Background: Water polo performance depends on efficient neuromuscular coordination and biomechanical interaction within the kinetic chain, where muscle contractile properties play an important role in force production and transfer during shooting. Aim: The aim of this study was to determine differences in muscle contractile properties between elite and sub-elite water polo players and to examine their relationship with 5-meter shot velocity. Methods: The sample consisted of 22 male water polo players from the same club, divided into elite (n=12; *19 years) and sub-elite (n=10; 16-19 years) groups. Contractile properties of 11 muscles were assessed using tensiomyography, including contraction time, delay time, sustain time, relaxation time, maximal displacement, and symmetry. Shot velocity was measured in a swimming pool using a radar device. Differences between groups were analysed using t-tests, while relationships were examined using correlation analysis. The study was approved by the Ethics Committee of the Faculty of Kinesiology, University of Zagreb (approval number: 31/2025). Results: Statistically significant differences were found between elite and sub-elite water polo players in several tensiomyographic parameters, particularly in contraction time (Tc), with sub-elite players showing shorter reaction times in most upper-body muscles. Elite players achieved significantly higher shot velocity than sub-elite players (77.41 ± 3.32 vs. 72.24 ± 4.63 km/h; mean difference = 5.17 km/h, corresponding to 7.16%; 95% confidence interval = 1.46-8.88; p = 0.006; Cohen`s d = 1.30, large effect). Statistically significant correlations were found between shot velocity and parameters of m. deltoideus anterior (r = -0.464), m. deltoideus posterior (r = 0.570-0.610), m. erector spinae (r = 0.424-0.559), m. gastrocnemius medialis (r = 0.434), m. latissimus dorsi (r = -0.457-0.664), m. pectoralis major (r = 0.437), m. rectus abdominis (r = -0.495 to 0.473), m. tibialis anterior (r = 0.441), and m. triceps brachii (r = 0.509), with the highest number of significant associations observed for m. erector spinae. Conclusions: Muscle contractile properties are significantly related to shot velocity in water polo. Neuromuscular efficiency and coordination of the kinetic chain are key factors in shooting performance, and tensiomyography represents a valuable tool for performance assessment and training optimization.
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