Background & Aims: The aim of this study was to investigate the effect of six-week combined training on sand on time to stabilization, sens of position and Strength of ankle joint in volleyball players with chronic ankle instability. Ankle injury is one of the most common sports injuries. Among ankle injuries, sprains are among the most common injuries. On average, this injury results in the absence of the athlete for 7 sessions of training or competition (2). In research, it has been shown that the inability to sense the proprioception of the ankle joint has caused a change in coordination in movement programs, such as a delay in the start of the contractile activity of the muscles around the joint. Therefore, by reducing the range of contraction of the muscles around the joint, the possibility of ankle sprain increases (4). Resistance training is a type of training method that has gained a lot of popularity in the last two decades especially because of its role in improving sports performance by increasing strength, power, speed, local muscular endurance, balance and coordination (9). Volleyball is full of explosive and high-speed movements and techniques combined with power, which are performed repeatedly and consecutively by the players. These explosive and fast movements with maximum strength and muscle power are performed in a fraction of a second, the number of which is very high in one round (rally) of the game (10). The imbalance of muscle strength disturbs the extension of the body and provides the basis for putting unusual pressures on joints and other tissues (11). Resistance training is a type of training, especially because of its role in improving sports performance by increasing strength, power, speed, and endurance. One of the solutions that has rarely been explored in sports teams is the use of training levels. Wide access to different training surfaces such as sand surfaces that exist naturally (beach) and artificial, has made sports training on these surfaces a viable option for trainers and sports science practitioners (15). The high absorption quality in sand reduces the impact forces during high-intensity sports activities, which will potentially lead to a reduction in muscle pain and injury with a very small reduction in the performance capacity of athletes (17).
Methods: The present study was a quasi-experimental. For this purpose, 24 female volleyball players in two experimental and control groups were selected through purposive sampling. After completing the personal information questionnaire, the athletes were divided into two groups of ten. Both groups were tested using a force plate device to calculate the time to stabilization, a goniometer device to calculate the sense of ankle joint position and a dynamometer device to calculate the Strength of ankle joint in pre-test and post-test. The experimental group was then given combined exercises for six weeks, including plyometric and resistance exercises in the sand. The Functional Ankle Instability Questionnaire (IDFAI) assesses three ankle factors, including history of ankle instability, information about the first ankle sprain, and information about instability during daily activities and sports. Also, each question has a specific score and these scores range from 0 to 37. Higher scores indicate more instability and lower scores indicate less ankle instability. The right and left legs are examined separately and if the obtained score is greater than 11, the person has functional instability of the ankle (19). Kinetic information was collected using a force plate (Qurato Jump) made in Switzerland and a Besco test to measure the time to reach stability. The Bosco test includes different types of jumps, such as standing jumps, 90-degree squat jumps, and consecutive jumps. The time to reach stability (TTS) is the time required to minimize the result of the ground reaction forces caused by the drop-landing movement until reaching the stationary state. With this device, the time to reach stability is calculated through the Bosco test, which calculates the difference between the times a person lands on the force plate device and the time the person reaches stability, and the result shows the time to reach stability. The number of jumps is between 3 and 5 jumps and for consecutive jumps between 15 and 60 seconds. High validity and reliability have been reported for the Bosco test. So that the test-retest rate in Bosco's 30-second jump was reported (ICC = 0.94) and was (ICC = 0.98) to determine the average jump height (20). Data were analyzed using Spss software version 24 and two-way ANOVA statistical method at a significance level of α≤ 0.05. Two-way
Results: The results showed that there was a significant difference between the experimental and control groups after 6 weeks of training in the variable of time to stabilization (P = 0.01) and in the variable of sens of position (P = 0.07) and ankle joint strength No significant difference was observed (P = 0.15).
Conclusion: The results of the present study showed that performing combined exercises in the sand could improve the time to stabilization and sense of position in people with chronic ankle instability. Therefore, it is recommended to use sand exercises in the training program of athletes active in high-intensity traumatic disciplines, especially in the ankle joint area. Studies that showed that unstable training levels had an effect on the rehabilitation and recovery of ankle sprains. Balance exercises by creating unstable and turbulent conditions, while increasing strength tolerance; it causes simultaneous activation of the muscles and thereby improves the preliminary stiffness and reactive characteristics of the muscle, which can be a reason for the improvement of the instability index. In addition, the use of controlled perturbation exercises, by creating unexpected perturbations of the joint, stimulates the reflex recording, and the constant use of these reflex pathways can reduce response time and improve reactive strategies against sudden perturbations (23). In a research where the researchers studied the effect of neuro-muscular exercises along with Kinesiotape on the balance, performance and pain level of volleyball players with chronic ankle instability; the results showed that these exercises have a positive and significant effect on static and dynamic balance variables of volleyball players with chronic ankle instability (24). During a research, Melan and colleagues (2018) investigated the effect of overload using elastic bands on balance and functional activity in athletes with chronic ankle instability. The results showed that these exercises had a significant effect on the balance of athletes with chronic ankle instability (25).The inability to sense proprioception changes movement coordination and motor patterns, such as increasing the time it takes to start contracting the muscles around the joint and reducing their contraction range, which will reduce performance and result in joint sprains. Balance exercises have been proposed as a suitable method for strengthening joint ligaments, improving the balance process, retraining proprioception and preventing sprains (30). In the ankle joint, the supporting and opposing muscle groups that provide the strength of the joint include the flexor-extender muscle groups and the internal and external rotators of the ankle. Disruption in the functioning of this system causes the strength balance of these muscles to be disturbed and as a result, instability in the joint occurs (33). In recent years, resistance exercises are commonly used in rehabilitation exercises and sports medicine to increase strength and reduce clinical concerns (34). Since there is a disturbance in balance in a person after ankle sprain, improving balance can be effective in improving performance and quality of life. Therefore, it can be said that combined exercises by improving the strength of lower limb muscles and facilitating proprioception can improve balance in people with ankle sprains.