Knee extension measurement , design of the instrument
A special instrument was constructed to measure knee extension ( Fig.1). The design enabled recording the ROM of knee extension on a linear scale with an accuracy of 1 mm. The measurement plate was placed into a special box, fixed to the edge of the measurement table, on the same level. The subject was in sitting position, feet extended and heels on the measurement plate. The knee extension ROM was read from the scale and expressed the distance between the heel support (measurement plate in zero position) and maximally uplifted heels. The up-movement of the measurement plate A, during the knee extension performance, takes place due to the pressure of the springs constructed inside of the instrument. The fixing screw D enables to fix the height of the measurement plate at the end of the knee extension performance.
Reliability of measurement.
To estimate the reliability of the knee extension measurement procedure, intraobserver and interobserver testing was arranged previously 9 on 15 students of physical education at the age of 18-19 yr. . Analytic equation by Malina et al 10 , was used to estimate the technical error of measurements [in mm].There was a calculated intertester error 1.46 and correlation coefficient between two sessions was r=0.95 (p<0.001). The corresponding result for intratester intrassay error was 1.26 and r=0.96 (p<0.001). Intratester interassay error 1.85 was determined by 2 measurement sessions with one-week interval and correlation coefficient between those was r=0.95 (p<0.001).