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Correlations Between Stroke Structural Characteristics and Stroke Effect of Young Table Tennis Players

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Background: A perfect stroke is essential for winning table tennis competition. A perfect stroke is closely related to reasonable stroke structure, which directly affects the stroke effect. The main purpose of this study was to examine the correlations between the structural characteristics of stroke and the stroke effect. Methods: Forty-two young table tennis players were randomly selected from China Table Tennis College (M age = 14.21 ± 2.13; M height = 1.57 ± 0.14 m; M weight = 46.05 ± 6.52 kg, right-hand racket, shake-hands grip, no injuries in each joint of the body). The high-speed infrared motion capture system was used to collect the data of stroke structural characteristics, and the high-speed camera was used to measure the spin speed of the stroke. The influence of striking structural characteristics on striking effect was examined. Results: The time duration of backswing and forward motion were significantly correlated with ball speed (r = -0.403, p < 0.01; r = -0.390, p < 0.01, respectively) and spin speed (r = -0.244, p = 0.027; r = -0.369, p < 0.01, respectively). The linear velocity of right wrist joint was positively correlated with ball speed (r = 0.298, p < 0.01) and spin speed (r = 0.238, p = 0.031). The angular velocity of right elbow joint and right hip joint were positively correlated with ball speed (r = 0.219, p = 0.013; r = 0.427, p < 0.01, respectively) and spin speed (r = 0.172, p = 0.048; r = 0.277, p = 0.012, respectively). The angular velocity of right knee joint had a significantly negative correlation with placement (r = -0.246, p = 0.026). The angular velocity of right ankle joint had a significantly positive correlation with the ball speed (r = 0.443, p < 0.01). Conclusions: The time allocation of the three phases of backspin forehand stroke had an important impact on stroke effect, especially the ball speed and spin speed. The ball speed of the stroke was mainly affected by the translation of the right wrist joint. The spin speed of the stroke was mainly affected by the translation of the right wrist joint. The placement of the stroke was mainly affected by the rotation of the right knee joint.
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Correlations Between Stroke Structural
Characteristics and Stroke Effect of Young Table
Tennis Players
Yi Xiao ( cutexxx@163.com )
China Table Tennis College of Shanghai University of Sport, Shanghai 200438, China
https://orcid.org/0000-0002-8904-9083
Miaomiao Lu
Shanghai University of Sport
Yuxuan Zeng
Shanghai University of Sport
Yuanjie Xiao
School of Economics and Management, Southwest University of Science and Technology, Sichuan,
China
Research article
Keywords: Correlation, body joint, Structural characteristics, Stroke effect, Table tennis
DOI: https://doi.org/10.21203/rs.3.rs-104628/v1
License: This work is licensed under a Creative Commons Attribution 4.0 International License. 
Read Full License
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Abstract
Background: A perfect stroke is essential for winning table tennis competition. A perfect stroke is closely
related to reasonable stroke structure, which directly affects the stroke effect. The main purpose of this
study was to examine the correlations between the structural characteristics of stroke and the stroke
effect.
Methods: Forty-two young table tennis players were randomly selected from China Table Tennis College
(M age = 14.21 ± 2.13; M height = 1.57 ± 0.14 m; M weight = 46.05 ± 6.52 kg, right-hand racket, shake-hands
grip, no injuries in each joint of the body). The high-speed infrared motion capture system was used to
collect the data of stroke structural characteristics, and the high-speed camera was used to measure the
spin speed of the stroke. The inuence of striking structural characteristics on striking effect was
examined.
Results: The time duration of backswing and forward motion were signicantly correlated with ball speed
(
r
= -0.403,
p
< 0.01;
r
= -0.390,
p
< 0.01, respectively) and spin speed (
r
= -0.244,
p
= 0.027;
r
= -0.369,
p
<
0.01, respectively). The linear velocity of right wrist joint was positively correlated with ball speed (
r
=
0.298,
p
< 0.01) and spin speed (
r
= 0.238,
p
= 0.031). The angular velocity of right elbow joint and right
hip joint were positively correlated with ball speed (
r
= 0.219,
p
= 0.013;
r
= 0.427,
p
< 0.01, respectively)
and spin speed (
r
= 0.172,
p
= 0.048;
r
= 0.277,
p
= 0.012, respectively). The angular velocity of right knee
joint had a signicantly negative correlation with placement (
r
= -0.246,
p
= 0.026). The angular velocity
of right ankle joint had a signicantly positive correlation with the ball speed (
r
= 0.443,
p
< 0.01).
Conclusions: The time allocation of the three phases of backspin forehand stroke had an important
impact on stroke effect, especially the ball speed and spin speed. The ball speed of the stroke was mainly
affected by the translation of the right wrist joint. The spin speed of the stroke was mainly affected by the
translation of the right wrist joint. The placement of the stroke was mainly affected by the rotation of the
right knee joint.
Background
Table tennis is a skill-based confrontation sports and has the characteristics of fast ball speed and fast
spin speed, which requires table tennis players to master perfect techniques and tactics. The technique is
the basis of tactics, and only with strong and stable techniques can exible tactics be formed [1, 2]. The
rationality of technical action is the essential basis for table tennis players to reach a high skill level and
win a game. Unreasonable and unstable technical action not only affects the application of technical and
tactical combination, but also increases the incidence of injuries in daily training and competition [3].
The structural characteristics of stroke refer to the changes of kinematic parameters of human body
joints during a whole stroke. The kinematic parameters that describe the changes of human body posture
mainly include the displacement, angle, and changes (such as linear velocity and angular velocity) of
human body joints [4, 5].
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The stroke structure of table tennis is the way in which each part of the stroke is made up and the order
each part is combined [6]. Although different table tennis players may have different stroke structures,
there is still similar law in the stroke structure [7]. A whole stroke of table tennis can be divided into three
phases: backswing racket, swing forward, and restoration [7, 8]. A reasonable stroke structure plays an
important role in better use of techniques and improving stroke effect of young table tennis players [6].
Young table tennis players (especially in the enlightenment stage) are in the cognition, formation, and
xation stage of technical actions, so it is particularly crucial for them to cultivate correct and stable
technical actions [9, 10]. Scientic training and monitoring methods of technical actions can effectively
promote players’ competitive level, prevent and reduce the occurrence of sports injuries, and further
improve the stroke effect of young table tennis players [11].
The ve elements of table tennis technical actions are speed, spin, power, placement, and trajectory, in
which the speed, spin, and placement are the keys to win a game. The control of placement and trajectory
is also very important in today’s table tennis competition [12]. For table tennis, the ball speed and spin
speed of stroke are two dominant factors that determine the outcome of a competition, and also the two
main technical parameters to describe the stroke effect [13, 14].
When striking the ball, the faster the racket movement, the faster the ball speed [15]. Increasing the
rotation angle of the hip joint helped to improve the racket speed of swing [16]. At present, the D40 plus
(mm) plastic ball was designated for table tennis training and completion. As the increased diameter and
mass of the D40 plus plastic ball, the air resistance also increases, which reduces the ball speed and
rotation accordingly. Therefore, it has a negative impact on the improvement of stroke effect [17, 18].
There was a signicantly positive correlation between the ball speed and the swing speed of the end of
the racket. If the racket speed was increased before striking the ball, the ball speed will also be increased
after the stroke [15]. When striking the ball with forehand, the angles of many body joints changed, and
the best racket speed would be achieved by using the ordered rotation of the hip joint, upper body,
shoulder joint, and forearm. The angular velocity of shoulder internal rotation and shoulder adduction
had a signicant impact on the racket speed [19]. Without considering the rotation of the ball, the racket
speed was increased with the increase of the amount of energy transferred from the shoulder joint to the
forearm [20]. When striking topspin ball with backhand, the mechanical energy of the swing racket was
mainly transmitted by the force and torque of the shoulder joint [4]. Therefore, when striking the ball, the
mechanical energy would be transferred from the lower limbs of the body to the upper limbs by changing
the angle and angular velocity of the body joints, and the swing racket speed and ball speed could be
enhanced. Thus, the stroke effect could also be improved [21].
The methods used to analyze sports techniques are qualitative and quantitative, of which the quantitative
method is most used. Quantitative method involves collecting and analyzing objective data. For table
tennis, the data often concerns identifying the main structural characteristics of a stroke, such as
position, angle, range of motion, speed, phases of the stroke, etc. This data collection can be achieved by
motion capture and computer analysis of images [8].
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Motion capture technology uses the principle of computer graphics to track, measure, and record the
three-dimensional motion of the main joints of human body in the form of images through multiple
cameras arranged in space, and has been widely used in lm production, mechanical control, simulation
training and teaching, human posture research, ergonomics and other elds [22, 23 24, 25, 26, 27]. High-
speed motion capture system can not only capture the trajectory of a ying ball, but also calculate the
ball speed, which is widely used in the monitoring of sports training [21, 28, 29].
In this study, the structure characteristics of backspin forehand stroke of young table tennis players were
collected using a high-speed infrared motion capture system, and the correlations between the stroke
structural characteristics and stroke effect of young table tennis players were examined combined with
the stroke effect data. Thus, the factors that affect the stroke effect of young table tennis players can be
analyzed, which helps to improve the rationality of stroke action structure and also improve the stroke
effect of young table tennis players.
Methods
Participants
This study was approved by the ethics committee of Shanghai University of Sport. Participants were
randomly selected from China Table Tennis College. The inclusion criteria included: table tennis player, 12
to 18 years of age, right-striking arm, shake-hands grip. Forty-two young table tennis players (M age =
15.21 ± 2.13; M height = 1.57 ± 0.14 m; M weight = 46.05 ± 6.52 kg) who met the inclusion criteria were
chosen to attend this study. The average training time for them was 6.09 ± 2.63 years, and the table
tennis technical grade of them has been to the same level [31]. All subjects were informed of the study
procedure and provided written informed consent before the experiment.
Instruments
(1)High-speed infrared motion capture system (Qingtong Vision Technology Company, Shanghai, China)
was used to collect the real-time data of body joints’ spatial position and joint angle during the stroke.
The sampling frequency was 120 frames per second.
(2)Radar speed detector: SPEEDSTER radar (BUSHNELL Company, the United States) was used to
measure the ball speed of the stroke.
(3) High-speed camera: Miro R111 (the United States) was used to measure the spin speed of table
tennis. The focal length was 70mm, the exposure time is 330 μs, and the sampling frequency was 4500
fps.
(4) Serving machine: V-989H Serving machine was manufactured by Nittaku Company, Japan. The
parameter settings used for the study were: the serving machines upper wheel speed was set at level 3
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(10 levels in total, the higher level the faster speed), the bottom wheel speed at level 7, and the service
frequency was 40 balls per minute.
Experimental equipment layout
The layout of experimental equipment was shown in Fig 1.
In Figure 1, there are twelve infrared high-speed cameras arranged around the measurement area of 4x3
meters on steel consoles 4 meters above ground level, and the cameras are connected to the PC through
USB hubs [25]. The speedometer allocated approximately 3½ - 4 meters away from the table tennis player
(directly facing the player). The high-speed camera was set up on one side of the net, about 40cm from
the sideline and 90 centimeters above ground level. The measurement setup is located at the training hall
of China Table Tennis College of Shanghai University of Sport, China.
Marker placement
Before the experiment, participants were required to wear tight-tting clothes, and 38 reective spherical
markers (diameter: 16 mm) were attached to the body surface of each participant’s trunk, shoes, and all
limbs, as shown in Figure 2. The marker locations included: wrist joint, elbow joint, shoulder joint, hip
joint, knee joint, ankle joint, etc. The spatial position and angle of the marked body joints were recorded
by an infrared camera at a frequency of 120 Hz [32].
Calibration of spatial coordinate system
During the real-time data collection of body joints’ movement, the spatial coordinates of body joints were
collected based on the spatial coordinate system. The spatial coordinate origin was located on the
ground and the right side of the ball net, shown in Figure 3. The joint angle was described based on the
human body coordinate system. In this study, the hip joint was taken as the root node of the human body,
and the other joints take their parent node as their joint center.
Calculation of spin speed
Each experimental ball was marked with T-mark on its surface using a black marker. After each stroke, a
series of continuous images of the ball ying over the net were captured using the high-speed camera.
Then, using the computer processing software of the high-speed camera, the number of frames required
for the T-mark on the surface of the ball to rotate around (360 degrees) when ying over the net was
observed and calculated. Finally, the spin speed of the ball ying over the net was calculated by dividing
the sampling frequency of the high-speed camera (4500 fps) by the number of frames required for the
ball to rotate around. See equation (1).
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EquationSpin speed (r) =
Note.
The number of frames in the starting position of the T-mark on the ball was x1, and the number of
frames after the T-mark rotated one turn was x2. The sampling frequency of the high-speed camera (4500
fps).
Corner area
During the experiment, in order to evaluate the stroke effect of players, ve rectangles with a different
area of 20 cm by 20 cm to 60 cm by 60 cm were drawn at the two bottom corners of the table tennis table
on each side, as shown in Figure 4. The player scored 5 points if the ball placement was in the rectangle
of 20 cm by 20 cm, 4 points in the rectangle of 30 cm by 30 cm, 3 points in the rectangle of 40 cm by 40
cm, 2 points in the rectangle of 50 cm by 50 cm, and 1 point in the rectangle of 60 cm by 60 cm. The size
of the rectangle area represents the accuracy of players’ stroke. The larger the rectangular area, the lower
the accuracy and the lower the score. The higher the score, the better the stroke effect.
Outcome measures
The stroke structural characteristics of players were assessed using the position, angle, linear velocity,
and angular velocity of body joints movement. The stroke effect was assessed using the ball speed, spin
speed, and placement of stroke. These outcome measures were shown in Table 1.
Three-phase division of stroke
In this study, a whole stroke was divided into three phases, that is, backswing phase, forward phase
(including swing racket to hit the ball and follow-through), and recovery phase.
Selection of body joint
In this study, a total of 6 joints on the right side of the body (playing side) were selected to be observed,
that were: the upper limb three joints (right wrist joint, right elbow joint, and right shoulder joint) and lower
limb three joints (right hip joint, right knee joint, and right ankle joint).
Experimental protocol
In this paper, the data such as the changes of spatial position and joint angle of body joints were
collected during a stroke using the high-speed infrared motion capture system. The stroke ball speed, spin
speed, and placement of the ball were simultaneously collected using the high-speed camera. The
specic experimental protocol was shown in Figure 5.
(1) Calibration of high-speed motion capture system
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Before the data collection, the calibration of high-speed motion capture system should be nished using
an L-shaped ruler. The T-shaped wand was moved and rotated slowly in the three-dimensional
measurement area. The T-shaped wand was also moved at the edges of the experiment site and the
camera eld of views in order to help the software improve lens distortion. Calibration was rened until
no untracked rays were present around the measured markers using default reconstruction settings.
(2) Attachment of markers to the body surface of players
During the experiment, players were required to wear tight-tting clothes, and 38 reective markers were
attached to the body surfaces of players.
(3) Construction of 3D mannequin
After nishing the attachment of markers, players were required to stand statically in the T-pose position
(Figure 6) in the camera eld of views until the completion of 3D human model construction by the
motion capture software.
(4) 5 minutes’ warm-up exercise
Participants were requiredto warm up for 5 minutes before formal data collection in order to adapt to
stroke with tight-tting motion capture clothes.
(5) Data collection
During the experiment, the serving machine served backspin ball (ve balls for each player), and the
young table tennis players were required to stroke the ball with forehand and repeated for ve times.
Data processing
All statistical analyses were conducted by the Statistical Product and Service Solutions (SPSS 22.0, SPSS
Inc.). Descriptive statistics analysis was conducted on all study variables. Pearson product-moment
correlation was computed to assess the strengths of the association between stroke structural
characteristic variables (spatial position and joint angle of main body joints) and stroke effect (stroke ball
speed, spin speed, and placement). Statistical signicance was dened at 5% (
p
< 0.05).
Results
In order to examine the stroke structural characteristics and stroke effect of young table tennis players,
descriptive statistical analysis was conducted on the position and angle changes of upper and lower limb
three joints as well as the changes of these variables such as linear velocity and angular velocity of body
joints movement, respectively.
Stroke structural characteristics
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Position changes of the upper and lower limb three joints movement
The descriptive statistical analysis results of the position changes of the upper and lower limb three
joints in the three phases of backspin forehand stroke were shown in Table 2.
For each phase of the backspin forehand stroke, the position changes of the upper limb three joints
movement from large to small were right wrist joint, right elbow joint, and right shoulder joint. The
position changes of the right wrist joint movement in the three phases of the stroke were: 674.12±128.47
mm in the backswing phase, 910.42±121.30 mm in the forward phase, and 571.59±118.93 mm in the
backward phase (Table 2), of which the change in the forward phase was the largest, followed by the
backswing phase and, nally, the backward phase.
In the backswing phase of the backspin forehand stroke, the position changes of the lower limb three
joints movement from large to small were as followed: right hip joint (209.06±74.65 mm), right knee joint
(155.59±124.40 mm), and right ankle joint (120.89±115.77 mm). In the forward phase of the stroke, the
position changes of the lower limb three joints movement from large to small were as followed: right knee
joint (207.78±104.30 mm), right hip joint (203.80±80.19 mm), and right ankle joint (149.23±152.00 mm).
In the backward phase of the stroke, the position changes of the lower limb three joints movement from
large to small were as followed: right knee joint (195.98±110.13 mm), right ankle joint (175.68±116.33
mm), and right hip joint (175.00±107.95 mm) (Table 2).
Angle changes of the upper and lower limb three joints movement
The descriptive statistical analysis results of the angle changes of the upper and lower limb three joints in
the three phases of backspin stroke with forehand were shown in Table 3.
In the backswing phase of the backspin forehand stroke, the angle changes of the upper limb three joints
movement from large to small were as followed: right elbow joint (39.64±27.34), right wrist joint
(32.24±13.86), and right shoulder joint (16.29±11.01). In the forward phase of the stroke, the angle
changes of the upper limb three joints movement from large to small were as followed: right wrist joint
(34.70±15.39), right elbow joint (33.73±20.41), and right shoulder joint (23.74±15.90). In the backward
phase of the stroke, the angle changes of the upper limb three joints movement from large to small were
as followed: right wrist joint (35.08±14.25), right elbow joint (29.50±25.06), and right shoulder joint
(21.79±14.61) (Table 3).
In the backswing phase of the backspin forehand stroke, the angle changes of the lower limb three joints
movement from large to small were as followed: right hip joint (81.42±16.07), right knee joint
(28.72±14.12), and right ankle joint (27.91±9.20). In the forward phase of the stroke, the angle changes
of the lower limb three joints movement from large to small were as followed: right hip joint
(126.08±20.21), right ankle joint (45.51±15.75), and right knee joint (25.22±17.35). In the backward
phase of the stroke, the angle changes of the lower limb three joints movement from large to small were
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as followed: right hip joint (50.60±19.58), right ankle joint (28.70±11.70), and right knee joint
(15.53±12.48) (Table 3).
Changes of the linear velocity of the upper and lower limb three joints movement
The descriptive statistical analysis results of the changes of the linear velocity of the upper and lower
limb three joints movement in the three phases of backspin forehand stroke were shown in Table 4.
For each phase of the backspin forehand stroke, the linear velocity variation of the upper limb three joints
movement from large to small was right wrist joint, right elbow joint, and right shoulder joint. The linear
velocity changes of the right wrist joint movement in the three phases of the stroke were: 0.96 ±0.46 m/s
in the backswing phase, 2.40 ±0.85 m/s in the forward phase, and 0.89±0.40 m/s in the backward phase,
of which the change in the forward phase was the largest (Table 4). During the three phases of the whole
stroke, the linear velocity of each upper limb joint was increased at rst and then decreased at the end. In
the backward phase of the stroke, the linear velocity change of the right shoulder joint was the smallest,
which had a positive impact on maintaining the stability of the upper body.
In the backswing phase of the backspin forehand stroke, the linear velocity changes of the lower limb
three joints were in the following order: right hip joint, right knee joint, right ankle joint, and the largest
change of linear velocity was 0.29±0.11 m/s in the right hip joint. In the forward phase, the variation of
linear speed of the lower limb three joints was in the following order: right knee joint, right hip joint, and
right ankle joint. Among them, the linear speed of the right knee joint was the fastest, which was
0.53±0.24 m/s, and the linear speed of the hip joint was 0.52 ±0.18 m/s, which was close to that of the
right knee joint. In the backward phase, the linear velocity variation was in the following order: right knee
joint, right hip joint, and right ankle joint, of which the biggest variation was the right knee joint, which
was 0.30±0.18 m/s, followed by the right hip joint and right ankle joint (Table 4).
Changes of angular velocity of the upper and lower limb three joints movement
The descriptive statistical analysis results of the changes of angular velocity of the upper and lower limb
three joints movement in the three phases of backspin forehand stroke were shown in Table 5.
In the backswing phase of the backspin forehand stroke, the angular velocity changes of the upper limb
three joints were in the following order: right elbow joint, right wrist joint, and right shoulder joint, of which
the largest change of angular velocity was the right elbow joint (58.61 ±52.03/s), followed by the right
wrist joint (45.10±36.31/s) and the right shoulder joint (22.68±17.90/s). In the forward phase, the
angular velocity changes of the upper limb three joints were in the following order: right wrist joint
(92.48±101.20/s), right elbow joint (89.11±59.83/s), and right shoulder joint (63.07±47.17/s), of which
the change of the right wrist joint was the largest. In the backward phase, the angular velocity changes of
the upper limb three joints were in the following order: right wrist joint (53.40±66.31/s), right elbow joint
(46.56±42.27/s), and right shoulder joint (34.90±28.09/s), of which the change of the right wrist joint
was the largest (Table 5).
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In the backswing phase of the backspin forehand stroke, the angular velocity changes of the lower limb
three joints were in the following order: right hip joint, right ankle joint, and right knee joint, of which the
largest change of angular velocity was the right hip joint (115.41±42.00/s), followed by the right ankle
joint (39.15±16.74/s) and the right knee joint (37.85±17.15/s). In the forward phase, the angular velocity
changes of the upper limb three joints were in the following order: right hip joint (327.63±65.17/s), right
ankle joint (120.05±47.78/s), and right knee joint (65.52±46.60/s), of which the change of the right hip
joint was the largest. In the backward phase, the angular velocity of the right hip joint was the largest
(76.98±33.11/s), followed by the right ankle joint (44.75±22.23/s) and, nally, the right knee joint
(24.49±21.29/s) (Table 5).
Time duration of the three phases of backspin stroke with forehand
The descriptive statistical analysis results of the time duration of the three phases of players’ backspin
stroke with forehand were shown in Table 6.
The time duration of the three phases of players’ backspin stroke with forehand was 92.98 ±28.10 frames
in the backswing phase, 47.18 ±8.55 frames in the forward phase, and 82.39±22.84 frames in the
backward phase, respectively. During the whole stroke, the backswing phase’s time duration was the
longest, followed by the backward phase and the forward phase, which made the body fully expanded to
make a good preparation for the stroke and good preparation for the next stroke (Table 6).
Stroke effect of backspin stroke with forehand
The descriptive statistical analysis results of the stroke effect (ball speed, spin speed, and placement) of
players’ backspin forehand stroke were shown in Table 7.
The ball speed of players’ backspin stroke with forehand was 10.34 ± 2.09 m/s, the spin speed was
106.78 ±17.29 r/s, and the placement score was 2.93 ±1.33 points (table 7). According to the placement
score, the young players had a general ability to control the placement of backspin forehand stroke
(mainly in the 40*40cm corner area).
Correlation analysis between stroke structural characteristics and stroke effect
Pearson bivariate correlations were calculated to examine the relationships between the stroke structural
characteristics and stroke effect. These results were presented in Table 8.
As shown, there was a signicantly negative correlation between the time duration of the backswing
phase and the ball speed (
r
= -0.403,
p
< 0.01) and spin speed (
r
= -0.244,
p
= 0.027), respectively. The
longer the backswing time, the closer the coming ball to the body, and the more dicult for players to
return the ball, which makes the stroke effect reduced. There was a signicantly negative correlation
between the time duration of the forward phase and the ball speed (
r
= -0.390,
p
< 0.01
)
, spin speed (
r
=
-0.369,
p
< 0.01), and placement (
r
= -0.270,
p
= 0.014), respectively. There was also a signicantly
Page 11/20
negative correlation between the time duration of the backward phase and the ball speed (
r
= -0.272,
p
=
0.013).
The linear velocity of right wrist joint was positively correlated with ball speed (
r
= 0.298,
p
< 0.01) and
spin speed (
r
= 0.238,
p
= 0.031), and had no signicant correlation with the placement of the stroke (
r
=
-0.022,
p
= 0.847). As the nal power transfer point of the upper body when striking the ball, the linear
speed of the right wrist joint has a positive impact on the ball speed and spin speed of the stroke. The
linear speed of the right elbow joint was positively correlated with the spin speed of the stroke (
r
= 0.227,
p
= 0.040), and had no signicant correlation with the ball speed (
r
= 0.212,
p
= 0.056) and placement of
the stroke (
r
= -0.096,
p
= 0.392). The linear speed of the right shoulder joint and right hip joint had no
signicant correlations with the ball speed, spin speed, and placement of the stroke (all
p
> 0.05),
respectively. The linear speed of the right knee joint had a signicantly negative correlation with the spin
speed of the stroke (
r
= -0.255,
p
= 0.021), and had no signicant correlation with the ball speed (
r
=
-0.124,
p
= 0.268) and placement of the stroke (
r
= 0.082,
p
= 0.462). The linear velocity of right ankle joint
had no signicant correlation with the placement (
r
= -0.019,
p
= 0.869), but had a signicantly negative
correlation with the ball speed (
r
= -0.369,
p
< 0.01) and spin speed (
r
= -0.430,
p
< 0.01), respectively.
The angular velocity of right elbow joint had a signicantly positive correlation with the ball speed of the
stroke (
r
= 0.219,
p
= 0.013) and spin speed (
r
= 0.172,
p
= 0.048), and had no signicant correlation with
the placement (
r
= -0.018,
p
= 0.870). The angular velocity of the right wrist joint and right shoulder joint
had no signicant correlation with the ball speed, spin speed, and placement of the stroke (all
p
> 0.05),
respectively. The angular velocity of the right hip joint had no signicant correlation with the placement of
the stroke (
r
= 0.175,
p
= 0.115), however, it had a signicantly positive correlation with the ball speed (
r
=
0.427,
p
< 0.01) and spin speed (
r
= 0.277,
p
= 0.012), respectively. The angular velocity of the right knee
joint had a signicantly negative correlation with the placement of the stroke (
r
= -0.246,
p
= 0.026), and
had no signicant correlation with the ball speed (
r
= -0.197,
p
= 0.077) and spin speed (
r
= -0.150,
p
=
0.177), respectively. The angular velocity of the right ankle joint had a signicantly positive correlation
with the ball speed of the stroke (
r
= 0.443,
p
< 0.01), and had no signicant correlation with the spin
speed (
r
= 0.217,
p =
0.050) and placement (
r
= 0.102,
p
= 0.360), respectively.
Discussion
The technique of backspin forehand stroke was taken as an example in this study. The data of stroke
structural characteristics and stroke effect during the backspin forehand stroke were collected, and the
correlations between the stroke structural characteristics and stroke effect were explored. The results
showed that the stroke effect was affected by the different contributions of the upper and lower limb
three joints movement.
As the end of the power transfer segment of the upper body, the faster the wrist joint moves, the faster the
racket swings, which leads to faster ball speed when swinging the racket to hit the ball. Thus, the linear
Page 12/20
speed of the wrist joint movement has an obviously positive inuence on the ball speed of backspin
forehand stroke [32].
During the forward phase of the stroke, the angle of the elbow joint changes from large to small, thus
driving the movement of the wrist joint. Therefore, the larger the angular velocity of the elbow joint, the
faster the wrist joint moves, which means a larger linear speed of the wrist joint and a faster stroke of the
ball. The linear speed of the wrist joint movement has a positive correlation with the ball speed, so the
angular velocity of the elbow joint was positively correlated with the ball speed of the stroke.
The hip joint is the central part connecting the upper and lower limbs. The rotation of the hip joint can
increase the strength of turning the waist, thus increase the striking power and improve the rotation speed
and ball speed [16, 17, 33]. Therefore, the angular velocity of the hip joint had a signicantly positive
effect on the ball speed and spin speed of the stroke.
The movements of the knee joint and ankle joint are the two main lower limb joints that regulate the
center of gravity of the human body. In order to achieve a better stroke effect, players should keep their
body center of gravity as stable as possible. The unstable body center of gravity will lead to an
uncomfortable striking point and thus a decline in striking effect.
The translation of the ankle joint is mainly to adjust the body’s center of gravity in the horizontal
direction. The faster the linear speed of ankle joint, the more unstable of the body center of gravity, which
leads to poor stroke effect. Thus, the linear speed of ankle joint was negatively correlated with the ball
speed and spin speed of the stroke. The rotation of knee joint is mainly to change the body’s center of
gravity in the vertical direction. The larger the angular velocity of knee joint, the greater uctuation of the
body center of gravity, which leads to poor control of the hitting point and ball placement. Thus, the
angular velocity of the knee joint is negatively correlated with the stroke effect.
A perfect table tennis stroke requires players not only to strike the ball quickly, but also to distribute the
time of each phase of the stroke reasonably. The more reasonable the distribution of each phase’s time
duration of the stroke, the better the stroke effect. If the time duration of the backswing is too long, the
spin speed and ball speed will be reduced. The longer the backswing time, the closer the coming ball to
the body, and the closer the hitting point to the body, which leads to a shorter distance for players to
swing the racket to hit the ball, and results in limited striking power and reduced stroke effect [16].
The forward phase is the most important stage during the whole stroke. The longer the forward phase’s
duration is, the slower the wrist joint moves, which leads to a slower swing of the racket. The slower
swing of the racket results in a decrease of the spin speed and ball speed, and unstable control of the
placement of the stroke, thus affecting the stroke effect. For the recovery phase, the longer the recovery
time, the less time to prepare for striking the next ball, which also results in a decrease of stroke effect.
Conclusions
Page 13/20
This study investigated the relationships between the stroke structural characteristics and stroke effect of
young table tennis players. The results demonstrated that the time allocation of the three phases of the
stroke, especially the backswing phase and forward phase, had an important impact on the stroke effect,
especially on the ball speed and spin speed. During the process of striking the ball, the movements of
different joints had varying degrees of inuence on the stroke effect. The elbow joint, wrist joint, knee
joint, ankle joint, and hip joint had a signicant inuence on the stroke effect. The rotation of the elbow
joint drives the translation of the wrist joint, so the angular velocity of the elbow joint is signicantly
correlated with the speed of swing racket and also the ball speed of the stroke. As the central part of
connecting the upper and lower limbs, the rotation of the hip joint contributes to racket acceleration and
upper body rotation to performing shots. Thus, the angular velocity of the hip joint has a positive impact
on stroke effect. The movements of the knee joint and ankle joint are to adjust the uctuation of the body
center of gravity, thus, the motion of the knee joint and ankle joint is essential for the selection of the best
hitting point.
According to the above analysis, the ball speed of the stroke was mainly affected by the following
structural characteristics: the time allocation of the three phases of the stroke, the translation of the wrist
joint and ankle joint, the rotation of elbow joint, hip joint, and ankle joint, etc. The spin speed of the stroke
was mainly affected by the following structural characteristics: the time allocation of the three phases of
the stroke, the translation of the wrist joint, knee joint, and ankle joint, the rotation of the hip joint, etc. The
placement of the stroke was mainly affected by the time duration of the forward phase of the stroke and
the rotation of the knee joint.
Implication
During the daily training of young table tennis players, more attention should be paid to the following
aspects in order to improve the stroke effect of backspin forehand drive. Firstly, strengthenthe training of
hip joint rotation and the control ofthe transformation of the body’s center of gravity in order to improve
the coordination of the upper and lower limbs in the process of hitting the ball. Moreover, the body center
of gravity should not uctuate too much during the stroke in order to improve the stability of the stroke.
Secondly, strengthen the training of the exion movement of the elbow joint in the forward phase of
striking so as to improve the movement speed of the wrist joint. Thirdly, improve the rationality of time
allocation in the three phases of the stroke, and try to shorten the forward time duration under the
premise of full friction between the racket and the ball in order to improve the ball speed and rotation
velocity of the stroke.
Limitations
In this study, only six body joints (on the playing side), such as the shoulder joint, elbow joint, wrist joint,
hip joint, knee joint, and ankle joint, were selected to describe the structural characteristics of the stroke.
In the future study, more human body joints can be selected to illustrate the structural characteristics of
hitting, thus the inuence of the structural characteristics of young table tennis players’ striking action on
Page 14/20
the stroke effect of young table tennis players can be comprehensively analyzed. Besides, there may be
some differences in the stroke structural characteristics of young table tennis players between males and
females. In this study, the participants were not classied by gender. The differences of stroke structural
characteristics between males and females and their inuence on stroke effect can be explored in the
future study. Moreover, only kinematics-related indicators were selected for the description of the
structural characteristics of striking. The dynamics-related indexes can be selected for a more in-depth
and comprehensive analysis of the structural characteristics of striking in the follow-up research. Finally,
this study takes the technique of backspin forehand stroke as an example. Therefore, the ndings of this
study cannot be generalized to other techniques of stroke.
Abbreviations
Not applicable.
Declarations
Ethics approval and consent to participate
Ethical approval for this study was obtained from the ethics committee at Shanghai University of Sport.
All participants signed the written consent forms before they joined the study and written consent forms
were also obtained from a parent or guardian for participants under 16 years old. All participants were
provided a full explanation regarding the purpose and potential benets/risks of the study, condentiality,
and their right to withdraw from the study.
Consent for publication
Not applicable.
Availability of data and materials
The datasets generated during the current study are not publicly available, but are available from the
corresponding author upon reasonable request.
Competing interests
The authors declare that they have no competing interests.
Funding
This study was funded by the Shanghai Science and Technology Commission (No.18080503100),
Shanghai Education Commission Chenguang Program (No.17CG54), and Shanghai Pujiang Program
(No. 17PJC085).
Authors' contributions
Page 15/20
All authors (YX, YJX, MML, and YXZ) contributed to the conception of the study, drafting and critical
revision of the manuscript, and provided nal approval of the manuscript.
Acknowledgements
The authors would like to thank China Table Tennis College for their friendly cooperation in data
collection.
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Tables
Table 1. Outcome measures of a stroke
Primary index Secondary index
stroke structural characteristics position of body joints
angle of body joints
linear velocity of body joints movement
angular velocity of body joints
stroke effect ball speed
spin speed
placement
Table 2. Position changes of the upper and lower limb three joints movement in the three phases of
backspin stroke with forehand (mm)
Page 18/20
Body joints backswing-phase
(M±SD, N=42)
forward-phase
(M±SD, N=42)
backward-phase
(M±SD, N=42)
Upper limb
three joints
Right shoulder joint 311.07±75.82 339.11±67.29 173.22±64.27
Right elbow joint 470.87±110.43 738.88±86.10 540.57±134.41
Right wrist joint 674.12±128.47 910.42±121.30 571.59±118.93
Lower limb
three joints
Right hip joint 209.06±74.65 203.80±80.19 175.00±107.95
Right knee joint 155.59±124.40 207.78±104.30 195.98±110.13
Right ankle joint 120.89±115.77 149.23±152.00 175.68±116.33
Table 3. Angle changes of the upper and lower limb three joints movement (in degrees) in the three
phases of backspin stroke with forehand
Body joints backswing-phase
(M±SD, N=42)
forward-phase
(M±SD, N=42)
backward-phase
(M±SD, N=42)
Upper limb
three joints
Right shoulder joint 16.29±11.01 23.74±15.90 21.79±14.61
Right elbow joint 39.64±27.34 33.73±20.41 29.50±25.06
Right wrist joint 32.24±23.86 34.70±35.39 35.08±44.25
Lower limb
three joints
Right hip joint 81.42±16.07 126.08±20.21 50.60±19.58
Right knee joint 28.72±14.12 25.22±17.35 15.53±12.48
Right ankle joint 27.91±9.20 45.51±15.75 28.70±11.70
Table 4. Changes of linear velocity of the upper and lower limb three joints movement in the three phases
of backspin stroke with forehand (m/s)
Page 19/20
Body joints backswing-phase
(M±SD, N=42)
forward-phase
(M±SD, N=42)
backward-phase
(M±SD, N=42)
Upper limb
three joints
Right shoulder joint 0.43±0.29 0.90±0.52 0.26±0.17
Right elbow joint 0.66±0.34 1.94±0.61 0.83±0.36
Right wrist joint 0.96±0.46 2.40±0.85 0.89±0.40
Lower limb
three joints
Right hip joint 0.29±0.11 0.52±0.18 0.27±0.17
Right knee joint 0.20±0.14 0.53±0.24 0.30±0.18
Right ankle joint 0.16±0.15 0.37±0.33 0.26±0.20
Table 5. Changes of angular velocity of the upper and lower limb three joints movement in the three
phases of backspin stroke with forehand (degree/s)
Body joints backswing-phase
(M±SD, N=42)
forward-phase
(M±SD, N=42)
backward-phase
(M±SD, N=42)
Upper limb
three joints
Right shoulder joint 22.68±17.90 63.07±47.17 34.90±28.09
Right elbow joint 58.61±52.03 89.11±59.83 46.56±42.27
Right wrist joint 45.10±36.31 92.48±101.20 53.40±66.31
Lower limb
three joints
Right hip joint 115.41±42.00 327.63±65.17 76.98±33.11
Right knee joint 37.85±17.15 65.52±46.60 24.49±21.29
Right ankle joint 39.15±16.74 120.05±47.78 44.75±22.23
Table 6. The duration of the three phases of backspin stroke with forehand (unit: frame)
Three phases Duration (M±SD, N=42)
backswing-phase 92.98±28.10
forward-phase 47.18±8.55
backward-phase 82.39±22.84
Note.
The sampling frequency of the high-speed infrared motion capture system was 120 frames per
second.
Page 20/20
Table 7. Stroke effect of backspin stroke with forehand (N=42)
Stroke effect M±SD
Ball speed 10.34±2.09 (m/s)
Spin speed 106.78±17.29 (r/s)
Placement 2.93±1.33 (points)
Table 8. Correlation analysis between the stroke structural characteristics and stroke effect
Variables Ball speed Spin speed Placement
Duration backswing-phase -0.403** -0.244*-0.117
forward-phase -0.390** -0.369** -0.270*
backward-phase -0.272*-0.116 -0.013
Linear velocity Right wrist joint 0.298** 0.238*-0.022
Right elbow joint 0.212 0.227*-0.096
Right shoulder joint 0.134 0.118 -0.087
Right hip joint -0.140 -0.116 -0.212
Right knee joint -0.124 -0.255*0.082
Right ankle joint -0.369** -0.430** -0.019
Angular velocity Right wrist joint 0.130 0.102 -0.018
Right elbow joint 0.219*0.172*0.125
Right shoulder joint 0.076 -0.003 -0.002
Right hip joint 0.427** 0.277*0.175
Right knee joint -0.197 -0.150 -0.246*
Right ankle joint 0.443** 0.217 0.102
Note.
**
p
< .01; *
p
< .05.
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Objective: Sport research often requires human motion capture of an athlete. It can, however, be labour-intensive and difficult to select the right system, while manufacturers report on specifications which are determined in set-ups that largely differ from sport research in terms of volume, environment and motion. The aim of this review is to assist researchers in the selection of a suitable motion capture system for their experimental set-up for sport applications. An open online platform is initiated, to support (sport)researchers in the selection of a system and to enable them to contribute and update the overview. Design: systematic review; Method: Electronic searches in Scopus, Web of Science and Google Scholar were performed, and the reference lists of the screened articles were scrutinised to determine human motion capture systems used in academically published studies on sport analysis. Results: An overview of 17 human motion capture systems is provided, reporting the general specifications given by the manufacturer (weight and size of the sensors, maximum capture volume, environmental feasibilities), and calibration specifications as determined in peer-reviewed studies. The accuracy of each system is plotted against the measurement range. Conclusion: The overview and chart can assist researchers in the selection of a suitable measurement system. To increase the robustness of the database and to keep up with technological developments, we encourage researchers to perform an accuracy test prior to their experiment and to add to the chart and the system overview (online, open access).
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Biomechanical study of human upper limb is one of the most referenced aspects for the optimization of upper limb posture and the design of related products. Firstly, a real-time optical motion capture system was used to capture the real-time position of key points of the human body in the course of executing the specified action. The focus of the work was to calculate and deeply analyze the experimental data of the human upper limb by MATLAB software. Then, the human upper limb was simplified as a club model, and the variation value of each joint angle of the human upper limb during the motion process was calculated by the cosine theorem. The dynamic joint torque was computed by the inverse dynamics and the change of main muscle force was calculated by the optimization analysis. Lastly, the human upper limb motion comfort was evaluated by calculating the real-time load rate of human upper limb muscles, and the motion comfort index evaluation model of human upper limb was established. The experiment result proved that the human upper limb muscles were in the comfort state when the body executed the specified action at a sitting posture. The results provide a theoretical basis for the depth analysis of human upper limb motion.
Article
The aims of this study were to evaluate movement patterns of topspin forehand, to define the main principles of performing this shot, and to determine the essential differences in individual types of topspin forehand. In total, 10 female high-level athletes participated in this study. The BTS analysis system was used with a novel model for the range-of-motion measurement. An acoustic sensor was attached to the racket for identification of a ball-racket contact. Players, performing topspin forehand, attempt to achieve maximal racket velocity based on the principles of proximal-to-distal sequences and summation of speed with a stretch-shortening character of cycle. The essential differences between type of topspin forehand occurred in the range of motion. Increased power of topspin shot was accompanied by a significant increase in range of motion in most of the studied joints and body segments, in particular in the rotation movement of the upper body, pelvis and shoulders, flexion and rotation in the shoulder and elbow joints, and flexion and rotation in knee joints.