Reliability and validity of angular joint velocity using Peak Motus 2000 Motion Analysis and Kin-Com Isokinetic Dynamometer
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- Physical Therapy -- instrumentation; Physical Therapy
Background and Purpose: Use of motion analysis systems for the study of human motion in research settings and clinical settings are becoming more prevalent. In a traditional sense, motion analysis systems are used for gait analysis; most recently, they are being utilized to analyze spinal motion, foot motion, and components of motion during sporting activities. Questions about the accuracy of these computerized motion analysis systems and the precision and reliability of the digitizing process remains. The purpose of this study is to determine the validity of the Peak Motus 2000 motion analysis system® (Peak Performance) in calculating dynamic velocities and range of motion. Methods: Six healthy subjects (three females and three males) had reflective markers placed on the right ankle joint. Video cameras filmed the subject's ankle movements while on the Kin-Com Isokinetic Dynamometer®(Kin-Com). The subjects were taken through five repetitions each of the following passive speeds: 60, 150, and 240 degrees/second. The Kin-Com Isokinetic Dynamometer® was then utilized in a passive mode without subjects by placing reflective markers on the lever arm. The Peak Motus 2000 motion analysis® computer software program was used from recorded video motion with a subject attached to the apparatus to determine angular joint velocity. Statistical analysis was completed comparing data sets. Results: In summary, the compiled standard deviation values from lowest to highest are Kin-Com, Peak Performance lever arm and Peak Performance skin marker. This indicates that subject motion analyzed by skin marker angular velocity measurements had a greater variability and therefore a higher chance of being inaccurate. It was found that the Peak Performance had a trend towards overestimating set angular velocities, which became larger as the speed was increased. Conclusion: This study found that at 60 degrees/second there was no significant . difference in reported angular velocity between the Kin-Com and the Peak Performance and a significant difference in reported angular velocity at 150 and 240 degrees/second. It also showed that the Peak Performance tended to be more accurate at lower speeds and decreased in accuracy as the speeds increased. The Peak Performance generally overestimated the angular velocity at each speed. Thus, in the clinic the Peak Performance can be used to measure angular joint velocity at lower speeds and can be considered to be reliable.