Multivariate analysis of functional lateralities, myodynamic asymmetries and injuries at the lower extremities of soccer players

INTRODUCTION. Soccer as a composite kinetic protype contains maximal effort unilateral somatic movements (kicking and controlling the ball), and this, consequently, leads to asymmetrical loading and adaptations as well as to high epidemiological rate of musculoskeletal injuries at the player’s lower extremities. The present study aimed primarily at developing strategies for sufficient soccer injury prevention, through experimental analysis and recognition of their etiology. Furthermore, this study was focused on the composite statistical evaluation with a prospective design of the intrinsic kinesiological mechanisms (Footedness, asymmetries in myodynamic function, flexibility, proprioception, anatomical asymmetries and previous injuries) connected with injuries of different characteristics regarding severity, frequency and laterality. METHODS. One-hundred professional soccer players (age 23,4±4,8 years, weight 74,2±7,6 , height 178±6,7) were tested at the pre-seasonal period for lower extremity functional capacity and for specific anatomical and anatomical and anthropometrical characteristics. Knee myodynamic assessment (flexion-extension) wastested isokinetically (Biodex, System III) at 60o, 180o and 300o/sec for the concentric mode ofcontraction and at 60o and 180o/sec for the eccentric. The ankle joint was tested at 60o/sec for both the concentric and eccentric mode of contraction. Lower extremity flexibility was tested withgoniometrical methods while the anterior knee laxity with the KT1000 arthrometer. Anthropometrical characteristics (girths, lengths) were evaluated with the implementationof ISAK method (International Society of Kinanthropometry). Neuromuscular coordination wasassessed with the Prokin-200 kinaesthetic platform (TechnobodyItaly). All soccer injuries forcingplayers to miss at least one scheduled practise session or game were recorded. Data of the presentstudy was analyzed through multivariate (MANOVA) and logistic regression analysis. RESULTS.Significant knee and ankle multivariate asymmetries were found for (a) myodynamic function(directional: Wilks’ Λ=0.667, p=0.001; αbsolute: Wilks’ Λ=0.047, p=0.000 and fluctuatingasymmetries Wilks’ Λ=0.613, p=0.00), (b) muscle flexibility (directional: Wilks’ Λ=0.793,p=0.028 and αbsolute asymmetries: Wilks’ Λ=0.926, ρ=0.000) and (c) anterior knee laxity (directional: Wilks’ Λ=7.15, p=0.001; αbsolute: Wilks’ Λ=41.91, p=0.000 and fluctuating asymmetries: Wilks’ Λ=3.89, p=0.024). Several significant asymmetries were also revealed for the specific anthropometrical characteristics (lower extremity lengths and girths, p0.05). Sixty-two soccer players (62%) sustained one or more injury at their lower extremities, which caused them to miss training and/or playing time during the period of the study while the total number of injuries recorded was eighty-two (82). The incidence rate of these injuries was 21.8 and 1.1 injuries per 1000 game and training-hours, respectively. Anatomical sites with high injury rate was the thigh (35%), the ankle (25%) and the knee joint (21% ). Respectively, injuries with high incidence rate were muscle strains(46,3%) and ligament sprains (25,6%) while lesser percentages of injuries referred to tendinopathies (12.2%) and bone fractures (3,7%). Players with eccentric hamstrings strength asymmetries (>15%) (OR=3.88; 95% CI:1.13-13.23) and functional leg length asymmetries(>1,8 cm) (OR =3.80; 95% CI:1.08- 13.33) were at greater risk of sustaining a hamstrings musclestrains compared with players with no functional and anatomical asymmetries. Previous injuries were a protective factor for the development of new non contact hamstrings strains (OR=0.15; 95% CI:0.029-0.791, p= 0.025). The risk of a new non-contact ankle sprains was significantly increased in players with eccentric isokinetic strength asymmetries of ankle dorsal and plantar flexors (OR=4.25; 95% CI:1.135-19.411, p= 0.033), and increased body weight (OR=3.72;95% CI:1.035-51.530, p= 0.046) compared to those with no functional asymmetries (eccentricstrength) and somatic weight below mean value of sample (15%) (OR=3.88; 95% CI: 1.13-13.23, p= 0.030) των οπίσθιων μηριαίων όσο και στο λειτουργικό μήκος των κάτω άκρων (>1,8 cm) (OR =3.80; 95% CI:1.08-13.33, p= 0.037) εμφάνισαν σημαντικά μεγαλύτερη πιθανότητα να υποστούν θλάση μη-επαφής στους οπίσθιους μηριαίους, συγκριτικά με όσους δεν εμφάνισαν αντίστοιχες λειτουργικές και ανατομικές ασυμμετρίες. Οι προηγούμενοι τραυματισμοί των οπίσθιων μηριαίων αποτέλεσαν προστα- τευτικό παράγοντα για την πρόκληση νέων μυϊκών θλάσεων μη-επαφής σε αυτούς τους μύς (OR=0.15; 95% CI:0.029-0.791, p= 0.025). Οι ποδοσφαιριστές που εμφάνισαν έκκεντρες ισοκινητικές ασυμμετρίες στους ραχιαίους και πελματιαίους καμπτήρες της ποδοκνημικής (OR=4.25; 95% CI:1.135-19.411, p= 0.033)και είχαν βάρος πάνω από το μέσο όρο του δείγματος (OR=3.72; 95% CI:1.035- 51.530, p= 0.046) αντιμετώπισαν σημαντικά μεγαλύτερο κίνδυνο να υποστούν συνδεσμική κάκωση (διάστρεμμα) μη-επαφής στην ποδοκνημική, συγκριτικά με όσους δεν εμφάνισαν λειτουργικές ασυμμετρίες (έκκεντρης ισχύος) και είχαν σωματικό βάρος μικρότερο του μέσου όρου (