Inter-machine reliability of the Biodex and Cybex isokinetic dynamometers for knee flexor/extensor isometric, concentric and eccentric tests

Phys Ther Sport. 2015 Feb;16(1):59-65. doi: 10.1016/j.ptsp.2014.04.004. Epub 2014 May 15.


Objectives: To assess the inter-machine reliability of the Biodex System 3 Pro and Cybex Humac Norm Model 770 dynamometers for knee extensor and knee flexor peak torque measurements in isometric, concentric and eccentric tests.

Design: Randomized/crossover.

Setting: Exercise Research Laboratory, Federal University of Rio Grande do Sul (Brazil).

Participants: 25 healthy male subjects.

Main outcome measures: Isometric, concentric and eccentric knee extensor and knee flexor peak torques recorded in the same test procedure performed on both isokinetic dynamometers. One-way ANOVA, intraclass correlation coefficient (ICC), standard error of measurement (SEM) and coefficient of variation (CV) were used to verify significant differences, relative and absolute reliability between devices.

Results: No significant differences were found between tests performed on Biodex and Cybex (p > 0.05). ICC values indicated a high to very high reproducibility for isometric, concentric and eccentric peak torques (0.88-0.92), and moderate to high reliability for agonist-antagonist strength ratios (0.62-0.73). Peak torque did not show great difference between dynamometers for SEM (3.72-11.27 Nm) and CV (5.27-7.77%). Strength ratios presented CV values of 8.57-10.72%.

Conclusion: Maximal knee extensor and knee flexor tests performed in isometric (60° of knee flexion), concentric and eccentric modes at 60°/s in Biodex and Cybex dynamometers present similar values.

Keywords: Hamstring; Isokinetic dynamometry; Quadriceps; Test–retest.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Equipment Design
  • Exercise Test
  • Humans
  • Knee Joint*
  • Male
  • Muscle Contraction / physiology*
  • Muscle Strength Dynamometer / standards*
  • Muscle, Skeletal / physiology
  • Quadriceps Muscle / physiology*
  • Reproducibility of Results
  • Young Adult