1.    Introduction
Due to the specific anatomical structure of the foot and its position within the lower extremities of the kinetic chain, with a relatively small support surface bearing and balancing the entire body weight, it is logical that even small biomechanical changes in the body’s support surface can affect posture control (3). In this context, taekwondo, a martial art with rapid movements and complex techniques, exposes practitioners to various abnormalities (4), including increased Q angle and flat feet. The Q angle, the angle between the thigh and the shin, is commonly used as an indicator in diagnosing knee issues and comparing injured knees (5). Flat feet, on the other hand, are a common deformity affecting 2 to 23 percent of the adult population (10). This condition is characterized by the loss of the medial longitudinal arch and is often accompanied by external rotation of the heel and outward deviation of the forefoot (11). Flat feet can influence the kinematics of the lower limbs during dynamic activities, leading to difficulties in athletic performance (12). Therefore, implementing corrective exercises to address these abnormalities is crucial, and core stability exercises appear to be effective. Core stability exercises are recognized as a valuable method for improving athletic performance and preventing injuries in athletes.
2.    Methods
This quasi-experimental study was conducted in the field. The statistical population consisted of 30 female taekwondo practitioners, aged 15–25, from Mashhad, who were purposefully selected. Of the registered participants, 30 individuals (sample size determined using G*Power software) were selected based on the inclusion criteria and randomly assigned to two groups: 15 in the control group and 15 in the experimental group. All participants had a history of three years of regular taekwondo practice, attending at least three sessions per week (without competition experience), and training for 1.5 hours per session. Before participation, all individuals signed a written consent form. Inclusion criteria for the study were: being between 15 and 25 years old, having at least one year of regular exercise (three sessions per week for 1.5 hours), and being free from acute or chronic injuries or underlying health conditions. The Staheli index was used to assess foot arch, and a goniometer was used to measure the Q angle. The experimental group performed selected core stability exercises for six weeks, while the control group received no intervention. After six weeks, all assessments were repeated, and the results were recorded as post-test data.

3.    Results
The results of the Shapiro-Wilk test indicated that all research data were normally distributed. The findings showed that the six-week exercise program significantly improved flat feet (P = 0.001) and reduced the Q angle (P = 0.001) in the exercise group compared to the control group (Table 1). Core stability exercises enhance movement and stability in the body's central region. These exercises increase the strength and stability of the core, which improves an individual’s ability to maintain the center of mass within the limits of the base of support, thus contributing to better balance. Core stability is a vital component of overall performance. Activating different parts of the body that surround the movement chain improves performance. The core’s role is to generate the necessary force for motor activities, as it serves as the connection and force transfer point for all kinetic chains during dynamic activities, including sports. By controlling the force, balance, and movement of the core, the performance of the lower limb kinetic chain can be maximized.
4.    Conclusion
The aim of this study was to examine the effect of six weeks of core stability exercises on the Q angle and flat feet in female taekwondo practitioners. The results indicated that these exercises significantly improved the Q angle and reduced flatfoot deformity in the participants. aekwondo is one of the most popular martial arts worldwide, and flat feet are a common abnormality among its practitioners, leading to biomechanical and sensory-motor issues in the foot and ankle complex, as well as reduced postural stability (23). According to the kinetic chain model, flatfoot deformity can cause lateral rotation of the patella, which increases the Q angle and contributes to knee pain in athletes. Abnormal movement patterns caused by injuries or dysfunction in one part of the body lead to muscular imbalances around the affected joints, ultimately disrupting the movement chain (24-26). Previous studies have shown that strong core muscles stabilize the spine and help distribute compressive, translational, and shear forces to different parts of the body (27). Consequently, weak core muscles can impair the function of the limbs, exacerbating abnormalities like flat feet. Properly strengthening the core muscles, therefore, improves the function of the limbs (28). Research also demonstrates a positive correlation between core muscle strength and flatfoot severity, with flat feet contributing to increased knee valgus, which, in turn, elevates the Q angle (29, 30). Thus, the findings of this study demonstrate that core stability exercises improve flat feet and reduce the Q angle in female taekwondo practitioners, thereby enhancing their performance.
Ethical Considerations
Compliance with ethical guidelines
There were no ethical considerations to be addressed in this research.
Funding
This research did not receive any financial support from government, private, or non-profit organizations.
Authors' contributions
All authors contributed equally to preparing the article.
Conflicts of interest
The authors declare that there are no conflicts of interest associated with this article.