Hormonal influence on knee-stabilizing muscle activity across the menstrual cycle: a scoping review

Background Female athletes are at increased risk of non-contact anterior cruciate ligament (ACL) injuries, with incidence varying across the menstrual cycle (Wojtys et al., 1998). Hormonal fluctuations, particularly in estradiol and progesterone, have been linked to changes in ligament laxity and may also influence neuromuscular activation. Previous research has demonstrated phase-dependent changes in reflex excitability (Casey et al., 2014) and motor unit behavior (Tenan et al., 2013), suggesting potential alterations in the activity of muscles contributing to knee stability. However, the impact of these hormonal fluctuations on muscle activation during athletic movements remains insufficiently understood. This scoping review synthesizes current evidence on hormonal influences on neuromuscular activation, as reflected in EMG-based measurements of muscle activity relevant to knee stabilization across the menstrual cycle.

Methods Following PRISMA-ScR guidelines, PubMed, CINAHL, Scopus, and Cochrane databases were searched for studies investigating EMG activity of muscles influencing knee stability in healthy, eumenorrheic women performing athletic movements across menstrual cycle phases. Screening was conducted independently by two reviewers using Covidence (Covidence, Australia).

Results Six studies met the inclusion criteria, evaluating EMG activity during tasks such as drop landings, jumps, treadmill running, and perturbed squats. Across studies, both feedforward and reflexive muscle activation patterns varied by menstrual phase. In the luteal phase, findings included reduced gluteus maximus preactivation, delayed semitendinosus onset, and altered co-contraction timing. One study reported elevated quadriceps activation in the mid-luteal phase. In the follicular phase, quadriceps activity increased during preactivation and weight acceptance. No consistent phase-dependent differences were observed in rectus femoris or gluteus medius onset timing. Increased medial hamstring activity and quadriceps–hamstring co-contraction were reported during ovulation. One study reported no significant EMG differences across menstrual phases.

Conclusion Current evidence indicates that the activity of muscles involved in knee stabilization varies across menstrual cycle phases, with differences observed in both timing and magnitude of activation. Although the literature remains limited and methodologically heterogeneous, findings suggest hormone-related changes in neuromuscular activation. Further research with standardized methods and hormone-based profiling is needed. Improved understanding of these mechanisms may inform more individualized strategies for joint stabilization and injury prevention in female athletes.

Publication History

Article published online:
23 October 2025