## 1 Introduction  
In recent decades, technical innovations, rule changes, and a greater focus on the physical development of athletes have resulted in team sports becoming increasingly faster [1; 2; 3]. Especially in modern high-level basketball, drastic rule changes (shortened offensive time, less time to bring the ball over the midline, division of playing time into shorter quarters) have turned the game into one of the fastest team sports and altered the demands placed on players accordingly [4; 5]. In line with these changes, recent studies show an increase in the frequency of high-intensity actions, such as decelerations, accelerations, changes of direction (CoDs), and jumps, compared to earlier findings [6; 7; 8; 9]. Accordingly, the results of some studies show that high-level players differ from lower-level players in their speed, particularly their CoD speed [10; 11].  
In many cases, directional changes occur in response to an external stimulus [12; 13]. Thus, on the court, CoD speed manifests itself mostly in combination with the cognitive processes of perception and decision making. This complex interaction of cognitive and motor performance has recently been termed agility, and it is likely that CoD speed, as a physical and technical component, is an underlying quality of the more complex agility. Therefore, CoD speed is the result of the interplay between different conditional and coordinative factors, and it involves the ability to decelerate running speed in the shortest possible time, reorient the body, align it accordingly, and accelerate as quickly as possible in a new direction [14; 15].  
In response to these findings, scientists and strength and conditioning practitioners are continually searching for effective training approaches to optimize CoD speed, various examples of which (strength training, explosive strength training, pyometrics, sprint training, deceleration, acceleration, and CoD drills) have been proven effective [13; 16; 17; 18; 19]. Some recent studies have also suggested the use of sand as an effective alternative training surface to improve jumping and sprinting [19; 20; 21; 22]. Sand as a training surface potentially provides a natural tool for increasing resistance to movement, as it induces adaptations at the physiological, mechanical, and neuromuscular levels [23; 24]. The instability and force-absorbing properties of sand require heightened stabilization, elongated ground contact time, and increased muscular exertion [25] This makes sand training a potentially valuable tool for improving speed, especially CoD speed.  
Since speed and CoD training is usually associated with high loads on the musculoskeletal system, sand-based training might be a way to achieve this with reduced impact. Several studies have already demonstrated a positive effect on the speed performance of pyometric training on sand [19; 23; 26; 27], but to the best of our knowledge, no previous study has investigated the effects of combining CoD speed training specifically with pyometrics on a sand surface. Therefore, the objective of this study is to evaluate the effectiveness of sand as a training surface for enhancing jump performance, sprinting ability, and CoD speed on hard surfaces. This study focuses on assessing and comparing the effects of a combined training protocol consisting of pyometric exercises and CoD speed drills on a sand surface versus a hard surface, with a specific emphasis on evaluating CoD performance alongside jump and sprint capabilities.