Identification of Neuromuscular Performance Parameters as Risk Factors of Non-contact Injuries in Male Elite Youth Soccer Players: A Preliminary Study on 62 Players With 25 Non-contact Injuries

Abstract

Introduction: Elite youth soccer players suffer increasing numbers of injuries owing to constantly increasing physical demands. Deficits in neuromuscular performance may increase the risk of injury. Injury risk factors need to be identified and practical cut-off scores defined. Therefore, the purpose of the study was to assess neuromuscular performance parameters within a laboratory-based injury risk screening, to investigate their association with the risk of non-contact lower extremity injuries in elite youth soccer players, and to provide practice-relevant cut-off scores.Methods: Sixty-two elite youth soccer players (age: 17.2 ± 1.1 years) performed unilateral postural control exercises in different conditions, isokinetic tests of concentric and eccentric knee extension and knee flexion (60°/s), isometric tests of hip adduction and abduction, and isometric tests of trunk flexion, extension, lateral flexion and transversal rotation during the preseason period. Non-contact lower extremities injuries were documented throughout 10 months. Risk profiling was assessed using a multivariate approach utilizing a Decision Tree model [Classification and Regression Tree (CART) method].Results: Twenty-five non-contact injuries were registered. The Decision Tree model selected the COP sway, the peak torque for knee flexion concentric, the functional knee ratio and the path of the platform in that hierarchical order as important neuromuscular performance parameters to discriminate between injured and non-injured players. The classification showed a sensitivity of 0.73 and a specificity of 0.91. The relative risk was calculated at 4.2, meaning that the risk of suffering an injury is four times greater for a player, who has been classified as injured by the Decision Tree model.Conclusion: Measuring static postural control, postural control under unstable condition and the strength of the thigh seem to enable a good indication of injury risk in elite youth soccer players. However, this finding has to be taken with caution due to a small number of injury cases. Nonetheless, these preliminary results may have practical implications for future directions in injury risk screening and in planning and developing customized training programs to counteract intrinsic injury risk factors in elite youth soccer players.

Predictive modeling of lower extremity injury risk in male elite youth soccer players using least absolute shrinkage and selection operator regression

“…This shows the importance of multifactorial approaches in assessing the risk of non‐contact lower extremity injury. Moreover, identifying injury risk factors and assessing the individual risk of injury of each player enables customized injury prevention interventions to be provided as part of the player's daily training schedule 21 . Several reviews and meta‐analyses dealing with the effects of multicomponent exercise prevention programs have demonstrated an effective reduction in injury risk 49,50 …”

“…After the warm‐up, the players underwent these tests in a standardized order to avoid neuromuscular fatigue in the lower extremities and the trunk, particularly while undergoing 3D motion analysis and postural control testing, and to ensure equal test conditions for all players (see Figure 1). The procedures for data measurement and processing for the postural control testing, the strength testing and the 3D motion analysis have already been described in detail in previous studies 21,22 …”

“…The hands were attached to the hips, and the swinging leg was flexed 90° in the hip, knee, and ankle to minimize contributions from the contralateral leg 27 . Dynamic postural control was analyzed using the Dynamic Postural Stability Index (DPSI) devised by Wikstrom et al, 28 which was modified to simulate soccer‐specific movement 21 . The players were asked to jump off with both legs and perform an imaginary header before landing with one leg on a force plate (AMTI Inc.).…”

“…Contact injuries, illnesses, and injuries to the upper body were excluded because of their unpredictable nature compared to non‐contact injury mechanisms. Further information about the inclusion and exclusion criteria, as well as the injury data collection process, has been described in detail elsewhere 21 . The Ethics Committee of TU Dortmund University confirmed that the requirements of the Declaration of Helsinki were met.…”

“…The lowest values were used because players with a low value tend to have better postural control. 21…”