Reliability and Validity of a Modified Isometric Dynamometer in the Assessment of Muscular Performance in Individuals with Anterior Cruciate Ligament Reconstruction.

OBJECTIVES The aim of this study was to evaluate the reliability and validity of a modified isometric dynamometer (MID) in performance deficits of the knee extensor and flexor muscles in normal individuals and in those with ACL reconstructions. METHODS Sixty male subjects were invited to participate of the study, being divided into three groups with 20 subjects each: control group (GC), group of individuals with ACL reconstruction with patellar tendon graft (GTP, and group of individuals with ACL reconstruction with hamstrings graft (GTF). All individuals performed isometric tests in the MID, muscular strength deficits collected were subsequently compared to the tests performed on the Biodex System 3 operating in the isometric and isokinetic mode at speeds of 60°/s and 180o/s. Intraclass ICC correlation calculations were done in order to assess MID reliability, specificity, sensitivity and Kappa's consistency coefficient calculations, respectively, for assessing the MID's validity in detecting muscular deficits and intra- and intergroup comparisons when performing the four strength tests using the ANOVA method. RESULTS The modified isometric dynamometer (MID) showed excellent reliability and good validity in the assessment of the performance of the knee extensor and flexor muscles groups. In the comparison between groups, the GTP showed significantly greater deficits as compared to the GTF and GC groups. CONCLUSION Isometric dynamometers connected to mechanotherapy equipments could be an alternative option to collect data concerning performance deficits of the extensor and flexor muscles groups of the knee in subjects with ACL reconstruction.