Despite a decreasing gender gap in exercise and sport participation, a significant under-representation of women in biomechanics research exists. Only 4% to 13% of such studies have been performed exclusively on women. One reason posited for this disparity is the complexity of accounting for monthly sex hormone fluctuations in menstruating women. Previous studies have shown that menstruating individuals are 4-8 times more likely to rupture their anterior cruciate ligament (ACL) than non-menstruating individuals. Furthermore, when estrogen is the dominant circulating hormone during ovulation, knee joint laxity has been shown to increase; thus introducing a greater risk of ACL rupture. When studying the muscles surrounding the knee joint, the gastrocnemius and soleus have been suggested to load and unload the ACL, respectively. Understanding the muscle activation patterns of the muscles surrounding the knee is critical for injury prevention and rehabilitation purposes. The goal of this pilot study is to compare muscle activation patterns of the lateral gastrocnemius, medial gastrocnemius, and soleus muscles during the follicular, ovulatory, and luteal phases of the menstrual cycle. Currently, participants in the study provide menstrual cycle history and birth control type (if applicable) prior to data collection sessions. Urinalysis techniques are used to measure circulating estradiol concentrations on each of the three trial days to confirm the participant’s menstrual cycle phase and relative estradiol levels. Surface electromyography is used to measure the muscle activation patterns of the gastrocnemius and soleus muscles in both legs during a series of exercises. Participants are asked to perform a take-off task, a landing task, a vertical jump task, and a lateral hop task. During each of these tasks, 2-D motion capture is utilized to analyze the kinematics of the knee relative to the hip and ankle. We will draw correlations between muscle activation patterns, knee joint kinematics, and estradiol concentrations at the follicular, ovulatory, and luteal phases of the menstrual cycle for each participant. The results of this study will provide useful insight on the interaction of circulating hormones, neuromuscular control, and joint kinematics during the menstrual cycle in an effort to develop research-based injury prevention and rehabilitation protocols for female athletes.