Intra-Individual Variation in the Jump Smash for Elite Malaysian Male Badminton Players

Abstract

The badminton jump smash is vital for winning rallies, but players can have unintended variations in performance. This study examines the causes of intra-individual smash speed variations among 19 Malaysian male elite players. Twenty-five jump smashes were recorded using a 3D motion capture system, with the three fastest (95.0 ± 3.6 m·s⁻¹) and three slowest (85.8 ± 5.8 m·s⁻¹) smashes per participant categorised into different groups. Six racket/shuttlecock variables and six upper body technique variables during the swing phase and at the point of contact were analysed. Five out of the six racket/shuttlecock variables, including post-impact shuttlecock speed, racket head speed at contact, impact location, distance from the racket’s geometric centre, and swing time, significantly differed between groups. Only the shoulder elevation angle differed significantly from 75% to 95% of the forward swing (p = 0.023), with less elevation during faster smashes. Consistency in producing high shuttlecock speeds during the jump smash for elite players is primarily achieved through variables linked to timing. Players/coaches should focus on being able to initially produce high racket head speeds, at which point ensuring a consistently efficient impact between the stringbed and shuttlecock should be the priority.

1. Introduction

The forehand smash was reported as the last shot played in 29% and 22% of the men’s and women’s singles rallies at the 2008 Beijing Olympic Games [1]. It is widely regarded as the most effective and aggressive stroke in badminton. The success of this stroke lies in creating a fast downward trajectory of the shuttlecock towards the desired location on the opposite court and putting the opponent in a defensive situation [2]. Unsurprisingly, the post-impact shuttlecock speed is often used to define the quality of the shot. As a result, substantial attention has been paid by researchers to understand the development of speed in badminton smash [3,4,5], as well as in other similar projectile-hitting sporting motions, such as the tennis serve [6,7,8] and volleyball jump spike [9,10,11]. At the elite level, the badminton smash shuttlecock speed may vary due to body positioning, technique, and the timing (impact location) of the smash, among other factors [12]. However, to the authors’ knowledge, there is no study to date that has conducted any intra-individual analysis investigating why a given player’s shuttlecock speed may vary between smash strokes.

A higher velocity in the smash is associated with specific characteristics at the moment of racket–shuttlecock contact, including a more internally rotated shoulder [3,4], as well as reduced elevation of the shoulder and less extension of the elbow [4]. Additionally, a faster smash is linked to greater angular velocity of the internal rotation of the shoulder, a factor contributing significantly (66%) to the development of racket head speed [13]. Other key elements contributing to the acceleration phase of the smash include forearm pronation [14,15] and wrist flexion [14]. Notably, the rotational motion of the trunk during both the backswing and forward acceleration phases also plays a substantial role in achieving a faster smash speed [5,16]. Furthermore, a consistent impact location of the shuttlecock on the racket face is critical to minimise reductions in smash speed due to the impact location [12].

Previous research has considered differences in technique for overhead sports such as badminton, tennis, and volleyball. In the badminton smash, significantly greater shoulder internal rotation, horizontal abduction, and wrist flexion torque were found for skilled players compared to unskilled players [17]. Furthermore, participants who produce faster smash speeds have been shown to have greater shoulder internal rotation upon impact and a greater pelvis–thorax separation angle in the transverse plane at the end of retraction compared to participants with slower smashes [3]. In the tennis serve, shoulder internal rotation has been shown to be a major contributor to the differences in horizontal racket head velocity between fast and slow servers [8]. In the volleyball spike, differences in upper-limb angular velocities during successful versus faulty spikes were found for different phases, covering 35% to 45% and 76% to 100% of the motion [18].

The parameters that contribute to intra-individual variations in badminton smash speeds are unknown when the goal is to maximise shuttlecock speed. This does not include cases where a reduction in speed may be the goal in favour of a different trajectory, e.g., a steeper smash (‘stick smash’). Previously, several key determinants have been identified to differentiate between shuttlecock speeds across a cohort of players; however, these results should not be generalised to an individual [3]. While cohort-based studies provide valuable insights into group trends and biomechanical factors associated with high-performance smashes, they often overlook intra-individual differences. These differences can arise due to unique player-specific techniques, variations in motor control, and adaptations developed through training or anatomical constraints. For instance, individual players may employ distinct smash techniques, including variations in arm kinematics, shoulder elevation, and trunk rotation [5]. They may also display unique sequencing and timing patterns within the kinetic chain, driven by their skill levels, anthropometric characteristics, or personal preferences [2]. As such, the objective of this study was to investigate causes of reduced intra-individual shuttlecock speed during the badminton smash among elite Malaysian players. Understanding whether technique and/or racket/shuttlecock variables cause reductions in shuttlecock speed at an individual level will allow coaches and practitioners to better advise players on how to consistently execute their fastest smash.

2. Materials and Methods

2.1. Participants

Nineteen elite male right-handed Malaysian badminton players were recruited for this study (age: 20.2 ± 0.7 years; mass: 71.7 ± 4.5 kg; height: 1.77 ± 0.06 m; reported as mean ± SD). All players were actively competing in international-level tournaments and representing Malaysia, including BWF-sanctioned events. These players typically rank within the top tiers nationally and have demonstrated consistent performance in competitive settings.

All players were preparing for competitions and injury-free at the time of data collection. Ethical approval was obtained from the National Sports Institute of Malaysia (ISN) Research Ethics Committee, and written informed consent was obtained from participants prior to their participation. Players’ own rackets were used for all testing to reflect real match conditions, with a manufacturer-reported unstrung racket mass of 84.0 ± 1.8 g and self-reported string tensions of 29.8 ± 0.7 lb.

2.2. Data Collection

All data collection was conducted on an instrumented standard full-size badminton court at the Sports Biomechanics Laboratory at the ISN under controlled conditions (Figure 1a). The kinematics of each jump smash were recorded using 25 Oqus 7+ series infrared cameras (Qualisys AB 411 05, Goteborg, Sweden) at 700 Hz (Figure 1a).

A total of sixty-two, 12.5 mm reflective markers were attached to key bony anatomical landmarks (Figure 2a) using Qualisys double-sided and hypafix non-woven adhesive tape to create a 15-segment representation, including the head, thorax, pelvis, 2× upper arms, 2× forearms, 2× hands, 2× thighs, 2× shanks, and 2× feet [4] in Visual 3D v6.00.18 (C-Motion Inc., Germantown, MD, USA). The definition of each segment was constructed from a local reference frame using a minimum of three markers on the segment based on three axes (x: pointing to participants’ right; y: pointing forward; z: pointing from distal to proximal structures), as reported in a previous study [3]. Each racket was equipped with one 12.5 mm marker at the bottom of the handle and eight pieces of 10 mm² retro-reflective tape on the racket head and shaft (Figure 2b). New Yonex Aerosense 30 shuttlecocks were used for all data collection, with a piece of circle-reflective tape (diameter 19 mm) attached to the tip of the shuttlecock (Figure 2c). Misshaped or broken shuttlecocks were discarded.

All participants were given approximately 20 min for warm-up and 15–30 min for court familiarisation before data collection. During data collection, high serves/lifts were replicated using a Knight Trainer shuttle launcher (Black Knight, Canada) for the participants to perform their maximum jump smashes, taking off and landing on a fixed area with both feet (Figure 1b). Twenty-five maximum jump smashes aimed at a designated area on the opposite side of the court were performed by each participant. Trials where the shuttlecock did not land in the designated area were excluded.

2.3. Data Reduction

The three fastest and three slowest jump smashes (identified by the post-impact shuttlecock speed) for each participant were categorised into FAST and SLOW conditions, respectively, for further analysis. Position data were labelled using Qualisys Track manager (QTM2021.2; build 4260, Qualisys, Goteburg, Sweden), and gaps within the data were filled using a combination of linear and polynomial interpolation. All body marker position data were filtered within Visual 3D using a low-pass Butterworth filter with a cut-off frequency of 60 Hz, which was determined through a residual analysis [19] using MATLAB R2022a (The MathWorks Inc., Natick, MA, USA).

A 15-segment model in Visual 3D was used to calculate kinematic parameters during the swing phase for each trial according to two key instances: (a) the start, defined as the instance when the racket head speed reached 5 m/s during the backswing phase and did not subsequently drop below this threshold, and (b) shuttle–racket contact, defined by the frame where the anterior–posterior velocity of the shuttlecock changes from negative to positive [20]. Joint angles were calculated as Cardan angles (

Table 1. Cardan joint angle definitions.

Joint	Rotation	Anatomical Position	Positive Direction
thorax	axial rotation (x-factor)	0°	anti-clockwise (viewed from above)
shoulder	plane of elevation	90° a	horizontal flexion
	elevation	90° a	elevation
	internal/external rotation	180° a	internal rotation
elbow	flexion/extension	180°	extension

Note: ^a Shoulder angles are given for the upper arm elevated to the horizontal (abducted by 90° from the anatomical position) and internally rotated such that the forearm is horizontal when the elbow is flexed to 90° (similar to [24], with 90° and 180° added to the plane of elevation and internal rotation angles, respectively, due to the specific ranges of motion in badminton).

), where an xyz rotation sequence was used [21] for all angles except for the shoulder, where a zyz rotation sequence was used [22] following the ISB recommendation, and the thorax, where a yxz rotation sequence was used [23].

Post-impact shuttlecock speed, racket head speed, impact timing (swing time from the start of the forward swing to racket–shuttlecock contact), and impact location were calculated using a curve-fitting methodology [25], which was adapted for badminton [12] to include a 1 ms contact period [26]. Additionally, the racket face angle relative to the vertical upon contact and the shuttlecock angle post-impact relative to the horizontal were calculated [26,27,28].

2.4. Data Analysis

2.4.1. Technique Variables

The technique variables include the following kinematic parameters: namely, the shoulder plane of elevation, elevation and rotation, elbow flexion/extension angle and angular velocity, and trunk angle data during the swing phase. All angle and angular velocity curves were time-normalised to the start of the forward swing period to the point of racket–shuttle contact. The reliability of each variable for both the FAST and SLOW conditions was analysed using an integrated pointwise index (intraclass correlation, ICC) test.

2.4.2. Racket/Shuttlecock Variables

The post-impact shuttlecock speed, racket head speed, swing time, and impact location (longitudinal and mediolateral) relative to the racket head centre were separated into FAST and SLOW conditions based on the post-impact shuttlecock speed.

2.4.3. Statistical Analysis

Integrated pointwise indices using the ICC (type: consistency) were calculated using variance components of an ANOVA based on a two-way mixed model [29] with pointwise confidence intervals set to 95% supplemented at each time point to analyse the test–retest reliability for the curve data. The classification of ICCs according to another study [30] was adapted for interpretation: poor < 0.4; 0.4 ≤ fair < 0.6; 0.6 ≤ good ≤ 0.74; and 0.74 < excellent. Data were tested for normality using the Shapiro–Wilk test, where the assumption of normality was met if p > 0.05. If a high similarity within each participant’s conditions (FAST vs. SLOW) was found (indicated by a high ICC value), the three trials for each condition were averaged (mean) into two single time histories to provide a representative time history of the technique used during each condition. A within-measures ANOVA and statistical parametric mapping (SPM) were performed to assess any significant differences in the technique variables between the conditions over the normalised swing phase. A significance threshold of alpha < 0.05 was set for ANOVA measurements, whilst a Bonferroni correction was used to adjust for post hoc analysis. Paired T-tests were performed in order to detect differences between the racket/shuttlecock variables for each of the two conditions (FAST vs. SLOW). A within-measures ANOVA using 1D statistical parametric mapping (1D-SPM) [31] was performed in MATLAB R2022a (The MathWorks Inc., Natick, MA, USA), and an ICC test and a paired t-test were performed in IBM SPSS Statistics 26 (IBM, Armonk, NY, USA).

3. Results

Overall, the ICC test revealed excellent similarities in all the participants’ technique variables in both the FAST and SLOW conditions, identified by a high average ICC value of 0.983 ± 0.065 (mean ± SD). Hence, the three fastest and three slowest trials for each participant were combined into two single time histories (FAST and SLOW) for each technique variable studied to represent the technique used when performing fast and slow smashes, respectively.

3.1. Technique Variables

Of the five technical variables analysed, namely the shoulder elevation angle (Figure 3), shoulder plane of elevation (Figure 4), shoulder internal/external rotation (Figure 5), elbow flexion/extension (Figure 6), and trunk x-factor angle (Figure 7), no significant differences were observed between the FAST and SLOW conditions during the swing phase, except for the shoulder elevation angle (Figure 3). A significant difference in the shoulder elevation angle was identified from 75% to 95% (Figure 3) of the forward swing between the FAST and SLOW trials (p = 0.023), with players being less elevated at the shoulder joint during their FAST trials compared to their SLOW trials.

3.2. Racket/Shuttlecock Variables

The overall range of badminton smash speeds was 75.8–100.6 m·s⁻¹, with the largest variation for an individual being 13.4 m·s⁻¹ (13% difference) and the smallest difference for an individual being 3.3 m·s⁻¹ (3% difference). Across the 19 participants, significant differences were observed between the FAST and SLOW trials in terms of post-impact shuttlecock speed (95.0 ± 3.6 m·s⁻¹ vs. 85.8 ± 5.8 m·s⁻¹, p < 0.001), racket head speed at contact (66.3 ± 3.4 m·s⁻¹ vs. 64.3 ± 3.7 m·s⁻¹, p < 0.0005), and longitudinal impact location (8.5 mm vs. −2.6 mm, p = 0.027) (

Table 2. Paired-samples T-test on the six racket/shuttlecock variables.

Variable	Unit	Mean (SD)		p-Value
		FAST	SLOW
post-impact shuttlecock speed	m·s−1	95.03 ± 3.58	85.79 ± 5.83	<0.0005 *
racket head speed upon contact	m·s−1	66.25 ± 3.43	64.32 ± 3.72	<0.0005 *
mediolateral impact location	mm	−15.31 ± 8.12	−19.57 ± 18.56	0.209
longitudinal impact location	mm	8.46 ± 15.65	−2.58 ± 27.74	0.027 *
absolute distance of impact location from geometric centre of the racket face	mm	29.48 ± 10.09	42.89 ± 13.76	0.001 *
swing time	ms	162.7 ± 10.5	166.3 ± 12.4	0.001 *

Notes: * denotes statistically significant difference between groups; all results are presented as means (SD).

). Interestingly, the paired T-test also revealed that there were significant differences in the swing duration and impact location between the FAST and SLOW trials. The swing duration during the FAST condition was, on average, 0.0036 s (3.6 ms) shorter than that in the SLOW trials (p = 0.0012). Meanwhile, the players were observed to demonstrate ‘worse’ impact locations in their SLOW trials, demonstrated by the greater absolute distance of the impact location from the geometric centre on average (13.41 mm; p = 0.001) compared to in their FAST trials.

4. Discussion

The intra-individual variation in shuttlecock smash speed across the 25 trials for each participant varied from 3.3 to 13.4 m·s⁻¹, with significant differences between the FAST and SLOW groups for both post-impact shuttlecock speed and racket head speed. A maximum difference of 3.3 m·s⁻¹ (3%) across 25 trials could be considered a small difference and perhaps what might be expected for elite players, but 13.4 m·s⁻¹ (13%) is over three times greater than this value and for an elite player is perhaps surprising. This drop of 13% would bring an ‘elite’ player in line with ‘regional’-level players based on data from [3], where elite players achieved similar shuttlecock speeds of 94.6 m·s⁻¹ whilst regional players achieved 84.6 m·s⁻¹.

A comparison of technique and racket/shuttlecock variables revealed several important differences between the FAST and SLOW conditions. Unsurprisingly, significant differences existed between the FAST and SLOW conditions for post-impact shuttlecock speed and racket head speed, respectively, given the high correlation between the two variables (r = 0.90; [3]).

Overall the participants performed smashes with greater longitudinal impact locations (11 mm closer to the racket tip) in the FAST group compared to the SLOW group. It is not obvious why this difference in impact location occurred across a group of elite players, but it could indicate that coordinating the timing of the racket shuttle impact was challenging even for elite players. Having an impact location closer to the tip of the racket does result in a faster racket speed at the point of impact on the racket, and therefore, it makes sense that the fastest shuttlecock speeds came from impacts slightly closer to the tip of the racket. There becomes a point at which an increase in longitudinal impact location would cause a reduction in shuttlecock speed due to the impact efficiency between the stringbed and shuttlecock. The mean longitudinal and mediolateral impact locations during the FAST condition were similar to the ‘optimal’ impact location reported by another study [12], namely 8.5 vs. 11.6 mm and −15.3 vs. −5.7 mm, respectively.

The ‘impact quality’ may also be related to the significant difference in swing duration, where players performed, on average, 3.6 ms shorter swing durations during the FAST condition. The small amount of extra time taken during the SLOW condition swings perhaps allowed the shuttlecock more time to drop and thus produce impact locations lower on the racket head and further away from the optimal position [12].

The technique of the participants did not vary substantially between the FAST and SLOW conditions, with only one upper-body joint angle differing between the FAST and SLOW conditions, namely the shoulder elevation angle between 75 and 95% of the swing phase. The players held their arm in a less elevated position during the FAST trials compared to the SLOW trials, and this is supported by [4], where the arm is placed in a more favourable position to generate greater angular velocities of shoulder internal rotation. A lower shoulder elevation angle reduces the distance between the racket and the body, effectively shortening the moment arm of the racket–hand system. This potentially reduces the rotational inertia of the arm–racket complex, allowing for faster angular acceleration during the swing phase. The closer proximity of the arm to the body also potentially reduces the torque required to achieve higher racket head speeds, along with the work done against gravity. Given the ability level of the participants, it was unlikely that their technique would differ between the two conditions. Whilst the technique (joint kinematics) used at the various joints remained similar between the conditions, and, therefore, so did the overall ranges of motion, they were completed over shorter periods of time during the FAST condition, implying greater angular velocities and thus greater racket head speeds, transferring more momentum to the shuttlecock (assuming an equivalent impact efficiency).

Previous studies have found shoulder internal rotation upon contact to be an important technique variable, with a more internally rotated shoulder being linked to greater shuttlecock speeds [3,4]. Similarly, players who achieve a more counter-rotated trunk position at the end of the backswing phase have been shown to achieve greater shuttlecock speeds [3,4,5]. Neither of these technique variables showed any differences between the FAST and SLOW conditions when assessing intra-individual variation throughout the entire swing phase. These results suggest that players changing their technique is unlikely to be the cause of variations in shuttlecock speed, and instead, successfully executing and timing their technique to ensure an efficient impact is likely to explain this variation in shuttlecock speed.

Future work should investigate technique differences with non-elite populations or different age groups, as well as carrying out longitudinal studies, to see what technique changes are made as players progress through various stages and performance groups, thereby highlighting which technique factors are important for consistently developing greater racket head speed and shuttlecock smash speed. It is also likely that players of a lower standard have more variability in their technique, allowing for a greater understanding of what technique factors cause a reduction in shuttlecock speed.

In conclusion, for elite players, the differences in shuttlecock speeds between smash and slow strokes are likely to be caused by racket/shuttlecock variables, not specific changes in technique. In particular, more distal longitudinal impact locations, within sensible limits where impact efficiency is not significantly impacted, and completing the swing phase over a shorter period of time have been shown to generate greater racket head speeds.

5. Limitations

This study’s design differentiated between FAST and SLOW smash conditions rather than assigning athletes to distinct groups. This choice may not fully encapsulate motor control or technical variability across different performance levels or fatigue states. All the players in this study were right-handed; the findings should be applicable to left-handed players, but future studies should address this. No specific fatigue assessments were conducted, but rest intervals were provided as required, and there was no specific evidence of fatigue in terms of smash speed, as for some players, their fastest smashes occurred towards the end of the 25 smashes. However, some of the variation found between the conditions could be attributable to factors beyond the designated conditions, such as muscular fatigue. The uniform population of elite male Malaysian players is both a strength and limitation of this study; future studies should look to consider female athletes as well as junior and non-elite participants to broaden the applicability of the findings to the whole population.

6. Conclusions and Recommendations

In summary, this study presents preliminary insights into biomechanical differences in badminton smashes under FAST and SLOW conditions, providing an initial step toward understanding movement variability and performance in sport-specific contexts. Despite the limitations, the findings highlight the importance of nuanced analysis methods in biomechanical studies, particularly in complex, high-performance movements such as the badminton smash. More sophisticated design and analysis choices may be necessary to capture the full scope of the motor control mechanisms underlying elite badminton techniques, especially when addressing intra-individual variations and compensatory joint mechanics. Additionally, from a tactical perspective, it may also be relevant to create conditions where players have a particular focus on generating a maximal shuttlecock speed vs. accuracy balance and evaluate what technique factors change in the likely scenario that players reduce the racket head speed and shuttlecock speed to increase the smash accuracy. A longitudinal study tracking the progression from junior to senior levels could provide valuable insights into the biomechanical changes that occur over time and their impacts on performance. Such an approach would help deepen our understanding of how technique evolves with experience and its influence on smash performance.