, PT2ew studies have examined validity and reliability of an isokinetic device using instrumentation that had "proven" technical accuracy instead of human subjects, who are inherently unreliable. One example is the study by Farrell and Richards (5). who looked at validity and reliability of the Kincom (Chattecx Corporation, Chattanooga, TN). While they were able to show significant validity and reliability for both angular velocity and torque, their measurements of force were averaged over the middle 25" of the lever arm stroke rather than being compared at specific angles throughout the arc of motion.Bemben et al (2) evaluated the technical accuracy of the Cybex I1 (Lumex, Inc., Ronkonkoma, NY) for velocity, torque, and the effects of damping on velocity and torque. Their results indicated that the Cybex I1 was accurate for both velocity and peak torque, provided that damping was set at four during calibration and testing. As with the Farrell and Richards study, Bemben et al failed to assess validity and reliability over a broad range of motion. They looked instead at peak torque, which had a variable angle of occurrence.Aitkens et al (1) examined the validity of the LIDO Digital isokinetic system (Loredan, Inc., Davis, CA) by dropping weights ranging from 1.36 to 99.5 Ib using a 2-ft leWhen evaluating a strength testing method, reliability rather than validity, the most critical component, is most frequently addressed. The purpose of this study was to assess the validity and reliability of the 11170 Active system in the isokinetic mode. Velocity and torque were continuously monitored while torques of 10.4, 25.6, 30.6, and 89.6 ft-lb ver arm through a 180" arc. Their study was done at velocities of 5 and 60°/sec. They recorded only peak torque and neglected to measure the angle of occurrence. Although the Lido Digital was accurate for peak torque, the authors failed to determine validity over a broad range of motion.Davies (4) concluded that the power to body weight ratio is the single most important value that can be obtained from isokinetic testing. In order for power to be measured accurately, however, the isokinetic device must be validated at many angles throughout the arc of motion. The purpose of the present study is to determine the validity and reliability of the LIDO Active isokinetic device (Loredan, Inc., Davis, CA), using preselected angles over a broad range of motion. MATERIALS AND METHODSThe first step in the study was to test the quality of data that could be obtained from the measurement devices. The validity and reliability of an RCA VHS camcorder (model #CC250, Indianapolis, Indiana) and a Sears DA4 Head H Q VHS videocassette recorder (Sears, Roebuck and Co., Chicago, IL) were determined using the following protocol. A Casio Databank wristwatch (model #DBC-6 1, Japan) was filmed to record time accurate to 0.0 1 sec and played back on the VCR using single-framed advance to determine the number of frames per second. This