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 The usefulness of balance test in preseason evaluation of injuries in amputee football players: a pilot prospective observational study

Reference: PeerJ. 2024 Jan 5:12:e16573. doi: 10.7717/peerj.16573. eCollection 2024.
Authors: Zofia Kasińska, Tomasz Tasiemski, Teresa Zwierko, Piotr Lesiakowski, Monika Grygorowicz
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10773449/pdf/peerj-12-16573.pdf
Summary: Low balance ability is generally associated with an increased risk of ligament injuries. It seems that assessing the level of stability in amputee football players can help evaluate the accompanying risk of sports injuries. Thus, the study aimed to examine the usefulness of the balance test in preseason evaluation by calculating between-group differences in stability parameters between injured and non-injured amputee players. The study was designed as a pilot prospective observational study. Twenty-five elite amputee football players representing the Polish National Team and the highest division in Polish League completed one-leg preseason balance tests on the Biodex Balance System before the start of the football season. All players in this study were male, with an average age of 29 years (SD = 7.9), a stature of 174.2 cm (SD 5.2) and a body mass of 80.1 kg (SD = 13.1). Then, players were prospectively observed over one football season, and lower leg injury data were prospectively collected through the nine months. The between-group differences were tested using the non-parametric Mann-Whitney U test for players who sustained an injury (yes) and those who did not within the analysed season (no). Overall (OSI), medial-lateral (MLSI), and anterior-posterior stability index (APSI) were analysed as primary outcomes. The preseason values of the balance tests were not predictive (p > 0.05) regarding sustaining an injury during the season. No between-group differences were noted for any analysed outcomes (p values ranged from 0.093 to 0.453). Although static balance tasks offer a chance to make a preliminary assessment of injury prediction in amputee footballers, in overall, the balance test results cannot be regarded as the sole predictive injury risk factor in amputee football.

2 Changes in physical and technical match performance variables in football players promoted from the Spanish Second Division to the First Division

Reference: Biol Sport. 2024 Jan;41(1):217-225. doi: 10.5114/biolsport.2024.127386. Epub 2023 Aug 8.
Authors: Jordi Ferrandis, Juan Del Coso, Víctor Moreno-Pérez, Roberto López-Del Campo, Ricardo Resta, Joaquín González-Rodenas
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10765445/pdf/JBS-41-50670.pdf
Summary: The aim of this study was to compare physical and technical match performance variables in football players who competed in the Spanish second division for one season and were promoted to the top (first) division in the following season. A total of 97 male outfield football players who were promoted from the second to the first division of the Spanish professional football league within the same team were analysed. Data were recorded using the TRACAB (ChyronHego, New York, USA) multicamera computerised optical tracking system during five seasons (2015-2016 to 2019-2020). A one-way ANOVA repeated measures analysis showed that players executed a greater number of high-intensity running (HIR) efforts (P < 0.001; ES: 0.258), as well as covering greater HIR distance (P < 0.010; ES: 0.106) and total running distance (TD) (P < 0.010; ES: 0.080), when they played in the first division compared with the second division. Moreover, players performed a lower number of passes (P < 0.01; ES = 0.116), short passes (P < 0.01; ES = 0.106), long passes (P < 0.05; ES = 0.067), dribbles (P < 0.001; ES = 0.146) and shots (P < 0.01; ES = 0.074) in the first division compared to the second division. No significant differences were found for any of the defensive variables evaluated. In conclusion, being promoted from the second to the first division of professional football requires players to adapt to greater physical demands and a reduced number of technical actions.

3 The combined effects of growth and maturity status on injury risk in an elite football academy

Reference: Biol Sport. 2024 Jan;41(1):235-244. doi: 10.5114/biolsport.2024.129472. Epub 2023 Aug 8.
Authors: Xabier Monasterio, Sean P Cumming, Jon Larruskain, David M Johnson, Susana M Gil, Iraia Bidaurrazaga-Letona, Jose A Lekue, Gontzal Diaz-Beitia, Juan M Santisteban, Sean Williams
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10765440/pdf/JBS-41-51086.pdf
Summary: This study aimed to explore the interaction between growth rate on specific injury incidence and burden on pre-, circa- and post-peak height velocity (PHV) periods. Injury and stature data collected during the 2000-2020 seasons in an elite football academy were retrospectively analysed. Only players with height measurements from childhood until the attainment of adult height were included in the study (N = 84). Growth data were smoothed using a cubic spline to calculate daily growth rate and height. Growth rate was categorised into three groups: fast (> 7.2 cm/year), moderate (3.5-7.2 cm/year) and slow (< 3.5 cm/year). Percentage of observed adult height was used to classify players as pre-PHV (< 88%), circa-PHV (88-95%) or post-PHV (> 95%). Overall and specific injury incidence and burden and rate ratios for comparisons between growth rate groups were calculated on pre-, circa- and post-PHV periods, separately. Overall injury incidence and burden were greater in pre-PHV players with quicker growth rates compared to players growing moderately and slowly. All in all, players with more rapid growth-rates were at higher risk for growth-related injuries in all pre-, circa- and post-PHV periods. Post-PHV, the incidence and burden of joint/ligament injuries were 2.4 and 2.6-times greater in players growing slowly compared to players growing moderately. Practitioners should monitor growth rate and maturity status and consider their interaction to facilitate the design of targeted injury risk reduction strategies.

4 Snus use in football: the threat of a new addiction?

Reference: Biol Sport. 2024 Jan;41(1):201-205. doi: 10.5114/biolsport.2024.130050. Epub 2023 Jul 24.
Authors: Daniel Read, Sarah Carter, Phil Hopley, Karim Chamari, Lee Taylor
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10765442/pdf/JBS-41-51148.pdf
Summary: The use of Snus, an oral nicotine pouch, is becoming increasingly common in English professional football. As a nicotine product, Snus raises important questions about health and performance for practitioners. The purpose of this short communication is to explain the current regulatory status of Snus, performance relatedeffects, and associated health outcomes. Further, based on player statements and evidence from the general public, we argue that Snus is used as a coping mechanism to deal with the stressors of professional football. Accordingly, the communication concludes with guidance for club-level multidisciplinary interventions to support player welfare, aimed at reducing Snus use as well as future research recommendations.

5 Hamstring muscle injury is preceded by a short period of higher running demands in professional football players

Reference: Biol Sport. 2024 Jan;41(1):227-233. doi: 10.5114/biolsport.2024.127387. Epub 2023 Aug 8.
Authors: Victor Moreno-Perez, Víctor Sotos-Martínez, Alejandro Lopez-Valenciano, Roberto Lopez Del-Campo, Ricardo Resta, Juan Del Coso
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10765438/pdf/JBS-41-50671.pdf
Summary: The aim of this study was to examine match running patterns before a hamstring muscle injury occurs during a match in male professional football players. A total of 281 male professional football players belonging to 7 teams from LaLiga were prospectively monitored over three seasons. Among these, 36 players suffered a non-contact hamstring muscle injury during an official match. The injuries were recorded by the medical staff, including the minute when the injury occurred. Running distances at different speed thresholds for 5 min and 15 min before the injury were compared to mean values of the previous 5 matches for the same time points. There were a total of 44 non-contact hamstring muscle injuries, which represents a hamstring muscle injury incidence of 3.34 injuries/1000 h of match exposure. The average time loss for these injuries was 33 ± 28 days (range 7 to 117 days). In the 15 min prior to the injury, players ran a similar distance as in control matches (p from 0.22 to 0.08). However, players ran a greater distance in the 5-min period before the injury than in control matches at 21.0-23.9 km/h (p < 0.001) and at ≥ 24 km/h (p < 0.001). The odds ratio for a hamstring muscle injury was 7.147 for those players who ran > 30.0 m at ≥ 21 km/h in a 5-min period (p < 0.001). Hamstring muscle injuries during competition were preceded by 5 min of higher running demands at > 21 km/h, compared with control matches. This suggests that a short period of unusual running increases the risk of hamstring muscle injury in professional football players.

6 Investigation of Head Kinematics and Brain Strain Response During Soccer Heading Using a Custom-Fit Instrumented Mouthguard

Reference: Ann Biomed Eng. 2024 Jan 19. doi: 10.1007/s10439-023-03430-8. Online ahead of print.
Authors: M Barnes-Wood, H McCloskey, S Connelly, M D Gilchrist, A Ni Annaidh, P S Theobald
Summary: Association football, also known as soccer in some regions, is unique in encouraging its participants to intentionally use their head to gain a competitive advantage, including scoring a goal. Repetitive head impacts are now being increasingly linked to an inflated risk of developing long-term neurodegenerative disease. This study investigated the effect of heading passes from different distances, using head acceleration data and finite element modelling to estimate brain injury risk. Seven university-level participants wore a custom-fitted instrumented mouthguard to capture linear and angular acceleration-time data. They performed 10 headers within a laboratory environment, from a combination of short, medium, and long passes. Kinematic data was then used to calculate peak linear acceleration, peak angular velocity, and peak angular acceleration as well as two brain injury metrics: head injury criterion and rotational injury criterion. Six degrees of freedom acceleration-time data were also inputted into a widely accepted finite element brain model to estimate strain-response using mean peak strain and cumulative strain damage measure values. Five headers were considered to have a 25% concussion risk. Mean peak linear acceleration equalled 26 ± 7.9 g, mean peak angular velocity 7.20 ± 2.18 rad/s, mean peak angular acceleration 1730 ± 611 rad/s2, and 95th percentile mean peak strain 0.0962 ± 0.252. Some of these data were similar to brain injury metrics reported from American football, which supports the need for further investigation into soccer heading.

7 Postural Balance in Boys With Intellectual Disabilities Who Participate in Soccer Training

Reference: Pediatr Exerc Sci. 2024 Jan 19:1-9. doi: 10.1123/pes.2023-0098. Online ahead of print.
Authors: Ghada Jouira, Haithem Rebai, Dan Iulian Alexe, Sonia Sahli
Summary: The aim of this study is to investigate the postural balance in children with intellectual disabilities who participate in soccer training compared with their sedentary peers. Two groups of boys with intellectual disabilities aged 8-10 years participated in this study: a soccer group (n = 12) and a sedentary group (n = 12). Postural balance was assessed using a force platform under 4 different conditions: open eyes, and closed eyes, on firm and foam surfaces. The Timed Up and Go Test, 10-m Walking Test, and Four-Square Step Test were also conducted. The soccer group had significantly lower (P < .05) center of pressure values compared with the sedentary group, on both firm and foam surfaces, but only under the open eyes condition. They were significantly faster (P < .05) in the Timed Up and Go Test, 10-m Walking Test, and Four-Square Step Test compared with their sedentary peers. However, there were no significant differences between the 2 groups on the sit-to-stand and turn-to-sit phases of the Timed Up and Go Test. Soccer participation may have a positive effect on postural balance in boys with intellectual disabilities. These findings may have implications for the development of exercise programs to improve postural balance and reduce the risk of falls in this population.

8 Child Soccer Players‘ Perceptions of Strength and Conditioning Training: A Multimethod Approach Using Write, Draw, Show and Tell

Reference: Pediatr Exerc Sci. 2024 Jan 19:1-11. doi: 10.1123/pes.2023-0102. Online ahead of print.
Authors: Ricardo Martins, Emma Eyre, Matteo Crotti, Rhys Morris, Will Pattison, Michael Duncan
Summary: The use of strength and conditioning training in childhood is a hot topic surrounded by myths and misconceptions. Despite scientific evidence supporting the safety and benefits of this training for children, the lack of representation of their voices poses a challenge in designing training programs that meet their specific needs and requirements. Children’s views, experiences, and perceptions of strength and conditioning training were explored by Write, Draw, Show and Tell techniques. Sixteen grassroots soccer players aged 11-12 years took part in one of 3 focus groups exploring the topic. Data were analyzed following an inductive approach enabling themes to be explored and later deductive analyses using the Youth Physical Activity Promotion model to create pen profile diagrams. Strength and conditioning were frequently associated with muscle growth, coordination, endurance, and rest. Enabling factors included autonomy, resilience, physical development, and training opportunities. Reinforcing factors included social support, social interference, coaches‘ communication, role models, and the ways of implementation. Participants favor integrating strength and conditioning into their soccer training rather than conducting it as a separate session, which is reflected in their enjoyment. Nonetheless, children remain apprehensive about the potential effects of this type of training on their growth.

9 Effect of Pre-exercise Sodium Citrate Ingestion on Repeated Sprint Performance in Soccer Players

Reference: J Strength Cond Res. 2024 Jan 19. doi: 10.1519/JSC.0000000000004651. Online ahead of print.
Authors: Dilara Kuru, Selin Aktitiz, Muhammed M Atakan, Mehmet G Köse, Hüseyin H Turnagöl, Şükran N Koşar
Summary: This study aimed to test the hypothesis that sodium citrate (CIT) administered 180 minutes before exercise improves repeated sprint performance in athletes within a field-based setting. Twenty male soccer players (mean ± SD: age = 20.9 ± 2.3 years; body mass [BM] = 73.8 ± 5.9 kg) performed a running-based anaerobic sprint test (RAST) with 0.5 g·kg-1 BM of CIT or with placebo (PLC; NaCl) ingestion 180 minutes before exercise in a randomized, crossover, and double-blind design, with at least 6 days between the trials. Blood samples were collected before exercise and at first, third, fifth, and seventh minutes after exercise to analyze blood pH, bicarbonate, and lactate levels. Gastrointestinal symptoms were also monitored at 30-minute intervals for 180 minutes after CIT and PLC ingestion. Pre-exercise blood pH (CIT = 7.49 ± 0.03 vs. PLC = 7.41 ± 0.02) and bicarbonate (CIT = 30.57 ± 1.33 vs. PLC = 25.25 ± 1.52) increased with CIT compared with PLC (p < 0.001). Blood pH, bicarbonate, and lactate at the first, third, fifth, and seventh minutes after RAST with CIT were higher than PLC (p < 0.05), except for lactate at first minute (p > 0.05). Compared with PLC, CIT ingestion significantly improved minimum power output (p = 0.024) and percentage decrement score (p = 0.023). Gastrointestinal symptoms were significantly higher after CIT ingestion vs. PLC at 30th (p = 0.003) and 60th minutes (p = 0.010). However, there were no significant differences at 90th, 120th, 150th, or 180th minutes (p > 0.05). The ingestion of 0.5 g·kg-1 BM of CIT 180 minutes before exercise is an effective ergogenic aid for improving repeated sprint ability as evidenced by improvements in minimum power output and percentage decrement score.

10 In-situ acceleration-speed profile of an elite soccer academy: A cross-sectional study

Reference: J Sports Sci. 2024 Jan 19:1-7. doi: 10.1080/02640414.2024.2305005. Online ahead of print.
Authors: Pedro Cardoso, Francisco Tavares, Nuno Loureiro, Ruben Ferreira, João Pedro Araújo, Joana Reis, João R Vaz
Summary: Speed is an essential skill in sports performance and an important performance metric in talent identification. This study aims to evaluate and compare the sprint acceleration characteristics across different age groups in an elite soccer academy. A total of 141 elite academy soccer players were recruited to participate in the study, and they were assigned to their respective competitive age groups, ranging from under-14 to the B-team. An individual in-situ acceleration-speed (A-S) profile was assessed and derived from Global Position System (GPS) speed-acceleration raw data, from 10 consecutive football sessions, in the beginning of the season. The results showed that under-14 players exhibited significantly lower theoretical maximum speed (S0) (η2p��2 = 0.215, p < 0.01) when compared with all other age groups. However, no differences were found between maximum theoretical acceleration (A0) and A-S slope between age groups. The results suggest that sprint mechanical profiles of young soccer athletes remain stable throughout their athletic development. Nevertheless, younger athletes have less capacity to apply horizontal force at higher speeds (S0).

11 Relationship between coordination variability and Osgood-Schlatter disease in male junior youth soccer players -cross-sectional study using an inertial measurement unit

Reference: Clin Biomech (Bristol, Avon). 2024 Jan 12:112:106182. doi: 10.1016/j.clinbiomech.2024.106182. Online ahead of print.
Authors: Naoya Wada, Yota Abe, Rie Nakazawa, Masaaki Sakamoto, Tsuyoshi Tajika
Summary: Osgood-Schlatter disease is a common overuse injury, and motor coordination is discussed as a risk factor; however, no reports have examined motor coordination in young soccer players with Osgood-Schlatter disease. This study aimed to investigate the difference in motor coordination between Osgood-Schlatter disease-affected and non-affected soccer players on a junior youth soccer team. This cross-sectional study investigated 35 young soccer players of 12-15 years of age, who completed a self-administered questionnaire covering general information, injury history, and athletic experience. An inertial measurement unit was attached to the participant’s thoracic spine, lumbar spine, pelvis, thigh, and lower leg. The sagittal plane tilt angle of each body segment during squatting was analyzed. The continuous relative phase was calculated using the sagittal plane tilt angle. The mean absolute relative phase and continuous relative phase variabilities were calculated and compared between Osgood-Schlatter disease-affected and non-affected players. The sagittal plane tilt angle of each body segment during static standing and maximum flexion did not differ between the two groups. However, the Osgood-Schlatter disease group had significantly less continuous relative phase variability between the lumbar spine and pelvis (P < 0.01, Cohen’s d = 0.91). The Osgood-Schlatter disease group had significantly fewer participants with other sports experience (P = 0.032, φ = 0.36). Dysfunctional lower trunk and hip muscles may be leading to Osgood-Schlatter disease. It is suggested that a variety of physical activities should be performed in the junior age group to allow players to acquire a variety of movement patterns.

12 3D Kinematics of Male and Female Soccer Players for a Variety of Game-Specific Skills

Reference: Appl Bionics Biomech. 2024 Jan 8:2024:9588416. doi: 10.1155/2024/9588416. eCollection 2024.
Authors: Danyon Loud, Paul Grimshaw, Richard Kelso
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC10789512/pdf/ABB2024-9588416.pdf
Summary: Soccer is played by a variety of individuals with varying abilities. The complicated lower limb movements involved within the game often lead to knee and ankle injuries, with anterior cruciate ligament injuries being the most severe with regard to rehabilitation time and ongoing health risks. This research explores the biomechanical kinematics of male and female soccer players on synthetic grass to determine whether trends in lower limb biomechanics over a variety of movements could explain injury risk. Both male and female players (n = 10) aged between 19 and 24 years performed running-based and stationary-start movements. Biomechanical measurements at the hip, knee, and ankle were recorded. Observations showed that specific differences in joint angles were largely dependent on the movements performed; however, for male players, on average, across all movements, 84.6% and 72.6% of the variation in joint angles could be explained by internal/external rotation at the hip and knee, respectively. For female players, internal/external knee rotation, as well as hip abduction and adduction, accounted for 83.6% and 80.2% of the variation in joint angles, respectively, across all the tested movements. This highlights the importance of hip mechanics and knee alignment for players when performing a variety of movements.

13 Apophyseal injuries in soccer players

Reference: Skeletal Radiol. 2024 Jan 15. doi: 10.1007/s00256-023-04542-x. Online ahead of print.
Authors: Vitor Neves Sato, Tatiane Lumi Moriwaki, Marcos Hiroyuki Ikawa, Leonardo Massamaro Sugawara, Artur da Rocha Correa Fernandes, Abdalla Youssef Skaf, André Fukunishi Yamada
Download link: https://link.springer.com/content/pdf/10.1007/s00256-023-04542-x.pdf
Summary: Soccer is the most popular sport worldwide, and it is associated with high injury rates, with most of these injuries occurring in the lower extremities. Particularly, in youth soccer players with immature skeleton, the physeal plate is two to five times weaker than the surrounding fibrous structures, and therefore more vulnerable to injury. The physeal plate consists of epiphyses and apophyses, with the former serving as tendon attachment sites and being subject to traction forces. There are two types of apophyseal injury: (i) apophyseal avulsion, which consists of an acute separation across the physeal plate; and (ii) apophysitis, an injury caused by chronic and repetitive contraction of musculotendon unit, leading to inflammation of the growth plate cartilage. Apophyses of the hip and pelvis are the most commonly injured in youth soccer players, due to vigorous contractions during sports activities and the fact that they tend to fuse later compared to other epiphyseal centers, making them more susceptible to injury. In this review, we will discuss the anatomy of lower limb apophyses and clinical and imaging findings of apophyseal injuries in youth soccer players, as well as briefly review treatment options and complications.

14 #ReadyToplay: hamstring injuries in women’s football – a two-season prospective cohort study in the Norwegian women’s premier league

Reference: Sci Med Footb. 2024 Jan 19:1-9. doi: 10.1080/24733938.2024.2305389. Online ahead of print.
Authors: R Amundsen, S Thorarinsdottir, A Larmo, R Pedersen, T E Andersen, M Møller, R Bahr
Summary: In this two-season prospective cohort study (2020-2021), we aimed to describe the characteristics, clinical findings and magnetic resonance imaging (MRI) findings of hamstring injuries in the Norwegian women’s premier league. Hamstring injuries were examined by team physiotherapists using a standardised clinical examination and injury form. Injury location and severity (modified Peetrons classification) were graded based on MRI by two independent radiologists. Fifty-three hamstring injuries were clinically examined, 31 of these with MRI. Hamstring injuries caused 8 days (median) lost from football (interquartile range: 3-15 days, range: 0-188 days), most were non-contact and occurred during sprinting. Gradual-onset (53%) and sudden-onset injuries (47%) were evenly distributed. The injuries examined with MRI were classified as grade 0 (52%), grade 1 (16%) or grade 2 (29%). One proximal tendinopathy case was not graded. Grade 2 injuries caused more time loss than grade 0 (19 ± 8 vs. 7 ± 7 days, p = 0.002). Of injuries with MRI changes, 60% were in the m. biceps femoris, mainly the muscle-tendon junction, and 40% in the m. semimembranosus, most in the proximal tendon. Compared to previous findings from men’s football, a higher proportion of hamstring injuries in women’s football had a gradual onset and involved the m. semimembranosus, particularly its proximal tendon.

15 Hamstrings mechanical properties profiling in football players of different competitive levels and positions after a repeated sprint protocol

Reference: Front Physiol. 2024 Jan 4:14:1315564. doi: 10.3389/fphys.2023.1315564. eCollection 2023.
Authors: Ricardo Pimenta, Hugo Antunes, Paula Bruno, A P Veloso
Summary: This study compares the average speed, knee flexor peak torque and shear modulus of the hamstrings after a repeated sprint task, in football players of different competitive levels and playing positions. Fifty-four football field players without hamstring strain injury history participated, 15 being categorized as professional (2nd league) and 39 as semi-professional (17 in 3rd and 22 in 4th league). Muscle shear modulus was assessed using ultrasound-based shear wave elastography at rest and at 20% of maximal voluntary isometric effort before and immediately after the repeated sprint protocol. No significant differences were seen in average sprint speed between competitive levels (p = 0.07; η2p = 0.28) and positions (p = 0.052; η2p = 0.29). Moreover, the sprint fatigue index showed no significant differences between competitive levels (p = 0.14; η2p = 0.08) and playing positions (p = 0.89; η2p = 0.05). No significant differences were observed in hamstring shear modulus changes between competitive levels (p = 0.94; η2p = 0.03) and positions (p = 0.92; η2p = 0.03). Peak torque changes also showed non-significant association with competitive levels (p = 0.46; η2p = 0.03) and positions (p = 0.60; η2p = 0.02). The results of this study suggest that the average sprint speed performance parameter and mechanical parameters are not able to distinguish football players of different competitive levels and positions.