
promote postexercise hypotension. Additionally, traditional resistance training for the upper and lower
limbs increases BP immediately after exercise (7,16,19). Nonetheless, comparisons with abdominal
exercises are limited due to the distinct characteristics (i.e., given the supine position and low-tomoderate efforts).
Regarding the autonomic responses to the abdominal exercises, a small reduction of 0.5 ms (of
RMSSD-logarithmic units) was observed in the vagal-related HRV index RMSSD. This finding
occurred only during the LHF exercise. Interestingly, the small magnitudes in HR and HRV responses
suggest that the acute and immediate effects of a 3-exercise abdominal routine may be safe for
vulnerable populations (including but not limited to cardiac patients). Second, considering that the
significant chronotropic effects appeared only during the 3rd exercise of the exercise protocol (LHF),
it cannot be ruled out that the possible influence of additional exercises may have result in a more
favorable effect on the cardiac autonomic responses. In fact, submaximal and maximal aerobic
sessions and also supramaximal anaerobic and resistance sessions have been observed to produce
a significant autonomic cardiovascular stress that is characterized by a prominent vagal reduction and
increased sympathetic activity (3,11).
Overall, the exercise intensity used throughout the present study is likely the primary reason for the
small changes in autonomic distress. Supporting this assumption, a previous study (29) has shown
that, independently of the session duration, the postexercise HR and HRV dynamics were more
affected after exercise protocols were performed at higher intensities. Other studies (3,21) have also
demonstrated a reduction of HRV after maximal or supramaximal exertion. This reinforces the point
that high exercise intensities may result in more consistent changes in HRV. Taken together, the
present study seems to indicate the exercise prescription for vulnerable population may be started not
only by low exercise intensities, but also by a limited amount of exercise within the same session.
Limitations of the Present Study
There are several limitations to the present study. First, blood pressure was not determined by way of
intra-arterial or beat-by-beat measurements. Although it may affect the accuracy of the data, it is
widely common to use the oscillometry in the clinical practice. Also, it appears to provide very useful
information when the objective is to control blood pressure in different conditions. Second, the HRV
measurements give only partial insight on the cardiac autonomic modulation during the abdominal
exercise. Thus, it is important that the interpretation should be restricted to the type of exercise
intervention used in the present study. It may not represent the neuromodulation in the peripheral
vasculature. Finally, it is also possible that the RMSSD response might have been influenced by the
breathing pattern.
CONCLUSIONS
Abdominal exercises of mild-to-moderate intensity result in significant but small increases in SBP. At
the end of the 3-exercise routine, there was also a decrease in the RMSSD index from HRV. The
latter finding indicates a reduction in the subjects’ vagal tone. Collectively, while the present results
suggest that the abdominal exercise protocol may be used in rehabilitation programs, it is important to
further evaluate the exercises when it comes to different clinical considerations.
47
ACKNOWLEDGMENTS
The authors thank Rhenan Bartels Ferreira for his support in statistical analyses. This work was
supported in part by grants from FAPEG, Goiás, Brazil.
Address for correspondence: Raphael Martins Cunha. Exercise Physiology Laboratory - LAFEX
/ESEFFEGO. State University of Goiás. Av. Anhanguera, n.1420, Vila Nova CEP: 74.705-010,
Goiânia- GO, Brasil, Email: prof.raphaelcunha@gmail.com
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