This study was just published Open Access in the Journal of Science and Medicine in Sports. It identified the causal relationship between growth velocity and injury in elite-level youth football players and assessed the mediating effects of motor performance in this causal pathway.
Background
Injuries in youth academy football (soccer) are a risk for the careers of talented players. Therefore, injury risk assessment and management are of great importance for youth academies to retain their high potential athletes. Injury incidence in elite-level football players increases with age and peaks during adolescence.
Previous work has only investigated associations between growth velocity and injury or between motor performance and injury in youth elite-level football players. These studies did not apply analytical models based on causal concepts to determine injury risk, so no causal conclusions could be drawn. Furthermore, no previous study investigated the potential role of modifiable motor performance parameters in the growth-injury relationship.
Therefore, the aim of this prospective cohort study was to use a causal inference approach to gain further insights into the causal effect of growth velocity on injury risk and the role of motor performance measures as modifiable mediating factors in pubertal elite-level male youth football players.
Methods
We measured the body height of 378 male elite-level football players of the U13 to U15 age categories three to four months before and at the start of the competitive season. At the start of the season, players also performed a motor performance test battery, including motor coordination, muscular performance, flexibility, and endurance measures. Injuries were continuously registered by the academies’ medical staff during the first two months of the season. Based on the causal directed acyclic graph (DAG) that identified our assumptions about causal relations between growth velocity (standardized to cm/y), injuries, and motor performance, the causal effect of growth velocity on an injury was obtained by conditioning on maturity offset. We determined the natural indirect effects of growth velocity on injury mediated through motor performance.
Directed Acyclic Graph (DAG) of causal pathways investigated from growth velocity to injury event.
Results
In total, 105 players sustained an injury. Odds ratios (OR) showed a 15% increase in injury risk per centimetre/year of growth velocity (1.15, 95%CI: 1.05–1.26). There was no causal effect of growth on injury through the motor performance mediated pathways (all ORs were close to 1.0 with narrow 95%CIs).
Conclusions
Higher growth velocities were causally related to an increased risk of medical attention injuries in our sample of U13 to U15 male youth elite-level football players. The motor coordination, muscular performance, flexibility, and endurance measures used in this study did not appear to mediate this causal effect and were not risk factors of injuries themselves. Future studies could build upon our findings and investigate further possible causal pathways from general motor performance to injury risk, in order to identify specific targets for injury risk management in growing athletes.
Practical implications
Monitoring growth velocity in young athletes should become part of a risk management strategy to identify individuals being in periods of higher injury risk.
Screening of preseason motor performance measures does not allow assessing injury risk in the near future.
This study does not provide evidence to specifically target general motor performance when aiming at injury prevention in pubertal elite-level football players.
The full article can be accessed here (Open Access)
Rommers N, Rössler R, Shrier I, Lenoir M, Witvrouw E, D'Hondt E, Verhagen E. Motor performance is not related to injury risk in growing elite-level male youth football players. A causal inference approach to injury risk assessment. J Sci Med Sport. 2021 Mar 16:S1440-2440(21)00056-6. doi: 10.1016/j.jsams.2021.03.004. Epub ahead of print. PMID: 33752967.