Latest research in football - week 20 - 2023

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases. 


Following studies were retrieved for this week:


#1 Training matters: Heading incidence and characteristics in children's and youth football (soccer) players

Reference: Scand J Med Sci Sports. 2023 Jun 1. doi: 10.1111/sms.14408. Online ahead of print.

Authors: Rebecca Reeschke, Franziska Katharina Haase, Lena Dautzenberg, Werner Krutsch, Claus Reinsberger

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Summary: Concerns about short- and long-term consequences of repetitive heading contributed to heading restrictions in youth football in some countries. This prospective longitudinal cohort study aims to describe heading exposure in children's and youth football over two seasons using standardized video analysis. All matches and training sessions of a male Under-11 (n = 29), Under-15 (n = 28), Under-19 (n = 38), and female Under-17 (n = 39) team were videotaped during the seasons 2019-2020 and 2020-2021. Heading frequencies and characteristics were analyzed. Individual heading exposure is presented as average incidence rates (IR) per 1000 match/training hours. In 275 matches and 673 training sessions, 22 921 headers were observed. Heading IR per player in matches was 1256 (Under-11 m), 1608 (Under-15 m), 1050 (Under-17 f), and 1966 (Under-19 m). In training sessions, IR per player was 739 (Under-11 m), 2206 (Under-15 m), 1661 (Under-17 f), and 1419 (Under-19 m). Five Under-15 males headed the ball five to eight times per training on average. Most headers were performed without heading duels. Flight distance was predominantly 5-20 m (54%) in matches and <5 m (65%) in training. While head impact location most frequently was at frontal areas, one-third of all headers in Under-11 in matches hit temporal, parietal, and occipital parts of the head. Heading incidence was low in the youngest age group, whereas (predominantly five) Under-15 males showed very high heading exposures in training. In assessment and regulation of heading burden, training sessions and individual heading behavior should specifically be addressed. Recommendations for heading the ball in practice should account for individual and age-related differences.



#2 Brain glucose metabolism and gray matter volume in retired professional soccer players: a cross-sectional [18F]FDG-PET/MRI study

Reference: Arq Neuropsiquiatr. 2023 May;81(5):433-443. doi: 10.1055/s-0043-1768666. Epub 2023 May 31.

Authors: Mateus Rozalem Aranha, Artur Martins Coutinho, Camila de Godoi Carneiro, Bruno Fraccini Pastorello, Adalberto Studart-Neto, Carla Cristina Guariglia, Miriam Harumi Tsunemi, Everton Luis Santos Moreira, Jéssica Natuline Ianof, Renato Anghinah, Ricardo Nitrini, Giovanni Guido Cerri, Juan Fortea, Carlos Alberto Buchpiguel, Claudia Costa Leite

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Summary: Professional soccer athletes are exposed to repetitive head impacts and are at risk of developing chronic traumatic encephalopathy. The aim was to evaluate regional brain glucose metabolism (rBGM) and gray matter (GM) volume in retired soccer players (RSPs). Male RSPs and age and sex-matched controls prospectively enrolled between 2017 and 2019 underwent neurological and neuropsychological evaluations, brain MRI and [18F]FDG-PET in a 3.0-Tesla PET/MRI scanner. Visual analysis was performed by a blinded neuroradiologist and a blinded nuclear physician. Regional brain glucose metabolism and GM volume were assessed using SPM8 software. Groups were compared using appropriate statistical tests available at SPM8 and R. Nineteen RSPs (median [IQR]: 62 [50-64.5] years old) and 20 controls (60 [48-73] years old) were included. Retired soccer players performed worse on mini-mental state examination, digit span, clock drawing, phonemic and semantic verbal fluency tests, and had reduced rBGM in the left temporal pole (pFDR = 0.008) and the anterior left middle temporal gyrus (pFDR = 0.043). Semantic verbal fluency correlated with rBGM in the right hippocampus, left temporal pole, and posterior left middle temporal gyrus (p ≤ 0.042). Gray matter volume reduction was observed in similar anatomic regions but was less extensive and did not survive correction for multiple comparisons (pFDR ≥ 0.085). Individual [18F]FDG-PET visual analysis revealed seven RSPs with overt hypometabolism in the medial and lateral temporal lobes, frontal lobes, and temporoparietal regions. Retired soccer players had a higher prevalence of septum pellucidum abnormalities on MRI. Retired soccer players had reduced rBGM and GM volume in the temporal lobes and septum pellucidum abnormalities, findings possibly related to repetitive head impacts.



#3 Bone bending strength and BMD of female athletes in volleyball, soccer, and long-distance running

Reference: Eur J Appl Physiol. 2023 May 31. doi: 10.1007/s00421-023-05231-2. Online ahead of print.

Authors: Jose Rocha-Rangel, Michael T C Liang, Anderson Hwa-Te Tsai, Alexandra T Auslander, Patricia Robles, Yuan-Lieh Kwoh, Sara B Arnaud

Summary: The purpose of the study was to determine whether sports training comprised of (1) high-impact loading sport in volleyball (VOL), (2) odd impact loading sport in soccer (SOC), and (3) low impact sport in distance running (RUN) were associated with tibial bending strength and calcaneus bone mineral density (BMD), and ulnar bending strength and wrist BMD. Female athletes comprised of 13 VOL, 22 SOC, and 22 RUN participated in the study. Twenty-three female non-athletes (NA) served as the comparison group. Tibial and ulnar bending strength (EI, Nm2) were assessed using a mechanical response tissue analyzer (MRTA). Calcaneus and wrist BMD were assessed using a peripheral X-ray absorptiometry. Group means differences among the study groups were determined using ANCOVA with age, weight, height, percent body fat, ethnicity/race, and training history serving as covariates. Tibial EI of VOL (228.3 ± 138 Nm2) and SOC (208.6 ± 115 Nm2) were greater (p < 0.05) compared to NA (101.2 ± 42 Nm2). Ulnar EI of SOC (54.9 ± 51 Nm2) was higher (p < 0.05) than NA (27.2 ± 9 Nm2). Calcaneus BMD of VOL (0.618 ± 0.12 g/cm2), SOC (0.621 ± 0.009 g/cm2), and RUN (0.572 ± 0.007 g/cm2) were higher (p < 0.05) than NA (0.501 ± 0.08 g/cm2), but not different between athletic groups. Wrist BMD of VOL (0.484 ± .06 g/cm2) and SOC (0.480 ± 0.06 g/cm2) were higher (p < 0.05) than NA (0.443 ± 0.04 g/cm2). Female VOL athletes exhibit greater tibial bending strength than RUN and NA, but not greater than SOC. Female SOC athletes exhibit greater ulnar bending strength and wrist BMD than NA.



#4 Effects of a neuromuscular training program on physical performance and asymmetries in female soccer

Reference: Front Physiol. 2023 May 2;14:1171636. doi: 10.3389/fphys.2023.1171636. eCollection 2023.

Authors: Alberto Roso-Moliner, Elena Mainer-Pardos, Antonio Cartón-Llorente, Hadi Nobari, Svein Arne Pettersen, Demetrio Lozano

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Summary: Women's football require optimal neuromuscular system development for injury prevention and performance optimization. Standardized neuromuscular training programs have shown promising results in reducing injuries and functional asymmetries, but evidence on their impact on performance is limited. This research examined the effects of a 10-week neuromuscular training program on physical performance and asymmetries in female football players. Thirty-eight female players from two Spanish Second Division women's football teams participated in the study. The physical performance tests used were: ankle dorsiflexion, bilateral and unilateral horizontal jump, bilateral and unilateral vertical countermovement jump, 40 m sprint including partial times at 10, 20 and 30 m and the 505 test for change of direction evaluation. For 10 weeks, players in the experimental group performed three weekly 24-min neuromuscular training sessions. Participants in the control group completed their normal 24-min strength and conditioning program. The main results were that maximal linear velocity and change of direction skills showed the most notable improvements [effect size (ES), 0.46 to 0.59] after implementation of the training program, ankle dorsiflexion and jumping skills, also improved although, to a lesser extent (ES, <0.35) while asymmetries between limbs were reduced. Maximal running speed improved in the intervention group (p < 0.001) with a mean ES -0.59. We conclude that a 10-week neuromuscular training program can be a sufficient stimulus to improve football-specific performance variables in high-level female football players. Therefore, female players and coaches should be aware that weekly inclusion of strength, power and dynamic balance exercises following a neuromuscular paradigm is helpful for football-specific performance improvement.



#5 Hamstring Stiffness and Strength Responses to Repeated Sprints in Healthy Nonathletes and Soccer Players With Versus Without Previous Injury

Reference: Sports Health. 2023 May 31;19417381231175474. doi: 10.1177/19417381231175474.

Authors: Sandro R Freitas, Régis Radaelli, Raúl Oliveira, João R Vaz

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Summary: The effect of 10 × 30 m repeated sprints on passive and active stiffness of semitendinosus (ST) and biceps femoris long head (BFlh), and knee flexor maximal voluntary isometric contraction (MVIC) and rate of force development (RFD), and whether athletes with previous hamstring injury have a different response, is unknown. Repeated sprints would (1) increase BFlh stiffness and decrease ST stiffness and knee flexors MVIC and RFD in healthy participants; and (2) greater magnitude of response would be seen in athletes with previous hamstring injury. Case series (experiment I) and case control (experiment II) study designs was used. Healthy nonathletes attended 2 replicated sessions (experiment I, n = 18), while soccer players with (n = 38) and without (n = 67) previous hamstring injury attended 1 testing session (experiment II). In both experiments, the knee flexors MVIC and RFD decreased after the sprints (P < 0.05). In experiment I, the ST and BFlh passive stiffness reduced after the sprints (P < 0.02), while a small BFlh active stiffness increase was noted (P = 0.02); however, no correlation was observed between the 2 testing sessions for the postsprint muscle stiffness responses (r = -0.07-0.44; P > 0.07). In experiment II, only an ST passive stiffness reduction was observed after the sprints (P < 0.01). No differences were noted between injured and noninjured lower limbs for any variable (P > 0.10). Repeated sprints are likely to decrease the knee flexor's maximal and rapid strength, and to alter the hamstring stiffness in the nonathlete population. Previous hamstring injury does not apparently affect the footballer's hamstring functional and mechanical responses to repeated sprints. The responses of hamstring stiffness and knee flexor strength to repeated sprints are unlikely to be associated with hamstring injury.



#6 Training and match load ratios in professional soccer-should we use player- or position-specific match reference values?

Reference: Front Sports Act Living. 2023 May 16;5:1151828.  doi: 10.3389/fspor.2023.1151828. eCollection 2023.

Authors: Linda Ammann, Stefan Altmann

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Summary: Careful load management is needed to optimize the physical capacity, a key performance component, of soccer players. The training load of soccer players is often expressed as a percentage of match load. However, no study has yet evaluated how training match load ratios are affected by using either a player-specific or position-specific reference for match load. Therefore, this study aimed to compare training match load ratios of professional soccer players per day of a microcycle with match load being player-specific and position-specific, respectively. Additionally, the load that players typically experience per day of a microcycle and its variation should be analyzed. Therefore, a retrospective observational cohort study was conducted over a 14-month period, analyzing 11 external load measures during sessions of 20 players belonging to a team competing in the highest Swiss league. Within a microcycle, typical full matches presented a unique load for players, and they experienced higher training loads on days with a greater temporal distance to a match. Load variation proved to be highly associated with the day in a microcycle and the load measure. Substantial differences in typical load were evident in (i) trainings between players, (ii) matches both between players and positions, and (iii) training match load ratios when using player-specific or position-specific match references. The importance of individual load management in professional soccer was reaffirmed. When consulting training match load ratios for that purpose, one should be aware of the aim, select appropriate reference values depending on it, and interpret the ratios accurately to finally draw adequate conclusions.



#7 Perception of higher-order affordances for kicking in soccer

Reference: J Exp Psychol Hum Percept Perform. 2023 May;49(5):623-634. doi: 10.1037/xhp0001108.

Authors: Alper Tunga Peker, Veysel Böge, George S Bailey, Jeffrey B Wagman, Thomas A Stoffregen

Summary: We investigated the perception of higher-order interpersonal affordances for kicking that emerged from lower-order personal and interpersonal affordances in the context of soccer. Youth soccer players reported the minimum gap width between two confederates through which they could kick a ball. In Experiment 1, we independently manipulated the egocentric distance of gaps from participants, and the nominal role of the confederates, either as teammates or opponents. In Experiment 2, we additionally varied the direction in which the confederates were facing, either together (i.e., into the gap) or away (i.e., away from the gap). Perceived minimum kickable gap width was larger for farther egocentric distances, when confederates were identified as opponents rather than as teammates, and (in Experiment 2) when confederates faced toward, rather than away from the gap. In both experiments, these main effects were subsumed in statistically significant interactions. We argue that these interactions reveal perception of higher-order interpersonal affordances for kicking that emerged from the simultaneous influence of lower-order affordances. The results are compatible with the hypothesis that these higher-order affordances were perceived, as such, and were not additively combined from independent perception of underlying, lower-order affordances. (PsycInfo Database Record (c) 2023 APA, all rights reserved).



#8 Sleep and chronotype influence aerobic performance in young soccer players

Reference: Front Physiol. 2023 May 11;14:1190956. doi: 10.3389/fphys.2023.1190956. eCollection 2023.

Authors: Andrea Ciorciari, Antonino Mulè, Lucia Castelli, Letizia Galasso, Fabio Esposito, Eliana Roveda, Angela Montaruli

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Summary: People can be classified into three chronotypes (CT): morning-type (M-type), Neither-type (N-type) and Evening-type (E-type). M-types perform better in the morning, E-types in the evening. It seems that bad sleep worsens physical performance. The impact of sleep and CT on specific sports and populations is unclear. Therefore, we wanted to assess agility, strength and endurance in young soccer players in relation to their sleep and chronotype. 58 players (13-19 years) were recruited. Sleep and CT were assessed by questionnaires. The physical trial was performed at 8:30 a.m. and 6:00 p.m., and included three tests to determine agility, strength and endurance. The sample was classified by CT as M-types (n = 11), N-types (n = 29) and E-types (n = 18). Furthermore, they were categorized as people with Good Sleep/Wake quality (GSW, n = 28) and people with Bad Sleep/Wake quality (BSW, n = 30). Comparing the three CTs in the aerobic test, M-types performed better in the morning (p = 0.01), while E-types in the evening (p < 0.001). GSW performed better than BSW (p = 0.019) in the aerobic test in the p.m. session. These results underline the difference in aerobic power between M-and E-types during the morning and evening session; moreover, they show a difference in p.m. aerobic performance according to sleep quality.



#9 Effect of Different Nonstarter Compensatory Strategies on Training Load in Female Soccer Players: A Pilot Study

Reference: Sports Health. 2023 May 30;19417381231176555. doi: 10.1177/19417381231176555.

Authors: Elba Díaz-Serradilla, Daniel Castillo, José Antonio Rodríguez-Marroyo, Javier Raya González, José Gerardo Villa Vicente, Alejandro Rodríguez-Fernández

Summary: In soccer, the day of the week with the highest external load is match day (MD), with starters (>60 minutes per match) showing higher levels of physical fitness and seasonal high-intensity loading. It is necessary, therefore, to determine training strategies to reduce the differences between starters and nonstarters. The aim of this study was to analyze and compare the external load of different training compensatory strategies with match external load in female nonstarters. A strategy combining small-sided games (SSG) and running-based drills (RBD) would reproduce match demands, with RBD leading to greater high-intensity running and SSG leading to a greater number of accelerations and decelerations. The training and match external load of 14 female players belonging to the same reserve squad of a Spanish First Division Club (Liga Reto Iberdrola) was registered. In the first session after the match (MD+1), nonstarters (<60 minutes in the match) performed 1 of 3 different compensatory strategies: RBD, SSG, or a mixed intervention combining the previous strategies (RBD+SSG). Starters carried out a recovery session. A marked difference in load was observed between the compensatory training strategies and MD. In comparison with MD, RBD showed greater high-intensity and sprint distances and lower acceleration, SSG showed less high-intensity running and sprint distances, lower peak velocity, and greater acceleration, and RBD+SSG registered lower accelerations. In addition, nonstarters covered greater high-intensity running and sprint distances in RBD and achieved higher accelerations in SSG. RBD and SSG compensatory strategies could be recommended to nonstarter female soccer players in MD+1 to compensate for match external load deficits. This study provides comprehensive information on the compensatory exercises of female soccer players, which can be useful for strength and conditioning coaches when developing recovery strategies during a microcycle.



#10 Red blood cell omega-3 fatty acid content is negatively associated with purposeful gameplay header frequencies in collegiate women soccer players: Implications for diet and brain health

Reference: Nutr Health. 2023 May 29;2601060231178333. doi: 10.1177/02601060231178333. Online ahead of print.

Authors: Aaron F Carbuhn, Linda J D'Silva

Summary: Frequent soccer heading negatively affects brain health. Omega-3 fatty acids are neuroprotective against head impacts. A biomarker of omega-3 tissue status, red blood cell (RBC) omega-3 content is reduced during soccer activity. However, whether these changes are associated with frequent heading impacts is unknown. Explore the association between soccer heading frequencies and RBC omega-3 status. A prospective cohort study in collegiate women soccer players (n = 16). Players' RBC omega-3 status, Omega-3 Index, and self-reported gameplay header frequencies collected during a competitive season. Mean Omega-3 Index (i.e., pre/postseason) was low (3.95 ± 0.44%). Postseason Omega-3 Index negatively correlated (r = -0.545, p = 0.029) with heading frequencies. Change in Omega-3 Index negatively correlated (r = -0.663, p = 0.005) with average headers per game. RBC omega-3 status is negatively influenced by frequent soccer heading throughout a competitive season which may have concerning implications for player brain health.



#11 Neurocognitive errors are common in non-contact ACL injuries in professional male soccer players

Reference: J Athl Train. 2023 May 26. doi: 10.4085/1062-6050-0209.22. Online ahead of print.

Authors: Alli Gokeler, Filippo Tosarelli, Matthew Buckthorpe, Francesco Della Villa

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Summary: Evidence is emerging that core neurocognitive function such as working memory or inhibitory control (more response inhibition, attention) are linked to ACL injury risk. Thus far, research has been conducted in laboratory settings and the contribution of neurocognition to actual ACL injuries under real world conditions is unknown. We hypothesized that errors in motor response inhibition and attentional inhibition contribute to non-contact ACL injuries in professional soccer players. In addition, we hypothesized high inter-rater agreement for the neurocognitive assessment based on the video analysis.Neurocognitive errors in inhibitory control of professional football players were operationalized as 1) motor response inhibition was scored when a player demonstrated poor decision making and approached the opponent with high speed which reduced the ability to stop or change the intended action; 2) an attentional error was scored in case the player shifted the selective attention away from the relevant task to irrelevant stimuli. Three independent reviewers evaluated each video. A total of 47 actual ACL injury videos were analyzed. Out of 47 non-contact ACL injuries, 26 were related to a pressing type injury and in 19 (73%) there was a deceiving action made by the opponent suggestive for poor inhibitory control of the defender. For the remaining 21 non-contact ACL injuries, 16 (76%) could be attributed to attentional errors. The agreement between the three raters was very good for all items, except for item poor decision making which showed fair to good agreement (0.71). Inter-rater reliability was excellent (ICC = 0.998-1.00). The current student found that errors in motor response inhibitory control and attentional inhibition are common during non-contact ACL injury events in professional male soccer players. The inter-rater agreement to detect neurocognitive errors in general is very good.



#12 The genetic association with athlete status, physical performance and injury risk in soccer

Reference: Int J Sports Med. 2023 May 30. doi: 10.1055/a-2103-0165. Online ahead of print.

Authors: Conall F Murtagh, Elliott C Hall, Thomas E Brownlee, Barry Drust, Alun Gwyn Williams, Robert M Erskine

Summary: The aim of this review was to critically appraise the literature concerning the genetic association with player status, physical performance and injury risk in soccer. The objectives were to provide guidance on which genetic markers could potentially be used as part of future practice in soccer; and to provide direction for future research in this area. The most compelling evidence identified six genetic polymorphisms to be associated with soccer athlete status (ACE I/D; ACTN3 rs1815739; AGT rs699; MCT1 rs1049434; NOS3 rs2070744; PPARA rs4253778), six with physical performance (ACTN3 rs1815739; AMPD1 rs17602729; BDNF rs6265; COL2A1 rs2070739; COL5A1 rs12722; NOS3 rs2070744), and seven with injury risk (ACTN3 rs1815739; CCL2 rs2857656; COL1A1 rs1800012; COL5A1 rs12722; EMILIN1 rs2289360; IL6 rs1800795; MMP3 rs679620). As well as replication by independent groups, large-scale genome-wide association studies are required to identify new genetic markers. Future research should also investigate the physiological mechanisms associating these polymorphisms with specific phenotypes. Further, researchers should investigate the above associations in female and non-Caucasian soccer players, as almost all published studies have recruited male participants of European ancestry. Only after robust, independently replicated genetic data have been generated, can genetic testing be considered an additional tool to potentially inform future practice in soccer.



#13 Characteristics of participants in a public rubella antibody testing program conducted at a Japan professional football league venue

Reference: J Gen Fam Med. 2023 Feb 16;24(3):194-198. doi: 10.1002/jgf2.611. eCollection 2023 May.

Authors: Toshinori Nishizawa, Kuniyoshi Hayashi, Noriyuki Amano, Gautam A Deshpande, Hiroko Arioka

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Summary: Hypothesizing that soccer-associated public health campaigns influence men more than women, we investigated the characteristics and motivations of participants who received rubella antibody testing at a Japanese professional football league event. This was a survey-based cross sectional study, comparing the characteristics and motivations between men and women regarding rubella antibody testing. Free and convenient testing was the biggest behavioral influencer, but the information provided by healthcare professionals and athletes also played a strong motivating role. Men reported more influence from celebrity athletes than women. Public health attention raised by celebrity athletes may facilitate rubella awareness among male spectators.



#14 Implementation of the injury prevention exercise programme Knee Control+: a cross-sectional study after dissemination efforts within a football district

Reference: Inj Prev. 2023 May 31;ip-2023-044863. doi: 10.1136/ip-2023-044863. Online ahead of print.

Authors: Hanna Lindblom, Sofi Sonesson, Josefin Forslind, Markus Waldén, Martin Hägglund

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Summary: The Reach, Effectiveness, Adoption, Implementation, and Maintenance (RE-AIM) framework can be used for evaluation of implementation initiatives in sports injury prevention. The aim was to evaluate the implementation of the injury prevention exercise programme Knee Control+ among amateur clubs and coaches in one regional football district using all five dimensions of the RE-AIM framework. Dissemination of Knee Control+ during the 2021 season with information and webinars within one regional football district. This was followed by a cross-sectional study with questionnaires to club personnel and coaches after the season. The reach of Knee Control+ was fair to high, 83% of club personnel and 66% of coaches knew about the programme. 41% of club personnel and 51% of coaches had adopted it. Perceived programme effectiveness was high (6 on a 1-7 Likert scale) among coaches. Regarding implementation and maintenance, 27% of club personnel had informed coaches about Knee Control+ and 57% planned to inform coaches. The coaches had implemented the programme mainly as recommended, but half used the programme once per week or less. Intention to maintain use of the programme was high (7 on a 1-7 Likert scale) among coaches. The reach of Knee Control+ was fair to high, and adoption was fair in clubs, but there was a lack of policies for preventive training. Active strategies probably need to accompany dissemination of programme material. Reach, perceived effectiveness, adoption, implementation and planned maintenance were positive among coaches, but further studies are needed to analyse long-term maintenance.



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