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  1. Rogério Pereira1,2,3,4,
  2. Renato Andrade1,2,4,
  3. Ricardo Vidal1,2,
  4. Filipe Castanheira1,2,
  5. Ana Leal1,2,5,
  6. Cátia Saavedra1,2,
  7. Nuno Pais1,2,
  8. Hugo Duarte7,
  9. Luís Silva1,2,
  10. Alberto Monteiro1,2,
  11. Nuno Loureiro1,2,11,12,
  12. João Espregueira-Mendes1,2,7,8,9,10
  1. 1Clínica do Dragão, Espregueira-Mendes Sports Centre, FIFA Medical Centre of Excellence, Porto, Portugal
  2. 2Dom Henrique Research Centre, Porto, Portugal
  3. 3University Fernando Pessoa, Porto, Portugal
  4. 4Faculty of Sports, University of Porto, Porto, Portugal
  5. 5CMEMS Center for MicroElectroMechanical Systems, Mechanical Engineering Department, University of Minho, Braga, Portugal
  6. 6ULS Nordeste, Macedo De Cavaleiros, Portugal
  7. 7Faculty of Medicine, University of Porto, Porto, Portugal
  8. 8Orthopaedics Department of Minho University, Braga, Portugal
  9. 93B's Research Group - Biomaterials, Biodegradables and Biomimetics, University of Minho, Headquarters of the European Institute of Excellence on Tissue Engineering and Regenerative Medicine, Braga/Guimarães, Portugal
  10. 10ICVS/3B's - PT Government Associate Laboratory, Braga/Guimarães, Portugal
  11. 11Futebol Clube Paços de Ferreira, Paços de Ferreira, Portugal
  12. 12Portuguese Federation of Cycling, Lisboa, Portugal


    Background Neuromuscular isokinetic screening as a pre-season test may identify players at risk of injury or undertrained players.

    Objective Identify, assess and describe unilateral and bilateral knee muscular deficits in elite football players at pre-season screening.

    Design Retrospective cohort.

    Setting Elite football divisions.

    Patients (or Participants) Of 99 eligible male elite footballers, older than 17 years and without knee injury within the last 6 months, 3 were excluded, resulting in a final sample of 96 players (25 yrs old, BMI 23.7 kg·m−2).

    Assessment of Risk Factors Knee isokinetic assessment of both limbs was performed, starting with the non-dominant limb. The test range was set and gravity correction was performed. Before each isokinetic test, players were allowed 4 submaximal repetitions. The isokinetic test consisted of concentric sets of 6 and 8 repetitions, at 60˚/s and 180˚/s, respectively.

    Main Outcome Measurements Peak torque of knee extensors and flexors at 60˚/s and 180˚/s and conventional ratio at 60˚/s and 180˚/s. Individuals were also analysed for bilateral differences (>10%) and conventional ratio – Con/Con – (<0.47 and >0.80).

    Results Subgrouping by position, bilateral statistically significant differences were more frequent among defenders and goalkeepers, both for knee extensors and flexors (p<0.05). After individual analysis, 19% and 31% of players displayed significant bilateral asymmetries (>10%) for extensor peak torque at 60˚/s and 180˚/s, respectively; while 21% and 44% showed significant bilateral asymmetries for flexor peak torque at 60˚/s and 180˚/s, respectively. The conventional ratio was abnormal among 7% of players, for both dominant and non-dominant limbs at 60˚/s, and among 11% and 9% for dominant and non-dominant limbs, respectively, at 180˚/s.

    Conclusions Defenders and goalkeepers tended to present bilateral differences for isokinetic parameters more frequently than other player positions. There was a considerable proportion of players with clinically meaningful bilateral asymmetries, also impacting on unilateral balance. This screening is important to tailor neuromuscular programmes addressing deficits believed to be associated with injury risk, relevant in both primary and secondary injury prevention.

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