Knee Surgery, Sports Traumatology, Arthroscopy

, Volume 23, Issue 7, pp 1907–1916 | Cite as

Inter- and intrarater reliability of four single-legged hop tests and isokinetic muscle torque measurements in children

  • Marianne Bakke Johnsen
  • Ingrid Eitzen
  • Håvard Moksnes
  • May Arna Risberg



Single-legged hop tests and isokinetic muscle torque are common outcome measures in the evaluation of knee function. The reliability of the single-legged hop tests in children has not been documented. The aim was to examine inter- and intrarater reliability of four single-legged hop tests and isokinetic muscle torque measurements in children.


Twenty-eight sports-active children (12.4 ± 0.3 years old) were tested three times in two test sessions separated by 1 week. They performed four single-legged hop tests and concentric isokinetic torque measurements during knee extension and flexion. Inter- and intrarater reliability were calculated using the intraclass correlation coefficient (ICC 2,1). Relative terms of the standard error of measurement (SEM %) and smallest real difference (SRD %) were emphasized to allow comparison between the different variables.


Twenty-six children were included for statistical analysis. ICCs for inter- and intrarater reliability were moderate to high for the hop tests (0.62–0.91) and isokinetic measurements (0.76–0.87). SEMs % were low for the hop tests (3.9–7.4 %) and the isokinetic measurements (5.2–8.9 %). SRDs % were 20.5 % or less for the hop tests, 15.7 % or less for knee extension, and 24.6 % or less for knee flexion.


The single-legged hop tests and isokinetic muscle torque measurements demonstrated moderate-to-high reliability with low measurement error in sports-active children. A change above 20.5 % for the single-legged hop tests, 15.7 % for knee extension, and 24.6 % for knee flexion is necessary to represent a real change in knee function.

Level of evidence



Performance-based tests Lower extremity Hop tests Isokinetic dynamometry Muscle strength Reproducibility of results 



We would like to thank Kristin Bølstad for help with the preparation of the study. Maren Hjelle Guddal, Arnhild Bakken, Nina Markussen, and Carina Wold are acknowledged for their assistance on the test days. Thanks to Professor Ingar Holme, at the Norwegian School of Sport Sciences, for helpful advice on the statistical analysis. Additionally, the Norwegian Sports Medicine Clinic (NIMI) is acknowledged for the contribution of infrastructure.

Conflict of interest

The authors declare that there are no conflict of interests.


  1. 1.
    Ayalon M, Ben-Sira D, Hutzler Y, Gilad T (2000) Reliability of isokinetic strength measurements of the knee in children with cerebral palsy. Dev Med Child Neurol 42(6):398–402PubMedCrossRefGoogle Scholar
  2. 2.
    Bahr R, Holme I (2003) Risk factors for sports injuries—a methodological approach. Br J Sports Med 37(5):384–392PubMedCentralPubMedCrossRefGoogle Scholar
  3. 3.
    Baumgartner TA (2003) Measurement for evaluation in physical education and exercise science. McGraw-Hill, BostonGoogle Scholar
  4. 4.
    Bent NP (2009) Selecting outcome measures in sports medicine: a guide for practitioners using the example of anterior cruciate ligament rehabilitation. Br J Sports Med 43(13):1006–1012PubMedCrossRefGoogle Scholar
  5. 5.
    Caine D, Maffulli N, Caine C (2008) Epidemiology of injury in child and adolescent sports: injury rates, risk factors, and prevention. Clin Sports Med 27(1):19–50 viiPubMedCrossRefGoogle Scholar
  6. 6.
    de Vet HC, Terwee CB, Ostelo RW, Beckerman H, Knol DL, Bouter LM (2006) Minimal changes in health status questionnaires: distinction between minimally detectable change and minimally important change. Health Qual Life Outcomes 4:54PubMedCentralPubMedCrossRefGoogle Scholar
  7. 7.
    Deighan MA, De Ste Croix MBA, Armstrong N (2003) Reliability of isokinetic concentric and eccentric knee and elbow extension and flexion in 9/10 year old boys. Isokinet Exerc Sci 11(2):109–115Google Scholar
  8. 8.
    Eitzen I, Hakestad KA, Risberg MA (2012) Inter- and intrarater reliability of isokinetic thigh muscle strength tests in postmenopausal women with osteopenia. Arch Phys Med Rehabil 93(3):420–427PubMedCrossRefGoogle Scholar
  9. 9.
    Eitzen I, Moksnes H, Snyder-Mackler L, Engebretsen L, Risberg MA (2010) Functional tests should be accentuated more in the decision for ACL reconstruction. Knee Surg Sports Traumatol Arthrosc 18(11):1517–1525PubMedCentralPubMedCrossRefGoogle Scholar
  10. 10.
    Hartmann A, Knols R, Murer K, De Bruin ED (2009) Reproducibility of an isokinetic strength-testing protocol of the knee and ankle in older adults. Gerontology 55(3):259–268PubMedCrossRefGoogle Scholar
  11. 11.
    Holm I, Fredriksen P, Fosdahl M, Vollestad N (2008) A normative sample of isotonic and isokinetic muscle strength measurements in children 7–12 years of age. Acta Paediatr 97(5):602–607PubMedCrossRefGoogle Scholar
  12. 12.
    Hopkins WG (2000) Measures of reliability in sports medicine and science. Sports Med 30(1):1–15PubMedCrossRefGoogle Scholar
  13. 13.
    Janarv PM, Nystrom A, Werner S, Hirsch G (1996) Anterior cruciate ligament injuries in skeletally immature patients. J Pediatr Orthop 16(5):673–677PubMedCrossRefGoogle Scholar
  14. 14.
    Kellis E, Kellis S, Gerodimos V, Manou V (1999) Reliability of isokinetic concentric and eccentric strength in circumpubertal soccer players. /Fiabilite des mesures de la force isocinetique concentrique et excentrique chez des joueurs de football autour de la puberte. Pediatr Exerc Sci 11(3):218–228Google Scholar
  15. 15.
    Lexell JE, Downham DY (2005) How to assess the reliability of measurements in rehabilitation. Am J Phys Med Rehabil 84(9):719–723PubMedCrossRefGoogle Scholar
  16. 16.
    Merlini L, Dell’Accio D, Granata C (1995) Reliability of dynamic strength knee muscle testing in children. J Orthop Sports Phys Ther 22(2):73–76PubMedCrossRefGoogle Scholar
  17. 17.
    Mohtadi N, Grant J (2006) Managing anterior cruciate ligament deficiency in the skeletally immature individual: a systematic review of the literature. Clin J Sport Med 16(6):457–464PubMedCrossRefGoogle Scholar
  18. 18.
    Mohtadi NG, Kiefer GN, Tedford K, Watters S (1990) Concentric and eccentric quadriceps torque in pre-adolescent males. Can J Sport Sci 15(4):240–243PubMedGoogle Scholar
  19. 19.
    Moksnes H, Engebretsen L, Eitzen I, Risberg MA (2013) Functional outcomes following a non-operative treatment algorithm for anterior cruciate ligament injuries in skeletally immature children 12 years and younger. A prospective cohort with 2 years follow-up. Br J Sports Med 47(8):488–494PubMedCrossRefGoogle Scholar
  20. 20.
    Moksnes H, Engebretsen L, Risberg MA (2012) Management of anterior cruciate ligament injuries in skeletally immature individuals. J Orthop Sports Phys Ther 42(3):172–183PubMedCrossRefGoogle Scholar
  21. 21.
    Munro AG, Herrington LC (2011) Between-session reliability of four hop tests and the agility t test. J Strength Cond Res 25(5):1470–1477PubMedCrossRefGoogle Scholar
  22. 22.
    Noyes FR, Barber SD, Mangine RE (1991) Abnormal lower limb symmetry determined by function hop tests after anterior cruciate ligament rupture. Am J Sports Med 19(5):513–518PubMedCrossRefGoogle Scholar
  23. 23.
    Parkkari J, Pasanen K, Mattila VM, Kannus P, Rimpela A (2008) The risk for a cruciate ligament injury of the knee in adolescents and young adults: a population-based cohort study of 46,500 people with a 9 year follow-up. Br J Sports Med 42(6):422–426PubMedCrossRefGoogle Scholar
  24. 24.
    Portney LG, Watkins MP (2000) Foundations of clinical research: applications to practice. Prentice Hall, Upper Saddle RiverGoogle Scholar
  25. 25.
    Reid A, Birmingham TB, Stratford PW, Alcock GK, Giffin JR (2007) Hop testing provides a reliable and valid outcome measure during rehabilitation after anterior cruciate ligament reconstruction. Phys Ther 87(3):337–349PubMedCrossRefGoogle Scholar
  26. 26.
    Ross MD, Irrgang JJ, Denegar CR, McCloy CM, Unangst ET (2002) The relationship between participation restrictions and selected clinical measures following anterior cruciate ligament reconstruction. Knee Surg Sports Traumatol Arthrosc 10(1):10–19PubMedCrossRefGoogle Scholar
  27. 27.
    Ross MD, Langford B, Whelan PJ (2002) Test-retest reliability of 4 single-leg horizontal hop tests. J Strength Cond Res 16(4):617–622PubMedGoogle Scholar
  28. 28.
    Santos AN, Pavao SL, Avila MA, Salvini TF, Rocha NA (2013) Reliability of isokinetic evaluation in passive mode for knee flexors and extensors in healthy children. Braz J Phys Ther 17(2):112–120PubMedGoogle Scholar
  29. 29.
    Shrout PE, Fleiss JL (1979) Intraclass correlations: uses in assessing rater reliability. Psychol Bull 86(2):420–428PubMedCrossRefGoogle Scholar
  30. 30.
    Sole G, Hamren J, Milosavljevic S, Nicholson H, Sullivan SJ (2007) Test–retest reliability of isokinetic knee extension and flexion. Arch Phys Med Rehabil 88(5):626–631PubMedCrossRefGoogle Scholar
  31. 31.
    Streiner DL, Norman GR (2008) Reliability. In: Streiner DL, Norman GR (eds) Health measurement scales: a practical guide to their development and use, 4th edn. Oxford University Press, Oxford, pp 167–210CrossRefGoogle Scholar
  32. 32.
    Tsiros MD, Grimshaw PN, Schield AJ, Buckley JD (2011) Test–retest reliability of the biodex system 4 isokinetic dynamometer for knee strength assessment in paediatric populations. J Allied Health 40(3):115–119PubMedGoogle Scholar
  33. 33.
    Turner D, Schunemann HJ, Griffith LE, Beaton DE, Griffiths AM, Critch JN, Guyatt GH (2010) The minimal detectable change cannot reliably replace the minimal important difference. J Clin Epidemiol 63(1):28–36PubMedCrossRefGoogle Scholar
  34. 34.
    Walter SD, Eliasziw M, Donner A (1998) Sample size and optimal designs for reliability studies. Stat Med 17(1):101–110PubMedCrossRefGoogle Scholar
  35. 35.
    Weir JP (2005) Quantifying test–retest reliability using the intraclass correlation coefficient and the SEM. J Strength Cond Res 19(1):231–240PubMedGoogle Scholar

Copyright information

© Springer-Verlag Berlin Heidelberg 2013

Authors and Affiliations

  • Marianne Bakke Johnsen
    • 1
  • Ingrid Eitzen
    • 2
  • Håvard Moksnes
    • 1
  • May Arna Risberg
    • 1
  1. 1.Department of Sport Medicine, Norwegian School of Sport SciencesNorwegian Research Center for Active Rehabilitation (NAR)OsloNorway
  2. 2.Department of Orthopedic Surgery, Oslo University HospitalNorwegian Research Center for Active Rehabilitation (NAR)OsloNorway

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