Introduction: Menstrual cycle is characterized by an intense activity of endogenous sex hormones. Autonomic nervous system (ANS) maintains the internal milieu of the body. Among the various organ systems that are influenced by the ANS, the cardiovascular system has a major role in the maintenance of homeostasis. Internal and external influences such as physical activity, food intake, pregnancy, menstruation are immediately balanced by specific adaptation mechanisms influenced by the ANS. Cyclical phases in menstrual cycle bring about changes in the stress levels which has a major influence on cardiovascular derangements which can be best studied by HRV.

Aim of the study: To study the effects of different phases of menstrual cycle on short-term Heart rate variability in young adult women.

Materials and Methods: 126 female students of age group 17-22 years have been included in the study from 2016-2017. A detailed questionnaire regarding their menstrual history was taken. After 5 minutes of supine rest, a five-minutes lead II ECG was recorded and digitized @ 256 Hz sampling rate and a vertical resolution of 10bits by NVQUIRE© software and two-channel digital polygraph hardware by INCO, Ambala. Throughout the procedure Taskforce recommendations for HRV was followed.

Results: As expected, an increased sympathetic tone and decreased parasympathetic tone was found in the luteal phase when compared to the follicular phase, as shown by decreased RMSSD and HF indices and increased low-frequency (LF) values (p= 0.05).

Conclusion: From the study, it can be concluded that exists a sympathovagal imbalance which is depicted by increased sympathetic activity in luteal phase than proliferative phase, and vice versa in the proliferative phase.

Keywords: Menstrual Phases; Sympatho-Vagal Imbalance; Parasympathetic Activity; HRV.