## 1 Introduction  
Shot put (SP) is a cornerstone event in track and field athletics and has been a mainstay of the Summer Olympics since 1896 [1]. As a power-dominant sport, it exemplifies the integration of strength, technique, and biomechanical precision [2, 3]. SP aims to optimize horizontal throw distance by achieving efficient energy transfer through a well-coordinated kinetic chain [3]. Shot put techniques have evolved significantly over decades, with the glide and rotational techniques emerging as dominant approaches to optimize performance. The glide technique employs a linear trajectory across the throwing circle, culminating in an explosive delivery phase. Its relative simplicity makes it ideal for biomechanical analysis, and most athletes begin using the glide technique, which assists more athletes in winning the Olympic and world championships [4]. On the other hand, the rotational technique, introduced later, utilizes a discus-like spin to generate momentum [5]. While both techniques are used at elite levels, the glide technique remains popular for its linear nature, which facilitates biomechanical analysis. Moreover, the glide technique of SP, characterized by its linear and controlled motion, is more readily accepted by female athletes due to its biomechanical and practical advantages [1]. The glide technique can be broadly divided into four phases: the initiation phase, flight phase, landing phase, and completion phase [6]. The completion phase is pivotal, as it encompasses the explosive motions that dictate shot put performance, emphasizing key kinematic and kinetic parameters [6]. Understanding the intricate biomechanics of this phase, especially the role of often-overlooked body segments like the non-throwing arm, is vital for optimizing performance. Extensive biomechanical research has focused on key determinants of shot-put performance in the completion phase, such as throwing arm mechanics [7], leg drive [8], hip rotation, and trunk rotation [9]. Lower body contribution has been well documented, with research highlighting the importance of leg drive and hip rotation in generating power [10]. Trunk rotation has been identified as a critical factor in energy transfer from the lower body to the upper extremities [11,12]. Additionally, investigations into release parameters, such as angle, height, and velocity, have provided insights into optimizing throw distance [11]. Recent studies have also explored the kinetic chain in SP, emphasizing the sequential activation of body segments for maximum performance [13]. Despite substantial advancements in SP biomechanics, the role of the non-throwing arm remains nearly underexplored. [PERSON] found that the functions of the non-throwing arm were concentrated on improving the velocity of the throwing side by the motion of swinging [14]. In contrast, extensive studies have explored the role of the non-throwing arm in baseball [15,16,17]. These studies highlight its critical function in generating rotational momentum and optimizing throwing efficiency. These findings provide valuable insights into shot put biomechanics. Preliminary studies have suggested its potential role in contributing to rotational momentum. Addressing this gap is essential, as whole-body coordination plays a pivotal role in optimizing throwing performance. In recent years, Chinese female shot-putters have consistently exhibited exceptional performances in international competitions. A focused analysis of the non-throwing arm mechanics of China's best elite female shot-putters offers valuable insights into the technical nuances of the glide shot put technique, contributing to a deeper understanding of the biomechanical factors underlying her success. This study specifically aims to investigate the biomechanical contributions of the non-throwing arm in elite female shot-putters. The primary objective is to analyze how the non-throwing arm influences the glide technique during the completion phase.