# Kinematic Analysis of Short and Long Services in Table Tennis
###### Abstract  
Background: The kinematics of table tennis is a growing topic of scientific research. This study aimed to assess the kinematics and determine the coordination of the movements of most body segments during the execution of two types of serves (short and long) in table tennis, as well as to indicate the main differences between these serves when performed by high-level athletes. Methods: The study involved 15 male table tennis players. Each participant performed two tasks, performing short and long forehand serves with back-sidespin rotation, with up to 10 hits in the designated field for each type. The players' movements were registered using an IMU system. Results and Conclusion: The research allowed for the development of a model for executing two types of serves in table tennis. The differences between short and long serves were mainly in the ranges of movement and angular velocities (higher for long serves). These were found in the shoulder rotation, elbow joint and wrist joint (primarily the flexion-extension movement), hand supination, and movement in the elbow joint, which also played an important role. Coaches and players should seriously consider these joints and movements in the training process. In the coordinated movement of the performed serves, a phenomenon of movement variability was observed, manifested by a large variability in execution and a low variability in the maximum speeds of the hand with the racket. biomechanics; kinematics; table tennis; services; variability +
Footnote †: journal: Applied sciences  
considerably. However, the objectives of the above works were very often linked to the practical application of the results--training materials for coaches and table tennis players, searching for the best solutions in sports techniques, or presenting a number of solutions for techniques that bring similar results. According to [PERSON] et al. [8], the main shots were classified into eight main types: service, drive attack, topspin attack, block, backspin defense, chop, flick, and balloon defense. Service is the only stroke in table tennis that a player performs during the game that is not directly influenced by the opponent. All the other strokes are strokes performed in response to the opponent's play. Therefore, the role of the serve in a game is fundamental. From a tactical point of view, the player serving can score a point directly, create a situation to attack, and score a point or serve in such a way that the opponent does not attack. Statistical analyses have shown that winning points is more often associated with service actions than receiving ones [8; 9; 10]. [PERSON]'s works confirmed that the quality of serves performed by players is of great importance for the possibility of winning individual actions in modern table tennis [11; 12]. Recent studies by [PERSON] et al. [13] and [PERSON] and [PERSON] [14] showed that serving actions (serve or serve and attack) constitute the vast majority of actions won by players. Many criteria can be used to determine the type of serve, such as its length (short, half-long, or long), speed (slow or fast), or the side you use to serve (forehand or backhand). An important criterion is the type of rotation the ball is given during the serve. In this respect, there are serves with side rotation (sidespin), bottom rotation (backspin), topspin rotation, and no-spin (fake topspin) attacks [15]. Often, serves have a combination of several types, so-called mixed spin (e.g., top-sidespin), which is a mixture of pure topspin and pure sidespin. The rotation is determined by how the player hits the ball, which results in the setting of the axis around which the ball rotates [16]. The above-mentioned classification, which takes into account long, half-long, and short serves, is of great importance from a tactical point of view. The criterion for their division is the distance of the bounce of the ball (close to the net, intermediate, and close to the baseline, respectively). Short serves are often used by players who attack primarily with topspin.