Reliability and Variability of Performance and Kinematic Measures in Seated Shot Put: A Case Study of a Paralympic Thrower

Background: Seated shot put is a core Paralympic event in which lower-limb-impaired athletes generate throwing power primarily through the trunk and upper limbs. The configuration of the throwing frame may influence performance stability and biomechanics. This study aimed to evaluate the effect of two seated orientations on throwing performance, kinematics, and within-subject reliability in a Paralympic F55 athlete using markerless motion capture. Methods: A para-athlete F55-class (age: 37 years; body mass: 93 kg; height: 180 cm; training experience: 20 years) performed 20 throws (10 per seat position: perpendicular and 54.5° rotated). Kinematic data were recorded with an eight-camera, 250 Hz markerless motion capture system. Variables included throw distance, trial time, release angle, wrist acceleration and velocity, and torso angular velocities. Reliability was assessed using intraclass correlation coefficients (ICC), standard error of measurement (SEM), coefficient of variation (CV%), Bland–Altman analysis, and ROC curve discrimination. Results: Throw distance did not differ significantly between positions (p = 0.1086), but trial duration was significantly shorter in the rotated position (p = 0.0114). Most kinematic variables showed poor-to-moderate reliability (ICC = −0.51 to 0.40). Bland–Altman and ROC analyses indicated stable performance measures but higher variability in torso motion, with torso rotation (AUC = 0.72) showing the strongest discriminative ability. Conclusions: Seated orientation minimally affected performance but influenced trunk kinematics and reliability, emphasizing the need for individualized biomechanical assessment in Paralympic shot put training.