For the increasing progress in science and the continuous development of table tennis skills, more and more players and researchers are being attracted to table tennis, a sport that can benefit from high quality biomechanical research. This method can objectively reflect the difference in ground reaction force between chasse-step and cross-step work and provide information for the generation of optimization power. A researcher new to the field must first understand the principle of a ground reaction and what a ground reaction can reflect.
To begin, insert the USB dongle into the PC's parallel port and switch on the motion capture infrared cameras and the analog to digital converter. After ensuring that there are no obstacles in the experimental environment, double click the software icon on the desktop to open the tracking software. Every camera node will show a green light if the hardware connection is fine.
Then, in the local system, select eight cameras, and click on camera in the perspective window. Set the strobe intensity between 0.95 to 1, gray scale mode to auto, gain to times one, threshold between 0.2 to 0.4, minimum circularity ratio to 0.5, and max blob height to 50. Next, place the T correction rack in the center of the shooting area.
After selecting eight cameras in the system, use a 2D model to confirm that the camera can discern T correction and that there are no noise points. Then, place the T correction rack in the center of the camera area, and click on system preparation. From the L-frame dropdown list, select 5 marker wand and L-frame.
Then, click on the start button under the AiM MX cameras option. After clicking on system preparation again, move to the calibrate MX camera section in the tool pane, and click on the start button. Wave the T wand in the capture range.
When the blue light on the infrared camera stops flashing, stop the action. Observe the progress bar until the calibration process is complete at 100%and returns to 0%At the same time, observe the image error. When the image error is less than 0.3, place the T-shaped correction frame in the center of the moving area, ensuring that the axis direction is consistent with the boundary direction of the force platform.
Then, from the set volume origin section in the tool pane, select the start button. Ensure that all participants are wearing professional table tennis match shoes, identical T-shirts, and tight-fitting pants, and are using the same professional table tennis racket. After adapting to the experimental environment for five minutes, let each participant warm up for 15 minutes with light running on the professional treadmill, followed by stretching.
For static calibration, ask the participants to stand on the force platform, maintaining a stable posture while looking ahead with their hands folded and raised on their chest and their feet shoulder width apart. Next, click on the data management button on the toolbar, and then on the new database tab. Click on location, and import the description of the trial.
Select clinical template, then click on the create button. In the open database window, select the name of the database created. Once the new screen appears, click on the green new patient category button, the yellow new patient button, and the gray new session button to create experimental information.
To create a new subject dataset in the Nexus main pane, click on subjects. Then in the subject capture section, click on the start button to create a static model. When the image frames are at 140 to 200, click on the stop button to finish the establishment of the static model.
To conduct the dynamic trials, place the table tennis table and ball basket in the experimental environment to ensure that the subjects have enough space to execute two kinds of footwork. Then ask the participant to hold the ready position on the left side of the table, about half a meter away from the table, and ask the coach to serve a table tennis ball to the first impact area, followed by another to the final impact area. Ask the participants to hit the first and second served ball by forehand using maximum force and return to the ready position after finishing the second stroke task.
Ask the participants to first use the chasse-step footwork to complete five successful strokes, and then use the cross-step footwork to complete another five successful strokes. In the software, click on the capture button in the pressure platform to start the recording, and click on the stop button to end the recording. Repeat this five times for each participant.
For processing the data, double-click on the trial name in the data management window. Then, in the tool bar, click on the reconstruct pipeline and labels buttons to display the experiment demonstration. In the perspective window, move the blue triangle on the time bar to intercept the desired time interval.
Then from the subject calibration pane, select the dynamic plug-in gate, and click on the start button to run and export the data. Upon comparing the ground reaction force between the cross-step and chasse-step footwork, the posterior ground reaction force of the cross-step footwork was significantly larger than that of the chasse-step footwork. However, the lateral ground reaction force of cross-step footwork was significantly lower than that of the chasse-step footwork.
Additionally, the vertical ground reaction force of the cross-step footwork was significantly lower than that of the chasse-step footwork. No differences were observed between the medial or anterior ground reaction forces between the cross-step and the chasse-step footwork during stroke in table tennis. The key steps are to intercept the motion interval accurately, and activate the motion phase.
By combining this method with the insole type pressure measuring system, the relationship between the dynamic characteristics of each area of the sole and the ground reaction force can be understood.
