Changes in cardiac contractility during graded exercise are greater in subjects with smaller body mass index, and greater in men than women: analyses using wave intensity and force–frequency relations
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Introduction and purpose
Estimation of the contractility of the left ventricle during exercise is an important part of the rehabilitation protocol. It is known that cardiac contractility increases with an increase in heart rate. This phenomenon is called the force–frequency relation (FFR). Using wave intensity, we aimed to evaluate FFR noninvasively during graded exercise.
We enrolled 83 healthy subjects. Using ultrasonic diagnostic equipment, we measured wave intensity (WD), which was defined in terms of blood velocity and arterial diameter, in the carotid artery and heart rate (HR) before and during bicycle ergometer exercise. FFRs were constructed by plotting the maximum value of WD (WD1) against HR. We analyzed the variation among FFR responses of individual subjects.
WD1 increased linearly with an increase in HR during exercise. The average slope of the FFR was 1.0 ± 0.5 m/s3 bpm. The slope of FFR decreased with an increase in body mass index (BMI). The slopes of FFRs were steeper in men than women, although there were no differences in BMI between men and women.
The FFR was obtained noninvasively by carotid arterial wave intensity (WD1) and graded exercise. The slope of the FFR decreased with an increase in BMI, and was steeper in men than women.
KeywordsCardiac contractility Echocardiography Graded exercise Force–frequency relation Wave intensity
This work was supported in part by the Grant-in-Aid for Scientific Research (C 16k01570 and C 16H04264) from the Ministry of Education, Culture, Sports, Science and Technology of Japan.
Compliance with ethical standards
All studies involved in this manuscript received approval from the Ethics Committee of Himeji Dokkyo University before study initiation. All subjects provided written informed consent prior to measurements.
Conflict of interest
The authors declare that they have no conflicts of interest.
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