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Relationships between whole-body kinematics and badminton jump smash racket head speed


Abstract and Figures

The purpose of this study was to identify kinematic determinants of shuttlecock speed in the badminton jump smash. Three-dimensional kinematic (400 Hz) data were collected for 18 experienced male badminton players using an 18 camera Vicon Motion Analysis System. Each participant performed 12 jump smashes. The trial with the fastest shuttlecock speed per participant was analysed using an 18-segment rigid body model. Parameters were calculated describing elements of the badminton jump smash technique. Four kinematic variables were significantly correlated with racket head speed. Greater peak wrist joint centre linear velocity, jump height, shorter acceleration phase, and greater shoulder internal rotation at shuttlecock / racket impact.
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Romanda Miller1,2, Harley Towler1, Stuart McErlain-Naylor1,3, and Mark King, 1
School of Sport, Exercise and Health Sciences, Loughborough University, UK.1
Centre for Student Success, University of East London, UK2
School of Health and Sports Sciences, University of Suffolk, UK3
The purpose of this study was to identify kinematic determinants of shuttlecock speed in
the badminton jump smash. Three-dimensional kinematic (400 Hz) data were collected for
18 experienced male badminton players using an 18 camera Vicon Motion Analysis
System. Each participant performed 12 jump smashes. The trial with the fastest shuttlecock
speed per participant was analysed using an 18-segment rigid body model. Parameters
were calculated describing elements of the badminton jump smash technique. Four
kinematic variables were significantly correlated with racket head speed. Greater peak
wrist joint centre linear velocity, jump height, shorter acceleration phase, and greater
shoulder internal rotation at shuttlecock / racket impact.
KEYWORDS: velocity; technique; overhead; racket; swing; stroke
INTRODUCTION: The forehand smash is an effective attacking shot in badminton, accounting
for 54% of ‘unconditional winner’ and ‘forced failure’ shots in international matches (Tong &
Hong, 2000). A shuttlecock with a greater post-impact speed will give an opponent less time
to return the shuttlecock. Few studies have investigated the kinematic determinants of
shuttlecock speed in the badminton smash by elite players. Ramasamy et al. (2019) revealed
three kinematic variables significantly associated with shuttlecock speed: maximal wrist
angular velocity during the acceleration phase (i.e. start of the forward swing to contact);
maximal racket head speed between backswing and contact; and jump height, defined as
minimum to maximum centre of mass height. Ultimately, racket head speed is the most
important variable for producing shuttlecock speed as shuttlecock speed is determined by the
transfer of momentum during the collision between the racket stringbed and shuttlecock.
Previous research has reported that linear velocities of the distal segments best explain
variation in shuttlecock speed/racket head speed, however, it is unclear how the distal segment
velocities and subsequent racket head and shuttlecock speeds are generated. Rambely et al.
(2005) found that the wrist was the predominant contributor (26.5%), whilst the elbow and
shoulder joints contributed 9.4% and 7.4%, respectively, towards racket tip velocity.
Additionally, use of low frame rates and unclear methodologies for defining both shuttlecock
speed and racket head speed mean that it is difficult to compare results. This study aimed to
identify full-body kinematic parameters that best explain the generation of post-impact racket
head velocities in the badminton jump smash.
Eighteen male badminton players (24.3 ± 7.1 years; 1.84 ± 0.08 m; 79.6 ± 8.8 kg) of regional
(n = 9), national (n = 4), and international (n = 5) standard participated in this study. Each
performed twelve forehand jump smashes from a racket-fed lift via an international coach /
player, representative of match conditions. Testing procedures were explained to each
participant, and informed written consent was obtained in accordance with the institutional
ethics committee.
Data Collection
Forty-seven 14 mm retro-reflective markers were attached to the participant (Figure 1). An 18
camera Vicon Motion Analysis System (400 Hz; OMG Plc, Oxford, UK) collected 3D kinematic
data of the participant, racket and shuttlecock on a badminton court. Joint centres were
calculated from a pair of markers placed across the joint so that their midpoint coincided with
the joint centre (McErlain-Naylor et al., 2014). Hip, thorax, neck and head joint centres were
calculated according to Worthington et al. (2013). A further marker was placed on the bottom
of the racket handle, seven pieces of 3M Scotchlite reflective tape were attached to the racket
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frame, and a single piece of reflective tape was attached around the base of the cork of the
shuttlecock (Figure 1). Participants used their own racket and new Yonex AS40 shuttlecocks
Figure 1. Marker locations for the participants; racket and shuttlecock marker locations.
Data Reduction
Position data were labelled within Vicon Nexus 1.7.1 and imported into Matlab v.2018b for all
further processing. Position data of all body markers were filtered using a fourth-order, zero-
phase, low-pass Butterworth filter with a cut-off frequency of 30 Hz, determined through
residual analysis. Six angles were calculated for each trial: shoulder internal / external rotation;
elbow flexion / extension; elbow pronation / supination; wrist palmar flexion / extension; wrist
ulnar / radial deviation; and X-factor. Joint angles were calculated using three-dimensional
rotation matrices, defining the rotation applied to the proximal segment coordinate system in
order to bring it into coincidence with the coordinate system of the distal segment. An XYZ
rotation sequence was used, representing flexion-extension, adduction-abduction and
longitudinal axis rotation, respectively. When describing humerothoracic motion, a YZY
rotation sequence was used as recommended by ISB (Wu et al. 2005). Wrist angles were
normalised based on the player adopting their normal grip within a static trial, which was
considered the neutral position. X-factor referred to the separation angle between vectors
connecting the right and left shoulder joint centres and, the right and left hip joint centres,
respectively, in the global transverse plane. Instantaneous post-impact shuttlecock speed and
racket- shuttlecock contact timing were determined using a logarithmic curve-fitting
methodology (Peploe et al., 2018) with minor adjustments for application to the badminton
smash. Pre- impact racket head centre velocity was interpolated to the calculated time of initial
shuttlecock contact. Due to the focus on investigating maximal performance each player’s trial
with the greatest shuttlecock speed was used for further analysis.
The movement was defined around the backswing and acceleration phases, divided by five
discrete instants: preparation was the point at which the centre of mass height was minimal;
end of retraction was the point at which the racket was most medio-laterally positioned towards
the non-dominant side of the participant within the global coordinate system; racket lowest
point was when the racket tip was at its lowest vertical point (Martin et al. 2012); turning point
was the point, after minimum (most negative), at which the racket head velocity normal to
stringbed became positive; and shuttlecock contact was the closest motion capture frame to
the previously defined instant of racket-shuttlecock contact. The backswing phase was the
time between preparation and turning point, whilst the acceleration phase was the time
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between turning point and shuttlecock contact. Joint angles were defined at each key instant
and their maximum range of motion through to contact calculated. Furthermore, post-impact
shuttlecock speed, racket head speed at impact, jump height and peak shoulder, elbow, wrist
joint centre linear velocities were calculated for each trial. Duration of phases, as well as total
swing time were also calculated for each trial.
Statistical Analysis
All statistical analyses were performed in Matlab v.2018b. Pearson product moment correlation
analyses, including 90% confidence intervals (CI) were performed between each kinematic
(independent) variable and racket head speed. An alpha of 0.1 determined significance.
RESULTS: Maximal shuttlecock speeds for the cohort were 89.6 ± 5.3 m·s-1 (range: 80.1 - 99.8
m·s-1). Racket head speeds were 56.3 ± 4.0 m·s-1 (range: 46.7 - 64.6 m·s-1). Four kinematic
variables were significantly correlated with racket head speed. Greater peak wrist joint centre
linear velocity (r = 0.712; CI: 0.507, 0.917; p < 0.001), jump height (r = 0.494; CI: 0.035, 0.781;
p = 0.037), shorter acceleration phase (r = -0.600; CI:-0.833, -0.184; p = 0.009) and greater
shoulder internal rotation at shuttlecock contact (r = 0.563; CI: 0.131, 0.816; p = 0.015) were
associated with greater shuttlecock speeds. It should be noted that the elbow pronation angle
at preparation (r = 0.495; CI: 0.036, 0.781; p = 0.037) was found to be significantly correlated
with racket head speed, however upon inspection of the data it was evident that this correlation
was entirely due to one player. This player had a very large pronation angle at this key instant,
which was coincidentally the player with both the slowest shuttlecock and racket head speed.
This result was therefore discounted and ignored.
DISCUSSION: Racket head speeds achieved by the participants showed good agreement with
previously reported values by elite players (Ramasamy et al., 2019; Kwan. M., 2010; Kwan et
al., 2011). Racket head speed at impact, normal to the stringbed plane, correlated very highly
with instantaneous post-impact shuttlecock speed (r = 0.903; CI: 0.753, 0.964; p < 0.001)
justifying the use of racket head speed as a performance variable. Whilst jump height was
significantly correlated with racket head speed and Ramasamy et al. (2019) also found that our
thoughts are that jump height in the smash is a characteristic of more able players attempting
to produce steeper smash strokes, rather than being a causal variable of faster racket head
speeds and shuttle speeds.
Distal linear velocities (wrist) explained the variation in racket head speed, yet proximal angles
of the trunk and shoulder also explained the variation in racket head speed. This is suggestive
of the kinetic link principle whereby movements of a proximal-to-distal nature generate and
conserve angular momentum to produce high distal end-point velocities. Important longitudinal
axis rotations, typically difficult to measure and observe, may not always follow this strict
sequence with regards to timing, however the proximal-to-distal nature of overhead strokes
provides a good general understanding of how high distal end-point velocities can be generated
(Marshall, 2000; Fleisig et al., 2003). A more negative X-factor at end of retraction causing
greater racket head speed endorses the idea of the stretchshortening cycle, whereby more
elastic energy is stored and recovered to enhance the concentric phase. The stretch
shortening cycle has been linked to greater velocities in throwing actions due to enhancement
of the concentric phase (Elliott, 2006; Elliot et al., 1999). Finally, no ranges of motion were
found to significantly correlate with racket head speed although Lees et al. (2008) previously
suggested that increasing the range of motion can improve performance (racket head speed)
by increasing the acceleration path of the racket, allowing more muscular force to be generated
and applied to accelerate the racket.
The velocity principle, not explored in this study, may also be critical to understanding the
development of greater distal velocities in the badminton smash motion (Lees et al. 2008). This
principle relates to how the angle between segments influences the effect of proximal rotations.
For example, if the elbow angle is 90 the effect of shoulder internal rotation is maximised.
Similarly, if the racket is held at 90 to the forearm segment, the contribution from radio-ulnar
pronation is maximised. This is a difficult principle to observe, due to the complex nature of the
badminton smash motion, where multiple joint rotations are responsible for generating racket
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head speed (Liu et al. 2002). Tang et al. (1995) reported that amongst four elite players, the
forearm-racket angle was 147, which suggests a compromise between the height and speed
at contact between racket and shuttlecock.
Potential limitations existed during this study, including lack of experimental control over the
racket and therefore the impact mechanics between the racket and shuttlecock, as well as the
effect that the racket properties may cause to the technique and kinematics of the player
(Whiteside et al., 2014).
CONCLUSION: This study has shown that proximal kinematic joint angles caused greater
linear velocities at distal joint centres and greater racket head speeds. Greater peak wrist joint
centre linear velocity, jump height, shorter acceleration phase, and greater shoulder internal
rotation at shuttlecock contact were all found to have a significant correlation to racket head
speed. It is suggested that players and/or coaches should aim to decrease the length of the
acceleration phase of the racket though technique/strength to increase racket head speed.
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... An alternative approach for sports action recognition is to use inertial sensors for data collection. e sensors are wearable and composed of gyroscopes, accelerometers, and magnetometers [7,8]. Wearable devices with embedded inertial sensors are commonly used in various applications such as gait analysis, activity recognition healthcare, disease monitoring, and navigation [9]. ...
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In this communication, the Standardization and Terminology Committee (STC) of the International Society of Biomechanics proposes a definition of a joint coordinate system (JCS) for the shoulder, elbow, wrist, and hand. For each joint, a standard for the local axis system in each articulating segment or bone is generated. These axes then standardize the JCS. The STC is publishing these recommendations so as to encourage their use, to stimulate feedback and discussion, and to facilitate further revisions. Adopting these standards will lead to better communication among researchers and clinicians.
This study was designed to analyze the jumping forehand smash of elite players based on three-dimensional kinematic data, and to get insight into the basic badminton smash technique. Jumping smashes of four male elite players were filmed with two high speed camears operating at 250 frames per sec with exposure time of 1/1500 and 1/1250 sec. The nine jumping smashes were selected for the analysis, and were digitized from the take-off of the jump to the end of the swing in the air. Thirty three-dimensional coordinates for the segment endpoints and racket were computed by a Direct Linear Transformation Method. Small reference poles were fixed on the forearm of the swing arm of the subjects to detect their movements of the radio-ulnar joint and wrist joint. Following six joint angle changes were obtained throughout the smash motion. (a) pronation/supination angle at the radio-ulnar joint. (b) radial flexion/ulnar flexion angle at the wrist joint. (c) palmar flexion/dorsi flexion angle at the wrist joint. The resultd showed that pronation of the radio-ulnar joint seemed to contribute to produce great velocities of the racket head, because the rotation occurred the greatest range in the shortest time in the three rotations immediately before contact with the shuttle. Preliminary to the motions were motions in the opposite direction; e. g., supination of the forearm was detected. These motions in the opposite direction would be useful to extend the range of the motion in each joiot angle. The order of time of the last joint rotation starting immediately before contact was ulnar flexion, palmar flexion and pronation. Respective times required for the rotation until contact became shorter in turn of late occurring. The faster the rotation was, the later the rotation occurred and the shorter the rotation time was. This kind of chain and continuous movements of different joints, and different freedom in the same joint may accelerate the racket head efficiently. The averages of the racket angle (the angle between the forearm and racket shaft) was 147.0゜at the contact.
This research examined the influence on performance of no-pause and mean delays of 0.97 s and 1.5 s between the eccentric and concentric phases of the stretch-shorten cycle movement of internal rotation (IR) of the upper arm. Videography and surface electromyography were used in the assessment of 19 athletes throwing a baseball in a manner that constrained all degrees of freedom other than upper-arm IR. Results demonstrated that the pectoralis major, latissimus dorsi, and anterior deltoid muscles were all active at above 100% maximum voluntary contraction (MVC) during IR. The maximum velocity of the wrist decreased with increasing pause time between the eccentric and concentric phases of the IR movement. A mean 21.9% augmentation to the maximum wrist velocity was recorded when the no-pause delay and a mean delay of 1.5 s were compared. There were no electromyographically discernible differences recorded either prior to or after release for any of the monitored muscles during IR across the pause conditions. It is evident therefore that the bene fits of a prestretch during external rotation (ER) have a significant influence on the subsequent velocity of IR.
Objectives: Collision models for hitting implements denote how ball speed and swing weight increase proportionally when swing speed and impact location are held constant. The biomechanical effects of swing weight interventions are less understood. This study examined the effects of swing weight on serving arm mechanics, racquet kinematics, impact location and ball speed in the tennis serve. Design: Repeated measures design, where racquet swing weight parameters distinguished between serve conditions. Methods: Eleven elite adolescent female tennis players performed serves in three conditions: (1) regular, unperturbed racquet; (2) 5% increase in swing weight; and (3) 10% increase in swing weight. A 500 Hz Vicon motion analysis system captured three-dimensional serving arm, racquet and ball kinematics. Results: When racquet swing weight was increased, the peak shoulder internal rotation and wrist flexion velocities during the forwardswing both decreased. The peak accelerations of shoulder internal rotation, elbow extension and wrist flexion also appeared to share an inverse relationship with swing weight. As swing weight increased, the impact location shifted significantly closer to the racquet tip and resultant racquet at impact decreased. Ball speed remained similar in all conditions. Conclusions: The assumptions underlying the collision model appear to be violated by the biomechanical effects of a swing weight intervention in a sample of elite adolescent female players. Consequently, added swing weight fails to effect faster serves. From a dynamical systems perspective, the inherent response of the movement system deserves consideration prior to, and during, the administration of swing weight interventions.
The kinematics of a badminton racket during a smash stroke was observed in this study with the purpose of investigating stroke dynamics and racket behaviour. Motion capture measurements of the racket during several smash strokes performed by three players of different skill levels indicated a clear increase in racket velocity at impact with increasing skill level. Variations between translational and rotational contributions to the impact speed could also be seen between the players. The advanced player produced a much higher peak angular velocity and also relied much less on translation, with a translational velocity of only 8% of the total velocity versus the 20% for the recreational player. It is proposed that, as an alternative to shuttlecock speeds, racket head speed measurements can be used as an indicator of performance, and can also provide some insight into the interaction between the racket and player. KeywordsBadminton smash–Racket speed–Player skill–Racket elasticity–Impact speed