Comparison of Kinetic Characteristics of Footwork during Stroke in Table Tennis: Cross-Step and Chasse Step

Summary

This study presents a protocol to investigate the ground reaction force characteristics between cross-step and chasse step during stroke in table tennis.

Abstract

The cross-step and chasse step are the basic steps of table tennis. This study presents a protocol to investigate the ground reaction force characteristics between cross-step and chasse step during stroke in table tennis. Sixteen healthy male national level 1 table tennis players (Age: 20.75 ± 2.06 years) volunteered to participate in the experiment after understanding the purpose and details of the experiment. All participants were asked to hit the ball into the target zone by cross-step and chasse step, respectively. The ground reaction force in the anterior-posterior, medial-lateral, and vertical directions of the participant was measured by a force platform. The key finding of this study was that: the posterior ground reaction force of cross-step footwork (0.89 ± 0.21) was significantly large (P = 0.014) than the chasse step footwork (0.82 ± 0.18). However, the lateral ground reaction force of cross-step footwork (-0.38 ± 0.21) was significantly lower (P < 0.001) than chasse step footwork (-0.46 ± 0.29) as well as the vertical ground reaction force of cross-step footwork (1.73 ± 0.19) was significantly lower (P < 0.001) than chasse step footwork (1.9 ± 0.33). Based on the mechanism of the kinetic chain, the better lower limb dynamic performance of sliding stroke may be conducive to energy transmission and thus bring gain to the swing speed. Beginners should start from the chasse step to hit the ball technically, and then practice the skill of cross-step.

Introduction

Table tennis has developed continuously in sports training and competition practice for more than 100 years¹. With economic globalization and cultural exchanges, table tennis has developed rapidly in various countries^2,3. In Croatia, for example, table tennis is not only played in clubs, but also in universities, schools, and even in dormitories⁴. For athletes, the establishment of sports analysis is helpful for training and competition⁵. In table tennis competitions, players need good strategies to try to win the match⁶. Additionally, footwork is a skill that must be mastered in table tennis, and it is also the basis and one of the key points of table tennis training. The chasse step and cross-step are the basic steps of table tennis⁷. Every sports skill has a basic mechanical structure. The study of biomechanics is of high interest to the progress and development of table tennis skills. In training and competition, table tennis players find the accurate position through their steps⁷. Therefore, it is necessary to study the step of table tennis.

There are differences in the step of table tennis players from different regions, with Asian players using steps more frequently than European players both during training and in competition⁸. During competition, a high-level table tennis player will hit the ball in a shorter time, at a more steady step, and have enough time to hit the next ball⁹. In table tennis, because of the cross-step hitting action, in most cases it is a technical action to save the ball, leading to the inability to complete the hitting action with high quality. On the contrary, different from cross-step hitting, chasse step hitting is a common technical action, so athletes can better grasp the hitting technical action through practice to ensure the quality of their stroke. A chasse step is when the drive leg (right leg) moves to the right side (toward the ball) and then the left leg follows to move. A cross-step is when the drive leg (right leg) moves to the right side (toward the ball) with a large distance, and the left leg does not move.

Through previous studies, lower limb muscles play an important role in table tennis performance¹⁰. Table tennis has similarities with tennis moves. There are differences in the driving stability of lower limbs of tennis players with different levels of serving skill¹¹. Table tennis involves knee flexion and asymmetrical torsion of the trunk¹². In order to improve the skills of table tennis players, attention should be paid to the rotation of the pelvis¹³. When playing forehand loop, excellent table tennis players have a better sole control ability¹⁴. High-level table tennis players can better control the plantar pressure deviation, increase the inner and outer pressure deviation, and reduce the front and back pressure deviation¹⁵. Compared with a straight shot, a diagonal shot has a greater knee extension during the swing¹⁶. Table tennis service technology is diverse and has complex biomechanical characteristics. Compared with standing serves, squatting serves require higher lower-limb drive¹⁷. Compared with beginners, elite athletes are more flexible in their stride in cross-step exercises⁷.

In light of the above, with the increasing progress of science and the continuous development of table tennis skills, more and more players and researchers have joined table tennis, which requires high-quality biomechanical research to support the sport. However, due to the complexity of table tennis, it is difficult for researchers to measure the biomechanics¹. There are few studies on the biomechanics of the lower limbs of table tennis. The purpose of this study was to measure the ground reaction force of elite college table tennis players in the movement of the racket lead and swing in chasse step and cross-step. The ground reaction force data of the two steps are compared. The first hypothesis of this study is that the chasse step and cross-step have different ground reaction force characteristics. The ground reaction force of chasse step and cross-step is used to obtain the kinetic data of two kinds of steps, which provides guidance and suggestions for table tennis players.

Protocol

This study was approved by The Human Ethics Committee of Ningbo University, China. Written informed consent was obtained from all subjects after they were told about the goal, details, requirements, and experimental procedures of the table tennis experimental.

1. Laboratory preparation for table tennis

1. Insert the USB dongle into the PC's parallel port and open the motion-capture infrared cameras and analog-to-digital converter.
   NOTE: In this laboratory, the force platform (sampling frequency of 1000 Hz) is used together with the motion acquisition system, and the data collected by the force platform was displayed and preliminarily analyzed through the same system. The default sampling frequency of the force platform is 1000 Hz.
2. Double-click the software icon on the desktop to open the tracking software.
   NOTE: Before opening the software, remove all obstacles in the experimental environment and clean the ground.
3. Every camera node will show a green light if the hardware connection is true. When the indicator light of all cameras is green, select eight cameras in the Local System.
4. Click on Camera in the Perspective window and adjust the Strobe Intensity as 0.95-1, Gain to times 1 (x1), Threshold as 0.2-0.4, Minimum Circularity Ratio as 0.5, Grayscale Mode to Auto, as well as Max Blob Height to 50.
5. Place the T correction rack in the center of the shooting area, and select eight cameras in the system. Using a 2D model, confirm that the camera can discern T correction and that there are no noise points.
   1. Place the T correction rack in the center of the camera area. Click on the System Preparation, the L - Frame drop-down list, and select 5 Marker Wand & L - Frame. Then, click on the Start button under the AimMX cameras option.
6. Select the System preparation button, and click on the Start button in the Calibrate MX Camera section in the Tool pane. Then, wave the T-wand in the capture range. When the blue light on the infrared camera stops flashing, stop the action.
   1. Observe the progress bar until the calibration process is complete at 100% and returns to 0%. At the same time, observe the error of the image. When the error of the image is less than 0.3, continue the following operation.
7. Place the T-shaped correction frame in the center of the moving area to ensure that the axis direction is consistent with the boundary direction of the force platform.
8. Select the Start button under the Set Volume Origin section in the Tool pane.

2. Participants' preparation

NOTE: Sixteen healthy male national level 1 table tennis players volunteered to participate in the experiment (Ages: 20.75 ± 2.06year; Height: 173.25 ± 6.65 cm; Weight: 66.50 ± 14.27 kg; Training Year: 12.50 ± 2.08 year). All of them belong to the Ningbo University table tennis team. Before the formal start of the experiment, the details and process of the experiment were briefly explained to the participants again, and the written informed consent of the participant who met the conditions of the experiment were obtained.

1. Select participants that are right-handed, have the right leg as dominant, and are in good physical health, free of any form of lower limb disease or injury in the last 6 months. A total of 16 male participants who met the experimental conditions were included in this experiment. The demographic information of participants is shown in Table 1.
   NOTE: Because there are few left-handed racket users, it was easier to find enough right-handed racket users to participate in this experiment.
2. Ask all participants to fill out a questionnaire related to fitness.
   NOTE: Questions include: Have you had a history of table tennis competition? How often do you take part in table tennis training in a week? Have you suffered any lower-limb disorders and injuries in the last 6 months?
3. Ensure that all participants wear professional table tennis match shoes as well as identical t-shirts and tight-fitting pants. Have all participants use the same professional table tennis racket.
4. Give each participant 5 min to adapt to the experimental environment and 15 min to warm up with light running on the professional treadmill and stretching. Due to the short duration of the experiment, restrict subjects from eating and drinking during the formal experiment in order to keep them in a stable state.
   NOTE: Participants first completed a 5 min jog at an adaptive speed on the lab's professional running table, followed by a 5 min stretch of their lower limb muscles. Finally, they practiced table tennis footwork technique for 5 min. After completing the warm-up task, the participants were given 2 min to adjust their state. The formal data collection began.

3. Static calibration

1. Click on the Data Management button on the toolbar.
2. Click on the New Database tab on the toolbar, click on the Location, and then import the description of the trial. Select Clinical Template and click on the Create button.
3. Select the name of the database created in the Open Database window. Then, click on the green New Patient Category button, the yellow New Patient button, and the gray New Session button to create experimental information in the newly opened screen.
4. Click on Subjects to create a New Subject data set in the Nexus main pane.
5. Click on the Start button in the Subject Capture section to create a static model. Click on the Stop button when the image frames are at 140-200 to finish the establishment of the static model.
   ​NOTE: The participants were asked to stand on a force platform during the experiment. They were asked to maintain a stable posture with their hands folded and raised on their chest, looking ahead, and their feet shoulder-width apart.

4. Dynamic trials

1. As shown in Figure 1, 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.
   NOTE: The table tennis table and balls are up to the standards of professional events.
2. Ask the participant to hold the ready position, When the experimenter gives the start command, ask the coach to serve the table tennis balls to the first and final impact area, respectively.
   1. Before the formal experiment begins, give the participants enough time to get accustomed to this position through practice.
   2. Ask the participants to start on the left side of the table, about half a meter away from the table. Then, ask them to hit the first and second served ball by forehand with maximum force and return to the ready position after finishing the second stroke task.
   3. Ask the participants to first use the chasse step footwork to complete 5 successful strokes, and then use the cross-step footwork to complete 5 successful strokes.
3. 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 five times for each participant.
   ​NOTE: If the shot is not within the range of the target area, or if the subject's right foot is not fully on the force platform, the measurement will be re-taken.

5. Post-processing

1. Double-click on the trial name in the Data Management window. Click on the Reconstruct Pipeline and Labels buttons in the toolbar to display the experiment demonstration.
2. In the Perspective window, move the blue triangle on the time bar to intercept the desired time interval.
3. Select the Dynamic Plug-in Gait that is in the Subject Calibration pane. Click on the Start button to run and export the data.

6. Statistical analysis

1. Analyze all data using professional statistical software. Run the Shapiro-Wilks tests to check the normal distribution for all variables.
2. Use a paired t-test to compare kinetics characteristics of chasse step footwork and cross-step footwork during table tennis stroke.
3. Set the significance level at p < 0.05. The results are presented as the mean ± the standard deviation throughout the text unless otherwise stated.

Results

As shown in Figure 2 and Table 2, the posterior ground reaction force of the cross-step footwork (0.89 ± 0.21) was significantly larger (P = 0.014) compared with the chasse step footwork (0.82 ± 0.18). However, the lateral ground reaction force of cross-step footwork (-0.38 ± 0.21) was significantly lower (P < 0.001) than the chasse step footwork (-0.46 ± 0.29). Additionlly, the vertical ground reaction force of cross-step footwork (1.73 ± 0.19) ...

Discussion

The aim of this study is to investigate the ground reaction force characteristics between cross-step and chasse steps during stroke in table tennis. The key findings of this study are stated here. The anterior ground reaction force of cross-step footwork was significantly larger than the chasse step footwork. The lateral ground reaction force of cross-step footwork was significantly lower than the chasse step footwork. The vertical ground reaction force of cross-step footwork was significantly lower than the chasse step ...

Materials

Name	Company	Catalog Number	Comments
14 mm Diameter Passive Retro-reflective Marker	Oxford Metrics Ltd., Oxford, UK		n=22
Double Adhesive Tape	Oxford Metrics Ltd., Oxford, UK		For fixing markers to skin
Force Platform	Advanced Mechanical Technology, Inc.		Measure ground reaction force
Motion Tracking Cameras	Oxford Metrics Ltd., Oxford, UK		n= 8
T-Frame	Oxford Metrics Ltd., Oxford, UK		-
Valid Dongle	Oxford Metrics Ltd., Oxford, UK		Vicon Nexus 1.4.116
Vicon Datastation ADC	Oxford Metrics Ltd., Oxford, UK		-