## 4 Discussion
Specifically, the higher velocities observed before the CoD maneuver (Avg Vel 1a), along with the tendency toward a reduction in Dec Dist, suggest a delayed deceleration onset compared to the SG. Although statistical significance in the comparison of Dec Dist was not reached, the magnitude-based inferences strongly suggest a beneficial effect of training on hard surfaces in the reduction in Dec Dist (Figure 3). These findings indicate that training on hard surfaces may enhance an athlete's ability to decelerate effectively, enabling them to maintain higher speeds for a longer duration before executing the CoD maneuver [55]. These observations may be attributed to the biomechanical demands imposed by deceleration on a hard surface, which may enhance the eccentric strength capacity of the muscles to a greater extent than on soft surfaces [23]. The nature of hard surfaces requires greater force absorption and eccentric muscle actions during deceleration, leading to increased loading and adaptation of the muscles involved [22, 23, 55]. Consequently, athletes training on hard surfaces may experience greater improvements in eccentric strength, which can contribute to their ability to decelerate effectively and maintain higher speeds before initiating a CoD. The delayed deceleration onset observed in the HG implies the potential for improved deceleration capabilities, which could be advantageous in sports requiring rapid CoDs [27, 55]. Furthermore, the slight increase in Dec Dist observed in the SG, although not statistically significant, implies a potential adjustment to the deceleration strategy when training on sand surfaces, and this may result in longer deceleration distances compared to training on hard surfaces (Figure 3). Moreover, the correlations between the improvements in the CMJ, the PSJT, and the 20 mT to those of AVG Vel 1a suggest that improvement in force production derived from the long SSC is also reflected in the performance improvement in this variable (Figure A3). These findings highlight the adaptability of athletes to different training surfaces and the potential for specific adaptations to CoD performance. In contrast, the higher Avg Vel 1b value observed in the SG indicates superior acceleration compared to the HG, and this discrepancy in velocity can be attributed to the kinematic and kinetic adaptations induced by sand-based training, which likely contribute to enhanced acceleration performance. Importantly, these improvements may carry over to acceleration performance on hard surfaces, as discussed earlier [22; 54; 55; 56]. Interestingly, the correlation analyses did not reveal any relationship to other variables (Figure A3). This could indicate that the acceleration after the CoD is more dependent on other factors than the force production generated in the long SSC. Therefore, an additional explanation for the higher Avg Vel 1b value observed in the SG could be attributed to the inherent instability of the sand surface, which may lead to increased activation of the muscles responsible for stabilizing the leg axis and trunk, thereby enhancing the stability and balance of the lumbo-pelvic complex during explosive sports activities. Supporting this assumption, studies have shown an improvement in dynamic and static balance as a result of sand-based training [44; 49]. The increased activation of the stabilizing muscles on sand can be explained by the need to counteract the unpredictable and shifting nature of the grains, demanding greater motor control and coordination. This activation may result in improved neuromuscular adaptations, which could enhance the ability to maintain stability and balance during movements, including CoD maneuvers [19]. The ability to stabilize the lumbo-pelvic complex effectively allows athletes to generate and transfer forces more efficiently, resulting in an increased average velocity after the CoD [58].