Is Non-dominant Leg a Key Factor for Endurance Performance in Male Youth Soccer Players? Data-Driven Knowledge-Adjusted Causal Analysis and Literature Synthesis.

Abstract

Background: Soccer performance in youth players arises from a complex interaction of anthropometric, physiological, technical, and maturational factors. However, most studies emphasize correlation analyses, offering limited insight into causal mechanisms that shape athletic development and physical performance. This study aimed to identify causal pathways underlying potential targets for practical intervention in male youth soccer players.

Results: Data from 275 male Caucasian youth soccer players aged 8-18 years from youth soccer academy (Mazovian region) were collected during the pre-season and analyzed using the Greedy Fast Causal Inference algorithm to generate a data-driven directed acyclic graph. Complementarily, a scoping review of publications indexed in PubMed and Web of Science (search conducted up to July 2025) identified 102 eligible studies on associations between parameters in apparently healthy male youth soccer players. Data from studies were used to construct a chord diagram illustrating associations among players' characteristics. This approach revealed sprint ability, countermovement jump, agility as well as maturity as central nodes in performance networks. However, causal modeling and literature synthesis highlighted the non-dominant leg and functional deficits as a potentially modifiable determinants linked to sport-specific skills and endurance-related performance.

Conclusions: The integration of data-driven causal discovery and review-based associations offers a methodological bridge from observational evidence toward hypothesis generation. The findings establish a rationale for a future randomized controlled trial aimed at testing whether intervention focused on reducing interleg asymmetries (i.e., differences in power/strength between lower extremities) can improve endurance capacity and specific soccer skills in male youth soccer players.