Cardiac Efficiency and Work Performance Variations Across Menstrual Cycle Phases: A Bicycle Ergometric Study in Young Women.

Background Menstrual cycle-related physiological variations represent a complex, multifaceted phenomenon with significant implications for female work performance and cardiovascular function. This study aimed to systematically evaluate the influence of menstrual cycle phases on cardiac efficiency and work performance among young women, utilizing a comprehensive bicycle ergometric assessment methodology. The research sought to quantify physiological variations during mid-follicular and mid-luteal phases, providing nuanced insights into hormonal dynamics and performance metrics. Methodology A prospective observational study was conducted among 100 young women volunteers aged 18-25 years in Chennai, Tamil Nadu, India. Participants underwent standardized bicycle ergometer testing during two distinct menstrual cycle phases: mid-follicular (seventh day) and mid-luteal (21st day). A bicycle ergometer (KH-695, Viva Fitness Company, New Delhi, India) was employed to measure energy expenditure, work performance, and cardiac efficiency. Subjects initially underwent a five-minute resting period, with baseline pulse rate and blood pressure recorded. Participants then performed cycling at a 2 kg resistance for a maximum of five minutes, with pulse rates monitored during post-exercise recovery intervals. Cardiac efficiency was calculated using a comprehensive formula incorporating exercise duration and post-exercise pulse rates, while work done was determined through precise mechanical measurements. Results Statistical analysis revealed significant physiological variations across menstrual cycle phases. Cardiac efficiency demonstrated a remarkable increase from 79.98 (SD ± 17.618) in the mid-follicular phase to 112.58 (SD ± 13.086) in the mid-luteal phase, with 95 out of 100 participants exhibiting enhanced performance (Z-statistic = -8.625, p = 0.000). Total work done similarly showed substantial improvements, increasing from 185.77 (SD ± 35.82) to 242.97 (SD ± 31.275), with 97 observations indicating superior luteal phase performance (Z-statistic = -8.374, p = 0.000). Notably, work done per minute remained consistently stable across both phases, suggesting an intrinsic physiological adaptation mechanism. The Wilcoxon signed-rank test confirmed statistically significant differences in cardiac efficiency and total work done, highlighting the complex interplay between hormonal fluctuations and physiological performance. Conclusions The study demonstrates significant menstrual cycle phase-related variations in cardiac efficiency and work performance, providing crucial insights into female physiological adaptability and underscoring the importance of personalized performance management strategies across different reproductive cycle stages.