Duration of the Hemodynamic Effects of 6 Weeks Repeated Moderate

Aerobic Exercise after Its Cessation

Midori Tanaka

1 a

, Motoaki Sugawara

, Yasuo Ogasawara

, Tadafumi Izumi

Kiyomi Niki

and Fumihiko Kajiya

Faculty of Health Care Sciences, Himeji Dokkyo University, Himeji, Japan

Department of Medical Engineering, Kawasaki University of Medical Welfare, Kurashiki, Japan

Biomedical Engineering Department, Tokyo City University, Tokyo, Japan

Keywords: Moderate-intensity Exercise, Cardiopulmonary Exercise Test, Anaerobic Threshold, Respiratory

Compensation, Cardiac Contractility.

Abstract: Purpose: We investigated changes in hemodynamic parameters at one-week intervals for 6 weeks after the

cessation of the aerobic exercise. Methods: A total of 20 young healthy volunteers were recruited. Using

ultrasonic diagnostic equipment, we measured wave intensity (WI) in the carotid artery. The maximum value

of WI during a cardiac cycle (W

) increases with an increase in Peak dP/dt. The exercise sessions were 30

min in duration on the bicycle ergometer. Subjects were asked to make an effort to maintain the heart rate

during the session at anaerobic threshold (AT) point determined during the pre-exercise cardiopulmonary

exercise testing (CPET). Exercise sessions were conducted three times per week over a period of 6 weeks,

and then stopped. After the cessation of the exercise sessions, WI was measured during CPET at one-week

intervals for six weeks. Results: The work rate (WR) at AT point and at RC point, V

at RC point increased

and remained increased significantly up to 2 weeks after the cessation of the exercise. Oxygen consumption

) at AT point also increased, but remained increased significantly only up to 1 week after. RC point W

increased and remained increased significantly up to 1 week after.

1 INTRODUCTION

Aerobic exercise has been reported to be one of the

most effective methods to keep one’s health (Racil et

al., 2016) (Ozaki et al., 2015) and to help prevent

cardiovascular disease (Pantelic et al., 2013). Li J et

al. (Li and Siegrist, 2012) reported that high level of

leisure time physical activity had a beneficial effect

on cardiovascular health by reducing the overall risk

of incident coronary heart disease (CHD) and stroke

among men and women by 20% to 30%, while

moderate level of occupational physical activity

might reduce 10% to 20% risk of cardiovascular

disease. However, it is not well documented how long

the effects of exercise continue after its cessation. We

investigated changes in hemodynamic parameters at

one-week intervals for six weeks after the cessation

of the aerobic exercise.

https://orcid.org/0000-0002-1730-5594

2 METHOD

2.1 Noninvasive Measurements of

Wave Intensity

Wave intensity (WI) is a novel hemodynamic index,

which is defined as

WI = (dP/dt)·(dU/dt) (1)

at any site of the circulation, where dP/dt and dU/dt

are the derivatives of blood pressure and velocity with

respect to time, respectively. WI was obtained from

the carotid artery using a color Doppler system for

blood velocity measurement combined with an echo-

tracking system for detecting vessel diameter

changes. The vessel diameter changes were

automatically converted to pressure waveforms by

calibrating its peak and minimum values by systolic

and diastolic brachial blood pressures. The WI shows

two sharp positive peaks (Niki et al., 2002). The first

Tanaka, M., Sugawara, M., Ogasawara, Y., Izumi, T., Niki, K. and Kajiya, F.

Duration of the Hemodynamic Effects of 6 Weeks Repeated Moderate Aerobic Exercise after Its Cessation.

DOI: 10.5220/0008073501530156

In Proceedings of the 7th International Conference on Sport Sciences Research and Technology Support (icSPORTS 2019), pages 153-156

ISBN: 978-989-758-383-4

153

peak （W

） appears in early phase of LV ejection

(Figure. 1). The magnitude of W

significantly

correlates with the maximum rate of LV pressure rise

which is a conventional index of contractility (r =

0.74, P < 0.001)(Ohte et al., 2003).

2.2 Cardiopulmonary Exercise Testing

(CPET)

Graded cardiopulmonary exercise test (CPET) was

performed by using a bicycle ergometer combined

with a computerized breath-by-breath expiration gas

analyzer system. The system measured tidal volume,

oxygen concentration and carbon dioxide

concentration, and automatically displayed oxygen

consumption (V

), carbon dioxide production (V

CO2

minute ventilation (V

), V

, V

CO2

, partial

pressure of end-tidal carbon dioxide (PETCO

partial pressure of end-tidal oxygen (PETO

anaerobic threshold (AT), and respiratory

compensation point (RC).

2.3 Subjects

We studied 20 healthy young volunteers (9 men, 11

women, mean age 20.6 ± 0.5 years, age range 19 – 23

years). We obtained informed consent from all the

subjects. The study was approved by the Himeji

Dokkyo University Research Ethics Committee and

conformed with guidelines of the Declaration of

Helsinki.

2.4 Experimental Protocol

The exercise sessions were 30 min in duration on the

bicycle ergometer. Subjects were asked to make an

effort to maintain the heart rate during the session at

anaerobic threshold (AT) point determined during the

pre- exercise CPET.

Bicycle work rate (WR) was quantified in Watts

(W). The initial work rate was 20 W and increased by

20 W every 1 minutes until limitation. The limitation

criteria for the establishment of peak Vo

included a

plateau in the Vo

with increasing WR, attainment of

HR to 158 bpm ((220 bpm ─ age) x 0.8) and

Figure 1: Representative recordings of wave intensity

obtained from the carotid artery of a normal subject. Blood

pressure waveform, blood velocity waveform, wave

intensity waveform, and ECG are shown in order from the

top. The first peak of wave intensity (W1) appears in early

ejection phase.

attainment of fatigue to the maximum, or

impossibility of continuing exercise. Electro-

cardiogram was continuously monitored. The blood

pressure was measured approximately every 30 s.

Exercise sessions were conducted three times per

week over a period of 6 weeks, and then stopped.

After the cessation of the exercise sessions,

measurements were performed during CPET at one-

week intervals for six weeks in the same manner as

the exercise session. We measured W

，Vo

, and

Vco

during CPET, and analyzed at AT point and RC

point.

2.5 Statistical Analysis

The obtained data were presented as mean ± SD.

Repeated measures ANOVA, followed by Bonferroni

test when necessary, was used to evaluate the changes

after the cessation of the exercise. A value of p < 0.05

was considered statistically significant.

Table 1: Baseline data of the subjects.

icSPORTS 2019 - 7th International Conference on Sport Sciences Research and Technology Support

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3 RESULTS

After 6-weeks exercise training, Ps, Pd and HR at AT

and RC point did not change significantly.

However, WR at AT point increased and

remained increased significantly up to after 2 weeks.

at AT point also increased, but remained

increased only up to 1 week after (Figure. 2).

W1 at RC point increased and remained increased

significantly up to after 1 week. WR and Vo

at RC

point increased and remained increased significantly

up to 2 weeks after (Figure. 3).

Figure 2: Changes in indices at anaerobic threshold (AT)

point after the cessation of the 6 weeks exercise. Values are

compared with those before the commencement of the

exercise. mean ± SD.

Figure 3: Changes in indices at Respiratory compensatory

(RC) point after the cessation of the 6 weeks exercise.

Values are compared with those before the commencement

of the exercise. mean ± SD.

4 DISCUSSION

The anaerobic threshold (AT) is an index used for

estimating exercise capacity. During the initial

aerobic phase of CPET, which lasts until 50 – 60% of

max is reached, minute ventilation (VE)

increases linearly with Vo

. This indicates that

aerobically produced Co

in the muscles blood lactate

levels do not change substantially during this phase,

since muscle lactic acid production is minimal

(Takano, 2000).

In this study of 6 weeks exercise, Vo

at AT point

increased and remained increased significantly up to

1 week after the cessation of the exercise. WR at AT

point also increased and remained increased up to 2

weeks after the cessation of the exercise. RC point is

an indicator that exercise intensity has reached the

physiological maximum level to start compensation

for acidosis by increasing Co

excretion. Therefore,

RC point ascent indicates increase in exercise

tolerance. In our study, RC point WR, and RC point

increased by the 6 weeks exercise and remained

increased significantly up to 2 weeks after the

cessation of the exercise. RC point W

(cardiac

contractility index) also increased and remained

increased 1 week after.

5 CONCLUSIONS

In healthy young subjects, W

, WR and Vo

were

increased by intermittent, moderate-intensity aerobic

exercise for 6 weeks. The effects of the exercise

continued up to 2 weeks after its cessation.

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