Matthew T. Robins

Is movement variability important for sports biomechanists

This paper overviews the importance for sports biomechanics of movement variability, which has been studied for some time by cognitive and ecological motor skills specialists but, until quite recently, had somewhat been overlooked by sports biomechanists. The paper considers biomechanics research reporting inter- and intra-individual movement variability in javelin and discus throwing, basketball shooting, and locomotion. The overview does not claim to be comprehensive and we exclude such issues as the theoretical background to movement and coordination variability and their measurement. We overview evidence, both theoretical and empirical, of inter-individual movement variability in seeking to achieve the same task goal, in contrast to the concept of “optimal” movement patterns. Furthermore, even elite athletes cannot reproduce identical movement patterns after many years of training, contradicting the ideas of motor invariance and “representative” trials. We contend that movement variability, far from being solely due to neuromuscular system or measurement “noise” – as sports biomechanists may have previously supposed – is, or could be, functional. Such functionality could allow environmental adaptations, reduce injury risk, and facilitate changes in coordination patterns. We conclude by recommending that sports biomechanists should focus more of their research on movement variability and on important related topics, such as control and coordination of movement, and implications for practice and skill learning.

Analysing team co-ordination patterns from player movement trajectories in soccer: Methodological considerations

We analysed player trajectories from five eleven-a-side soccer games in the group stage of the European Champions League to reveal the coordination dynamics between opposing teams in open play attacks, through the use of team centroids and various measures of team dispersion. We found that the team centroids moved synchronously both along and across the pitch, the former showing a stronger coupling (e.g. r = 0.994 vs 0.756 for goals) of the teams’ coordination dynamics, as expected. No crossing of the centroids of the two teams along the pitch occurred for any of the 14 goals scored from open play, and only six for all 305 open play attacks. We found little support for any general rule that team centroids converge along the pitch during critical moments in play, such as goals, shots on goal and tackles. Our results revealed few differences in coordination dynamics for attacks ending in a defensive tackle or a turn-over in possession from those ending in a goal, shot or header shot; nor did attacks ending in a goal, or a shot or header shot have more volatile, less predictable coordination dynamics than unsuccessful attacks. We recommend the use of smaller groupings of players within a team and self-organising maps to gain a greater insight into team coordination dynamics in eleven-a-side soccer in future research.

Defending Corner Kicks: Analysis from the English Premier League

The aim of this study was to explore tactical behaviour when defending corner kicks within the English Premier League. Specifically, the types of marking and defensive players positioned at the goalposts were investigated. A total of 436 corner kicks from 50 English Premier League games were analysed. The most commonly used marking system was one-to-one marking (90.1% of total corners), with zonal marking being used less often (9.9% of total corners). There was no significant association between the marking set-up and the number of attempts at goal conceded when defending corner kicks (p>0.05). However, teams who applied zonal marking conceded fewer goals and fewer attempts at goal than teams who used one-to-one marking. The most common set-up for defenders positioned at the goalposts was having a defender positioned only on the far post (47.3% of total corners). There was no significant association between the positioning of defensive players at goalposts and the number of attempts at goal conceded when defending corner kicks. A further detailed analysis of defending corner kicks is still required and suggestions have been made for future studies.

Analysis of crossing at the 2014 FIFA World Cup

ABSTRACT The aim of this study was to analyse open play crosses in the FIFA 2014 soccer World Cup. A total of 1332 open play crosses were observed from all 64 games of the FIFA 2014 soccer World Cup. The dominant themes of analysis included delivery side, delivery type, defensive pressure, time of cross and delivery outcome. Chi-squared tests of association were utilised to examine the association between each variable (e.g. delivery type) and each outcome category (e.g. goal-scoring attempts). A total of 42 goals (3.2%) were scored from the 1332 open play crosses analysed. The zone of the outcome of the cross was significantly associated (p < 0.05) with all outcome categories. Delivery type and zone of the crosser were significantly associated with defensive outcomes and attacking outcomes (p < 0.05). Defensive pressure was significantly associated with goal-scoring attempts and attacking outcomes (p < 0.05). Pitch side of the delivery and time of the cross were not significantly associated (p > 0.05) with any of the outcome categories. Coaches should reflect on the variables presented and the impact they have on crossing outcomes.