Latest research in football - week 3 - 2023

#1 Effects of sprint versus strength training on risk factors for hamstring injury in football players

Reference: J Sports Med Phys Fitness. 2023 Jan 18. doi: 10.23736/S0022-4707.22.14529-9. Online ahead of print.

Authors: Alessandro Sancese, Luke Taylor, Greg Walsh, Erin Byrd, Anne Delextrat

Summary: This study aimed to compare the effects of in-season sprint training vs. Nordic hamstring exercise (NHE) training on risk factors for hamstring strain injuries (HSI). Eighteen male university football players (20.9±2.5 years; 181±7 cm; 75.8±9.1 kg; 15.2±3.5% of body fat) were randomly allocated to a sprint group or NHE group. They completed baseline isokinetic strength and sprint mechanics assessments prior to their assigned intervention performed twice weekly for 4-weeks, before post-testing. A mixed design ANOVA with repeated measures assessed time, group and interaction effects for all risk factors. There were significant increases in hamstring eccentric peak torque at 60°·s-1 (+8% - 9.9%), the torque produced at 20° (+15%) and 10° (+21% - 31%), as well as a rightward shift in angle of peak torque towards knee extension (-27% - -36%) in both groups (P<0.05). We also observed a significant increase (+24.5%) in hamstring eccentric peak torque at 180°·s-1 in the strength group only and significant improvements (+29.4%) in the rate of torque development of the dominant leg at 60°·s-1 in the sprint group only (P<0.05). No significant effect was noted on sprint performance or sprint mechanics (P>0.05). These findings suggest that both training programs can be effective to mitigate the risk of HSI, but through different mechanisms.

 

 

#2 Using machine learning pipeline to predict entry into the attack zone in football

Reference: PLoS One. 2023 Jan 18;18(1):e0265372. doi: 10.1371/journal.pone.0265372. eCollection 2023.

Authors: Leandro Stival, Allan Pinto, Felipe Dos Santos Pinto de Andrade, Paulo Roberto Pereira Santiago, Henrik Biermann, Ricardo da Silva Torres, Ulisses Dias

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9847968/pdf/pone.0265372.pdf

Summary: Sports sciences are increasingly data-intensive nowadays since computational tools can extract information from large amounts of data and derive insights from athlete performances during the competition. This paper addresses a performance prediction problem in soccer, a popular collective sport modality played by two teams competing against each other in the same field. In a soccer game, teams score points by placing the ball into the opponent's goal and the winner is the team with the highest count of goals. Retaining possession of the ball is one key to success, but it is not enough since a team needs to score to achieve victory, which requires an offensive toward the opponent's goal. The focus of this work is to determine if analyzing the first five seconds after the control of the ball is taken by one of the teams provides enough information to determine whether the ball will reach the final quarter of the soccer field, therefore creating a goal-scoring chance. By doing so, we can further investigate which conditions increase strategic leverage. Our approach comprises modeling players' interactions as graph structures and extracting metrics from these structures. These metrics, when combined, form time series that we encode in two-dimensional representations of visual rhythms, allowing feature extraction through deep convolutional networks, coupled with a classifier to predict the outcome (whether the final quarter of the field is reached). The results indicate that offensive play near the adversary penalty area can be predicted by looking at the first five seconds. Finally, the explainability of our models reveals the main metrics along with its contributions for the final inference result, which corroborates other studies found in the literature for soccer match analysis.

 

 

#3 Analysis of scored goals in the cerebral palsy football World Cup

Reference: J Sports Sci. 2023 Jan 18;1-9. doi: 10.1080/02640414.2023.2167257. Online ahead of print.

Authors: Iván Peña-González, Juan F Maggiolo, Alejandro Javaloyes, Manuel Moya-Ramón

Summary: This study aimed to report the goal patterns in cerebral palsy (CP) football for a better understanding of the performance of this para-sport. All goals (270) of the 48 2019 IFCPF World Cup matches were analysed through match reports, and 65% of them were analysed by video footage. The results showed 5.6 goals per match. Teams that scored more and conceded fewer goals correlated to a better ranking position in the championship (r= 0.72-0.73; p< 0.01). The distribution of goals scored was not biased by halves (49.3% vs 50.7%; χ2= 0.1; p= 0.88) nor by 15-min periods (26.3% vs 23.0% vs 23.3% vs 27.4%; χ2= 0.5; p= 0.92). In 91.7% of the matches, the team which scored the first goal went on to win the match (χ2= 81.5; p< 0.01). FT3 players scored more goals by player (χ2= 22.1; p< 0.01), while there were no statistical differences in the distribution of goals conceded by goalkeepers according to their sport class (χ2= 4.7; p= 0.09). The goals were scored mainly from organized attacks (74.4%), from the penalty area (52.5%) and through individual action (51.9%). All this information could be crucial for coaches in CP football to plan their game strategies.

 

 

#4 The Five-substitution Option Enhances Teams' Running Performance at High Speed in Football

Reference: Int J Sports Med. 2023 Jan 20. doi: 10.1055/a-1982-9808. Online ahead of print.

Authors: Alejandro López-Valenciano, Víctor Moreno-Perez, Roberto López-Del Campo, Ricardo Resta, Juan Del Coso

Summary: The aim of this investigation was to describe how the introduction of the five-substitution option affected football teams' running performance. A comparative analysis was performed in 17 professional football teams for the 2019-2020 (up to three substitutions) vs 2020-2021 (five substitutions option) seasons in LaLiga. The five-substitution option increased the number of substitutions (from 2.9±0.1 to 4.2±1.0 substitutions/match, respectively; p<0.01, Effect Size (ES)=2.11) but it did not change the time selected for the first substitution (from 57.5±13.0 to 56.2±13.7 min; p=0.06, ES=0.1). Total running distance was similar between seasons but running distance at 21.0-23.9 km/h (from 3.0±0.4 to 3.2±0.4 km; p=0.01, ES=0.6) and at≥24.0 km/h (from 3.0±0.6 to 3.2±0.5 km; p=0.01, ES=0.3) were higher with the five-substitution option. These increases were associated with a higher distance covered by starting players (p<0.05) rather than an effect of substitute players.: With the five-substitution option, team coaches increased the number of substitutions per match which enhanced the possibilities of the team's staff to manage players' physical load. The five-substitution option allowed also increased running performance at≥21.0 km/h during the matches.

 

 

#5 Relationships Between Sprint, Acceleration, and Deceleration Metrics with Training Load in Division I Collegiate Women's Soccer Players

Reference: J Hum Kinet. 2023 Jan 4;85:53-62. doi: 10.2478/hukin-2022-0109. eCollection 2022 Dec.

Authors: Dieanna C Prudholme, Jared W Coburn, Scott K Lynn, Robert G Lockie

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9808812/pdf/hukin-85-053.pdf

Summary: Player load is a variable derived from GPS technology that quantifies external load demands. Sprints and change-of-direction movements are high-intensity activities that place stress on the body. Research is needed to determine which sprint metrics may relate to and predict player load during practice sessions in collegiate women's soccer players, as coaches could manipulate the most impactful variables. This study analyzed which sprint metrics related to GPS player load in women's soccer players from one Division I team. Data from 19 practice sessions for 18 field players were analyzed. Players wore GPS sensors during all training sessions, and the variables assessed were player load, sprint count, sprint volume, sprint distance, average top speed, maximum top speed, and the number of accelerations and decelerations in different speed zones (±1, ±2, ±3, ±4, ±5 m/s2). Pearson's correlations (p < 0.05) analyzed relationships between the sprint variables and player load. Stepwise regression analyses (p < 0.05) determined if any metrics predicted player load. The results indicated significant relationships between player load and sprint count, maximum top speed, sprint distance, sprint volume, number of decelerations at -1, -2, and -3 m/s2, and accelerations at 1, 2, and 5 m/s2(r = 0.512-0.861, p ≤ 0.025). Sprint distance and decelerations at 1 m/s2predicted player load (p = 0.001, r2= 0.867). Maximal sprinting and decelerations and accelerations at different speeds were significant contributors to player load in collegiate women's soccer players. Sprint distance, decelerations, and accelerations could be targeted in training drills via dimension and movement manipulation to adjust training intensity for collegiate women's soccer players.

 

 

#6 Validation of a motion model for soccer players' sprint by means of tracking data

Reference: Sci Rep. 2023 Jan 17;13(1):865. doi: 10.1038/s41598-023-27999-1.

Authors: Takuma Narizuka, Kenta Takizawa, Yoshihiro Yamazaki

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9845223/pdf/41598_2023_Article_27999.pdf

Summary: In soccer game analysis, the widespread availability of play-by-play and tracking data has made it possible to test mathematical models that have been discussed mainly theoretically. One of the essential models in soccer game analysis is a motion model that predicts the arrival point of a player in t s. Although many space evaluation and pass prediction methods rely on motion models, the validity of each has not been fully clarified. This study focuses on the motion model proposed by Fujimura and Sugihara (Fujimura-Sugihara model) under sprint conditions based on the equation of motion. A previous study indicated that the Fujimura-Sugihara model is ineffective for soccer games because it generates a circular arrival region. This study aims to examine the validity of the Fujimura-Sugihara model using soccer tracking data. Specifically, we quantitatively compare the arrival regions of players between the model and real data. We show that the boundary of the player's arrival region is circular rather than elliptical, which is consistent with the model. We also show that the initial speed dependence of the arrival region satisfies the solution of the model. Furthermore, we propose a method for estimating valid kinetic parameters in the model directly from tracking data and discuss the limitations of the model for soccer games based on the estimated parameters.

 

 

#7 Effect of High-Intensity vs. Moderate-Intensity Resistance Training on Strength, Power, and Muscle Soreness in Male Academy Soccer Players

Reference: J Strength Cond Res. 2023 Jan 18. doi: 10.1519/JSC.0000000000004387. Online ahead of print.

Authors: Stephen J McQuilliam, David R Clark, Robert M Erskine, Thomas E Brownlee

Summary: The aim of this study were to investigate the impact of high-intensity, low-volume (HRT) vs. moderate-intensity, and high-volume resistance training (MRT) vs. soccer training only (control group [CON]) on changes in strength, power, and speed and to compare delayed onset muscle soreness (DOMS) between groups in male academy soccer players (ASP). Twenty-two ASP (age: 18 ± 1 years) were assigned to HRT (n = 8), MRT (n = 7), or CON (n = 7). High-intensity resistance training completed 2 sets of 4 repetitions parallel back squat (PBS) repetitions at 90% 1 repetition maximum (1RM), while MRT performed 3 sets of 8 repetitions PBS repetitions at 80% 1RM, both once a week for 6 weeks in-season, alongside regular soccer training. All groups completed the following pretraining and posttraining assessments: 3RM PBS, bilateral vertical and horizontal countermovement jumps (CMJ), squat jump (SJ), and 30-m sprint. Delayed onset muscle soreness was assessed using a visual analog scale throughout training. High-intensity resistance training and MRT experienced similar increases compared with CON in absolute PBS 3RM (p < 0.001), SJ height (p = 0.001), and CMJ height (p = 0.008) after training. There was a greater increase in PBS 3RM relative to body mass after HRT than MRT and CON (p = 0.001) and horizontal CMJ distance improved in HRT but not in MRT or CON (p = 0.011). There was no change in 10-m, 20-m, or 30-m sprint performance in any group. High-intensity resistance training volume was 58 ± 15% lower than that of MRT (p < 0.001), and DOMS measured throughout training did not differ between groups (p = 0.487). These findings suggest that 1 HRT session a week may be an efficient method for improving strength and power in ASP in-season with minimal DOMS.

 

 

#8 Effect of a Four-Week Soccer Training Program Using Stressful Constraints on Team Resilience and Precompetitive Anxiety

Reference: Int J Environ Res Public Health. 2023 Jan 16;20(2):1620.  doi: 10.3390/ijerph20021620.

Authors: Juan Martin Tassi, Jesús Díaz-García, Miguel Ángel López-Gajardo, Ana Rubio-Morales, Tomás García-Calvo

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9863658/pdf/ijerph-20-01620.pdf

Summary: The present study examined the effects of stressful constraints during soccer trainings on psychological skill development and internal load when compared with control (nonstressful) trainings. A total of 51 elite male youth soccer players (27 in the experimental group, M = 16.54 years; 24 in the control group, M = 15.44 years) participated in the study. In a 12-week longitudinal survey, team resilience, using the Spanish version of the Characteristics of Resilience in Sports Teams Inventory, and anxiety, using the Sport Anxiety Scale, were measured at baseline (after 4 weeks of regular trainings), postprotocol (after 4 weeks of control or experimental trainings), and follow-up (after 4 weeks of regular trainings). Results show that, when compared with the control group, a program with stressful constraints helped young soccer players to develop better psychological skills: specifically, increased ability to cope with impairments in resilience (both resilience characteristics and team vulnerability under pressure; p &lt; 0.001). Increases in anxiety (p = 0.06) and decreases in preoccupation (p &lt; 0.001) and lack of concentration (p &lt; 0.001) were also observed. The adaptation of human behavior to specific trainings may explain these results. In conclusion, the regular exposure of young soccer players to stressful situations during trainings shows benefits for their psychological skill development in soccer. Then, benefits on internal load were also observed.

 

 

#9 Mental health problems, health risk behaviors, and prevention: A qualitative interview study on perceptions and attitudes among elite male soccer players

Reference: Front Public Health. 2023 Jan 5;10:1044601. doi: 10.3389/fpubh.2022.1044601. eCollection 2022.

Authors: Pia Kvillemo, Anders Nilsson, Anna K Strandberg, Karl Björk, Tobias H Elgán, Johanna Gripenberg

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9850108/pdf/fpubh-10-1044601.pdf

Summary: The purpose of this study was to investigate the perception of mental health problems and health risk behaviors among Swedish male elite soccer players and their attitudes toward possible prevention strategies. Twenty elite soccer players, aged 15-30 years, were recruited through purposive sampling and interviewed via a digital video calling platform. A semi-structured interview guide, encompassing questions about mental health problems, health risk behaviors among soccer teams, peer-relations, relations to coaches, and attitudes toward health risk behaviors, along with proposals for effective interventions, was employed. The interviews were transcribed verbatim and analyzed with qualitative content analysis. The informants reported positive feelings in relation to playing soccer, good health, and few health risk behaviors. Risk factors included a large income, excessive free time, and the need for excitement. Stress and mental health problems were linked to performance pressure, social media, and injuries. Hesitation to talk openly about personal problems due to concerns about negative consequences and the "macho culture" was highlighted as barriers to admit and seek help for personal problems. Some statements indicated openness and the club's efforts to destigmatize personal problems. Positive attitudes toward prevention and suggestions for various measures were prominent. Future research and implementation of interventions should focus on the prevention of health risk behaviors and alleviation of stress and performance pressure, as well as continue the efforts to destigmatize mental health problems and raise awareness among coaches of the importance of their communication and behavior for players' mental health and performance. This could be achieved by developing strategic and systematic policy work, information, and dialogue among players and coaches, in addition to individual digital or face-to-face support, provided by professionals outside the soccer context.

 

 

#10 Effect of core training on skill-related physical fitness performance among soccer players: A systematic review

Reference: Front Public Health. 2023 Jan 5;10:1046456. doi: 10.3389/fpubh.2022.1046456. eCollection 2022.

Authors: Shengyao Luo, Kim Geok Soh, Lingling Zhang, Xiuwen Zhai, Jaka Sunardi, Yongqi Gao, He Sun

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9850239/pdf/fpubh-10-1046456.pdf

Summary: This study aims to present an in-depth review of the available literature on the effect of core training on skill-related physical fitness performance among soccer players, as well as to offer suggestions for researchers and coaches. The data in this study were presented based on the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guideline. Using scientific databases and web search engines including Scopus, Ebscohost, Web of Science, PubMed, and Google Scholar, researchers collected studies from the published literature. Only 26 of the 84 articles satisfied all the inclusion criteria and were thus included in the systematic review. The quality of each study was determined using the PEDro scale. The scores for 26 studies range between three and six. Core training can improve soccer players' skill-related physical fitness, including their power, speed, balance, and agility. The core is the anatomic and functional center of the body as well as its "engine." All movements emanate from the center of the body and are transmitted to the extremities. The core muscles differ from the limb muscles because they frequently cocontract, thus making the torso hard to the point whereby all the muscles work together to become synergists. Theoretically, a strong core permits the passage of force from the lower body to the upper body with minimal energy loss in the torso. Based on the 26 studies, this review suggests that core training should be incorporated into the daily training sessions of soccer players, with a minimum frequency and length of 15 min per training session, twice per week, for 4 weeks.

 

 

#11 Seasonal analysis of match load in professional soccer players: An observational cohort study of a Swiss U18, U21 and first team

Reference: Front Physiol. 2023 Jan 4;13:1023378. doi: 10.3389/fphys.2022.1023378. eCollection 2022.

Authors: Linda Ammann, Stefan Altmann, Ludwig Ruf, Billy Sperlich

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9846105/pdf/fphys-13-1023378.pdf

Summary: The aim of this study was to quantify and compare various external match load measures in three age groups and leagues in male soccer (U18 in highest league of their age group vs U21 in fourth highest league vs first team in highest league). In this retrospective observational cohort study accelerations, decelerations, absolute and relative high-speed running as well as sprint distance, dynamic stress load, explosive distance, high intensity bursts total distance, high metabolic load (HML) distance, speed intensity, total distance, total time, and total loading were assessed in 416 individual player matches of 59 players. All these external load measures showed large inter-individual variability. At a group level, one-way ANOVAs or Kruskal-Wallis tests revealed statistically significant differences between the three teams for all measures analyzed (all p < 0.05), except accelerations. The first team displayed statistically significant higher dynamic stress load, explosive distance, HML distance, speed intensity, total distance and total loading compared to the two youth teams (all p < 0.05). The U18 featured statistically significant higher number of decelerations, absolute and relative high-speed running distance, high metabolic load distance, speed intensity, relative sprint distance, total distance, and total time than the U21, while for U21 higher dynamic stress load was observed than for U18 (all p < 0.05). Based on our data we conclude a routinely monitoring of match loads of different age groups and competitive settings to be required to 1) provide an indication of what players need to be prepared for, 2) track the athletic and match evolution, and 3) individually tailor training programs allowing players to fulfill the short- and long-term sport-specific requirements.

 

 

#12 The Relationship Between Subjective Wellness and External Training Load in Elite English Premier League Goalkeepers and a Comparison With Outfield Soccer Players

Reference: Int J Sports Physiol Perform. 2023 Jan 23;1-6. doi: 10.1123/ijspp.2022-0205. Online ahead of print.

Authors: Sophie Grimson, Gary Brickley, Nicholas J Smeeton, Adam Brett, Will Abbott

Summary: The aim was to investigate the relationship between training load and subjective wellness in English Premier League goalkeepers (GKs) and examine potential positional differences in subjective wellness. A total of 34 players (GK = 7, outfield = 27) completed a daily subjective wellness questionnaire assessing sleep quality, sleep hours, fatigue, mood, soreness, and total wellness over two and a half seasons. Ten-Hertz GPS devices were worn during training to calculate previous-day and 7-day total distance, player load, total dives, total dive load, average time to feet, and high, medium, and low jumps. All previous 7-day training loads were associated with all wellness markers (r = .073 to .278, P < .05). However, associations between previous 7-day dive load and mood, average time to feet, and both sleep quality and quantity, and between low jumps and sleep quality, were not significant. For previous-day metrics, total distance was associated with all wellness markers (r = .097 to .165, P < .05). In addition, player load and high jump were associated with fatigue, soreness, and wellness (r = .096 to .189, P < .05). Total dives and soreness were also related (r = .098, P < .05), and relationships were evident between average time to feet, medium jumps, and all wellness markers excluding sleep quality (r = .114 to .185, P < .05). No positional differences in subjective wellness occurred (P > .05). Some GK GPS variables are associated with subjective wellness, which could inform training-load prescription to maximize recovery and performance. In addition, GKs are no more vulnerable to poorer subjective wellness when compared with outfield players.

 

 

#13 Can prognostic factors for indirect muscle injuries in elite football (soccer) players be identified using data from preseason screening? An exploratory analysis using routinely collected periodic health examination records

Reference: BMJ Open. 2023 Jan 24;13(1):e052772. doi: 10.1136/bmjopen-2021-052772.

Authors: Tom Hughes, Richard Riley, Michael J Callaghan, Jamie C Sergeant

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9884927/pdf/bmjopen-2021-052772.pdf

Summary: In elite football, periodic health examination (PHE) may be useful for injury risk prediction. The objective was to explore whether PHE-derived variables are prognostic factors for indirect muscle injuries (IMIs) in elite players. 134 outfield elite male players from an English Premier League football club, over 5 seasons (1 July 2013-19 May 2018) were observed. The outcome was any time-loss, lower extremity index IMI (I-IMI). Prognostic associations were estimated using odds ratios (ORs) and corresponding statistical significance for 36 variables, derived from univariable and multivariable logistic regression models. Missing data were handled using multiple imputation. Non-linear associations were explored using fractional polynomials. During 317 participant-seasons, 138 I-IMIs were recorded. Univariable associations were determined for previous calf IMI frequency (OR 1.80, 95% CI 1.09 to 2.97), hamstring IMI frequency (OR 1.56, 95% CI 1.17 to 2.09), if the most recent hamstring IMI occurred >12 months but <3 years prior to PHE (OR 2.95, 95% CI 1.51 to 5.73) and age (OR 1.12 per 1-year increase, 95% CI 1.06 to 1.18). Multivariable analyses showed that if a player's most recent previous hamstring IMI was >12 months but <3 years prior to PHE (OR 2.24, 95% CI 1.11 to 4.53), this was the only variable with added prognostic value over and above age, which was a confirmed prognostic factor (OR 1.12 per 1-year increase, 95% CI 1.05 to 1.18). Allowing non-linear associations conferred no advantage over linear associations. PHE has limited use for injury risk prediction. Most variables did not add prognostic value over and above age, other than if a player experienced a hamstring IMI >12 months but <3 years prior to PHE. However, the precision of this prognostic association should be confirmed in future.

 

 

#14 Influence of the time-task constraint on ocular metrics of semi-elite soccer players

Reference: Sci Med Footb. 2023 Jan 27;1-8. doi: 10.1080/24733938.2023.2172203. Online ahead of print.

Authors: Vicente Luis-Del Campo, Jesús Morenas Martín, Juan Luis León Llamas, Juan Francisco Ortega Morán, Jesús Díaz-García, Tomás García-Calvo

Summary: This study novelty aimed to investigate the influence of manipulating the available time to perform the training tasks on soccer players´ ocular metrics, following training. Specifically, pupillary response (pupil diameter) and saccadic features (latency, accuracy, velocity, and number) were measured with a portable eye tracker following training to reflect the mental load accumulated by players during the training sessions. Nine semi-elite soccer players performed two training sessions, based on large-sided games, on an artificial grass field. These two sessions were composed of the same tasks but varying the required time to complete the task goals (Session 1: No time limitations to perform the tasks; Session 2: Limited time to perform the tasks). The participants performed, before (pre-test) and after (post-test) each training session, a prosaccade task in a room near the playing field. Findings revealed a differentiated effect of the available time to complete the training tasks on ocular metrics because significant differences were found in all variables after training (p < .001 for pupil diameter; p < .01 for saccade accuracy and number of saccades; p < .05 for saccade velocity and latency). Ocular metrics could be a promising tool to evaluate mental load following practice because they were sensitive to the time-task constraint, providing researchers a valuable information for a better planning of the mental workload when designed training tasks.

 

 

#15 Focus of Attention During ACL Injury Prevention Exercises Affects Improvements in Jump-Landing Kinematics in Soccer Players: A Randomized Controlled Trial

Reference: J Strength Cond Res. 2023 Feb 1;37(2):337-342. doi: 10.1519/JSC.0000000000004201. Epub 2021 Dec 23.

Authors: Nazanin Dalvandpour, Mostafa Zareei, Hamed Abbasi, Behrouz Abdoli, Mohammad A Mohammadian, Nikki Rommers, Roland Rössler

Summary: Anterior cruciate ligament tears are severe and complex knee injuries that commonly occur in soccer. Prevent injuries enhance performance (PEP) is an exercise-based prevention program to effectively reduce anterior cruciate ligament injuries. It is, however, unclear how the delivery of the program contributes to its effectiveness. Therefore, we aimed to investigate the effect of the focus of attention that was emphasized during the delivery of the PEP program on jump-landing kinematics in male, elite-level, U21 soccer players. Forty-two players participated in this randomized controlled trial and were allocated to (a) the internal focus of attention (IF) group, receiving instructions focusing on the execution of the exercise (b), the external focus of attention (EF) group, receiving instructions focusing on the outcome of the exercise, or (c) the control group. Before and after the 8-week intervention, players performed a jump-landing task during which we measured hip and knee angles at the initial contact, peak knee flexion, and peak vertical ground reaction force using a 3-dimensional motion analyzer. A repeated-measures analysis of variance was used to compare groups over time. Significant time-by-group interaction effects with large effect sizes were found for hip flexion at all moments (p < 0.032; η2 > 0.15) and for the knee flexion angle at initial contact and maximum knee flexion (p < 0.001; η2 > 0.35), all in favor of the EF group. This shows that EF during PEP improves hip and knee joint kinematics in the sagittal plane more than IF. Therefore, EF during PEP instructions is preferred to increase the effectiveness of this injury prevention program.

 

 

#16 Soccer academy practitioners' perceptions and application of bio-banding

Reference: PLoS One. 2023 Jan 26;18(1):e0274079. doi: 10.1371/journal.pone.0274079. eCollection 2023.

Authors: Chris Towlson, Demi Jo Watson, Sean Cumming, Jamie Salter, John Toner

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9879534/pdf/pone.0274079.pdf

Summary: The primary aims of this study were to examine the application of maturity status bio-banding within professional soccer academy programmes and understand the methods employed, the intended objectives, and the potential barriers to bio-banding. Using a mixed method design, twenty-five professional soccer academy practitioners completed an online survey designed to examine their perceptions of the influence of maturation on practice, their perceptions and application of bio-banding, and the perceived barriers to the implementation of this method. Frequency and percentages of responses for individual items were calculated. In the next phase of the study, seven participants who had experience with, or knowledge of, the bio-banding process within an academy youth soccer setting were recruited to complete a semi-structured interview. Interview data was transcribed and analysed using a combination of deductive and inductive approaches to identify key themes. The main findings across the two phases of the study were that [1] there is consensus among the practitioners that the individual effect of maturation impacts their ability to accurately assess the soccer competencies, [2] the majority (80%) of the sample had implemented bio-banding, with practitioners showing a clear preference for using the Khamis and Roche method to bio-band players, with the greatest perceived benefit being during maturity-matched formats, specifically for late or post-PHV players, [3] Practitioners perceived that bio-banding enhances their ability to assess academy soccer players, and [4] practitioners who have used bio-banding believe that the method is an effective way of enhancing the perception of challenge thereby providing a number of psycho-social benefits. Findings suggest that a collaborative and multi-disciplinary approach is required to enhance the likelihood of bio-banding being successfully implemented within the typical training schedules across the adolescent phase of the player development pathway.

 

 

#17 A fully automatic method for segmentation of soccer playing fields

Reference: Sci Rep. 2023 Jan 26;13(1):1464. doi: 10.1038/s41598-023-28658-1.

Authors: Carlos Cuevas, Daniel Berjón, Narciso García

Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9879963/pdf/41598_2023_Article_28658.pdf

Summary: This paper proposes a strategy to segment the playing field in soccer images, suitable for integration in many soccer image analysis applications. The combination of a green chromaticity-based analysis and an analysis of the chromatic distortion using full-color information, both at the pixel-level, allows segmenting the green areas of the images. Then, a fully automatic post-processing block at the region-level discards the green areas that do not belong to the playing field. The strategy has been evaluated with hundreds of annotated images from matches in several stadiums with different grass shades and light conditions. The results obtained have been of great quality in all the images, even in those with the most complex lighting conditions (e.g., high contrast between sunlit and shadowed areas). In addition, these results have improved those obtained with leading state-of-the-art playing field segmentation strategies.

 

 

#18 Predictive modeling of lower extremity injury risk in male elite youth soccer players using LASSO Regression

Reference: Scand J Med Sci Sports. 2023 Jan 26. doi: 10.1111/sms.14322. Online ahead of print.

Authors: Mathias Kolodziej, Andreas Groll, Kevin Nolte, Steffen Willwacher, Tobias Alt, Marcus Schmidt, Thomas Jaitner

Download link: https://onlinelibrary.wiley.com/doi/epdf/10.1111/sms.14322

Summary: The purpose was to (1) identify neuromuscular and biomechanical injury risk factors in elite youth soccer players and (2) assess the predictive ability of a machine learning approach. Fifty-six elite male youth soccer players (age: 17.2 ± 1.1 years; height: 179 ± 8 cm; mass: 70.4 ± 9.2 kg) performed a 3D motion analysis, postural control testing, and strength testing. Non-contact lower extremities injuries were documented throughout 10 months. A least absolute shrinkage and selection operator (LASSO) regression model was used to identify the most important injury predictors. Predictive performance of the LASSO model was determined in a leave-one-out (LOO) prediction competition. Twenty-three non-contact injuries were registered. The LASSO model identified concentric knee extensor peak torque, hip transversal plane moment in the single-leg drop landing task and COP sway in the single-leg stance test as the three most important predictors for injury in that order. The LASSO model was able to predict injury outcomes with a likelihood of 58% and an AUC of 0.63 (sensitivity = 35%; specificity = 79%). The three most important variables for predicting the injury outcome suggest the importance of neuromuscular and biomechanical performance measures in elite youth soccer. These preliminary results may have practical implications for future directions in injury risk screening and planning, as well as for the development of customized training programs to counteract intrinsic injury risk factors. However, the poor predictive performance of the final model confirms the challenge of predicting sports injuries, and the model must therefore be evaluated in larger samples.