Para table tennis is recognized as the third most popular sport in Paralympic competitions with participants from over 100 countries worldwide [1]. The International Paralympic Committee's statistics indicate that over 40 million people now compete in this sport globally. The sport's popularity is due, in part, to its inclusivity, allowing athletes with various impairments to participate. Also, this sport is the fourth most rewarded sport in Paralympic competitions [2]. This sport requires complex techniques including acceleration, deceleration, change of direction, quick movements, balance, and stability to generate sufficient force in the athlete's upper limb [3]. In para table tennis, rotational movements, speed, and agility are crucial factors that affect a player's performance in a match [3]. Also, athletes need high levels of speed, strength, power, flexibility, and reaction [4]. Due to the type and severity of impairments in people with disabilities, creating movement adaptations is necessary to play para table tennis. Therefore, the biomechanics and force production in these people differ from those without impairments. |Individuals with motion impairment or reduced range of motion in the trunk may compensate for this weakness by exerting more force in their arm, elbow, or wrist region [5]. In sports such as para table tennis and wheelchair basketball, classification criteria including performance ability and 63 physiological criteria are used -[6]. These criteria encompass trunk stability, sitting balance, and body displacement in the sagittal, frontal, and horizontal planes [7]. The most essential of these indicators is sitting balance in wheelchair sports [8, 9]. Sitting stability is vital in transitions and performance during play [10, 11]. Moreover, the control of the trunk muscles is one of the most significant factors -contributing to the control of posture and balance. The central trunk muscles are pivotal for the success of para table tennis athletes [12]. In this sport, due to frequent rotation, flexion, extension, and lateral flexion of the trunk movements, the performance of the muscles in the central region is of great importance [13]. The key muscles needed for the successful performance of para table tennis skills are the deltoid, supraspinatus, biceps, triceps, and pectoralis major muscles [14, 15]. In addition, in the drop shot, due to the forward bending, the erector spinae muscles can play an important role in trunk control during both the forward, bending phase and return phases [16–18]. The internal and external abdominal oblique muscles are crucial for the forehand loop due to the rotation of the trunk [19]. Meanwhile, due to the extension of the elbow, the triceps muscle is essential for backhand actions. People with spinal cord injuries may experience impairment or deficiency in controlling trunk and upper limb movements, depending on the severity of their injury. This can lead to functional differentiation among individuals and is taken into account in the classification system for Paralympic sports. The purpose of classification is to ensure fair competition under equal conditions for athletes with similar impairments.[20–22]. This applies to para table tennis as well, and athletes must be classified before competing. [21, 22]. However, there have been concerns about the accuracy of the classification system, with some athletes potentially being placed in the wrong class. [22, 23]. Para table tennis classification is done at both clinical and technical levels, with participants undergoing medical examinations before being examined for technical classification. During a practice game, participants are evaluated by the class band based on their performance of various skills such as forehand, backhands, forehand loops, and trunk movements (Tweedy & Vanlandewijck, 2011; Weikert et al.). Players may have different may have different performance abilities for different reasons leading to discrepancies in the technical performance of those in the same class [20]. If these differences significantly affect the athlete's performance, it can compromise the fairness of the competition. For example, classification in para table tennis class 5 can be challenging and sometimes causes disputes among class bands. -This study focuses on examining participants with spinal cord injuries in sitting class 5. According to the classification rules published in 2018 by the International Table Tennis Federation (ITTF), participants in the sitting class 5 have normal function (range of motion, strength) in the trunk muscles. Also, the pelvic-thigh girdle muscles work optimally and there is no abnormal movement (range of motion, strength) when bending forward and laterally. These players also possess good sitting balance and have spinal cord injury (SCI) levels ranging from the L1 vertebra to the S2 vertebra. According to the American Spinal Cord Injury Association (ASIA), the spinal cord injury of these people can be both complete (complete paralysis of the lower limb) and incomplete (the function of the lower limb is not completely lost, but weakened). Based on this, individuals with varying levels of spinal cord injury may be classified in this class, leading to unique challenges [20]. The purpose of the present study was to compare the electromyographic variables (EMG activity, onset, and offset) of the muscles involving (deltoid, biceps, erector spinae, external oblique) during the execution of forehand loop and backhand techniques in elite para table tennis players with complete and incomplete spinal cord injuries within class 5.