A goalkeeper's performance in stopping free kicks reduces when the defensive wall blocks their initial view of the ball

Goalkeepers' plasticity during learning of a whole-body visuomotor rotation in a stable or variable environment

Postural adjustments performed in anticipation of uncertain visual events is a common sensorimotor control problem in open sport skills. In this study, we examined how expert soccer goalkeepers and non-athletes learn a whole body visuomotor rotation during postural tracking of constant and variable visual target motions. Twenty-one (21) soccer goalkeepers (18 ± 15 years, 75 ± 12 kg) and 25 age-matched non-athletes (18 ± 12 years, 75 ± 15 kg) practiced lateral weight shifting on a dual force platform while tracking the motion of a constant (11 goalkeepers and 12 non-athletes) or a variable (10 goalkeepers and 13 non-athletes) visual target with provision of online visual feedback (VF). After 40s of tracking (baseline), the visual presentation of the VF signal reversed direction relative to the participant's motion (180° visuo-motor rotation) for 60s (adaptation) and then returned to its veridical direction for another 20s (washout). During adaptation, goalkeepers reduced the spatiotemporal error to baseline levels at an earlier time block (3rd block) compared to non-athletes (6th block), but this difference was significant only for groups tracking of the constant and not the variable target motion. Only the groups tracking the constant target increased the spatiotemporal error during the 1st washout block demonstrating a significant aftereffect. It is concluded that goalkeepers adapt faster to the feedback rotation due to their prior field knowledge of relevant visuomotor transformations in anticipation of deceptive visual cues. This expertise advantage however is present only in a stable visual environment possibly because learning is compromised when tracking uncertain motion cues requiring closed loop control.HighlightsWe examined how expert goalkeepers and non-athletes adopt to a novel whole body visuomotor rotation when tracking a constantly or variably moving targetGoalkeepers adopted faster to the visuomotor rotation than non-athletesExpertise related differences were evident only for groups tracking the constant target motionGroups tracking the variable target motion did not learn the visuomotor rotation.

Analysis of defensive playing styles in the professional Chinese Football Super League

Describing and measuring different team styles of play during matches is a key step towards a more predictive and prescriptive performance analysis. The current study aimed to identify and measure different defensive playing styles in professional football via Principal Component Analysis (PCA). The sample comprised all 240 matches played in the Chinese Football Super League (CSL) during the 2018 season. Seventeen key performance indicators (KPIs), 15 defense-related and 2 physical-related were identified from sixty-two defensive performance indicators. Those metrices were significantly different between when teams lost and did not lose (p<0.05, ES=0.03-0.22). The value of Kaiser-Meyer-Olkin for KPIs was 0.81. Then PCA model based on 17 KPIs outputted eight principal factors representing 7 different styles of play (factor 6 and 8 represented one style) and explaining 83.01% of the total variance. Of all styles, defense close to own goal, which included clearance, ball gain in the zone 1, deep completion and unsuccessful cross of the opponent, was the most dominant style (31.92% of the total variance). The champion of the league (Shanghai SIPG FC) showed better scores in all styles of play, while the last ranked team (Guizhou Hengfeng) got the highest score in defense close to the own goal. The study indicated that a team's defensive style could be defined by specific KPIs, and teams are suggested to attune their defending styles consciously rather than maintaining a consistent strategy so as to achieve better performance. Moreover, the categorization of defensive styles could be used during scouting and match preparation.