Birth control pills have no impact on BP during exercise: study
New Delhi, 19 November 2024: Women sports persons could now relax. Certain oral contraceptives are known to increase the resting blood pressure. However, their impact on blood pressure during large muscle exercises like cycling or running was not well-understood. In addition, research so far has been equivocal on whether hormonal fluctuations during the menstrual cycle influenced blood pressure.
A new study by a team of researchers from Indian Institute of Technology (IIT) – Madras and University of Minnesota, U.S.A bridges the knowledge gap. The team has found that that neither oral contraceptive use nor general fluctuations in endogenous ovarian hormones like estrogens in young women (20-25 years of age), influence blood pressure with lower body exercise and the activation of skeletal muscle sensory neurons, which are known to contribute to exaggerated blood pressure responses in people with cardiovascular diseases.
Exercise generally increases blood pressure due to increased sympathetic nerve activity from skeletal muscle sensory neurons known as ‘Exercise Pressor Reflex’ (EPR). The EPR results in an increase in blood flow from the heart to the skeletal muscle to meet the needs of the muscle. The EPR is known to be greater in males compared with premenopausal females and is also known to be exaggerated in people with cardiovascular disease. Estrogens, in turn, are cardioprotective. They reduce sympathetic nerve activity and increase blood flow to the skeletal muscle via nitric oxide bioavailability.
The researchers expected that women would have lower EPR during the ovulation phase of their menstrual cycle, compared with the early part of the first phase of the menstrual cycle. That was because the level of estradiol, which is a type of estrogen, peaks during the ovulation phase. Likewise they expected some impact of contraceptive use on blood pressure since it results in low serum estradiol levels. However, their study showed that regardless of the phase of the menstrual cycle or oral contraceptive use, the EPR remain unchanged in the women.
The lead investigators of this research included Dr. Manda Keller Ross and Mr. Miguel Anselmo from the University of Minnesota and Dr. Ninitha A.J., Assistant Professor, Department of Biotechnology, IIT Madras. Dr. Ninitha AJ. received support through the Science and Engineering Research Board’s ‘Core Research’ Grant while Prof. Manda Keller Ross was supported by National Institutes of Health (NIH), U.S.
Elaborating on their study, Dr. Ninitha said, the findings of this study have wide application and are of importance since oral contraceptives are taken by women to not only prevent pregnancy, but also reduce acne, menstrual cramps, and risk of ovarian cysts.
Dr. Manda Keller Ross, said that the next step of their work would be to determine if the EPR is a contributing factor to the cardiovascular risk in menopausal females. “We have little information on how the EPR changes in women across the life span. Menopause, the cessation of hormone production in the ovaries, occurs at around 50 years old and cardiovascular risk increases in women throughout and after the menopause transition”.
The team has published their findings in the science journal American Journal of Physiology – Regulatory, Integrative and Comparative Physiology.
