Effects of the Menstrual Cycle Phase on Lower-Limb Isometric and Vertical Jumping Force-Time Characteristics in Eumenorrheic and Naturally Menstruating Women: A Systematic Review

Background: Eumenorrheic and naturally menstruating females experience cyclic variations in ovarian hormones attributed to the menstrual cycle (MC) which may impact neuromuscular function, musculoskeletal properties, and lower-limb performance. This systematic review aimed to examine the effects of MC phases on lower-limb multi-joint isometric and vertical jumping force-time characteristics derived from force platform or sensor assessments in eumenorrheic and naturally menstruating females, to establish whether a particular MC phase may impact performance. Methods: The review was conducted in accordance with PRISMA guidelines. PubMed, MEDLINE, SPORTDiscus, and Web of Science were searched from inception to Dec 15th, 2025, for studies examining MC phase effects on lower-limb multi-joint isometric and/or vertical jumping force-time characteristics. Inclusion criteria were: 1) injury-free females (16-40 years); 2) performed multi-joint isometric and/or vertical jumping assessments that collected force-time characteristics using force platforms/sensors; 3) observational comparative study designs that compared ≥ 1 force-time metric across ≥ 2 defined MC phases. Results: Six studies met the inclusion criteria, primarily examining team-sport or recreationally active female athletes. Most studies utilised vertical jumping tasks, observing generally non-significant, trivial differences in global outcome measures (e.g., jump height) between MC phases. However, conflicting phase-dependent fluctuations were noted in ratio and kinetic metrics (e.g., flight-time-to-contraction-time ratio, power), where superior performance was occasionally observed in either the mid-luteal or follicular phases. One study reported greater isometric relative peak force in the mid-luteal phase, yet markers of rapid force production (e.g., early-phase impulse) were superior during the early follicular phase. Methodological quality was generally moderate; however, inconsistent biochemical phase verification, limited reporting of reliability or familiarisation, and infrequent consideration of measurement error when interpreting changes in performance limit the certainty of these findings. Conclusion: While fluctuations in ovarian hormones may theoretically modulate physiological mechanisms and therefore force-generating capacity, evidence does not support consistent performance differences across MC phases. No phase was found to consistently enhance or inhibit isometric or vertical jump force-time characteristics. Practitioners should therefore avoid blanket, phase-based training adjustments and instead prioritise individualised autoregulatory monitoring strategies. Until higher-quality research integrates biochemical phase verification with detailed kinetic and kinematic analyses, lower-limb force-time performance can be considered relatively stable across the MC.