Latest research in football - week 44 - 2021

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 High-Intensity Intermittent Exercise Performed on the Sand Induces Higher Internal Load Demands in Soccer Players

Reference: Front Psychol. 2021 Jul 30;12:713106. doi: 10.3389/fpsyg.2021.713106. eCollection 2021.

Authors: Tiago Cetolin, Anderson Santiago Teixeira, Juliano Fernandes da Silva, Alessandro Haupenthal, Fábio Yuzo Nakamura, Carlo Castagna, Luiz Guilherme Antonacci Guglielmo

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Summary: This study aimed to examine the acute physiological effect of shuttle-run-based high-intensity intermittent exercise (HIIE) performed at the same relative speed (i. e., 100% PST-CAR) on sand (SAND) and grass (GRASS) in male junior soccer players. Seven Under-23 Brazilian national league ("Série A") soccer players completed four testing sessions in either SAND or GRASS surface condition. The first two testing sessions consisted of performing a maximal progressive shuttle-run field protocol until volitional exhaustion (Carminatti's test, T-CAR), whereas the third and fourth sessions comprised a HIIE session on each ground surface. The HIIE session consisted of three 5-min bouts [12 s shuttle-run (with a direction change every 6 s)/12 s of passive rest] performed at 100% of T-CAR peak speed (PST-CAR) with 3 min of passive recovery between sets. Measurements of oxygen uptake (VO2), heart rate (HR), blood lactate concentration ([La]), and rating of perceived exertion (RPE) were performed during all conditions. The SAND condition elicited significantly higher %VO2peak (94.58 ± 2.73 vs. 87.45 ± 3.31%, p < 0.001, d = 2.35), %HRpeak (93.89 ± 2.63 vs. 90.31 ± 2.87%, p < 0.001, d = 1.30), RPE (8.00 ± 0.91 vs. 4.95 ± 1.23 a.u., p < 0.001, d = 2.82), and [La] (10.76 ± 2.37 vs. 5.48 ± 1.13 mmol/L, p < 0.010, d = 2.84). This study showed that higher internal workloads are experienced by the players during a single HIIE session performed on a softer surface as SAND, even when the exercise intensity was individualized based on 100%PST-CAR.



#2 Assessing Inter-Limb Asymmetries in Soccer Players: Magnitude, Direction and Association with Performance

Reference: J Hum Kinet. 2021 Jul 28;79:41-53. doi: 10.2478/hukin-2021-0081. eCollection 2021 Jul.

Authors: Marc Madruga-Parera, Thomas Dos'Santos, Chris Bishop, Anthony Turner, David Blanco, Vicente Beltran-Garrido, Victor Moreno-Pérez, Daniel Romero-Rodríguez

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Summary: In this study, we aimed to analyze the magnitude and direction of inter-limb asymmetries in ankle dorsiflexion range of motion (ROM), power (using iso-inertial devices), and a neuromuscular skill (change of direction). Secondarily, we aimed to determine the relationship between inter-limb asymmetry scores for each test and also between these scores and the scores for the different performance tests. Sixteen semiprofessional male soccer players (age: 25.38 ± 6.08 years; body height: 1.78 ± 0.64 m; body mass: 79.5 ± 14.9 kg) participated in this study. We calculated inter-limb asymmetries using five tests: ankle dorsiflexion ROM, change of direction (COD 180º), and iso-inertial resistance tasks in the open (leg extension strength (LE), leg curl strength (LC)) and closed (crossover step (CRO)) kinetic chain. Our results showed that asymmetry magnitudes differed between all tests with highest inter-limb asymmetries displayed during iso-inertial overloading. In addition, we observed that the direction of asymmetries varied depending on the test-specificity, and that the CRO asymmetries had a negative association with LE and CRO performance. These findings highlight the independent nature of asymmetries and that CRO could be an appropriate test to detect asymmetries related with the performance of soccer-specific actions (such as changes of direction). Practitioners are encouraged to use multiple tests to detect existing inter-limb differences according to the specific characteristics of each sport.



#3 The Relationship Between Performance and Asymmetries in Different Multidirectional Sprint Tests in Soccer Players

Reference: J Hum Kinet. 2021 Jul 28;79:155-164. doi: 10.2478/hukin-2021-0069. eCollection 2021 Jul.

Authors: Alberto Fílter, Vicente Beltrán-Garrido, Thomas Dos'Santos, Daniel Romero-Rodríguez, Bernardo Requena, Irineu Loturco, Marc Madruga-Parera

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Summary: Practitioners usually include change of direction (COD) and linear speed measurements in the testing batteries of soccer players; however, despite being a commonly occurring action, curve sprint (CS) ability is rarely assessed in soccer. The aims of this study were to analyze the association between linear sprint, CS, and COD speed performances, and compare the association and direction of asymmetries between these skills. Thirty-three male soccer players performed linear sprint (17 m), CS (17 m), and COD-90⍛ speed tests (COD [8.5 + 8.5 m]). Our main findings were (a) a large relationship between linear and multidirectional tasks (COD-90⍛ and CS tests) (r = from 0.6 to 0.64, p < 0.05), (b) a moderate relationship between CS and COD-90⍛ tests (r = from 0.33 to 0.41, p < 0.05), with a certain opposite tendency (higher relationships between opposing directions [CurveLEFT - CODRIGHT; r = 0.41] than between equal directions [CurveLEFT - CODLEFT; r = 0.33]), and (c) no relationship (p > 0.05) between COD and CS asymmetries, with opposing directional dominance in ~70% of players (e.g., curve left and COD right dominance). These results indicate that performance in linear sprints is strongly related to performance in multidirectional trajectories, whereas CS and COD-90⍛ seem to be more independent actions. Additionally, the direction of asymmetry or dominance is generally opposite between the non-linear tasks measured.



#4 The effect of core stability-based corrective exercises on gait parameters in elite soccer players diagnosed with Middle Crossed Syndrome

Reference: J Bodyw Mov Ther. 2021 Jul;27:620-627. doi: 10.1016/j.jbmt.2021.04.016. Epub 2021 Apr 24.

Authors: Nima Nakisa, Mahboobeh Ghasemzadeh Rahbardar, Yahya Sokhangouei, Zohreh Afsharmand

Summary: The aim of this study was to investigate the effect of eight weeks of core stability-based corrective exercises, on gait parameters in elite soccer players diagnosed with middle crossed syndrome. 15 male elite soccer players (aged 18-28) were enrolled in a same-subject intervention trial to assess if the middle crossed syndrome could be influenced through core stability exercise. Core stability-based corrective exercises were completed 3 times per week for 8 weeks and changes in gait parameters (pre- and post- intervention) were measured. The results showed that most gait parameters including stride length (p = 0.025), gait speed (p = 0.023), number of strides (p = 0.007), length of shots (p = 0.003), and also soccer players' height (p = 0.011) improved significantly in post-intervention in comparison to pre-intervention. Stride width in post-intervention did not show changes in comparison with pre-intervention (p = 0.083). The results indicate the significant effectiveness of core stability-based corrective exercises on gait parameters in those with middle crossed syndrome. By doing corrective exercises based on core stability during the study period, gait parameters in the post-intervention surpass the results in the pre-intervention in most parameters. Therefore, it is proposed that corrective exercises based on core stability is a safe and useful method for improving function in those with middle crossed syndrome and it could be used as a therapy to help players identified with this finding. In this regard, it is suggested to researchers and coaches to correct imbalances in order to achieve better results in training programs.



#5 Kinesiotape on quadriceps and gluteus in counter movement jump and sprint in soccer players

Reference: J Bodyw Mov Ther. 2021 Jul;27:42-47.  doi: 10.1016/j.jbmt.2021.02.021. Epub 2021 Mar 4.

Authors: J Reina Abellán, Juan L Yuste, O Mora Cabrera, C Gómez-Tomás

Summary: Kinesiotape (KT) is a technique commonly used in sports practice. It may be beneficial in enhancing muscle function by additional cutaneous afferent stimulation. The objective of this study was to analyse the effect of KT on countermovement jump (CMJ) and 20-m sprints (sp) immediately and 24 h after its application on the quadriceps and gluteus maximus. 37 male soccer players (19.7 ± 0.9 years old) were randomly assigned to one of 3 groups: experimental group: KT activation (KTact), placebo group: sham tape (KTst), and control group (CG). Participants performed a 30-min preliminary warm-up, after which they conducted CMJ and 20-m sp tests. These tests were repeated later (with KT application or not) and after 24 h. Intergroup results found no significant differences either post-test (CMJ, p = 0.115; sp, p = 0.307) or after 24 h (p = 0.053). Intragroup results showed no significant results for CMJ, although 20-m sp seemed to display significant differences in the (KTst) (p = 0.002, post-hoc: 0.015 in pre_sp vs post_sp) and the (KTact) (0.021, in post-hoc: 0.007 in pre_sp vs post_sp), with a moderate effect in pre_sp vs post_sp (0.66) in the (KTact) after KT was applied. KT application on the gluteus maximus and quadriceps in young soccer players increases the sprint execution time immediately and 24 h after application, even that the sprint execution time had not been grater that one tenth of the second (0.08 s). It also has no effect on CMJ.



#6 Fascial therapy, strength exercises and taping in soccer players with recurrent ankle sprains: A randomized controlled trial

Reference: J Bodyw Mov Ther. 2021 Jul;27:256-264. doi: 10.1016/j.jbmt.2021.03.022. Epub 2021 Apr 2.

Authors: Ruben Allois, Adriano Niglia, Alessandro Pernice, Rubén Cuesta-Barriuso

Summary: Recurrent ankle sprains are common in soccer players, characterized by restricted range of motion, pain, and decreased proprioception, strength, and postural control. The objective was to evaluate the effectiveness of a fascial therapy and strength training program, combined with kinesiotaping, in improving ankle range of motion, pain, strength and stability in footballers with recurrent sprains. A simple blind randomized clinical trial was conducted on soccer players. Thirty-six federated footballers were recruited and randomized to the two study groups. The experimental group received an intervention using myofascial techniques applied to the subastragaline joint, eccentric training with an isoinertial device and neuromuscular taping. The control group was administered an intervention using myofascial techniques on the subastragaline joint and eccentric training with an isoinertial device. The results were recorded for all players at baseline, after 4 weeks of intervention, and at the end of the 4-week follow-up period. Subsequent to intervention and follow-up, we found statistically significant improvements in the experimental group in ankle mobility, strength and stability. The control group exhibited improvements in all study variables. No differences in the improvement of variables were found based on the allocation of athletes to one group or another. The combination of fascial therapy and eccentric strength training with an isoinertial device improves ankle mobility, strength and stability in footballers with recurrent ankle sprains. The use of taping techniques failed to provide a greater improvement of the study variables when combined with manual therapy and strength techniques.



#7 Scanning activity of elite football players in 11 vs. 11 match play: An eye-tracking analysis on the duration and visual information of scanning

Reference: PLoS One. 2021 Aug 20;16(8):e0244118.  doi: 10.1371/journal.pone.0244118. eCollection 2021.

Authors: Karl Marius Aksum, Lars Brotangen, Christian Thue Bjørndal, Lukas Magnaguagno, Geir Jordet

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Summary: Visual perception in football ("soccer" in the U.S.) is increasingly becoming a key area of interest for researchers and practitioners. This exploratory case study investigated a sub-set of visual perception, namely visual exploratory scanning. The aim of this study was to examine the scanning of four elite football midfield players in an 11 vs. 11 real-game environment using mobile eye-tracking technology. More specifically, we measured the duration and information (number of teammates and opponents) of the players' scanning behavior. The results showed that the players' scanning duration was influenced by the ball context and the action undertaken with the ball at the moment of scan initiation. Furthermore, fixations were found in only 2.3% of the scans. Additionally, the results revealed that the stop point is the most information-rich part of a scan and that the players had more opponents than teammates inside their video frame during scans. Practical applications and further research recommendations are presented.



#8 Associations of Vitamin D Levels with Physical Fitness and Motor Performance; A Cross-Sectional Study in Youth Soccer Players from Southern Croatia

Reference: Biology (Basel). 2021 Aug 5;10(8):751. doi: 10.3390/biology10080751.

Authors: Barbara Gilic, Jelena Kosor, David Jimenez-Pavon, Josko Markic, Zeljka Karin, Daniela Supe Domic, Damir Sekulic

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Summary: Vitamin D level is known to be a factor potentially influencing physical fitness, but few studies have examined this phenomenon among youth athletes. We aimed to evaluate the associations of vitamin D levels (as measured by 25-hydroxyvitamin D concentrations-25(OH)D) with various physical fitness and motor performance tests in youth football (soccer) players. This cross-sectional study included a total of 52 youth soccer players (15.98 ± 2.26 years old) from Southern Croatia. The participants were evaluated at the end of the winter period and data were collected of anthropometric measures (body mass and body height), vitamin D status (25(OH)D levels), physical fitness tests (sprints of 10 and 20 m, 20 yards test, the countermovement jump, the reactive strength index (RSI)) and motor performance tests (the soccer-specific CODS, the soccer-specific agility, and static balance). Among the studied players, 54% had 25(OH)D insufficiency/deficiency, showing a lack of 25(OH)D is widespread even in youth athletes living at a southern latitude. The 25(OH)D level was correlated with sprint 20 m, 20 yards tests, and RSI, showing a greater role of 25(OH)D in physical fitness tests where energetic capacity is essential than in sport-related motor performance tests where skills are crucial. Our results support the idea that vitamin D can play a determinant role in physical fitness tests with a clear physiological component, but is not crucial in motor performance tests related to specific sports where skills are a key component. Future studies should investigate the effects of vitamin D supplementation on the performance in physical fitness and motor performance tests among youth athletes.



#9 Quantifying Accelerations and Decelerations in Elite Women Soccer Players during Regular In-Season Training as an Index of Training Load

Reference: Sports (Basel). 2021 Jul 31;9(8):109. doi: 10.3390/sports9080109.

Authors: Tom Douchet, Allex Humbertclaude, Carole Cometti, Christos Paizis, Nicolas Babault

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Summary: Accelerations (ACC) and decelerations (DEC) are important and frequent actions in soccer. We aimed to investigate whether ACC and DEC were good indicators of the variation of training loads in elite women soccer players. Changes in the training load were monitored during two different selected weeks (considered a "low week" and a "heavy week") during the in-season. Twelve elite soccer women playing in the French first division wore a 10-Hz Global Positioning System unit recording total distance, distance within speed ranges, sprint number, ACC, DEC, and a heart rate monitor during six soccer training sessions and rated their perceived exertion (RPE). They answered the Hooper questionnaire (sleep, stress, fatigue, DOMS) to get an insight of their subjective fitness level at the start (Hooper S) and at the end of each week (Hooper E). A countermovement jump (CMJ) was also performed once a week. During the heavy week, the training load was significantly greater than the low week when considering number of ACC >2 m·s-2 (28.2 ± 11.9 vs. 56.1 ± 10.1, p < 0.001) and number of DEC < -2 m·s-2 (31.5 ± 13.4 vs. 60.9 ± 14.4, p < 0.001). The mean heart rate percentage (HR%) (p < 0.05), RPE (p < 0.001), and Hooper E (p < 0.001) were significantly greater during the heavy week. ACC and DEC showed significant correlations with most outcomes: HR%, total distance, distance per min, sprint number, Hooper index of Hooper E, DOMS E, Fatigue E, RPE, and session RPE. We concluded that, for elite women soccer players, quantifying ACC and DEC alongside other indicators seemed to be essential for a more complete training load monitoring. Indeed, it could lead to a better understanding of the reasons why athletes get fatigued and give insight into neuromuscular, rather than only energetic, fatigue.



#10 External and Internal Load Measures During Preseason Training in Men Collegiate Soccer Athletes

Reference: J Strength Cond Res. 2021 Sep 1;35(9):2572-2578. doi: 10.1519/JSC.0000000000004092.

Authors: Jennifer B Fields, Justin M Merigan, Sina Gallo, Jason B White, Margaret T Jones

Summary: Collegiate athletes are exposed to high volume loads during preseason training. Monitoring training load can inform training and recovery periods. Therefore, the purpose was to examine changes in and bidirectional relationship between external and internal load metrics in men collegiate soccer athletes (n = 20; age, 20 ± 1 year). Internal load measures of heart rate variability (HRV), salivary testosterone (T) and cortisol (C), and self-assessment wellness and ratings of perceived exertion scales were collected daily. External load measures of total distance, player load, high-speed distance, high inertial movement analysis, and repeated high-intensity efforts were collected in each training session using global positioning system/global navigation satellite system technology. A 1-way analysis of variance determined weekly changes in external load, physiological, hormonal, and subjective self-assessment measures of internal load. Bidirectional prediction of external load markers and self-assessment measures on physiological and hormonal markers of internal load were assessed by hierarchical linear regression models (p < 0.05). External load measures, C, energy, sleep, and rate of perceived exertion (RPE) decreased (p < 0.01), whereas T, T:C ratio, anger, depression, and vigor increased (p < 0.01) from week 1 to week 2. Morning C positively predicted afternoon external load and post-training RPE (p < 0.05); T:C ratio negatively predicted afternoon external load and post-training RPE (p < 0.05); and morning HRV negatively predicted post-training RPE (p = 0.031). Despite reduced hormonal stress and external load across weeks, negative perceptions of fatigue increased, suggesting fatigue patterns may have a delayed response. Load may have a more belated, chronic effect on perceptions of fatigue, whereas hormonal changes may be more immediate and sensitive to change. Practitioners may wish to use a variety of external and internal load measures to understand athletes' stress responses to training.



#11 Soccer Scores, Short-Term Mood and Fertility

Reference: Eur J Popul1. 2021 Apr 14;37(3):625-641. doi: 10.1007/s10680-021-09576-2. eCollection 2021 Jul.

Authors: Fabrizio Bernardi, Marco Cozzani

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Summary: Previous research has shown that seemingly irrelevant events such as unexpected outcomes in sporting events can affect mood and have relevant consequences for episodes of crime and violence, investing behavior and political preferences. In this article, we test whether mood shocks associated with unexpected results in soccer matches in Spain affect fertility. We use data on betting odds and actual scores to define mood shocks and link them to births by month and province in Spain, between 2001 and 2015. We find that unexpected losses of local teams lead to a small decrease in the number of births nine months thereafter. The effect is larger for more unexpected losses, in those provinces with the largest amount of support for the local team and robust to a number of placebo tests. We argue that these results are consistent with the gain-loss asymmetry predicted by prospect theory.



#12 Correlation between strength and skin temperature asymmetries in the lower limbs of Brazilian elite soccer players before and after a competitive season

Reference: J Therm Biol. 2021 Jul;99:102919. doi: 10.1016/j.jtherbio.2021.102919. Epub 2021 Apr 24.

Authors: Jorge L Rodrigues Júnior, Warley Duarte, Hugo Falqueto, André G P Andrade, Rodrigo F Morandi, Maicon R Albuquerque, Miller G de Assis, Tane K F Serpa, Eduardo M Pimenta

Summary: This study aimed to investigate the correlation between strength and skin temperature (Tsk) asymmetries in the lower limbs of elite soccer players before and after a competitive season. The sample (n = 20) was composed of elite male soccer players. Strength asymmetry and Tsk asymmetry was measured through the countermovement jump (CMJ) test and infrared thermography, respectively. Asymmetries were quantified using the symmetry angle (SA) equation. A strong correlation was found between the SA of rate of force development (RFD) and the SA of Tsk before (baseline) (r = 0.7; r2 = 0.43; p = 0.03) and after (r = 0.6; r2 = 0.42; p = 0.04) the competitive season. Moreover, after the competitive season there were significant decreases in Peak force (p < 0.018), Impulse (p < 0.04), RFD (p = 0.0001) and CMJ height (p = 0.05), and significant increases in Tsk (p < 0.03), C-reactive protein (p = 0.03), Creatine kinase (p = 0.0001) and Cortisol (p = 0.04), even after a 3-day rest interval (no training). These results suggest that the CMJ test can be combined with infrared thermography for monitoring strength asymmetry and contribute to the prevention of muscle injuries.



#13 Age-related differences in linear sprint in adolescent female soccer players

Reference: BMC Sports Sci Med Rehabil. 2021 Aug 22;13(1):97. doi: 10.1186/s13102-021-00327-8.

Authors: Elena Mainer-Pardos, Oliver Gonzalo-Skok, Hadi Nobari, Demetrio Lozano, Jorge Pérez-Gómez

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Summary: Several studies have observed the contribution of chronological age, biological maturation, and anthropometric characteristics to sprinting performance in young soccer players. Nevertheless, there are no studies that have analysed the contribution of these characteristics to running speed qualities in adolescent female soccer players. This study investigated age-related differences in sprint performance in adolescent female soccer players. Also, it examined the possible influence of anthropometry [body mass and body mass index (BMI)] and biological maturation [age at peak height velocity (APHV)] in sprint performance. Eighty adolescent female soccer players [under (U) 14, n = 20; U16, n = 37; U18, n = 23] participated in this study. Players were tested for 40 m sprint (each 10 m split times). Posthoc analysis revealed better performance in all split sprint times of older soccer players (U18 and U16) compared with younger category (F: 3.380 to 6.169; p < 0.05; ES: 0.64 to 1.33). On the contrary in all split sprint times, there were no significant changes between U16 and U18 (p < 0.05; ES: 0.03 to 0.17). ANCOVA revealed differences in all parameters between groups, controlled for APHV (p < 0.05). In contrast, all between-group differences disappeared after body mass and BMI adjustment (p > 0.05). Finally, the results indicate that BMI and body mass were significantly correlated with 40 m sprint (p < 0.05; r: -0.31) and 20 m flying (p < 0.01; r: 0.38), respectively. In the present players' sample, body mass and BMI had a significant impact on running speed qualities.



#14 Why are female soccer players experiencing a concussion more often than their male counterparts? A scoping review

Reference: Phys Ther Sport. 2021 Aug 8;52:54-68. doi: 10.1016/j.ptsp.2021.08.001. Online ahead of print.

Authors: Rebecca Jane Blyth, Mark Alcock, Dr Steve Tumilty

Summary: The risk of concussion is particularly high in female soccer players. There is no consensus as to why female soccer players are at an elevated risk. The aim was to synthesise current evidence investigating reasons for the increased concussion rate in female soccer players. Searching of six databases (MEDLINE, Scopus, CINAHL, SportDiscus, Web of Science and the Cochrane Library) and grey literature was performed between 13/07/2020-31/07/2020. Keywords were concussion-related terms, terms relating to female football/soccer and terms relating to the mechanism/cause. No constraints were placed on publication date and quantitative or exploratory studies meeting inclusion criteria were eligible. Exclusion criteria were studies not published in English and qualitative studies. Several hypotheses were identified to explain increased concussion rates in female soccer players, these include, reduced neck strength/anthropometrics, increased head acceleration, increased ball-to-head concussions, differences in hormones and brain structure/function, and reduced visual awareness. Promising ideas/reasons have been identified for increased concussion rates in female soccer players. Despite hypothesis generation there is scarce high-level evidence which is required to guide injury prevention and/or rule changes to protect female soccer players. The level of evidence for included studies is level 2-3 with most being observational cross-sectional or cohort studies.



#15 Relationship between Physical Fitness and Match Performance Parameters of Chile Women's National Football Team

Reference: Int J Environ Res Public Health. 2021 Aug 9;18(16):8412.  doi: 10.3390/ijerph18168412.

Authors: Rodrigo Villaseca-Vicuña, Fernando Manuel Otero-Saborido, Jorge Perez-Contreras, Jose Antonio Gonzalez-Jurado

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Summary: The aim of this study was to analyze the relationships between the level of physical fitness and the physical performance parameters recorded by GPS in official FIFA matches of the Chilean women's senior national football team in the period 2018-2020. Twenty-six female field players (age (mean ± SD) 26.8 ± 3.3 years, height 157.8 ± 21.5 cm, weight 58.9 ± 4.9 kg) participated in the study. Physical fitness variables were assessed: muscular strength, countermovement jump (CMJ), speed, agility and aerobic fitness. Physical performance variables were recorded by GPS in 26 official FIFA matches. The most notable associations with significant statistical significance (p < 0.001) were those observed between neuromuscular variables such as time to run 10 m (T10; r = -0.629) and jump (CMJ; r = 0.502) and the number of accelerations; aerobic fitness showed a highly significant relationship with meters run per minute (M/M; r = 0.589). The findings of this study provide evidence of how the level of physical fitness (neuromuscular and aerobic) relates to physical performance parameters recorded in official competitions.



#16 A comparison of the internal and external load demands imposed on professional soccer referees in FIFA's current model of physical test in relation to games

Reference: J Sports Med Phys Fitness. 2021 Sep 9. doi: 10.23736/S0022-4707.21.12104-8. Online ahead of print.

Authors: Artur A Preissler, Pedro Schons, Rochelle R Costa, Thaís Reichert, Henrique B Oliveira, Guilherme D DE Vargas, Felipe L Ribeiro, Giovanni R Brito, Jonas C Zanella, Lucas M Klein, Benedito S Denadai, Luiz F Kruel

Summary: Based on the need to investigate the demands imposed on referees in the current model of physical evaluation and during professional games, this study's objective was to compare these demands in the physical test versus the games. Thus, it evaluated the heart rate, distance covered, time, and speed of all 14 referees in the physical test and during Brazil's first division state championship games using a Global Positioning System enabled heart rate monitor. The maximum heart rate (HRmax) and maximum speed were higher in the physical test (183.86 ± 12.79 bpm) and (26.80 ± 0.96 km/h), respectively, than in the games (170.25 ± 17.71 bpm) (p = 0.008) and (24.27 ± 1.68 km/h) (p = 0.001), respectively. In the HRmax zone ≥90 and ≤100%, the time and percentage distance were greater in the physical test (47.87 ± 16.60% and 58.57 ± 22.78%), respectively, than in the games (17.82% ± 18.29% and 18.84% ± 18.92%, respectively; p < 0.001). However, in the speed zone <13 km/h, the time and the percentage distance were longer in the game (93.73 ± 1.26% and 86.13 ± 2.31%), respectively, than in the physical test (68.73 ± 12,31% and 39.65 ± 9.74%, respectively; p < 0.001). Thus, it is concluded that the professional referees perform at greater intensities during the physical test than in the games. In contrast, the demands for intensities corresponding to aerobic metabolism are greater in games or equal to those in physical testing, depending on the intensity reference.



#17 Soccer participation is associated with benefits in tibial bone cross-sectional geometry and strength in young women

Reference: J Sports Med Phys Fitness. 2021 Sep 9. doi: 10.23736/S0022-4707.21.12519-8. Online ahead of print.

Authors: Julie M Hughes, D Clark Dickin, He Wang

Summary: Soccer has been hypothesized to be an ideal sport to stimulate favorable changes in bone properties due the high-intensity, multidirectional movements performed during play. The purpose of this study was to determine if participation in soccer is associated with enhanced bone properties such as volumetric bone mineral density (vBMD), cross-sectional geometry, and estimated strength in the tibias of young, healthy women. Twenty female soccer players (20±1 yr) and twenty mass- and height-matched healthy women (21±1 yr) participated in this cross-sectional study. Peripheral quantitative computed tomography (XCT 3000; Stratec Medizintechnik, Pforzheim, Germany) was used to assess bone characteristics, including vBMD, cross-sectional moments of inertia (CSMI), and strength/strain index (SSI) at 14%, 38%, and 66% of the tibial length proximal to the distal end plate. One-way multivariate analysis of variances was run to determine the influence of soccer training history on tibial properties. Compared to healthy controls, soccer players had approximately 1.5% - 3% lower cortical vBMD but 18.5% - 30% greater CSMI and 16.5% -19% greater SSI at the three cross-sectional sites along the tibial diaphysis (all p < 0.05). These results suggest that soccer participation is associated with favorable bone cross-sectional geometry and estimates of bone strength. However, randomized controlled intervention trials are needed to confirm whether soccer participation results in favorable bone adaptations in young, healthy adults.



#18 Low back pain prevalence and risk factors in Italian adolescent male soccer players: results from an online survey

Reference: J Sports Med Phys Fitness. 2021 Sep 9. doi: 10.23736/S0022-4707.21.12696-9. Online ahead of print.

Authors: Lucia Cugusi, Andrea Manca, Ernest Fishback, Claudio Secci, Marco Bergamin, Stefano Gobbo, Andrea DI Blasio, Andrea Montella, Pasquale Bandiera, Franca Deriu

Summary: The purpose of this retrospective survey was to analyse the prevalence of low back pain (LBP) among Italian adolescent soccer players, and to identify potential risk factors. Participants were requested to answer an online survey based on the standardized Nordic questionnaires for musculoskeletal symptoms. Data were obtained from 204 male soccer players aged 14-17 years competing at the national and regional level. More than half of the players had experienced LBP in their lives. One-way ANOVA revealed that the players with LBP were taller, heavier and with a higher BMI (all p values<0.00001). When considering the playing position, ANOVA revealed that 14-15 years-old strikers displayed higher LBP scores than all other roles (all p values<0.05). Accordingly, strikers were exposed to a higher risk of LBP than midfielders (RR=1.48; 95%CI:1.10-2.01; p=0.01) and goalkeepers (RR=1.48; 95%CI:1.02-2.971; p=0.04), but not defenders (RR=1.23; 95%CI:0.93-1.63; p=0.15). Within the 14-15 age-class, strikers were, again, those most exposed to LBP risk (all p values<0.05). Anthropometric and soccer-related features should be monitored to ensure early identification of potential risk factors for LBP. This information should be considered along with the specific playing position as strikers emerged as the roles most exposed to LBP risk.



#19 Predictive Strength of Contextual and Personal Variables in Soccer Players' Goal Orientations

Reference: Int J Environ Res Public Health. 2021 Sep 6;18(17):9401. doi: 10.3390/ijerph18179401.

Authors: Enrique Iglesias-Martínez, Jorge Roces-García, David Méndez-Alonso

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Summary: Psychological variables, such as perceived motivational climate, goal orientation, self-determined motivation, and personality, have an influence on sports success performance. This study aimed to examine the relationships among a set of psychological variables (perceived motivational climate, goal orientation, self-determined motivation, and personality) in male and female footballers. Participants were 167 footballers (106 male, 61 female), aged 12 to 26, competing with clubs in the Spanish Football League. They all took four questionnaires aimed at evaluating motivational climate, goal orientations, self-determined motivation, and personality. The analyses of correlation and regression showed statistically significant relations among the variables. Neuroticism and psychoticism negatively relate to mastery motivational climate, the best predictor of self-determined motivation. It was concluded that contextual variables carry more weight in predicting goal orientations and self-determined motivation among participant footballers.



#20 Impact of the Result of Soccer Matches on the Heart Rate Variability of Women Soccer Players

Reference: Int J Environ Res Public Health. 2021 Sep 6;18(17):9414. doi: 10.3390/ijerph18179414.

Authors: Rosa Mª Ayuso-Moreno, Juan Pedro Fuentes-García, Hadi Nobari, Santos Villafaina

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Summary: The present study aimed to evaluate the effects of a match lost and a match won on post-competitive heart rate variability (HRV) in semi-professional female soccer athletes. A total of 13 players, with a mean age of 23.75 (5.32), from the Cáceres Women Football Club of the Spanish Second National Division participated in our study. They were evaluated in two microcycles which correspond to a match lost and a match won. For each microcycle, baseline and post-competitive measures were collected. Results indicate that HRV was significantly reduced before a match lost and won. Significant differences in HRV variables were observed when compared the lost match, and the match won. Results highlight the importance and usefulness of analyzing the HRV as an indicator of post-competitive fatigue in semiprofessional soccer players. Therefore, a competition's results could be considered a relevant variable to consider when programming training load.



#21 Win, Draw, or Lose? Global Positioning System-Based Variables' Effect on the Match Outcome: A Full-Season Study on an Iranian Professional Soccer Team

Reference: Sensors (Basel). 2021 Aug 24;21(17):5695. doi: 10.3390/s21175695.

Authors: Hadi Nobari, Norbert Keshish Banoocy, Rafael Oliveira, Jorge Pérez-Gómez 

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Summary: The aim of the study was to determine the between-match and between-halves match variability of various Global Positioning System (GPS) variables and metabolic power average (MPA) in competitions, based on the match results obtained by professional soccer players over a full season. Observations on individual match performance measures were undertaken on thirteen outfield players competing in the Iranian Premier League. The measures selected for analysis included total duration, accelerations in zones (AccZ1, 2, and 3), decelerations in zones (DecZ1, 2, and 3), and MPA collected by the Wearable Inertial Measurement Unit (WIMU). The GPS manufacturer set the thresholds for the variables analyzed as follows: AccZ1 (<2 m·s-2); AccZ2 (2 to 4 m·s-2); AccZ3 (>4 m·s-2); DecZ1 (<-2 m·s-2); DecZ2 (-2 to -4 m·s-2); DecZ3 (>-4 m·s-2). The results revealed significant differences between wins and draws for the duration of the match and draws compared to wins for the first- half duration (p ≤ 0.05; ES = 0.36 [-0.43, 1.12]), (p ≤ 0.05; ES = -7.0 [-8.78, -4.78], respectively. There were significant differences on AccZ1 during the first-half between draws and defeats (p ≤ 0.05; ES = -0.43 [-1.32, 0.46]), for AccZ3 in the second-half between draws and defeats (p ≤ 0.05; ES = 1.37 [0.48, 2.25]). In addition, there were significant differences between wins and draws (p ≤ 0.05; ES = 0.22 [-0.62, 1.10]), and wins and defeats for MPA in the first- half (p ≤ 0.05; ES = 0.34 [-0.65, 1.22]). MPA showed further differences between draws and defeats in the second- half (p ≤ 0.05; ES = 0.57 [-0.22, 1.35]). Descriptive analysis revealed differences between the first and second half for wins in AccZ2 (p = 0.005), DecZ2 (p = 0.029), and MPA (p = 0.048). In addition, draws showed significant differences between the first and second half in duration, AccZ1, AccZ2, and DecZ2 (p = 0.008), (p = 0.017), (p = 0.040), and (p = 0.037) respectively. Defeats showed differences between the first and second half in AccZ1, AccZ3, and MPA (p = 0.001), (p = 0.018), and (p = 0.003) respectively. In summary, the study reveals large variations between the match duration, accelerometer variables, and MPA both within and between matches. Regardless of the match outcome, the first half seems to produce greater outputs. The results should be considered when performing a half-time re-warm-up, as this may be an additional factor influencing the drop in the intensity markers in the second half in conjunction with factors such as fatigue, pacing strategies, and other contextual variables that may influence the results.



#22 REPIMPACT - a prospective longitudinal multisite study on the effects of repetitive head impacts in youth soccer

Reference: Brain Imaging Behav. 2021 Sep 10. doi: 10.1007/s11682-021-00484-x. Online ahead of print.

Authors: Inga K Koerte, Roald Bahr, Peter Filipcik, Jolien Gooijers, Alexander Leemans , Alexander P Lin, Yorghos Tripodis, Martha E Shenton, Nir Sochen, Stephan P Swinnen, Ofer Pasternak, REPIMPACT Consortium Investigators

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Summary: Repetitive head impacts (RHI) are common in youth athletes participating in contact sports. RHI differ from concussions; they are considered hits to the head that usually do not result in acute symptoms and are therefore also referred to as "subconcussive" head impacts. RHI occur e.g., when heading the ball or during contact with another player. Evidence suggests that exposure to RHI may have cumulative effects on brain structure and function. However, little is known about brain alterations associated with RHI, or about the risk factors that may lead to clinical or behavioral sequelae. REPIMPACT is a prospective longitudinal study of competitive youth soccer players and non-contact sport controls aged 14 to 16 years. The study aims to characterize consequences of exposure to RHI with regard to behavior (i.e., cognition, and motor function), clinical sequelae (i.e., psychiatric and neurological symptoms), brain structure, function, diffusion and biochemistry, as well as blood- and saliva-derived measures of molecular processes associated with exposure to RHI (e.g., circulating microRNAs, neuroproteins and cytokines). Here we present the structure of the REPIMPACT Consortium which consists of six teams of clinicians and scientists in six countries. We further provide detailed information on the specific aims and the design of the REPIMPACT study. The manuscript also describes the progress made in the study thus far. Finally, we discuss important challenges and approaches taken to overcome these challenges.



#23 Match-related physical performance in professional soccer: Position or player specific?

Reference: PLoS One. 2021 Sep 10;16(9):e0256695. doi: 10.1371/journal.pone.0256695. eCollection 2021.

Authors: Stefan Altmann, Leon Forcher, Ludwig Ruf, Adam Beavan, Timo Groß, Philipp Lussi, Alexander Woll, Sascha Härtel

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Summary: The purpose of this study was to examine to what extent the physical match performance of professional soccer players is both position and player specific. First, official match data from the 2019/20 German Bundesliga season was used to search for players that met the inclusion criteria of playing a minimum of four entire matches in at least two different playing positions. Overall, 25 players met the criteria prior to the COVID-19 induced break, playing a minimum of eight matches. Second, the physical match performance of these players was analyzed separately for each position they played. The following four parameters were captured: total distance, high-intensity distance, sprinting distance, and accelerations. Third, the 25 players' physical match performance data was then compared to normative data for each position they played to understand whether players adapted their physical performance (position dependent), or maintained their performance regardless of which position they were assigned to (position independent). When switching the position, the change in physical match performance of the respective players could be explained by 44-58% through the normative positional data. Moreover, there existed large individual differences in the way players adapted or maintained their performance when acting in different positions. Coaches and practitioners should be aware that some professional soccer players will likely incur differences in the composition of physical match performance when switching positions and therefore should pay special consideration for such differences in the training and recovery process of these players.


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