Concurrent validity of evaluating knee kinematics using Kinect system during rehabilitation exercise

Squats,ascending and descending stairs,and lunges are three functional movements popularly used in clinical rehabilitation.This study aimed to analyze the validity of the Kinect v2 for assessing the kinematics of three functional knee movements.An intelligent program was developed for real-time kinematic evaluation of the knee joint using the Kinect v2 system.Based on image recognition technology,images from the Kinect v2 depth camera were used to develop a kinematic evaluation program for knee joint movements.The kinematics of 30 healthy volunteers during stair ascent and descent,squatting,and lunging movements were collected synchronously with both VICON and Kinect systems.The peak knee angles in the sagittal and coronal planes were extracted and analyzed.A paired samples t-test and the relative coefficient within the groups were used for statistical analysis of the validity of the Kinect compared to the VICON.There was no significant difference(p>0.05)in bilateral knee flexion angle when lunging.No significant difference(p>0.05)was found in left knee flexion during squatting exercises.Although the Kinect generally underestimated knee flexion and valgus,it displayed excellent consistency and good to excellent agreement with the VICON motion analysis system.The results demonstrated that the Kinect based measurement tool for analyzing knee kinematics has the potential to be an effective clinical training device for maintaining knee alignment during exercise.

Toward more reliable stability measurements in stance: recommendations for number of measurements, foot position and feedback——a cross-sectional study among servicemen

Background:In the military,insufficient postural stability is a risk factor for developing lower extremity injuries.Postural stability training programs are effective in preventing these injuries.However,an objective method for the measurement of postural stability in servicemen is lacking.The primary objective of this study was to assess the influence of the number of repetitions,different foot positions and real-time visual feedback on postural stability,as well as their effects on the intrasession reliability of postural stability measurements in servicemen.The secondary objective was to assess the concurrent validity of the measurements.Methods:Twenty healthy servicemen between 20 and 50 years of age and in active duty were eligible for this quantitative,cross-sectional study.The measurements took place on a force plate,measuring the mean velocity of the center of pressure.The participants were asked to stand as still as possible in three different foot positions(wide stance,small stance,and on one leg),five times each for 45 s each time,and the measurements were performed with and without real-time visual feedback.Results:We observed a significant main effect of foot position(P<0.001),but not of visual feedback(P=0.119)or repetition number(P=0.915).Postural stability decreased in the more challenging foot positions.The ICC estimates varied from 0.809(one repetition in wide stance)to 0.985(five repetitions on one leg).The common variance(R2)between different foot positions without feedback varied between 0.008(wide stance)and 0.412.Conclusions:To yield reliable data,wide-stance measurements should be conducted three times,and small-stance measurements and measurements on one leg should be conducted two times.The scores of a measurement in a particular foot position cannot predict the scores of measurements in other foot positions.