Dr Tim Bennett

Instep kick research has shown that skilled soccer players display natural variations in their technique from trial-to-trial (Egan et al., 2007; Lees & Barton, 2005; Lees & Rahnama, 2013). This inherent movement variability (MV) has been described as a demonstration of ‘motor equivalence’, which has been defined as the ability to achieve an invariant end using variable means (Abbs & Cole, 1987). This movement strategy would benefit a soccer player by facilitating a consistent (stable) performance outcome whilst utilising a flexible range of solutions to adapt to different constraints. ‘Motor equivalence’ is closely associated with the concept of synergies, which can be identified and quantified using a motor control tool called the ‘uncontrolled manifold’ (UCM). The theoretical appeal of the UCM as an analysis tool has also been identified, but not implemented in recent sports biomechanics studies (Carson et al., 2014a; Carson et al., 2014b). Therefore, the UCM method was used as vehicle for evaluating MV structure and ‘motor equivalence’ within a sport-specific task, and to determine whether the UCM method could provide a better understanding of instep soccer kick technique and performance in comparison to a traditional biomechanics approach.  Twelve male university soccer players (age 20.8  ±  2.7 years, height 1.80  ±  0.03 m and mass 79.6  ±  6.2 kg) who were right foot dominant participated in this project and were instructed to perform a maximal instep kick at a 1m2 target at a distance of 11m. Three-dimensional kinematic data was recorded from a motion analysis system using a 15-segment whole-body model to compute kinematic variables for the traditional biomechanical analysis. For the UCM analysis, trial-to-trial variations of seven joint angles of the kicking leg, and principal components of the whole-body, were analysed across the normalised whole movement trajectory to investigate the MV structure of eight hypothesised performance variables. The dependent measures were UCM variability measures and strength of synergy. The main findings from the research project were:  Selected technique, performance and task variables produced values consistent with instep kicking literature. There was no clear differences between hit and missed kicks across all biomechanical variables. The UCM analysis across all participants revealed that eight hypothesised performance variables produced synergies, across all time periods of the instep kick. This finding provided empirical evidence to support the demonstration of ‘motor equivalence’ in instep soccer kicking technique.  Clear differences were noted between hit and missed kicks base on the UCM analysis. Missed kicks were characterised as producing lower strength of synergies, higher ranges of solutions, higher total variability and less stability across all performance variables for all time periods of the instep kick. A case study analysis showed clear differences between hit and missed kicks and highlighted unique differences in comparison to the group UCM analysis.  A comparison between UCM variables and instep kick task variables did not reveal any clear relationship between these different outcomes, which were attributed to the kicking task constraints used for this project.  This current project provided an original contribution to contemporary understanding of a complex technique through an evaluation of instep soccer kicking and MV structure.

The provision of sports science in elite sporting organisations is becoming vastly integral to the way in which global sports are enhancing and developing performance, safety, and innovation. The Badminton World Federation (BWF, 2022) in particular has invested in its development of research to further inform performance, development and participation. Over the last ten years the Badminton World Federation has provided research grants to numerous high profile institutions, universities and organisations specialising in the disciplines of sports science: Biomechanics, Physiology, Nutrition, Psychology, Training and Performance analysis. Here we provide an overview of academic peer-reviewed research projects conducted over the last ten years, in an attempt to outline key findings with clear, real-world practical applications for badminton coaches and players around the world.

Many studies have shown that focusing on an intended movement effect that is farther away from the body (distal external focus) results in performance benefits relative to focusing on an effect that is closer to the body (proximal external focus) or focusing on the body itself (internal focus) (see, Chua, Jimenez-Diaz, Lewthwaite, Kim & Wulf, 2021). Furthermore, the advantages of a distal external focus seem to be particularly pronounced in skilled performers (Singh & Wulf, 2020). The present study examined whether such benefits of more distal attentional focus may be associated with enhanced functional variability. Volleyball players (n = 20) performed 60 overhand volleyball serves to a target. Using a within-participants design, the effects of a distal external focus (bullseye), proximal external focus (ball) and an internal focus (hand) were compared. The distal focus condition resulted in significantly higher accuracy scores than did the proximal and internal focus conditions. In addition, uncontrolled manifold analysis showed that functional variability (as measured by the index of synergy) was greatest in the distal focus condition. These findings suggest that a distal external focus on the task goal may enhance movement outcomes by optimising compensatory coordination of body parts.

This report provides a detailed analysis of the men's final, including key parameters during the approach, take off and bar clearance. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

Movement systems are massively redundant, and there are always multiple movement solutions to any task demand; motor abundance. Movement consequently exhibits ‘repetition without repetition’, where movement outcomes are preserved but the kinematic details of the movement vary across repetitions. The uncontrolled manifold (UCM) concept is one of several methods that analyses movement variability with respect to task goals, to quantify repetition without repetition and test hypotheses about the control architecture producing a given abundant response to a task demand. However, like all these methods, UCM is under-constrained in how it decomposes a task and performance. In this paper, we propose and test a theoretical framework for constraining UCM analysis, specifically the perception of task-dynamical affordances. Participants threw tennis balls to hit a target set at 5m, 10m or 15m, and we performed UCM analysis on the shoulder-elbow-wrist joint angles with respect to variables derived from an affordance analysis of this task as well as more typical biomechanical variables. The affordance-based UCM analysis performed well, although data also showed thrower dynamics (effectivities) need to be accounted for as well. We discuss how the theoretical framework of affordances and affordance-based control can be connected to motor abundance methods in the future.

This report provides a detailed analysis of the women's final, including key parameters during each phase of the movement up to release. The motion path and velocity of the discus has been shown for each athlete's best attempt. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides a detailed analysis of the men's final, including key parameters during each phase of the movement up to release. The motion path and velocity of the discus has been shown for each athlete's best attempt. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides a detailed analysis of the men's final, including key parameters during each phase of the movement up to release. Spatiotemporal variables and motion path of each athlete has been shown. Additionally, an in-depth analysis of javelin release has been presented for each athlete's best attempt. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

This report provides a detailed analysis of the women's final, including key parameters during each phase of the movement up to release. Spatiotemporal variables and motion path of each athlete has been shown. Additionally, an in-depth analysis of javelin release has been presented for each athlete's best attempt. The full report is available from the IAAF website: https://www.iaaf.org/about-iaaf/documents/research

The relationship between focus of attention instructions and motor performance is a topic of significant research interest. It is widely accepted that attending to the mechanics of the movement when performing a motor task (internal focus) yields poorer performance and less effective movement organisation than attending to the movement outcome (external focus). Specifically, an external focus is suspected to promote more flexibility in the motor system, inducing more effective muscular activity and movement kinematics, which are mechanisms directly responsible for organisation of the resulting movements. However, no review has systematically assessed the influence focus of attention instructions have on muscular activity and movement kinematics. The purpose of this systematic review was to examine evidence on the effect that focus of attention instructions have on the underpinning mechanisms of movement organisation. Adhering to the Preferred Reporting Items for Systematic Reviews and Meta-Analysis (PRISMA) guidelines, a comprehensive electronic literature search yielded 36 research studies. Using a narrative methodological approach, the findings were thematically analysed and synthesised. Generally, external focus of attention instructions resulted in muscular activity and movement kinematic profiles that reflect more effective movement organisation than those resulting from the provision of internal focus instructions; thus, supporting a central tenet of the constrained action hypothesis.

The aims of this study were: (1) to quantify interlimb asymmetries in EPL soccer players in the context of kicking limb preference and (2) to establish the relationship between interlimb asymmetries and measures of physical performance. Twenty-two players (age: 21.8 ± 4.4 years) from an EPL club performed a running gait assessment (20 km/h) and unilateral countermovement jumps, a CoD assessment (modified 505 test), and an isokinetic knee extension/flexion protocol using each leg. Asymmetries were quantified using the percentage difference method and Pearson’s correlations were used to quantify the association between variables. Players displayed the greatest level of asymmetry in isokinetic strength measures (5.9-12.7%) and lower levels of asymmetry in gait (1.6-7.7%), jump (0.9-7.0%) and CoD (1.9-3.5%) assessments. The influence of the preferred kicking limb was most evident in the isokinetic assessment with the players showing dominance in the preferred limb for knee flexor strength and in the non-preferred limb for knee extensor strength. These manifested in the asymmetry values calculated for the hamstring:quadricep (H:Q) ratios at 60°/s (8.80 ± 7.82%) and 240°/s (11.22 ± 7.04%) and in the functional H:Q ratio (12.67 ± 8.25%). The asymmetry values for peak extensor moment at 240°/s showed a significant correlation (ρ = ─0.55, p = 0.034) with 10 m time in the CoD assessment. These findings provide benchmark asymmetry data for soccer practitioners and reveal that kicking limb preferences may bring about interlimb differences in the H:Q ratio which raises important considerations in the design of testing batteries and injury reduction interventions.

INTRODUCTION: Markerless motion capture (MMC) is increasing in popularity among biomechanists because of the reduced data collection time and removal of subjects needing to wear tight, minimalist clothing [1]. However, gait analysis often requires subjects to walk or run at multiple speeds, such as in an incremental exercise test. The sensitivity of MMC to detect kinematic changes across speeds has yet to be thoroughly explored, so the aim of this study was to compare kinematic responses to changes in gait speed when measured with a widely used marker-based system versus a MMC system. METHOD: Fifteen healthy, adult participants walked on an instrumented treadmill (1,000 Hz; Gaitway3D; h/p/cosmos) at 3 and 5 km/h and ran at 10, 11, and 12 km/h. A 14-camera optoelectronic motion capture system (Oqus 7+, Qualisys) was used to collect marker data, where markers were placed according to Cappozzo et al. [2]. Markerless video data were collected synchronously with 12 high-speed video cameras (Miqus, Qualisys). Both systems were sampling at 100 Hz. Markerless data were exported to Theia3D for processing, before being exported to Visual3D for modelling alongside marker data. Gait events were determined using the kinetic data, which was the same for both motion capture systems. Kinematic data were exported to MATLAB to calculate changes in sagittal angular data between gait speeds. RESULTS: For walking (changes between 3-5 km/h), MMC demonstrated the capacity to measure similar changes in joint range of motion (ROM), peak flexion, and peak extension for hip, knee, and ankle joints (ICC[3,1] ≥ 0.892) when compared to marker-based data, and there were no significant differences between the change in joint kinematics between systems (p > 0.05). MMC also displayed moderate-to-excellent agreement for knee and ankle joint kinematics during running (changes between 10-11 and 11-12 km/h), including ROM and peak flexion/extension (ICC ≥ 0.626). However, the hip joint was less consistent, with poor-to-moderate agreement generally being found, especially in peak hip extension (ICC = 0.198 when comparing differences between 11-12 km/h). There were no significant differences between systems during running (p < 0.05). CONCLUSION: MMC was able to measure small changes in joint angles during walking at similar magnitudes to traditional marker-based motion capture, which is promising for clinical biomechanists and gait analysis clinics. However, MMC importantly performs less well when trying to measure joint angle changes during different running speeds, with varying results between lower limb joints. Researchers and practitioners should be cautious when interpreting sagittal-plane kinematic changes during running when employing MMC as the chosen method of motion capture. REFERENCES: [1] Kanko, RM et al. (2021) J Biomech;127:110665 [2] Cappozzo, A et al. (1995) Clin Biomech;10:171-8