The high-intensity activity of soccer players during a match are affected by the basic contractile properties of lower limb muscles. Several studies have confirmed that playing position crucially determines absolute performance and physical load and also determines the intensity of fast movements during matches. However, little is known whether muscle contractile properties vary in relation to a specific playing position. The aim of this paper is to describe differences in functional contractility of muscles in young soccer players in the context of playing position. U14-U15 soccer players (n = 127) were divided into 6 groups based on their playing position: G - Goalkeeper (n = 14), FB - Fullback (n = 23), CB – Centre-back (n = 28), W – Winger (n = 15), M – midfielder, (n = 28), F - Forward (n = 19). Functional contractility of the biceps femoris and rectus femoris in the dominant lower limb was assessed from the following variables: contraction time (tc), maximal displacement of the muscle contraction (dm) and contraction velocity (vc) measured by a non-invasive method of tensiomyography using a TMG S2 system (TMG-BMC Ltd, Slovenia). The Shapiro-Wilk test showed a violation of normality of the data distribution. Differences in contractile properties in terms of the playing position factor were evaluated using Kruskal-Wallis analysis of variance (K-W Anova) with multiple pairwise comparisons. The K-W Anova results showed significant differences in the maximal amplitude (dm) and velocity of contraction (vc) for the biceps femoris muscle (H = 19.008; p = 0.002 and H = 24.421; p = 0.001, respectively). In the variable of time of contraction (tc), a significant difference between the playing positions was identified for the rectus femoris muscle (H = 18.257; p = 0.003). The results of the study suggest that different playing positions of young soccer players are associated with specific muscle contractility requirements. These differences suggest that muscle characteristics are influenced by the functional demands of each playing position. The findings point to the need for personalised training interventions that consider the specific biomechanical and functional demands of playing positions, which may contribute to performance enhancement and injury prevention.
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