Features of prototyping the kinematic movements of human extremities during the implementation of demonstration robots

The features of prototyping the movement kinematic of human extremities during in the implementation of demonstration robots based on a hinged three-link are considered. Keywords demonstration robot; three-link manipulator; trajectory of movement; coordination of robot arm movements

Modeling Judges’ Scores in Artistic Gymnastics

Background: In artistic gymnastics, performance is observed and evaluated by judges based on criteria defined in the code of points. However, there is a manifold of influences discussed in the literature that could potentially bias the judges’ evaluations in artistic gymnastics. In this context, several authors claim the necessity for alternative approaches to judging gymnastics utilizing biomechanical methods. Objective: The aim of this study was to develop and evaluate a model-based approach to judge gymnastics performance based on quantitative kinematic data of the performed skills. Methods: Four different model variants based on kinematic similarity calculated by a multivariate exploratory approach and the Recurrent Neural Network method were used to evaluate the relationship between the movement kinematics and the judges’ scores. The complete dataset consisted of movement kinematic data and judgment scores of a total of N = 173 trials of three different skills and routines from women’s artistic gymnastics. Results: The results exhibit a significant relationship between the predicted score and the actual score for six of the twelve model calculations. The different model variants yielded a different prediction performance in general across all skills and also in terms of the different skills. In particular, only the Recurrent Neural Network model exhibited significant correlation values between the actual and the predicted scores for all three investigated skills. Conclusion: The results were discussed in terms of the differences of the models as well as the various factors that might play a role in the evaluation process.

Effects of training against elastic resistance on jab punch performance in elite junior athletes

Ability to perform rapid open-kinetic chain movements (e.g. kicking, throwing, hitting, or punching) is an important prerequisite for success in various sports. The aims of the present study were (1) to investigate the effect of elastic resistance training (ERT) on the performance of jab punch, (2) to explore the associated changes in movement kinematic and kinetic patterns, and (3) to assess possible differences among competitors of different specializations. The national level junior competitors in kick boxing, savate, and boxing practiced jab punch against elastic resistance for 15 minutes per day, 3 times a week for 6 weeks, while the control group participated only in their regular training (N=10+10+10+10; age 17.2±1.0 years; M±SD). The results revealed a marked increase in the maximum jab punch velocity in all experimental groups (6-11%; all p<.01), but not in the control group (p>.05). This finding was associated with an increase in both the maximum velocity and displacement of the ipsilateral elbow, shoulder, and, particularly, hip joint, while no change in the movement time was observed. The ERT-associated increase was also revealed in the agonist (7-11%, all p<.01), but not antagonist muscle strength. Therefore, we conclude that addition of a relatively small amount of ERT could be recommended for the purpose of improving punching performance and, possibly, other rapid limb movement even in top-level junior athletes. The observed performance improvement could be partly based on increased motion amplitudes particularly regarding the pelvis movement, as well as on increased strength of agonist muscles

The StartReact Effect on Self-Initiated Movements

Preparation of the motor system for movement execution involves an increase in excitability of motor pathways. In a reaction time task paradigm, a startling auditory stimulus (SAS) delivered together with the imperative signal (IS) shortens reaction time significantly. In self-generated tasks we considered that an appropriately timed SAS would have similar effects. Eight subjects performed a ballistic wrist extension in two blocks: reaction, in which they responded to a visual IS, and action, in which they moved when they wished within a predetermined time window. In 20–25% of the trials, a SAS was applied. We recorded electromyographic activity of wrist extension and wrist movement kinematic variables. No effects of SAS were observed in action trials when movement was performed before or long after SAS application. However, a cluster of action trials was observed within 200 ms after SAS. These trials showed larger EMG bursts, shorter movement time, shorter time to peak velocity, and higher peak velocity than other action trials (P<0.001for all), with no difference from Reaction trials containing SAS. The results show that SAS influences the execution of self-generated human actions as it does with preprogrammed reaction time tasks during the assumed building up of preparatory activity before execution of the willed motor action.