Use of Nonlinear Analysis Methods for Visual Evaluation and Graphical Representation of Bilateral Jump Landing Tasks

Nonlinear analysis methods enable the evaluation of signal chaos parameters such as variability, persistence, and complexity. In order to assess the differences between individual bilateral jump landing tasks and between IMU estimated angle and the gold standard, data obtained from Qualysis optical Mocap (Qualisys AB, Göteborg, Sweden) and Delsys inertial measurement systems (Delsys Inc., Boston, MA, USA) were used. 24 subjects were recruited in this study (6 females and 18 males, age: 22.6 ± 2.6 years old; height: 172.6 ± 10.3 cm; weight: 72.2 ± 16.02 kg). All of them perform double-leg landing tasks from a 30 cm height platform and a distance of half of their body height while wearing 8 IMU sensors on the sternum, L5, bilateral thigh, shank, and foot. In addition to IMU sensors on 8 locations, the subject wore retroreflective markers on the upper and lower parts for 3D motion capture data analysis. Multiscale Poincaré plots and recurrent quantification analysis were employed for subjective visual evaluation. Nonlinear analysis methods are promising practical applications, particularly with the use of recurrent quantification analysis and multiscale Poincaré plots for easier interpretation. In the case of multiscale Poincaré analysis, a difference between the estimated angle from the IMU and the gold standard in terms of confidence ellipse parameters was found. Additionally, the quantification parameters of these methods are suitable for integration with other evaluation methods in the time domain, frequency domain, and time-frequency domain.