An Inertial Sensor-Based Method for Estimating the Athlete's Relative Joint Center Positions and Center of Mass Kinematics in Alpine Ski Racing

Abstract

For the purpose of gaining a deeper understanding of the relationship between external training load and health in competitive alpine skiing, an accurate and precise estimation of the athlete's kinematics is an essential methodological prerequisite. This study proposes an inertial sensor-based method to estimate the athlete's relative joint center positions and center of mass (CoM) kinematics in alpine skiing. Eleven inertial sensors were fixed to the lower and upper limbs, trunk, and head. The relative positions of the ankle, knee, hip, shoulder, elbow, and wrist joint centers, as well as the athlete's CoM kinematics were validated against a marker-based optoelectronic motion capture system during indoor carpet skiing. For all joints centers analyzed, position accuracy (mean error) was below 110 mm and precision (error standard deviation) was below 30 mm. CoM position accuracy and precision were 25.7 and 6.7 mm, respectively. Both the accuracy and precision of the system to estimate the distance between the ankle of the outside leg and CoM (measure quantifying the skier's overall vertical motion) were found to be below 11 mm. Some poorer accuracy and precision values (below 77 mm) were observed for the athlete's fore-aft position (i.e., the projection of the outer ankle-CoM vector onto the line corresponding to the projection of ski's longitudinal axis on the snow surface). In addition, the system was found to be sensitive enough to distinguish between different types of turns (wide/narrow). Thus, the method proposed in this paper may also provide a useful, pervasive way to monitor and control adverse external loading patterns that occur during regular on-snow training. Moreover, as demonstrated earlier, such an approach might have a certain potential to quantify competition time, movement repetitions and/or the accelerations acting on the different segments of the human body. However, prior to getting feasible for applications in daily training, future studies should primarily focus on a simplification of the sensor setup, as well as a fusion with global navigation satellite systems (i.e., the estimation of the absolute joint and CoM positions).

Recent Kinematic and Kinetic Advances in Olympic Alpine Skiing: Pyeongchang and Beyond

“…Recent advances in GNSS technology allow precise biomechanical analysis of performance over an entire course in real-time (Supej et al, 2008, 2013; Supej, 2012; Gilgien et al, 2013), providing much more detailed information about such factors. In addition to measuring performance, inertial motion sensors and GNSS allow recording of 3D body kinematics over several turns or even an entire race course, providing accurate kinematic values on-snow (Brodie et al, 2008; Krüger and Edelmann-Nusser, 2010; Supej, 2010; Fasel et al, 2017). Continuous miniaturization of mechanical, electrical and optical sensing technologies for assessing the kinematics and kinetics of human motion and performance, as well as of other chemical sensing technologies designed to detect physiological parameters (not dealt with here) will allow more comfortable and flexible monitoring of technique, performance, tactics and training load (Heikenfeld et al, 2018).…”

Using Sensors and Deep Learning to Enable On-Demand Balance Evaluation for Effective Physical Therapy

“…A. RELATED WORK ON CoM ESTIMATION 1) CoM ESTIMATION USING IMU SENSORS [33], [34] Some studies used Inertial Measurement Unit (IMU) sensors to estimate the CoM position. Esser et al proposed to estimate the subject's vertical CoM movements from the acceleration data collected by the IMU sensor by [33].…”

Using Magneto-Inertial Measurement Units to Pervasively Measure Hip Joint Motion during Sports

“…There is a strong focus on using wireless sensors to monitor athletes [ 12 , 13 , 14 , 15 , 16 ] with emphasis on performance assessment [ 9 , 12 , 17 , 18 , 19 , 20 ] and injury prevention [ 21 , 22 ]. To evaluate player performance, single IMU acceleration-derived measures have been adopted to analyze intensity throughout the course of sports practices.…”