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THE EFFECTS OF THE MENSTRUAL CYCLE ON BODY COMPOSITION AND LOWER BODY FLEXIBILITY

Abstract

Bianca A. R. Galletti1, Ashley N. Fox1, Brian Pribble1, Ryan Miller1, Grant Chesbro1, Christopher D. Black, FACSM1, Daniel J. Larson1, & Rebecca D. Larson1

1The University of Oklahoma, Norman, Oklahoma

Regular menstrual cycle phases are known for their hormonal fluctuations during a month, which could influence body composition and muscle connective tissue laxity. Purpose: To investigate differences in lower body flexibility and total body composition across three different menstrual cycle phases: early follicular (EF), ovulation (O), and mid-luteal (L). Methods: 27 participants were separated into 3 groups: 8 female non-contraceptive users (NC), 10 female oral-contraceptive users (OC) and 9 males in the control group (CON). Each visit included flexibility assessments of hip extension/flexion and knee extension/flexion via goniometer of the dominant leg and a Dual-Energy X-Ray Absorptiometry (DXA) scan. Results: CON had significantly less body fat (25.45±4.86%, 32.98±8.97% and 32.5±6.05%, respectively) and higher lean mass (62.79± 7.12kg, 41.16±6.32kg and 40.44±5kg, respectively) than the NC and OC groups across all menstrual cycle phases. There was no significant differences in body composition across different phases, demonstrating an excellent reliability in males and females (ICC > 95%). Hip extension flexibility was significantly higher for NC (22.37±4.34°) compared to OC (14.2±5°) and CON (15.22±5.93°) in the luteal phase as well as significantly higher for NC (16.88±7.53°) in the ovulation phase when compared to OC (12.7±8.37°) and CON (14.78±10.84°). Knee extension flexibility was significantly higher for OC (7.9±3.57°) when compared to CON (4.22±2.95°) in the luteal phase, while knee flexion did not demonstrate significant differences between groups or across phases. Conclusion: This study suggests that assessments of body composition via DXA are remarkably reliable across different phases of the menstrual cycle. The higher hip mobility in NC during ovulation and luteal phases could be due to fluctuations in estrogen concentration, which is thought to have a laxative effect on tendons and ligaments in females by decreasing sinew stiffness.

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