Accuracy in the badminton short serve: A methodological and kinematic study

In sports, accuracy is an essential component of actions such passing, shooting, and aiming. Executing a movement or action that requires a high degree of accuracy is a critical determinant of success in many individual and team sports. Each sport has different methods for evaluating accuracy, however an overarching goal is to determine whether an object hits its target, or assess the distance by which it misses. However, in some sports accuracy is not readily measureable because an object might not reach a target, i.e. the object is intercepted, or it collides with another object or a person, or an endpoint might not be visible. One example of this is the badminton serve, where the shuttlecock is normally hit by a receiving player before it reaches the ground, its intended endpoint. The goal of one common serve type, the short serve, is to force the opponent into hitting the shuttlecock upward at a steep angle in order to clear the net, allowing a serving player to hit the shuttlecock from a point high above the net from which it is easier to score. The optimal trajectory of the short serve, therefore, is one in which the apex occurs before the shuttlecock crosses the net and results in a steep downward trajectory. To accomplish this, the swing trajectory of the racquet must be accurate itself, which is usually accomplished by use of a short period of swing (i.e. swing length). In practice the analysis of both swing technique and shuttlecock trajectory is usually done subjectively (by the coach), however objective quantification is necessary in order to determine the shuttlecock trajectories and racquet swing techniques that provide the best serve result to allow correct representation of serve accuracy. The main issue is that an objective measurement is needed, and since the shuttlecock doesn’t land on the ground, it makes it difficult to determine serve accuracy with the existing protocols. The broad aims of this Master’s thesis were to (i) develop a new method of measuring accuracy of the short serve;(ii) compare and contrast the technique/s of elite badminton players using principal component analysis; and, (iii) determine the magnitude of variability in the movement patterns of elite players performing the short serve. In the first study (Study I), a specific definition of accuracy was presented that allowed assessment when the endpoint is not reached (i.e. when the shuttlecock does not land on the court). The accuracy of an object’s trajectory is typically evaluated by determining whether it hits a target, or measuring the distance by which it misses. For the badminton short serve, the rules dictate that the shuttlecock must land on or beyond the service line (1.98 m from the net) after traversing the net. However these constraints are insufficient to distinguish poor from good serves; a serve where the shuttlecock clears the net by a small margin but continues and does not reach its apex until after it passes the net might be considered poorer in accuracy (easier for receiver to return) than one in which the shuttlecock reaches its apex before the net even if its height over the net is greater. In this study, short serve trajectories were recorded with and without a receiver present. Two separate data collection sessions and 13 players were tested across both sessions (Session A and B) (age: 23.4 ± 5.1 years, body mass: 73.2 ± 11.1 kg, height: 175 ± 8.6 cm). Data from trials with full trajectory (without an opponent) were used to create a model enabling the prediction of shuttlecock landing. This model was then used to predict the shuttlecock landing point in trials with a receiver, with an important finding being that 69% of serves would have landed on or short of the service line. Thus, receivers might benefit from leaving a majority of serves in competition in order to win the point; servers make the assumption that receivers will return most serves and therefore choose to serve short. Using the new accuracy method, serve accuracy was categorised as accurate, inaccurate, apex good, and clearance good. This provided individual and group accuracy ratings. In Study II a three-dimensional model was developed to examine the upper body kinematics during the badminton short serve. Textbook definitions hold that push-like movement patterns produce trajectories of the highest accuracy, however reducing complexity (i.e. degrees of freedom) is also stated as essential. Nonetheless, these patterns may be mutually exclusive, since push-like patterns may exhibit considerable complexity. The purpose of Study II was to describe the short serve movement patterns used by elite badminton players to determine whether push-like or low-complexity (or both) patterns predominate. Eight participants were recruited from the Senior Australian National Doubles Badminton squad (mean age: 23.4 ±5.1 years, body mass: 73.2 ±11.1 kg, height: 175 ±8.6 cm). Three-dimensional kinematics were measured with an opponent present and analysed using principal component analysis to determine what movement patterns were used in this accuracy-based skill. Results showed that all players adopted a push-like movement pattern, but the most accurate servers also constrained the number of degrees of freedom by allowing movements of the elbow and wrist joints only in a single plane. The main objective of Study III was to understand the role that movement variability plays in a precision-based movement. Little research has been published examining movement variability in sports, specifically in skills that require accuracy. The badminton short serve provided a unique opportunity to examine how elite athletes vary their movement patterns, since it requires precise multi-joint coordination to achieve an accurate serve. Recent research has shown that a rigid or inflexible system may not be good for performance and that it is more appropriate to understand the adaptability of a movement in an ever-changing environment. A three-dimensional motion analysis of eight elite badminton players performing30 short serves with an opponent present to replicate match condition s was conducted. The results identified that players incorporate variability in specific phases of their movements reduce variability at racquet-shuttlecock contact. Higher medio-lateral (transverse plane) variability was displayed in most joint angles across all players. This strategy incorporated variability in the task-redundant dimension (transverse) to reduce variability in the task-relevant dimension (sagittal), which directly impact accuracy of the serve. Variability was also present in the timing of the swing itself, varying the timing of the backswing to reduce the variability at the contact point was a common feature displayed across all subjects, irrespective of whether the serve was accurate or not. Findings suggest elite badminton players use joint and timing variability in a functional capacity. In conclusion, the methods developed to analyse the accuracy and kinematics of an accuracy-based task such as the badminton short serve revealed a greater insight into what defines an accurate serve, and how elite players coordinate and vary their movement to achieve accuracy. The results from Study I suggest that training either with an opponent present or serving on or slightly short of the service line may lead to better serve performance. The results from Study II provide the coach or player with information on the ideal movement patterns for short serve accuracy i.e. reducing the number of degrees of freedom involved (i.e. reduce movement complexity), using a push-like movement, and paying close attention to the movement from the elbow and wrist joints. The final study (Study III) revealed that elite badminton players vary their movement in a plane (transverse) that has less impact on the outcome of the task, thus reducing the variability in the plane (sagittal) that has the larger impact on the serve movement

Using the trajectory of the shuttlecock as a measure of performance accuracy in the badminton short serve

Accuracy of a projectile is typically quantified as the proportion of successful target hits, or the distance an object finishes from the target. Serving in sports such as badminton differs since the shuttlecock is usually intercepted by the opponent before landing on the target (i.e. court surface). Therefore, landing accuracy measures are inappropriate and a new method of determining accuracy of the serve is needed. During interviews, elite coaches and players described an accurate short serve as crossing the net with low clearance and having an apex before the net. Three-dimensional trajectory of the shuttlecock was therefore tracked from eight national-level players who performed 30 short serves in simulated match conditions (i.e. with an opponent); 27% of all serves were classified as ‘accurate’, 27% of serves as ‘inaccurate’, 21% with a ‘good apex’ position, and 25% with a ‘good clearance’ height. The proposed method of assessing shuttlecock trajectory as a measure of accuracy could be adopted by coaches and players to assess and improve short serve accuracy. Furthermore, this method is more representative of a match environment since the shuttlecock rarely lands because the opponent returns the serve

Fatigue does not increase limb asymmetry or induce proximal joint power shift in habitual, multi-speed runners

During prolonged jogging, joint moment and work tend to decrease in the distal (ankle) joint but increase at proximal (hip/knee) joints as performance fatigue manifests, and such adaptations might be expected to occur in sprinting. Fatigue is also thought to increase inter-limb asymmetries, which is speculated to influence injury risk. However, the effects of fatigue on sprint running gait have been incompletely studied, so these hypotheses remain untested. Using statistical parametric mapping, we compared 3-D kinematics and ground reaction force production between the dominant (DL) and non-dominant (NDL) legs of 13 soccer players during both non-fatigued and fatigued sprint running. Contrary to the tested hypotheses, relative between-leg differences were greater in non-fatigued than fatigued sprinting. DL generated higher propulsive impulse due to increased ankle work, while NDL exhibited greater vertical impulse, potentially due to greater hip flexion prior to downward foot acceleration. Whilst few changes were detected in DL once fatigued, NDL shifted towards greater horizontal force production, largely resulting from an increase in plantar flexion (distal-joint) moments and power. After fatiguing running, inter-limb asymmetry was reduced and no distal-to-proximal shift in joint work was detected. These adaptations may attenuate decreases in running speed whilst minimising injury risk

Does fatigue influence joint-specific work and ground force production during the first steps of maximal acceleration?

During initial acceleration, the first steps of a maximal-effort (sprint) run often determine success or failure in the capture and evasion of an opponent, and is therefore a vital factor of success in many modern sports. However, accelerative events are commonly performed after having already run considerable distances, and the associated fatigue should impair muscle force production and thus reduce acceleration. Despite this, the effects of running-induced fatigue on our ability to accelerate as well as the running technique used to achieve it have received little attention. We recorded 3-D kinematics and ground reaction forces during the first three steps of the acceleration phase from a standing start before and after performing a high-speed, multi-directional, fatiguing run-walk protocol in well-trained running athletes who were habituated to accelerative sprinting. We found that the athletes were able to maintain their acceleration despite changing running technique, which was associated with use of a more upright posture, longer ground contact time, increased vertical ground reaction impulse, decreased hip flexion and extension velocities, and a shift in peak joint moments, power, and positive work from the hip to the knee joint; no changes were detected in ankle joint function. Thus, a compensatory increase in knee joint function alleviated the reduction in hip flexor-extensor capacity. These acute adaptations may indicate that the hip extensors (gluteal and hamstring muscle groups) were more susceptible to fatigue than the ankle and knee musculature, and may thus be a primary target for interventions promoting fatigue resistance

A survey to evaluate the association of COVID-19 restrictions on perceived mood and coping in Australian community level athletes

Australian community level athletes faced unprecedented changes to their training andcompetition options as the global COVID-19 pandemic took a stronghold. This disruptionwas predicted to have a negative impact on emotional well-being as communitiesbraced through periods of social isolation and physical distancing requirements. Thisstudy provides an Australian perspective on the emotional well-being of communitylevel athletes and the extent to which they coped during the COVID-19 pandemic.Emotional well-being and coping were measured using the Brief Emotional ExperienceScale and the 28-item Brief Cope Scale. Both instruments were administered alongwith other questions pertaining to participant demographics and training status via anonline survey between April and June 2020. The survey was disseminated to communityathletes through word-of-mouth and social media platforms. No significant differencesin emotional well-being were observed between athlete groups as a result of COVID-19and its associated restrictions. Coping scores also appeared to be preserved in Australiancommunity athletes, which contrasts the impact expected asa result of the COVID-19pandemic. While tentative, the observed preservation in coping may have bufferedpotential declines in emotional well-being, which has beendocumented in professionaland semi-professional athletes and the general population. These unexpected findingsand tentative suppositions warrant further investigationand highlight the importance ofconducting a country- or region-specific approach to examining the impact of COVID-19on community athletes, as responses to COVID-19 are undoubtedly not consistentthroughout the world

The effect of performance fatigue on sprint running technique

Sprint running is a complex, multi-joint movement that has been well studied in human research, largely through the analysis of 3-D kinematics and force-time signals obtained during non-fatigued running. In team sport, however, the unplanned nature of match play determines if and when sprint efforts occur, meaning that some efforts may be performed with minimal recovery and therefore likely in the presence of fatigue. While fatigue-induced changes in running technique have been shown to incite potentially injurious kinematic patterns, it is unclear whether these modifications occur because of altered lower limb joint torques, power generated and absorbed, or muscle lengths and contraction speeds adopted. Therefore, to explore the effect of running-induced fatigue on sprint running technique, 3-D kinematics and ground reaction forces were collected in thirteen intermediate-level soccer players during the first three steps of acceleration and sprinting at maximum speed before and after completing 45-minutes of a simulated soccer match. Study 1: During non-fatigued accelerative sprinting, horizontal impulse progressively decreased with each step (step 1 [S1] to step 2 [S2] to step 3 [S3]), while similar positive work was performed at the hip and ankle joints in S1 and S2 but greater relative ankle joint contribution was observed in S3. Thus, the proximal hip extensors and distal ankle plantarflexors contributed equally to forward acceleration. After fatiguing exercise, acceleration was maintained even though running technique was substantially altered. The sagittal trunk angle increased by ~15% (i.e., more erect posture) with a clear reduction in hip flexion angular velocity (22%) and hip extensor moment (8%). An increase in knee joint moments (7%) and powers (4%) compensated for reduced hip joint function. This acute adaptation alleviated hip flexor-extensor force requirement and preserved propulsive ground force application. These findings indicate that the muscles spanning the hip joint may be more susceptible to fatigue than those around the ankle and knee joints during accelerative sprinting, although technique alterations were sufficient to retain acceleration once fatigued. Study 2: In non-fatigued maximum speed sprinting, the dominant limb (DL) produced greater propulsive impulse as a result of greater work being done at the ankle joint, whilst the non-dominant limb (NDL) produced more vertical impulse. After fatiguing exercise, the mean maximum running speed decreased by 4%, with a notable shift toward horizontal force production in NDL, mainly resulting from an increase in plantarflexion (i.e. distal joint) moments and powers, while few kinematic and kinetic changes were detected in DL. Due largely to these changes in NDL, interlimb asymmetries were substantially reduced with fatigue. Thus, these results are consistent with a theory in which speed is prioritised during non-fatigued maximum sprinting, which may benefit from a less symmetrical sprint gait (i.e. each limb is utilised ‘maximally’ regardless of force imbalances), but injury risk reduction may be prioritised over speed during fatigued sprinting, with a more uniform sprint gait being adopted to distribute muscle forces more equally between limbs. Importantly, interlimb asymmetry decreased following fatigue as a result of changes in NDL, contrary to the hypothesis that asymmetry should increase with fatigue. Study 3: Musculoskeletal modelling was used to estimate lengths of the three bi-articular hamstring muscle-tendon units (MTU), which were found to operate at significantly longer lengths during maximum speed than accelerative sprinting, irrespective of fatigue. If peak hamstring MTU lengths are indeed a risk factor for injury, then this is speculatively unlikely to occur within the first three steps of acceleration. After fatiguing exercise, peak anterior pelvic tilt increased, and peak hip flexion decreased while peak knee extension angle remained unchanged during maximum speed sprinting. The adaptations, collectively, resulted in a lack of change in estimated hamstring MTU lengths in DL. Conversely, fatigue led to an increase in the peak length of biceps femoris long head (BFlh) MTU in NDL. Using simple linear regression, increased peak knee extension angle (before foot-strike) was associated with a longer BFlh MTU (in NDL), which may have some utility as a forewarning for an increasing BFlh MTU length in practical settings. An important finding from this study was that overall BFlh MTU excursion remained constant despite peak length increasing, demonstrating a longer mean operating length when fatigued. Given that the length at which a muscle is actively lengthened influences the magnitude of muscle damage incurred, the longer operating length observed within BFlh MTU (NDL) with fatigue may induce greater magnitudes of muscle damage, and thereby increase injury risk. The combined findings of this thesis demonstrate that the acute technique adaptions in response to fatiguing, running-based exercise varied considerably between each of the sprint phases. These findings may help inform performance and injury preventive practices, in particular, interventions targeting the gluteal and hamstring muscle groups to promote fatigue resistance