1.    Introduction
Athletes in various disciplines often engage in long-term exercises that induce fatigue in different parts of the neuromuscular control structures, including the central nervous system, nervous control of muscles, and muscles themselves, leading to reduced muscle efficiency and an increased likelihood of injury following fatigue (1). Among the joints prone to the most sports injuries is the ankle joint (2, 3). Lateral ankle sprains are amongst the most common injuries during both sports activities and daily tasks (4, 5). These injuries account for 15 to 30% of sports-related injuries, with a reported return rate of over 75% (4). They are particularly prevalent in football, basketball, volleyball, and sports requiring rapid changes in body movement direction (2). An ankle injury not only hinders an athlete's participation in competitions but can also result in long-term disability, impacting the athlete's health and increasing overall costs (6), potentially leading to chronic ankle instability (7). This emphasizes the importance of implementing diverse exercises to mitigate complications arising from such injuries.
2.    Methods
This study followed an applied and semi-experimental approach. Participants were selected through available and purposeful random sampling. The statistical population consisted of 80 volleyball players in Isfahan suffering from chronic ankle instability. Thirty-six athletes aged between 18 to 25 years were selected as the primary sample, divided into three groups: a control group (12 individuals), a core stability training group (12 individuals), and a Trampoline training group (12 individuals). Identification of participants with functional ankle instability occurred through a questionnaire and clinical tests conducted by a physiotherapist. Entry criteria included scoring equal to or below 90% on the ankle disability index questionnaire and equal to 80% on the ankle and foot disability sports index questionnaire (8). Other criteria involved a history of at least one acute ankle sprain causing pain, swelling, and temporary performance reduction (not within the last month) and repeated ankle sprains within the last six months (9). The Stork and Wei tests assessed static and dynamic balance, respectively, while proprioception was evaluated using a goniometer. After pre-test evaluations, the core stability and trampoline training groups underwent a 6-week exercise regimen. Post-test evaluations mirrored the pre-test assessments. Data analysis utilized analysis of covariance, Bonferroni's post hoc test for inter-group comparison, and correlated t-tests for intra-group comparisons. Ethical considerations were observed, and ethical approval (IR.IAU.KHUISF.REC.1398.286) was obtained from the Islamic Azad University, Khorasgan branch.
3.    Results
The findings indicate the significant impact of both training programs on static balance (p≤0.01), dynamic balance (p≤0.01), ankle proprioception in dorsiflexion (p≤0.01), and plantar flexion (p≤0.01). Additionally, a notable difference was observed between the effects of the two training programs on posterior-medial orientation, total dynamic balance score, and proprioception in plantar flexion. However, while the trampoline training program was more effective than the core stability program, no significant difference was noted between the two training groups in static balance, anterior and posterior-lateral dynamic balance, and proprioception in dorsiflexion (p>0.05). Furthermore, both training groups demonstrated a significant difference in research variables compared to the control group (p≤0.01) (Table 1).

4.    Conclusion
This research highlights the significant effects of both central stability and trampoline training programs on improving balance and proprioception in female volleyball players experiencing chronic ankle instability. In regard to the central stability training program's impact on balance, it can be concluded that the larger muscles in the central body region establish a stable foundation, enhancing body inertia against disturbances (10, 11). Studies suggest that central body stability exercises can enhance trunk muscle activation patterns, crucial for maintaining static posture control (12, 13). Trampoline exercises, characterized by kinetic movements such as hopping at a stable level, significantly impact balance and proprioception improvement. Injury negatively affects proprioception and neuromuscular control (14), leading to deficiencies in ankle and hip strategies during single-leg stance. The research results demonstrate the efficacy of trampoline exercises in enhancing these variables (15).
Ethical Considerations
Compliance with ethical guidelines
Adherence to ethical guidelines was maintained throughout this research.
Funding
This research did not receive grants from public, commercial, or non-profit sectors.
Authors' contributions
All authors equally contributed to the preparation of this article.
Conflicts of interest
The authors declared no conflict of interest.