This systematic review examined the influence of menstrual cycle phases on lower-limb muscle activation patterns in eumenorrheic women. Following the PRISMA guidelines, a comprehensive search was conducted in PubMed, Web of Science, and SPORTDiscus using the keywords: (menstrual cycle OR menstrual phase* OR menstruation) AND (neuromuscular activation OR muscle activation OR muscle activity OR neuromuscular control patterns) AND (electromyography OR EMG). Inclusion criteria required participants to be eumenorrheic women with regular menstrual cycles, verified through blood analysis and other physiological confirmation methods, and without menstrual disorders or hormonal contraceptive use. Additionally, eligible studies had to assess lower-limb muscle activation using electromyography. Seven studies met the criteria, comprising a total of 116 eumenorrheic women. Most studies reported no statistically significant differences in muscle activation patterns across menstrual cycle phases. Overall, hormonal fluctuations may influence muscle activation depending on the nature of the task performed (dynamic vs. static; fatiguing vs. non-fatiguing). Future research should incorporate larger sample sizes, longer monitoring periods, and more standardized methodological approaches.