Latest research in football - week 6 - 2017

#1 Mechanisms and situations of anterior cruciate ligament injuries in professional male soccer players: a YouTube-based video analysis
Reference: Eur J Orthop Surg Traumatol. 2017 Jan 25. doi: 10.1007/s00590-017-1905-0. [Epub ahead of print]
Authors: Grassi A, Smiley SP, Roberti di Sarsina T, Signorelli C, Marcheggiani Muccioli GM, Bondi A, Romagnoli M, Agostini A, Zaffagnini S
Summary: Soccer is considered the most popular sport in the world concerning both audience and athlete participation, and the incidence of ACL injury in this sport is high. The understanding of injury situations and mechanisms could be useful as substratum for preventive actions. The purpose was to conduct a video analysis evaluating the situations and mechanisms of ACL injury in a homogeneous population of professional male soccer players, through a search entirely performed on the YouTube.com Web site focusing on the most recent years. A video analysis was conducted obtaining videos of ACL injury in professional male soccer players from the Web site YouTube. Details regarding injured players, events and situations were obtained. The mechanism of injury was defined on the basis of the action, duel type, contact or non-contact injury, and on the hip, knee and foot position. Thirty-four videos were analyzed, mostly from the 2014-2015 season. Injuries occurred mostly in the first 9 min of the match (26%), in the penalty area (32%) or near the side-lines (44%), and in non-rainy conditions (97%). Non-contact injuries occurred in 44% of cases, while indirect injuries occurred in 65%, mostly during pressing, dribbling or tackling. The most recurrent mechanism was with an abducted and flexed hip, with knee at first degrees of flexion and under valgus stress. Through a YouTube-based video analysis, it was possible to delineate recurrent temporal, spatial and mechanical characteristics of ACL injury in male professional soccer players.


#2 Timing Effect on Training Session Rating of Perceived Exertion in Top-Class Soccer Referees
Reference: Int J Sports Physiol Perform. 2017 Jan 25:1-18. doi: 10.1123/ijspp.2016-0626. [Epub ahead of print]
Authors: Castagna C, Bizzini M, Povoas SC, D'Ottavio S
Summary: The purpose was to examine the effect of recall timing on training session rating of perceived exertion (S-RPE) in a population of method procedures well-familiarized athletes, during a 5-days training micro-cycle. Fifty-one top class Field Referees (FR, age 38.4±3.3 years; height 181±5.6 cm; body mass 76.8±6.8 kg; body max index, 23.4±1.7 kg·m2; body fat 20.4±3.6%; international refereeing experience 5±3.5 years) from 43 National Football Associations worldwide, preselected by FIFA Refereeing Department for officiating during the FIFA WC 2014 Brazil volunteered for this study. The FR were randomly allocated into three assessment groups (n=17 each), defined according to the timing of the S-RPE, i.e., immediately at the end, 30 min or 7 hours after the training sessions' ending (G0min, G30min and G7h, respectively). The CR10 Börg scale was used to rate the training sessions (n=5). All FR rated again each training session of the 5-days training micro-cycle in the consecutive morning (~20h after) for confirmation (absolute and relative reliability). No significant timing effect was found between and within groups. Relative reliability ranged from large to very large with trivial within and between groups differences. This study showed no effect of recall timing on post-exercise RPE when well familiarized athletes are submitted to training during a weekly micro-cycle. Post-training RPE was reported to be a reliable subjective measure, however, specific timing is advisable to reduce magnitude difference in RPE values.


#3 Analysis of physical fitness and technical skills of youth soccer players according to playing position
Reference: J Exerc Rehabil. 2016 Dec 31;12(6):548-552. doi: 10.12965/jer.1632730.365. eCollection 2016.
Authors: Joo CH, Seo DI
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5227316/pdf/jer-12-6-548.pdf
Summary: The purpose of this study was to compare performance factors of youth soccer players according to position. A total of 101 high school soccer players were selected and were classified into goalkeeper (n=7), defense (n=37), midfield (n=39), and forward (n=18) positions. All subjects were subjected to the Wingate test for anaerobic capacity, shuttle run test for aerobic capacity, and pass, kick, dribble, and shooting tests for soccer skills. There was no significant difference in aerobic capacity according to position. However, anaerobic capacity was significantly higher in defenders than midfielders (P<0.05), and soccer skills were significant lower in goalies than in other positions (P<0.01). The results show significant differences in anaerobic capacity and soccer skills according to position in youth soccer players. Therefore, we suggest that middle and high school soccer players should improve aerobic, an-aerobic capacity, and soccer skills irrespective position to achieve high-level soccer performance.


#4 Director's Cut: Analysis and Annotation of Soccer Matches
Reference: IEEE Comput Graph Appl. 2016 Sep-Oct;36(5):50-60. doi: 10.1109/MCG.2016.102.
Authors: Stein M, Janetzko H, Breitkreutz T, Seebacher D, Schreck T, Grossniklaus M, Couzin ID, Keim DA.
Summary: For development and alignment of tactics and strategies, professional soccer analysts spend up to three working days manually analyzing and annotating professional soccer matches. In an effort to improve soccer player and match analysis, a visual-interactive and data-analysis support system focuses on key situations by using rule-based filtering and automatically annotating key types of soccer match elements. The authors evaluate the proposed approach by analyzing real-world soccer matches and several expert studies. Quantitative measures show the proposed methods can significantly outperform naive solutions.


#5 Combination of Recreational Soccer and Caloric Restricted Diet Reduces Markers of Protein Catabolism and Cardiovascular Risk in Patients with Type 2 Diabetes
Reference: J Nutr Health Aging. 2017;21(2):180-186. doi: 10.1007/s12603-015-0708-4.
Authors: Vieira de Sousa M, Fukui R, Krustrup P, Dagogo-Jack S, Rossi da Silva ME
Summary: Moderate calorie-restricted diets and exercise training prevent loss of lean mass and cardiovascular risk. Because adherence to routine exercise recommendation is generally poor, we utilized recreational soccer training as a novel therapeutic exercise intervention in type 2 diabetes (T2D) patients. The objective of the study was to compare the effects of acute and chronic soccer training plus calorie-restricted diet on protein catabolism and cardiovascular risk markers in T2D. Fifty-one T2D patients (61.1±6.4 years, 29 females: 22 males) were randomly allocated to the soccer+diet-group (SDG) or to the diet-group (DG). The 40-min soccer sessions were held 3 times per week for 12 weeks. Nineteen participants attended 100% of scheduled soccer sessions, and none suffered any injuries. The SDG group showed higher levels of growth hormone (GH), free fatty acids and ammonia compared with DG. After 12 weeks, insulin-like growth factor binding protein (IGFPB)-3 and glucose levels were lower in SDG, whereas insulin-like growth factor (IGF)-1/ IGFBP-3 ratio increased in both groups. After the last training session, an increase in IGF-1/IGFBP-3 and attenuation in ammonia levels were suggestive of lower muscle protein catabolism. Recreational soccer training was popular and safe, and was associated with decreased plasma glucose and IGFBP-3 levels, decreased ammoniagenesis, and increased lipolytic activity and IGF-1/IGFBP-3 ratio, all indicative of attenuated catabolism.


#6 The Athletic Shoe in Football
Reference: Sports Health. 2017 Feb 1:1941738117690717. doi: 10.1177/1941738117690717. [Epub ahead of print]
Authors: Jastifer J, Kent R, Crandall J, Sherwood C, Lessley D, McCullough KA, Coughlin MJ, Anderson RB
Summary: Foot and ankle injuries are common in sports, particularly in cleated athletes. Traditionally, the athletic shoe has not been regarded as a piece of protective equipment but rather as a part of the uniform, with a primary focus on performance and subjective feedback measures of comfort. Changes in turf and shoe design have poorly understood implications on the health and safety of players. A literature search of the MEDLINE and PubMed databases was conducted. Keywords included athletic shoewear, cleated shoe, football shoes, and shoewear, and search parameters were between the years 2000 and 2016. The athletic shoe is an important piece of protective sports equipment. There are several important structural considerations of shoe design, including biomechanical compliance, cleat and turf interaction, and shoe sizing/fit, that affect the way an athlete engages with the playing surface and carry important potential implications regarding player safety if not understood and addressed. Athletic footwear should be considered an integral piece of protective equipment rather than simply an extension of the uniform apparel. More research is needed to define optimal shoe sizing, the effect that design has on mechanical load, and how cleat properties, including pattern and structure, interact with the variety of playing surfaces.


#7 No association between static and dynamic postural control and ACL injury risk among female elite handball and football players: a prospective study of 838 players
Reference: Br J Sports Med. 2017 Feb;51(4):253-259. doi: 10.1136/bjsports-2016-097068
Authors: Steffen K, Nilstad A, Krosshaug T, Pasanen K, Killingmo A, Bahr R
Summary: Research on balance measures as potential risk factors for ACL injury is limited. The objective was to assess whether postural control was associated with an increased risk for ACL injuries in female elite handball and football players. Premier league players were tested in the preseason and followed prospectively for ACL injury risk from 2007 through 2015. At baseline, we recorded player demographics, playing experience, ACL and ankle injury history. We measured centre of pressure velocity in single-leg stabilisation tests and reach distances in the Star Excursion Balance Test. To examine the stability of postural control measures over time, we examined their short-term and long-term reproducibility. We generated logistic regression models, 1 for each of the proposed risk factors. A total of 55 (6.6%) out of 838 players (age 21±4 years; height 170±6 cm; body mass 66±8 kg) sustained a non-contact ACL injury after baseline testing (1.8±1.8 years). When comparing normalised balance measures between injured and uninjured players in univariate analyses, none of the variables were statistically associated with ACL injury risk. Short-term and long-term reproducibility of the selected variables was poor. Players with a previous ACL injury had a 3-fold higher risk of sustaining a new ACL injury compared with previously uninjured players (OR 2.9, CI 1.4 to 5.7). None of postural control measures examined were associated with increased ACL injury risk among female elite handball and football players. Hence, as measured in the current investigation, the variables included cannot be used to predict ACL injury risk.


#8 Exploring Team Passing Networks and Player Movement Dynamics in Youth Association Football
Reference: PLoS One. 2017 Jan 31;12(1):e0171156. doi: 10.1371/journal.pone.0171156. eCollection 2017
Authors: Goncalves B, Coutinho D, Santos S, Lago-Penas C, Jimenez S, Sampaio J
Download link: http://journals.plos.org/plosone/article/file?id=10.1371/journal.pone.0171156&type=printable
Summary: Understanding how youth football players base their game interactions may constitute a solid criterion for fine-tuning the training process and, ultimately, to achieve better individual and team performances during competition. The present study aims to explore how passing networks and positioning variables can be linked to the match outcome in youth elite association football. The participants included 44 male elite players from under-15 and under-17 age groups. A passing network approach within positioning-derived variables was computed to identify the contributions of individual players for the overall team behaviour outcome during a simulated match. Results suggested that lower team passing dependency for a given player (expressed by lower betweenness network centrality scores) and high intra-team well-connected passing relations (expressed by higher closeness network centrality scores) were related to better outcomes. The correlation between the dyads' positioning regularity and the passing density showed a most likely higher correlation in under-15 (moderate effect), indicating a possible more dependence of the ball position rather than in the under-17 teams (small/unclear effects). Overall, this study emphasizes the potential of coupling notational analyses with spatial-temporal relations to produce a more functional and holistic understanding of teams' sports performance.


#9 Assessment of P wave duration and P wave dispersion in high level football referees
Reference: J Sports Med Phys Fitness. 2017 Jan-Feb;57(1-2):162. doi: 10.23736/S0022-4707.16.05983-1
Authors: Yucesir I, Sahin Yildiz B, Coskun O, Yakal S, Bayraktar B, Metin G, Altan M, Yildiz M


#10 Short versus long small-sided game training during Ramadan in soccer players
Reference: Phys Ther Sport. 2016 Oct 24;24:20-25. doi: 10.1016/j.ptsp.2016.10.002. [Epub ahead of print]
Authors: Baklouti H, Rejeb N, Aloui A, Jaafar H, Ammar A, Chtourou H, Girard O, Souissi N
Summary: The purpose was to compare the effects of two small-sided game (SSG) training formats (4 × 4 min (SSG-S) and 2 × 8 min (SSG-L)) conducted during Ramadan on Hoff and five-jump (5JT) tests' performances and session rating of perceived exertion. Twenty-four male soccer players were divided into 3 groups: 2 groups undertaking 4 weeks of SSG-S (n = 8) or SSG-L (n = 8) during Ramadan and a control group (n = 8) participated in this studz. The Profile of Mood States (POMS) and Hooper questionnaires' scores and 5JT and Hoff test's performances were measured before (BR) and at the end of Ramadan (R4). Compared to BR, fatigue estimated by POMS and Hooper questionnaires was higher at R4 in all groups (ES = 0.77-1.57, p < 0.05). Hoff test distance increased to the same extent in SSG-S and SSG-L groups (+7.38-7.39%, ES = 1.49-1.93, p < 0.001). Mean sRPE scores measured during Ramadan were higher after SSG-L (6.49 ± 0.38) than SSG-S (5.61 ± 0.14) sessions (+15.58%, ES = 2.79, p < 0.001). SSG training can be implemented as an efficient intervention to avoid detraining and equally improve soccer-specific physical performance during Ramadan. Given the lower perceptual responses associated with shorter SSG sequences, this modality would be better tolerated during the fasting month, and therefore is recommended.