Abstract
Introduction & Purpose
Flexibility and range of motion (ROM) are key determinants of movement efficiency, injury risk, and rehabilitation outcomes. At the tissue level, ROM and related mechanical behavior depend on the properties of the muscle–tendon unit and its extracellular matrix, which may be modulated by menstrual hormones (Hansen, 2018). Although previous work has not shown consistent menstrual-cycle effects on global athletic performance (Eloduy-Terrado et al., 2025), it is unclear whether sensitive endpoints (ROM, passive stiffness, and morphology) vary systematically across the cycle. This systematic review with meta-analysis aimed to determine whether these characteristics differ between menstrual phases, and how any effects depend on cycle-tracking quality, tissue type, and measurement conditions.
Methods
This review followed PRISMA guidelines and was registered in the PROSPERO database (CRD420261359522). Two independent reviewers (JN, AS) screened records found in three databases and extracted data. Eligible studies were original research in females comparing at least two out of three menstrual phases (follicular, ovulation, luteal) and reporting either ROM (e.g., sit and reach), mechanical muscle–tendon properties (e.g., shear wave velocity, stiffness), or muscle/tendon morphology. Paired standardized mean differences (Hedges’ g) between phases were computed using within-subject formulas accounting for repeated measures. Multiple outcomes were combined to a single study-level effect (Borenstein et al., 2009). Random-effects meta-analyses (Borenstein et al., 2009) were conducted for phase contrasts (follicular vs. ovulatory, follicular vs. luteal, ovulatory vs. luteal) for ROM, stiffness, and morphology, with subgroup analyses by cycle-tracking quality, tissue type, and muscle activation. All analyses were conducted in MATLAB (R2024a, Massachusetts, The MathWork Inc.)
Results
Across 25 eligible studies, cycle effects on ROM and stiffness were small and largely inconclusive. Muscle and muscle–tendon morphology showed effect sizes close to zero, indicating no meaningful phase-related changes in gross structure. However, when analyses were restricted to studies with accurate cycle tracking or muscle stiffness, a clearer pattern emerged: ROM was higher around ovulation than in the early follicular phase, and muscle stiffness was lower at ovulation than in both early follicular and luteal phases. These effects were small-to-moderate and based on few studies, so they remain provisional.
Discussion
Menstrual-cycle phase appears to exert small but coherent effects on ROM and muscle stiffness, whereas muscle–tendon morphology remains largely unchanged. The observed pattern aligns with hormonal mechanisms whereby high estradiol and low progesterone near ovulation reduce collagen cross-linking, which might promote a more compliant muscle–tendon unit, whereas elevated progesterone in the luteal phase may counteract estradiol’s effects and increase stiffness (Hansen, 2018; Hansen & Kjaer, 2016). This is consistent with epidemiological evidence of greater joint laxity around ovulation and supports the view that short-term hormonal fluctuations primarily modulate tissue mechanics rather than gross structure, although current evidence remains scarce (Hansen & Kjaer, 2016).
Conclusion
Menstrual-cycle phase may fine-tune flexibility and muscle stiffness in eumenorrheic women and could support phase-informed adjustments to flexibility training, load management, and injury prevention. However, the modest effect sizes, small number of high-quality studies, and variability in cycle verification highlight the need for research with precise hormonal profiling and standardized mechanical testing to confirm and refine these findings.
References
Hansen, M. (2018). Female hormones: do they influence muscle and tendon protein metabolism? Proceedings of the Nutrition Society, 77(1): 32-41. https://doi.org/10.1017/S0029665117001951
Eloduy-Terrado, A., Torres-Luque, G., Radesca, K., Muñoz-Andradas, G., Saenz-Bravo, M., Domíniquez-Balmaseda, D. (2025). Evaluation the Impact of Hormonal Fluctuations During the Menstrual Cycle on the Performance of Female Athletes-Systematic Review. Muscles 4. https://doi.org/10.3390/muscles4020015
Borenstein M., Hedges L.V., Higgins J.P.T., Rothstein H.R. (2009). Introduction to meta-analysis. https://doi.org/10.1002/9780470743386
Hansen, M., Kjaer, M. (2016). Sex Hormoes and Tendon. Advances in experimental medicine and biology, 920, 139–149. https://doi.org/10.1007/978-3-319-33943-6_13