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 How training loads in the preparation and competitive period affect the biochemical indicators of training stress in youth soccer players?
Reference: PeerJ. 2022 May 5;10:e13367. doi: 10.7717/peerj.13367. eCollection 2022.
Authors: Marcin Andrzejewski, Marek Konefał, Tomasz Podgórski, Beata Pluta, Paweł Chmura, Jan Chmura, Jakub Marynowicz, Kamil Melka, Marius Brazaitis, Jakub Kryściak
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9080429/pdf/peerj-10-13367.pdf
Summary: Physical fitness optimization and injury risk-reducing require extensive monitoring of training loads and athletes' fatigue status. This study aimed to investigate the effect of a 6-month training program on the training-related stress indicators (creatine kinase - CK; cortisol - COR; serotonin - SER; brain-derived neurotrophic factor - BDNF) in youth soccer players. Eighteen players (17.8 ± 0.9 years old, body height 181.6 ± 6.9 cm, training experience 9.7 ± 1.7 years) were blood-tested four times: at the start of the preparation period (T0), immediately following the preparation period (T1), mid-competitive period (T2), and at the end of the competitive period (T3). CK activity as well as concentrations of serum COR, SER and BDNF were determined. Training loads were recorded using a session rating of perceived exertion (sRPE). Statistical analyzes revealed significant effects for all biochemical parameters in relation to their time measurements (T0, T1, T2, T3). The statistical analyzes of sRPE and differences of biochemical parameters in their subsequent measurements (T0-T1, T1-T2, T2-T3) also demonstrated significant effects observed for all variables: sRPE (HKW = 13.189 (df = 2); p = 0.00), COR (HKW = 9.261 (df = 2); p = 0.01), CK (HKW = 12.492 (df = 2); p = 0.00), SER (HKW = 7.781 (df = 2); p = 0.02) and BDNF (HKW = 15.160 (df = 2); p < 0.001). In conclusion, it should be stated that the most demanding training loads applied in the preparation period (highest sRPE values) resulted in a significant increase in all analyzed biochemical training stress indicators. The reduction in the training loads during a competitive period and the addition of recovery training sessions resulted in a systematic decrease in the values of the measured biochemical indicators. The results of the study showed that both subjective and objective markers, including training loads, are useful in monitoring training stress in youth soccer players.
#2 Participation of Soccer Training Improves Lower Limb Coordination and Decreases Motor Lateralization
Reference: Biomed Res Int. 2022 Apr 30;2022:7525262. doi: 10.1155/2022/7525262. eCollection 2022.
Authors: Selcuk Akpinar
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9078790/pdf/BMRI2022-7525262.pdf
Summary: Athletes, who display less lateralization, are considered to be more successful in their sports. Therefore, it is important to test the lateralization profiles of the athletes to determine future prospects. Soccer is one of the sports where lateralization plays an important role because performing the passes and kicks with either foot may increase the success rate. Improved lower limb coordination is also very essential to perform the soccer skills more efficiently. Thus, the purpose of this study was to investigate the motor lateralization profiles of youth soccer players and to compare the same lateralization to non-athletes. A total of 28 healthy youth (14 soccer players) aged between 14 and 16 years voluntarily participated in this study. All participants were right-footed and were asked to hit the targets with their either foot maintaining accuracy in a custom-made virtual reality interface. Final position error (FPE) and foot path deviation from linearity (FPDL) were calculated to test motor lateralization for each foot and group. Two-way Mixed Model ANOVA was conducted for each dependent variable. Results indicated significant differences for FPDL between groups, while there were no significant differences between groups and within feet for FPE. Nonathletes had significantly higher FPDL with their nondominant foot compared to their dominant foot, which was not observed among soccer players. Overall, nonathletes' movements were more curvature path compared to soccer players, thus, can be considered as less coordinated. As soccer players did not show a difference between their feet on FPDL and performed better than nonathletes, soccer participation can improve lower limb coordination as well as alter motor performance and lateralization.
#3 Physical characteristics of elite youth male football players aged 13-15 are based upon biological maturity
Reference: PeerJ. 2022 May 5;10:e13282. doi: 10.7717/peerj.13282. eCollection 2022.
Authors: Shidong Yang, Haichun Chen
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9080430/pdf/peerj-10-13282.pdf
Summary: Older and more mature football players have been reported to gain advantages in the selection process during adolescence. The aim of this study was to investigate the influence of skeletal age (SA) on the physical characteristics of elite male football players aged 13-15 years through a cross-sectional study. We enrolled 167 elite players aged 13-15 from three academic football schools in China, and measured height, body mass, thigh circumference, skinfold (triceps and calf), 10 m/30-m sprint, T-tests (left and right), 5 × 25-m repeated-sprint ability (5 × 25 RSA), standing long jump, and YoYo intermittent recovery test level 1 (YYIR1). Subjects were divided into early-, average-, and late-maturity levels according to their SA and chronological age (CA) based on the following criteria: SA-CA > +1 year, SA-CA = ±1 year, and SA-CA < -1 year, respectively. The differences in parameters among the groups were analyzed using one-way analysis of variance and Bonferroni's post-hoc test, with statistical significance set at p < 0.05. Relative to the late-maturing players, the early- and average-maturing players aged 13-15 years were taller, heavier, had a larger thigh circumference, and scored higher on the standing long jump, 30 m sprint, and 5 × 25-RSA (p < 0.05). The physical (except for body-fat percentage) and athletic characteristics of players aged 13-15 were not only significantly influenced by biological maturity, but also increased significantly with CA. The influence of biological maturity on height, 30-m sprints, and 5 × 25-m RSA diminished with age and exerted no significant effect on body-fat percentage and on YYIR1. Late-maturing players exhibited the greatest increase in physical (except for body-fat percentage) and athletic performance (except for the 10-m sprint) compared to players of early and/or average maturity. Although early-maturing players aged 13-15 possessed better anthropometric and physical performance than late- and average-maturing players, the growth and development of physical function of late- and average-maturing players was significantly greater, particularly with respect to height, sprint speed, and muscular power.
#4 Is there a relationship between in-season injury risk and Y balance or vertical jump in elite youth soccer players?
Reference: FASEB J. 2022 May;36 Suppl 1. doi: 10.1096/fasebj.2022.36.S1.L7500.
Authors: Kristin Haraldsdottir, Michael Baer, Stacey Brickson, Andrew Watson
Summary: Injuries are relatively common among elite youth soccer players, and time lost participating in sport due to injury can have detrimental psychological effects on players. The purpose of this study was to determine whether the Y Balance Test (YBT), or vertical jump can identify those players at risk of suffering injury. 41 female elite soccer players (age 12-17) performed YBT and vertical jump testing prior to the competitive season. Time-loss injuries during the following season were recorded. Injured and uninjured athletes were compared with respect to YBT composite scores (absolute and relative to leg length), asymmetry, and vertical jump. Logistic regressions were performed to examine the relationships between YBT, vertical jump, and injury risk. Twelve athletes (29%) suffered a time-loss injury during the season. Athletes who suffered an in-season injury did not differ from uninjured athletes with respect to age (14.9 +/- 1.6 v 15.3 +/- 1.4 years, respectively), years of experience (9.7 +/- 1.7 v 10.2 +/- 2.4 years, p=0.26), YBT composite scores (111 +/- 16 v 109 +/- 17 cm, p=0.99), YBT composite scores relative to leg length (1.29 +/- 0.2 v 1.27 +/- 0.26, p=0.85), the difference in centimeters between composite scores of each leg (7.9+/-8.4 v 4.6+/-3.8, p=0.09) or vertical jump (15.3±1.6 v 15.3±2.6 in, p=0.96). In-season injuries were not significantly associated with YBT composite scores (OR= 0.99 [95% CI = .95-1.04] ,p= 0.80), relative YBT composite scores (1.0 [.97-1.03], p=0.98) or vertical jump scores (0.98 [.72-1.33], p=.91). Although not reaching statistical significance, higher asymmetry in composite scores showed some evidence of an increased risk of subsequent injury (1.2 [0.97-1.42], p=0.10). The composite YBT score and vertical jump did not predict in-season injury incidence in this sample of elite female adolescent soccer players. Higher YBT asymmetry may be associated with an increased risk of in-season injury, although this study may have been limited by sample size to identify a statistically significant difference. Although the YBT is widely used as an injury risk screening tool, our findings suggest that it may not be a strong predictor of subsequent time-loss injuries in elite female adolescent soccer players.
#5 Traumatic rupture of the midportion of the interosseous membrane: a rare cause of acute lower leg pain in two soccer players kicked in the anterior shin
Reference: Skeletal Radiol. 2022 May 18. doi: 10.1007/s00256-022-04071-z. Online ahead of print.
Authors: Mark S Collins, Taylor J North, Jacob L Sellon
Summary: The interosseous membrane (IOM) of the leg is a component of the tibiofibular syndesmosis that serves an important role in stabilization, as well as transferring forces to the fibula during weight-bearing. We present two separate cases of acute traumatic rupture of the midportion of the interosseous membrane in high school soccer players with blunt trauma to the anterior shin with MRI and ultrasound confirmation.
#6 Serum neurofilament light in professional soccer players: goal on safety
Reference: Neurol Sci. 2022 May 18. doi: 10.1007/s10072-022-06109-5. Online ahead of print.
Authors: Claudio Cornali, Paolo Amaddeo, Alberto Benussi, Federica Perrone, Marta Manes, Roberta Zanardini, Luisa Benussi, Francesco Belotti, Gianandrea Bellini, Andrea Bruzzone, Marco Bruzzone, Daniela Morelli, Silvana Archetti, Nicola Latronico, Alessandro Padovani, Marco Maria Fontanella, Roberta Ghidoni, Barbara Borroni
Summary: Sports-related concussion (SRC) is a subset of mild traumatic brain injuries occurring in contact sports. Most people recover spontaneously, but in retired professional players, the risk for neurodegenerative diseases is increased. A biomarker, such as neurofilament light chains (NfL), would help to address this issue and demonstrate sports' safety. Assessing NfL in professional soccer players may be the best way to investigate if repetitive head-impact exposure in the typical lower and asymptomatic range is harmful. The aim was to evaluate whether the NfL in serum is a sensitive biomarker to detect mild brain injury in professional soccer players. Thirty-six soccer players belonging to a professional Italian team underwent serum NfL assessment using ultrasensitive single-molecule array technology. Sixteen healthy nonathletic controls were also enrolled. Differences between groups and changes over time, considering pre-season vs. season, were considered. Serum NfL concentrations were comparable in the soccer professional players (median [interquartile range], 6.44 pg/mL [4.60-8.27] and controls (6.50 pg/mL [5.26-7.04]), with a median difference of - 0.06 pg/mL (95% CI -1.36 to 1.18), p = 0.957. No significant differences according to players' role (goalkeeper, defender, midfielder or forward) or according to timing of sampling (pre-season vs. season) were found. These results suggest that professional soccer, even when played at the highest level of competition, may be considered safe. Future studies assessing serum NfL levels after soccer-related concussions should be carried out, to evaluate their usefulness as a return-to-play marker avoiding second impact syndrome.
#7 Patellar fracture among elite-level European soccer players: 4-year case-control cohort analysis of return to play, re-injury, and player performance
Reference: Phys Sportsmed. 2022 May 20;1-10. doi: 10.1080/00913847.2022.2077087. Online ahead of print.
Authors: Sumit Patel, Ophelie Lavoie-Gagne, Nabil Mehta, Ghassan Farah, Avinaash Korrapati, Brian Forsythe
Summary: There is a paucity of literature investigating the relationship between patellar fracture and player performance of professional soccer players following return to play (RTP). Our goal is to determine the rate of RTP, time to RTP, and effect on player performance following patellar fracture. Twenty-one elite-level European professional soccer players who sustained a patellar fracture between 1999 and 2018 were identified via a publicly accessible database. Athletes with patellar fracture were matched to controls by age, height, years played in the league, season of injury, and position. Change in performance metrics between one season prior to injury and the following four seasons after injury were compared. Players with patellar fracture were absent for a mean 207.95 ± 135.55 days and 16.81 ± 31.79 games. Fifteen (71%) players returned to play after injury with 67% returning within 1 season after injury. Injured players did not demonstrate significant change in performance metrics at any of the follow-up timepoints compared to control. Subgroup analysis showed that attackers recorded approximately 1200 fewer minutes played per season than pre-injury levels 2 seasons following injury, significantly fewer (p < 0.05) than the control cohort recording similar minutes per season throughout the study period. Midfielders and defenders demonstrated similar fluctuations in performance to the control cohort for both field time and performance metrics (p > 0.05). Seventy-one percent of players RTP after patellar fracture with an associated absence of 7 months and 17 missed games. Overall, injured players did not demonstrate a significant decline in performance as demonstrated by games played, total minutes played per season, minutes per game, assists, and goals 1 season after injury. Attackers played fewer minutes during the season of and 2 seasons after the initial injury.
#8 Fecal microbiota monitoring in elite soccer players along the 2019-2020 competitive season
Reference: Int J Sports Med. 2022 May 20. doi: 10.1055/a-1858-1810.
Authors: Elisa Viciani, Monica Barone, Tindaro Bongiovanni, Sara Quercia, Roberta Di Gesu, Giulio Pasta, Paolo Manetti, F Marcello Iaia, Athos Trecroci, Simone Rampelli, Marco Candela, Elena Biagi, Andrea Castagnetti
Summary: Physical exercise affects the human gut microbiota that, in turn, influences athletes' performance. The current understanding of how the microbiota of professional athletes changes along with different phases of training is sparse. We aim to characterize the fecal microbiota in elite soccer players along with different phases of a competitive season using 16S rRNA gene sequencing. Fecal samples were collected after the summer off-season period, the pre-season retreat, the first half of the competitive season, and the 8 weeks COVID-19 lockdown that interrupted the season 2019-2020. According to our results, the gut microbiota of professional athletes changes along with the phases of the season, characterized by different training, diet, nutritional surveillance, and environment sharing. Pre-season retreat, during which nutritional surveillance and exercise intensity were at their peak, caused a decrease in bacterial groups related to unhealthy lifestyle and an increase in health-promoting symbionts. The competitive season and forced interruption affected other features of the athletes' microbiota, i.e. bacterial groups that respond to dietary fibers load and stress levels. Our longitudinal study, focusing on one of the most followed sports worldwide, provides baseline data for future comparisons and microbiome-targeting interventions aimed at developing personalized training and nutrition plans for performances maximization.
#9 Comparison of the Agonist/Antagonist Tensional Balance of the Knee between Two Isokinetic Positions: A Pilot Study on a Sample of High-Level Competitive Soccer Players
Reference: Int J Environ Res Public Health. 2022 Apr 28;19(9):5397. doi: 10.3390/ijerph19095397.
Authors: Jorge García-Pastor, Ildefonso Alvear-Ordenes, Diego Arias-Giráldez, María Mercedes Reguera-García, Beatriz Alonso-Cortés
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9099487/pdf/ijerph-19-05397.pdf
Summary: Isokinetic knee dynamometry evolves towards more precise techniques, such as the calculation of the functional ratio. This study evaluated the influence of an intermediate hip position called the unified reclined position (URP) compared to the classic sitting position, (CSP) on hamstring eccentric PT values (Hexc30) and conventional (Hcon60/Qcon60) and functional (Hexc30/Qcon60) ratios. Twenty Spanish high-level competitive soccer players (20.4 ± 4.44 years) were evaluated in CSP and in URP. The hip angle in URP (44°) was determined with a passive extensibility test (quadriceps and hamstrings), looking for an agonist/antagonist tension balance. The following were performed: three repetitions (60°/s) and five repetitions (240°/s) in concentric quadriceps and hamstrings mode; and three repetitions (30°/s) in concentric and eccentric for the hamstrings. At 30°/s, the CSP presents higher values of maximal eccentric hamstring strength than URP, (Dom + N-Dom leg (Nm): CSP = 148.3 ± 19.5 vs. URP 143.5 ± 23.2); p = 0.086 (n.s.). The conventional relationship did not show data justifying the preference for URP over CSP (p = 0.86 (n.s.)). However, although the functional index did not show significant values (p = 0.97 (n.s.), it did show a greater number of subjects with imbalances measured in URP (five in URP vs. two in CSP). An assessment angle of the hip closer to sports reality seems to favor the use of the URP as a complementary method to the CSP. These data stimulate new studies using URP together with the classic protocol.
#10 Correlation between the Positive Effect of Vitamin D Supplementation and Physical Performance in Young Male Soccer Players
Reference: Int J Environ Res Public Health. 2022 Apr 23;19(9):5138. doi: 10.3390/ijerph19095138.
Authors: Michał Brzeziański, Monika Migdalska-Sęk , Aleksandra Czechowska, Łukasz Radzimiński, Zbigniew Jastrzębski, Ewa Brzeziańska-Lasota, Ewa Sewerynek
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9101676/pdf/ijerph-19-05138.pdf
Summary: The aim of this study was to determine whether supplementation with vitamin D during eight weeks of high-intensity training influences muscle power and aerobic performance in young soccer players. A total of 25 athletes were divided into two groups: the supplemented group (GS; n = 12; vitamin D 20,000 IU, twice a week) and the non-supplemented group (GN; n = 13). A set of measurements, including sprint tests, explosive power test, maximal oxygen uptake (VO2max), and serum 25(OH)D concentration, were obtained before (T1) and after (T2) the intervention. A significant group x time interaction was found in the 25(OH)D serum levels (p = 0.002; ES = 0.36, large). A significant improvement in VO2max was found in the TG (p = 0.0004) and the GS (p = 0.031). Moreover, a positive correlation between 25(OH)D and VO2max (R = 0.4192, p = 0.0024) was calculated. The explosive power tests revealed insignificant time interactions in the average 10-jump height and average 10-jump power (p = 0.07, ES = 0.13; p = 0.10, ES = 0.11, respectively). A statistically insignificant trend was observed only in the group-by-time interaction for the sprint of 10 m (p = 0.05; ES = 0.15, large). The present study provides evidence that vitamin D supplementation has a positive but trivial impact on the explosive power and locomotor skills of young soccer players, but could significantly affect their aerobic performance.
#11 Effect of the COVID-19 Confinement Period on Selected Neuromuscular Performance Indicators in Young Male Soccer Players: Can the Maturation Process Counter the Negative Effect of Detraining?
Reference: Int J Environ Res Public Health. 2022 Apr 19;19(9):4935. doi: 10.3390/ijerph19094935.
Authors: Nikolaos D Asimakidis, Stylianos S Vasileiou, Athanasios A Dalamitros, Pantelis T Nikolaidis, Vasiliki Manou
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9105184/pdf/ijerph-19-04935.pdf
Summary: The COVID-19 outbreak has led to an unprecedented long-term cessation in athletes' training routines. This study examined the effect of a 32-week detraining period, caused by the COVID-19 pandemic lockdown, on selected neuromuscular performance indicators in 29 young male soccer players, assessed close to their adolescent growth spurt (age = 13.0 ± 0.8 years). Change of direction ability of both lower limbs (COD), linear sprint times (10 and 20 m), and vertical jump height (CMJ) was evaluated twice, once before the first national lockdown, and one week after the return to training activities. Paired-sample t-tests detected significant improvements in all three testing variables (COD: 2.82 ± 0.23 vs. 2.66 ± 0.22 s, p ≤ 0.005, 0.001, effect size [ES] = 0.91 to 1.05 for the right and left limb, respectively; 10 m: 2.12 ± 0.16 vs. 1.96 ± 0.15 s, p ≤ 0.001, effect size [ES] = 1.67, 20 m: 3.56 ± 0.3 vs. 3.42 ± 0.27 s, p ≤ 0.001, effect size [ES] = 1.02 and CMJ: 23.3 ± 7.5 vs. 24.5 ± 7.6 cm, p = 0.033, ES = 0.42). These results indicate that maturation-related adaptations can lead to enhanced change of direction, linear sprint, and vertical jump performance, even in the absence of exposure to any level of exercise. Soccer coaches and practitioners working with youth athletes should consider the stage of maturation when planning and implementing training programs aiming to enhance neuromuscular performance.
#12 Analysis of a double Poisson model for predicting football results in Euro 2020
Reference: PLoS One. 2022 May 19;17(5):e0268511. doi: 10.1371/journal.pone.0268511. eCollection 2022.
Authors: Matthew J Penn, Christl A Donnelly
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9119507/pdf/pone.0268511.pdf
Summary: First developed in 1982, the double Poisson model, where goals scored by each team are assumed to be Poisson distributed with a mean depending on attacking and defensive strengths, remains a popular choice for predicting football scores, despite the multitude of newer methods that have been developed. This paper examines the pre-tournament predictions made using this model for the Euro 2020 football tournament. These predictions won the Royal Statistical Society's prediction competition, demonstrating that even this simple model can produce high-quality results. Moreover, the paper also presents a range of novel analytic results which exactly quantify the conditions for the existence and uniqueness of the solution to the equations for the model parameters. After deriving these results, it provides a novel examination of a potential problem with the model-the over-weighting of the results of weaker teams-and illustrates the effectiveness of ignoring results against the weakest opposition. It also compares the predictions with the actual results of Euro 2020, showing that they were extremely accurate in predicting the number of goals scored. Finally, it considers the choice of start date for the dataset, and illustrates that the choice made by the authors (which was to start the dataset just after the previous major international tournament) was close to optimal, at least in this case. The findings of this study give a better understanding of the mathematical behaviour of the double Poisson model and provide evidence for its effectiveness as a match prediction tool.
#13 Comparison of the risk of cardiovascular diseases, stroke, and diabetes among the selected group of football referees and the group of general population men from Northern Poland - a pilot study
Reference: Eur Rev Med Pharmacol Sci. 2022 May;26(9):3151-3160. doi: 10.26355/eurrev_202205_28732.
Authors: J Wesołowska, A Jurczak, S Wieder-Huszla, K Jarosz, A Jurewicz, M Marchlewicz
Summary: We aimed at comparing the total body fat and visceral adipose tissue content in football referees and in the control group of general population men. An assessment of compliance with health promoting behavior in both groups was carried out. This study, conducted in Northern Poland, involved 112 men. The study group comprised 56 men, football referees. The control group consisted of randomly chosen general population men, not engaged in any sport activities. Assessment of compliance with health promoting behavior among football referees and general population men was based on ultrasound imaging using the BodyMetrix System device (IntelaMetrix, Poland). The study employed a survey questionnaire comprised of the original section and two standardized questionnaires: the Health Behavior Inventory (HBI) and the NEO-Five Factor Inventory (NEO-FFI): the Health Behavior Inventory (HBI) and the NEO-Five Factor Inventory (NEO-FFI). The visceral adipose tissue content in the study group (football referees) was found to be low, and the excess of body fat was 0-0.25 kg. In the control group, the trunk fat volume was found to be higher by more than 8% as compared with the study group. Also, the level of visceral adipose tissue was high, and the excess of body fat was 0-4 kg. Thanks to properly planned and systematically continued physical activity, despite non-compliance with certain pro-health principles (increased sweet supply and consumption of alcoholic beverages), football referees are characterized by the correct body fat volume and low level of visceral adipose tissue. The parameters were found to be markedly higher in the control group of randomly selected men from the general population. The risk of diabetes, stroke, and cardiovascular diseases among football referees was found to be very low.
#14 A Systematic Review of Head Impacts and Acceleration Associated with Soccer
Reference: Int J Environ Res Public Health. 2022 May 1;19(9):5488. doi: 10.3390/ijerph19095488.
Authors: Ioannis Basinas, Damien M McElvenny, Neil Pearce, Valentina Gallo, John W Cherrie
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9100160/pdf/ijerph-19-05488.pdf
Summary: Epidemiological studies of the neurological health of former professional soccer players are being undertaken to identify whether heading the ball is a risk factor for disease or premature death. A quantitative estimate of exposure to repeated sub-concussive head impacts would provide an opportunity to investigate possible exposure-response relationships. However, it is unclear how to formulate an appropriate exposure metric within the context of epidemiological studies. We have carried out a systematic review of the scientific literature to identify the factors that determine the magnitude of head impact acceleration during experiments and from observations during playing or training for soccer, up to the end of November 2021. Data were extracted from 33 experimental and 27 observational studies from male and female amateur players including both adults and children. There was a high correlation between peak linear and angular accelerations in the observational studies (p < 0.001) although the correlation was lower for the experimental data. We chose to rely on an analysis of maximum or peak linear acceleration for this review. Differences in measurement methodology were identified as important determinants of measured acceleration, and we concluded that only data from accelerometers fixed to the head provided reliable information about the magnitude of head acceleration from soccer-related impacts. Exposures differed between men and women and between children and adults, with women on average experiencing higher acceleration but less frequent impacts. Playing position appears to have some influence on the number of heading impacts but less so on the magnitude of the head acceleration. Head-to-head collisions result in high levels of exposure and thus probably risk causing a concussion. We concluded, in the absence of evidence to the contrary, that estimates of the cumulative number of heading impacts over a playing career should be used as the main exposure metric in epidemiological studies of professional players.
#15 Nature Scenes Counter Mental Fatigue-Induced Performance Decrements in Soccer Decision-Making
Reference: Front Psychol. 2022 Apr 29;13:877844. doi: 10.3389/fpsyg.2022.877844. eCollection 2022.
Authors: He Sun, Kim Geok Soh, Xiaowei Xu
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9105021/pdf/fpsyg-13-877844.pdf
Summary: It has been well investigated that nature exposure intervention can restore directed attention and improve subsequent cognitive performance. The impairment of decision-making skills in mentally fatigued soccer players was attributed to the inability of attention allocation. However, nature exposure as the potential intervention to counter mental fatigue and improve the subsequent decision-making skill in soccer players has never been investigated. This study aimed to evaluate the effects of nature exposure intervention on decision-making skills among mentally fatigued university soccer players. Moreover, different durations of nature exposure were also evaluated. A random control between-subject design was adopted. Players were randomly assigned into six groups with three different durations of the experimental group compared with the corresponding control group (4.17 min: Exp 1 vs. Con 1; 8.33 min: Exp 2 vs. Con 2; and 12.50 min: Exp 3 vs. Con 3). All players were first mentally fatigued by performing a 45-min Stroop task; then, they viewed virtual photos of natural or urban scenes; and finally, they performed a soccer decision-making task. The subjective ratings of mental fatigue were significantly higher following the Stroop task. Only Exp 3 (12.50 min viewing natural scenes) significantly improved decision-making reaction time compared with Con 3 (p = 0.09). Moreover, the accuracy slightly increased in Exp 3 after the intervention. In line with attention restoration theory, nature exposure significantly improved decision-making skills in mentally fatigue university players. However, the duration must be 12.50 min for each stimulus to stay longer to attract involuntary attention.
#16 Peak instantaneous PlayerLoad metrics highlight movement strategy deficits in professional male soccer players
Reference: Res Sports Med. 2022 May 20;1-11. doi: 10.1080/15438627.2022.2079985. Online ahead of print.
Authors: Andy Mitchell, Matt Greig
Summary: The aim was to investigate the influence of task, limb dominance and previous injury on single leg hop task performance and loading response, 25 professional male soccer players completed anterior, medial and lateral hop tests with an accelerometer at mid-calf. Performance outcome was defined as hop distance with loading response defined as the magnitude of, and time to peak instantaneous planar PlayerLoad. The performance was sensitive to task and previous injury (P < 0.001) but not limb dominance, with no evidence of bilateral asymmetry (P = 0.668). Despite impaired performance, previously injured players did not exhibit lower peak instantaneous PlayerLoad after impact in any plane (P ≥ 0.110). There was however a significantly (P = 0.001) longer time to peak medio-lateral loading after impact in previously injured players' affected limb. This observation was exacerbated when the injury was to the non-dominant limb (P = 0.041). Lower-limb accelerometry enhances understanding of movement strategy beyond task outcome, with practical implications in player screening and objective rehabilitation.
#17 Growth, body composition and bone mineral density among pubertal male athletes: intra-individual 12-month changes and comparisons between soccer players and swimmers
Reference: BMC Pediatr. 2022 May 13;22(1):275. doi: 10.1186/s12887-022-03321-2.
Authors: Daniela C Costa, João Valente-Dos-Santos, Paulo Sousa-E-Silva, Diogo V Martinho, João P Duarte, Oscar M Tavares, Joaquim M Castanheira, Tomás G Oliveira, Sandra Abreu, Neiva Leite, Ricardo R Agostinete, Rômulo A Fernandes, Daniel Courteix, Manuel J Coelho-E-Silva
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9102354/pdf/12887_2022_Article_3321.pdf
Summary: Puberty is a period of intense changes in human body and, additionally, participation in sports is viewed as prominent form of physical activity among male adolescent athletes. The current study was aimed to examine the intra-individual changes in body composition and bone tissue during years of maximal growth and the effect of 12-month participation in sports contrasting in mechanical impact. The sample included 40 male adolescent athletes (soccer: n = 20; swimming: n = 20) aged 12.57 ± 0.37 years who were followed for 12 months. Stature and body mass were measured, bone mineral content (BMC), areal bone mineral density (aBMD), lean soft and fat tissues assessed using DXA. Food intake was estimated using a questionnaires and training sessions individually monitored. Repeated measures ANOVA tested the differences between sports and 12-month intra-individual variation (time moments: TM1, TM2). The analyses on aBMD for total body and total body less head were repeated controlling for variation in stature at baseline. Soccer players completed 63 ± 31 sessions (95 ± 47 h). Respective values for swimmers were 248 ± 28 sessions and 390 ± 56 h. In general, the analysis of aBMD as dependent variable evidenced significant effect of sport-associated variation (F = 5.254, p < 0.01; η2 = 0.35) and 12-month increments, particularly at lower limbs (F = 97.238, p < 0.01; η2 = 0.85). Respective mean values for aBMD were SCCTM1 = 0.885 g.cm-2, SWMTM1 = 0.847 g.cm-2, SCCTM2 = 0.939 g.cm-2, SWMTM2 = 0.880. Regarding the lean soft tissue, the magnitude of effects was very large for intra-individual variation (F = 223.043, p < 0.01; η2 = 0.92) and moderate between sports (F = 7.850, p < 0.01; η2 = 0.41): SCCTM1 = 30.6 kg, SWMTM1 = 34.9 kg, SCCTM2 = 35.8 kg, SWMTM2 = 40.5 kg). Finally, d-cohen values reporting percentage of intra-individual changes in aBMD between soccer players ad swimmers were large for the trochanter (d = 1.2; annual increments: SCC = 8.1%, SWM = 3.6%). Puberty appeared as a period of significant intra-individual changes in lean soft tissue and bone mineral density. With increasing accumulated training experience, mean difference between sports contrasting in mechanical impact tended to me more pronounced in particular at the lower limbs.
#18 Muscle Glycogen in Elite Soccer - A Perspective on the Implication for Performance, Fatigue, and Recovery
Reference: Front Sports Act Living. 2022 Apr 25;4:876534. doi: 10.3389/fspor.2022.876534. eCollection 2022.
Authors: Magni Mohr, Jeppe F Vigh-Larsen, Peter Krustrup
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9106100/pdf/fspor-04-876534.pdf
Summary: Based on extrapolation of current trends in modern soccer, physiological loading has increased markedly, and the game will continue to become even more demanding in the future, which will exacerbate fatigue at the end of a game and between games. Soccer is a glycogen consuming activity due to its high-intensity intermittent nature, and muscle glycogen is a key factor associated with fatigue late in a game, as well as in determining recovery after a game or an intense training session. Low glycogen in individual muscle fibers and subcellular compartments in the muscle cell is likely to negatively affect several essential steps in the excitation-contraction coupling such as action potential propagation, calcium handling and cross-bridge cycling through reductions in muscle ATP which are suggested sites of muscle function impairment inducing muscle fatigue. Recovery of physical performance and muscle glycogen after a soccer game is a slow process, which challenges the reality in modern elite soccer with increased game and training frequency and physiological loading. We suggest a markedly higher prioritization of fitness training modalities, nutritional approaches and general recovery strategies that optimizes muscle glycogen storage prior to games and training sessions. Also, the soccer community including the governing bodies of the sport must acknowledge and plan according to the high and increasing demands of the modern game, as well as the consequences this has on fatigue and recovery. These aspects are paramount to consider in the planning of training and games, as well as in the process of structuring soccer tournaments and developing competitive regulations in the future to optimize performance and player health.
#19 The influence of maturation, fitness, and hormonal indices on minutes played in elite youth soccer players: a cross-sectional study
Reference: BMC Sports Sci Med Rehabil. 2022 May 17;14(1):89. doi: 10.1186/s13102-022-00480-8.
Authors: Ebrahim Eskandarifard, Hadi Nobari, Filipe Manuel Clemente, Rui Silva, Cain C T Clark, Hugo Sarmento, António José Figueiredo
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC9115988/pdf/13102_2022_Article_480.pdf
Summary: The main purpose of this study was to investigate the relationships between minutes played (MP) with maturity status, fitness, and hormonal levels, and to quantify their influence on minutes played. Twenty-four elite youth soccer players under-16 years participated in this study, over a full-season period. Anthropometric measures, maturity status, hormonal and physical fitness levels were collected. Participants were monitored during the season. After the end-season, players were assessed in 6 different tests over a four-day period. The maximum oxygen consumption (V̇O2max) was strongly correlated with MP (r = 0.75), maturity offset (r = 0.52), and countermovement jump (r = 0.53). Multiple linear regression explained 76% of MP (F (8, 15) = 6.05, p = 0.001), with an R2 of 0.76. Moreover, Growth hormone (GH) and V̇O2max. were the most influential factors in MP (F (2, 21) = 17.92, p ≤ 0.001), with an R2 of 0.63. High levels of GH and V̇O2max have a preponderant role in MP by elite youth soccer players, it appears to be more pragmatic to consider other contextual dimensions, as they can impact selection for competition and minutes of participation in a match.