Ground Reaction Forces and Kinematics of Ski Jump Landing Using Wearable Sensors

Abstract

In the past, technological issues limited research focused on ski jump landing. Today, thanks to the development of wearable sensors, it is possible to analyze the biomechanics of athletes without interfering with their movements. The aims of this study were twofold. Firstly, the quantification of the kinetic magnitude during landing is performed using wireless force insoles while 22 athletes jumped during summer training on the hill. In the second part, the insoles were combined with inertial motion units (IMUs) to determine the possible correlation between kinematics and kinetics during landing. The maximal normal ground reaction force (GRFmax) ranged between 1.1 and 5.3 body weight per foot independently when landing using the telemark or parallel leg technique. The GRFmax and impulse were correlated with flying time (p < 0.001). The hip flexions/extensions and the knee and hip rotations of the telemark front leg correlated with GRFmax (r = 0.689, p = 0.040; r = −0.670, p = 0.048; r = 0.820, p = 0.007; respectively). The force insoles and their combination with IMUs resulted in promising setups to analyze landing biomechanics and to provide in-field feedback to the athletes, being quick to place and light, without limiting movement.

Ski Jumping Trajectory Reconstruction Using Wearable Sensors via Extended Rauch-Tung-Striebel Smoother with State Constraints

“…The method implemented for detecting the time points for take-off t TO and touch-down t TD is introduced in this section: Due to the change of the ground reaction forces, both take-off and touch-down phase show abrupt changes in acceleration, which is measured by the accelerometer. Previous studies on ski jumping take-off [25] and landing [26,27] also presented similar acceleration changing behavior in their measurement-based results. Therefore, we propose to determine t TO and t TD by detecting these abrupt changes in the accelerometer measurement.…”

“…Finally, the take-off time points t TO is determined as the earlier peak. As presented in [26,27], the actual touch-down point in the landing process is a short moment before the maximal ground reaction peak, approximately 0.05 s as we estimated. Therefore, the touch-down time points t TD is determined as 0.05 s before the later peak as: Figure A1.…”

Wearable Monitoring and Predicting System for Knee Joint Fatigue Based on Curvature and Pressure Sensing

“…After obtaining the normalized acceleration redundancy w norm (i), the weighted curve fitting is able to be run on the database to figure out the prediction of knee fatigue using Equation (10). (11) where ŵ represents the fitting coefficient; S denotes the vector of total load s i at each point; F is the vectors of knee fatigue percentage f i ; W norm is a weight diagonal matrix as shown in Equation 11containing acceleration redundancy w norm (i) as its elements.…”

“…In order to improve the detecting accuracy and portability of the devices, the new structural sensor made by ordinary fabrics and conductive yarns [9] and mobile communication technique [10] are also involved in. The ground reaction forces of ski jump landing related to knee are studied using wearable sensors [11]. In that study, the plantar force insoles are combined with inertial motion units to determine the possible relationship of those forces.…”

An Exploration of Machine-Learning Estimation of Ground Reaction Force from Wearable Sensor Data

“…Recent advancements in wearable technology has opened the possibility of field-based GRF measurement, providing biomechanical insight in sports where laboratory-based measurement is challenging. For example, force insoles have been added to ski boots for analysis of ski jump landings [12], and bendable outsoles used for GRF measurement during walking [13]. Within a dance population, the addition of an insole or outsole to a ballet shoe is not possible due to the aesthetic and technical requirements of the athletic pursuit.…”