Evidence for Validity and Reliability of Multiarticular Leg Extension Machine
Christos Papadopoulos, Konstantinos Theodosiou, Georgios Noussios, Evaggelia Gantiraga, Konstantinos Meliggas, Michalis Sambanis, Ioannis Gissis

Abstract
The aim of this study was to evaluate the reliability and validity of a multiarticular leg extension machine (MaLEM) to assess the kinematic characteristics of MaLEM, the force time curve characteristics of isokinetic (concentric and eccentric), isometric force measurements, and two different jumps with slow (CMJ) and fast (DJ) stretch shortening cycle (SSC). Nineteen subjects (age: 20.6±1.6years, body mass: 75.3±6.5kg, height: 180±6cm) participated in this study. After familiarization, subjects were tested and retested 2 days later for isokinetic strength (eccentric and concentric peak force (Fisoki-ecc&conmax) and rate of force development (RFDecc&con)), maximal voluntary isometric contraction (MVIC) and RFD, as well as jumping ability (CMJ and DJ maximum height, force and power), to evaluate relative and absolute reliability and usefulness of the test. The criterion validity of the MaLEM was determined by examining the relationship between MaLEM indices and the isometric force and both vertical jumps performances. Reliability of the Fisoki-ecc&conmax and RFDecc&con of the MaLEM was very good, with intraclass correlation coefficient >0.90 and SEM <5% and low bias. The usefulness of the Fisoki-ecc&conmax and RFDecc&con of the MaLEM was rated as ‘‘good’’ respectively. Both, the Fisoki-ecc&conmax, and the RFDecc&con of the MaLEM had high significant correlations with both isometric force measurements (Fmax & RFDiso), and the Pmax of the vertical jumps; and good and high correlations with RFDiso and the Fmax of the two vertical jumps. With regard to HmaxCMJ&DJ good correlations observed only the Fisoki-ecc&conmax with the peak height jump of CMJ. These findings suggest that the MaLEM is a reliable and valid test for assessing force, explosiveness and power in the rehabilitation and sport. Consequently, the isokinetic MaLEM test is an easily applied, and can provide coaches, strength and conditioning professionals with relevant information concerning the choice and the efficacy of training programs.

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