## 1 Introduction  
Snowboard Big Air (SBA), which was officially introduced to the Winter Olympics in 2018, requires athletes to perform aerial maneuvers such as flips and spins from a large ramp. These maneuvers are judged based on execution, difficulty, amplitude, variety, and progression [1]. Maneuver difficulty plays a critical role in determining scores in SBA competitions [2,3]. Successfully completing high-difficulty tricks depends not only on external factors such as ramp design, weather conditions, and the athlete's psychological preparation and equipment [4, 5, 6], but also--importantly--on the athlete's technical skills, physical strength, and coordination [7, 8, 9]. These athlete-specific qualities underscore the need for precise monitoring and analysis of movement techniques, which are essential for optimizing performance and ensuring the safe execution of complex maneuvers. The primary stages of SBA include the in-run, takeoff, flight, and landing. The takeoff stage is critical, as it determines the height, direction, and rotational velocity for the subsequent flight phase and is closely linked to the braking and absorption techniques employed during landing [10, 11]. The takeoff phase is particularly important because it generates the majority of the angular momentum required for complex aerial maneuvers; errors during this stage often result in unsuccessful landings or incomplete rotations. By accumulating speed, performing explosive leg extensions, and coordinating upper body and arm movements to initiate and control rotation, athletes generate the necessary angular momentum to complete rotational maneuvers in the flight phase. This explains the positive correlations reported in previous studies between joint angles, angular velocities of the upper and lower limbs, center of mass velocity, and the number of rotational turns achieved [12]. Despite these insights, there remains a significant lack of technical analyses regarding how athletes execute maneuvers of varying--and especially high--difficulty. Technical maneuvers in SBA are largely characterized by rotational elements, including horizontal spins, off-axis rotations, and flips. These movements share similarities with skill-based sports such as gymnastics, diving, and figure skating, where technical analysis frequently focuses on rotational parameters [13, 14, 15]. However, fundamental differences exist in takeoff mechanics and environmental conditions among these sports. For example, figure skaters generate ground reaction forces by extending the hip and knee joints and adjust their moment of inertia through limb positioning during flight to achieve rotational performance [14]. In contrast, SBA athletes initiate jumps with downhill speed and upper body rotation on snow, with environmental factors such as weather and snow surface conditions exerting significant influence, whereas figure skating takes place indoors on ice under highly controlled conditions. As a result, the generation and control of angular momentum in SBA require a combination of classic biomechanical principles and sport-specific adaptations. While these differences limit the direct applicability of findings from figure skating and similar sports to SBA, the biomechanical principles established in those studies still provide valuable foundations for understanding and analyzing rotation in SBA. Therefore, it is essential to critically assess the limitations and relevance of research from related sports when exploring the unique biomechanics of SBA. Although previous studies have investigated general rotational variables--such as angular momentum and takeoff velocity--few have specifically quantified key SBA parameters like joint kinematics and rotational kinetics during takeoff, or addressed the impact of variable, outdoor environments. This research gap restricts a comprehensive understanding of the mechanisms underlying high-difficulty SBA maneuvers.