Pre-programmed aspects of the jump landing body kinematics are obscured by the overriding effects of the impact perturbation. Likewise, pre-programed muscular activity is difficult to distinguish form segmental stretch reflex activity due to the mechanical effects of the impact. The false platform jumping experiments are designed to provide insight into the control of jump landings by eliminating the impact perturbation during an otherwise "normal" jump. Removing the landing platform without the subject's knowledge permits measurement of the free trajectory of the body and limbs for a short time after impact would normally occur because the subject is still in free fall. the free trajectory and EMG activity during this period elucidate the role of pre-programmed motor control activity and permit estimation of limb impedance properties using appropriate models.
False platform jumping experiment, as the name implies, involves with a platform and a no-platform jump in which the subjects do not know about the point of impact (false platform), thus as subjects jumping through the nominal impact point (the point of impact of platform jump), a true trajectory can be recorded without any perturbations. Six subjects participated in the experiment and kinematics and EMG data were recorded.
Data analysis including both kinematics data and EMG data were performed, results and discussions of the experiment can be found in Development of Full-Body Models for Human Jump Landing Dynamics and Control, Keoki Jackson, 1997. However, additional data analysis has been done with two selected subjects (CZL and AQK) to further explore the difference between the platform jump and the no-platform jump as well as the jumping dynamics and control. For example,the actual jumping was modeled using VRML software by Qun Liang, to visually demonstrate the jumping motion. An EMG analysis using a MATLAB script, was generated by Rex Wu to determine the onset of the eight different muscle groups. The EMGs of Platform jumps and no-platform jumps are also being superimposed together for easy comparison. Finally, videos of the actual jumping of two selected subjects (CZL and AQK) along with the MATLAB-generated real-time EMG plots are presented.
© 1998 Professor Dava Newman. All rights reserved.