Estimation of the Knee Flexion-Extension Angle During Dynamic Sport Motions Using Body-worn Inertial Sensors

Abstract

Motion analysis has become an important tool for athletes to improve their performance. However, most motion analysis systems are expensive and can only be used in a laboratory environment. Ambulatory motion analysis systems using inertial sensors would allow more flexible use, e.g. in a real training environment or even during competitions. This paper presents the calculation of the flexion-extension knee angle from segment acceleration and angular rates measured using body-worn inertial sensors. Using a functional calibration procedure, the sensors are first aligned without the need of an external camera system. An extended Kalman filter is used to estimate the relative orientations of thigh and shank, from which the knee angle is calculated. The algorithm was validated by comparing the computed knee angle to the output of a reference camera motion tracking system. In total seven subjects performed five dynamic motions: walking, jogging, running, jumps and squats. The averaged root mean squared error of the estimated knee angle was 8.2 ± 2.4 over all motions, with an average Pearson-correlation of 0.971 ± 0.020. In the future this will allow the analysis of joint angles during dynamic sports movements.

Mobile assessment of the lower limb kinematics in healthy persons and in persons with degenerative knee disorders: A systematic review

“…According to the Downs and Black checklist [27], 12 studies were of substantial quality [30][31][32][33][34][35][36][37][38], 10 of moderate quality [39][40][41][42][43][44][45][46][47][48] and one of low quality [49]. Within the studies on kinematics in healthy persons, the methodological quality was 60% on average (range between 42-75%).…”

“…From these 18 papers, 16 focussed on reliability or validity assessment of the applied inertial sensor system [30,31,33,[35][36][37][38][40][41][42][43][44][45][46][47][48] and two studies on the description of kinematics [32,34]. In 12 studies the outcome of the inertial sensor system was compared against the outcomes registered by an optoelectronic or electromagnetic system [30,33,[35][36][37][38][41][42][43][44][45][46]. One study compared the sensors' outcomes to the judgement of trained physicians [47], another to outcomes from videoanalysis [48].…”

Categorized Uwb on-Body Radio Channel Modeling for Wbans

“…In [33], the same disease is monitored by using accelerometers installed at the trunk of a patient. For sports applications, [34] presents a motions tracking system based on inertial sensors placed at the hip, leg and foot.…”

Design and Development of Low-cost Smart Training Pants (STants)

“…The correlation coefficients are 0.987 and 0.991, respectively. The observed errors are in the range of previously proposed systems using the same type of IMUs under comparable conditions [26], however, leave room for improvement. The higher errors observed for the right joint resulted from unwanted sensor movement with respect to the body.…”