Latest research in football - week 48 - 2022

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 Associations of Masticatory Muscles Asymmetry and Oral Health with Postural Control and Leg Injuries of Elite Junior Soccer Players

Reference: J Hum Kinet. 2022 Nov 8;84:21-31. doi: 10.2478/hukin-2022-0086. eCollection 2022 Oct.

Authors: Henny Solleveld, Bram Slaets, Arnold Goedhart, Luc VandenBossche

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Summary: The influence of asymmetry between masticatory muscles on postural control is still under debate and only few studies examined the impact of oral health on injury risk. The present study investigated the relationships between masticatory muscles asymmetry, oral health, postural control and the prevalence of (non-contact or traumatic) leg injuries in a sample of 144 male elite junior soccer players. sEMG of the masseter and temporal muscles was performed during maximum teeth clenching, postural control was tested by measuring sway velocity during the unipedal stance with eyes closed, while oral health and the number of leg injuries were assessed using a questionnaire. The time-1 assessment was repeated in a subgroup of 69 players after one year. Pearson and partial correlation coefficients and adjusted odds ratios (OR) were used to assess associations. Asymmetry between the masseter and temporalis muscles (AMTM, quantified as anteroposterior coefficient, APC) was associated with higher sway velocity on the dominant leg (using time-1 data partial r = -0.24, p = 0.004, using longitudinal data partial r = -0.40, p = 0.005). Higher prevalence of two or more leg injuries throughout a competitive season was associated with poor oral health (adjusted OR (95%CI) using time-1 data = 2.14 (1.02-4.46), using longitudinal data = 4.47 (1.25-15.96)). These results indicate that AMTM has a negative influence on the sway velocity of the dominant leg only, possibly because frequent balancing exercises on the non-dominant leg may counteract negative influences of AMTM. The association of oral health with leg injuries underlines the need for oral health promotion and monitoring strategies in sports.



#2 Neuromuscular characteristics of agonists and antagonists during maximal eccentric knee flexion in soccer players with a history of hamstring muscle injuries

Reference: PLoS One. 2022 Dec 1;17(12):e0277949. doi: 10.1371/journal.pone.0277949. eCollection 2022.

Authors: Ramona Ritzmann, Sarah Strütt, Ignacio Torreno, Janine Riesterer, Christoph Centner, Luis Suarez-Arrones

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Summary: Muscle strain injuries (MSIs) in the hamstrings are among the most prevalent injuries in elite soccer. We aimed to examine the relation between biomechanical maladaptation in eccentric strength and neuromuscular factors separated by their time and frequency domains. 20 elite soccer players with a previous history of unilateral MSI in the M. biceps femoris (BF) long head and 20 without MSI participated. Knee flexion torques, rate of torque development (RTD) and electromyographic signals (EMG) of the BF, the M. semitendinosus (SMT) and knee extensors were obtained during unilateral maximal eccentric knee flexions performed at slow (30°/s) and fast (120°/s) angular speeds. Root mean squares and mean power frequency (MF) was calculated. In the group with a history of MSI, reduced maximal eccentric flexion torque (slow eccentrics -8±11, p<0.05; fast eccentrics -18±13 N*m, p<0.05) and RTD (-33±28 N*m/s, p<0.05; -95±47 N*m/s, p<0.05) concomitantly occurred with diminished agonistic myoelectrical activities (-4±5% of MVC, p<0.05; -10±7% of MVC, p<0.05) and MFs (-24±13 Hz, p<0.05; -24±18 Hz, p<0.05) in the BF. Simultaneously, antagonistic myoelectric activity was elevated (+4±3% of MVC, p<0.05; +3±3% of MVC, p<0.05) in MSI affected legs as compared to unaffected legs for both eccentric contractions. Deficits in myoelectrical activity (r2 = 0.715, p<0.05; r2 = 0.601, p<0.05) and MF (r2 = 0.484, p<0.05; r2 = 0.622, p<0.05) correlated with deficits in maximal torque in the affected leg in the MSI group. Analysis of SMT demonstrated no significant differences. Positive relationships between neuromuscular deficits and the reduced eccentric strength profile underpin neuronal inhibition after MSI. This persistent involvement of dysfunctional synergist and antagonist neural hamstring function in strength weakness is of clinical relevance in sports medicine for prevention and rehabilitation.



#3 Psychophysiological Responses to a Preseason Training Camp in High-Level Youth Soccer Players

Reference: Int J Sports Physiol Perform. 2022 Dec 1;1-9.  doi: 10.1123/ijspp.2022-0179. Online ahead of print.

Authors: Ludwig Ruf, Stefan Altmann, Sascha Härtel, Sabrina Skorski, Barry Drust, Tim Meyer

Summary: This study aimed to examine the responsiveness of commonly used measurement instruments to a short training camp by examining the time course of psychophysiological responses in high-level youth soccer players. Monitoring was carried out in 14 U15 male soccer players of 1 professional youth academy. Players provided data 3 days prior to (D - 3), during (D2-D4), and 1 (D + 1) and 4 days (D + 4) after the camp: 4 items for the Short Recovery and Stress Scale (SRSS), a countermovement jump (CMJ), and a submaximal run to assess exercise heart rate and heart-rate recovery. Training load during the camp followed an alternating low-high pattern, with lower training loads on D1 and D3 and higher training loads on D2 and D4. Changes in SRSS physical performance capability, emotional balance, overall recovery, muscular stress, and overall stress were small to moderate on D3 and moderate to large on D + 1, while changes were trivial on D + 4. Some CMJ parameters related to the eccentric phase were slightly improved on D3, and these parameters were slightly impaired on D4. Changes in CMJ parameters were trivial on D + 1 and D + 4. After a moderate decrease in exercise heart rate on D3, there was a small decrease on D + 4 and a moderate increase in heart-rate recovery. Measurement instruments such as the SRSS and submaximal runs can be used to monitor acute psychophysiological responses to load, while the CMJ may provide little insight during periods of intensified training load.



#4 Body composition variations between injured and non-injured professional soccer players

Reference: Sci Rep. 2022 Dec 1;12(1):20779. doi: 10.1038/s41598-022-24609-4.

Authors: Francisco Martins, Cíntia França, Ricardo Henriques, Andreas Ihle, Krzysztof Przednowek, Adilson Marques, Hélder Lopes, Hugo Sarmento, Élvio Rúbio Gouveia

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Summary: Professional soccer is characterized by its physical demands, making players' exposure to high injury risks a growing problem. It is crucial to study the factors associated with injuries in professional soccer. This study aimed to investigate the relationship between age, body composition, and others variables related with the injury profile of professional soccer players of a specific Portuguese team. Also, it analyzed the impact of the injury profile on soccer's variations in body fat (BF%), skeletal muscle mass (SMM) and total body water (TBW) throughout the season. The sample comprised 31 male professional soccer players competing in the First Portuguese Soccer League. Older players had a higher prevalence of muscular injuries. Midfielders and forwards showed the highest number of muscular injuries during the season being quadriceps the most affected zone. Considering players' BF% [Wilks' Lambda = 0.42, F (7, 23) = 4.61, p = 0.002, r = 0.58], SMM [Wilks' Lambda = 0.59, F (6, 23) = 2.70, p = 0.039, r = 0.41] and TBW [Wilks' Lambda = 0.54, F (7, 23) = 2.80, p = 0.029, r = 0.46] there was a substantial main effect for the assessments performed throughout the season and the injury status. Age assumes relevance in explaining the injury profile. The impact of the injury profile on soccer's variations in BF%, SMM and TBW throughout the season must be analyzed considering the clinical relevance.



#5 Workloads of Different Soccer-Specific Drills in Professional Players

Reference: J Hum Kinet. 2022 Nov 8;84:135-147. doi: 10.2478/hukin-2022-000075. eCollection 2022 Oct.

Authors: Marcos Chena, José Alfonso Morcillo-Losa, María Luisa Rodríguez-Hernández, Iván Asín-Izquierdo, Beatriz Pastora-Linares, Juan Carlos Zapardiel

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Summary: Soccer is a predominantly tactical sport and, therefore, tactical training has become the most widely used strategy to improve players' performance. The objective of the present study was to assess the workload of soccer-specific drills in professional players over a two-season period in an established context. GPS technology was used to record the data. One hundred and thirty-two (n = 132) soccer-specific drills were studied and grouped by categories. The individual demands of each task were related to the individual competitive profile of each player. The level of physical demand was significantly different in relation to the specific soccer drills analysed. Total distance covered, high-speed running, and the total number of high accelerations and decelerations were significantly higher in competition than in drills used for training sessions (p < .001). The Large-Sided Games (LSG), Big-Position Games (BPG) and Position Games (PG) showed higher maximum running speed values than the rest of the exercises (p < .01). The sum of high accelerations and decelerations values was greater in the Small-Sided Games (SSG) than in BPG (p < .001), Small-Position Games (SPG) (p < .001) and Physical-Technical Circuits (PTC) (p < .001). Significant differences were observed in the exercises analysed according to the player's position. The current findings provide a detailed description of conditional demands placed on soccer players in different soccer-specific drills during training sessions, in a professional soccer context and according to their playing position, which may be helpful in the development of individualized training programs in other contexts.



#6 Differences in the Contractile Properties of the Biceps Femoris and Semitendinosus Muscles Throughout a Season in Professional Soccer Players

Reference: J Hum Kinet. 2022 Nov 8;84:74-81. doi: 10.2478/hukin-2022-0088. eCollection 2022 Oct.

Authors: Daniel Fernández-Baeza, Germán Diaz-Ureña, Cristina González-Millán

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Summary: The aim of this study was to monitor seasonal changes in the mechanical and neuromuscular characteristics of the knee flexor muscles with tensiomyography, the biceps femoris (BF) and semitendinosus (ST) muscles, of 27 soccer players. All male professional soccer players (age 25 ± 4 years) were measured at the beginning of the preseason (second week) and in the competitive season (10 weeks later). The variables contraction time (Tc) and muscle displacement (Dm) showed significant differences in some muscles, and in others they indicated a tendency to change. In general, the BF improved (more explosive and better muscle tone) and the ST worsened (slower and worse muscle tone) its values during the season. The findings of this study suggest that usual daily soccer training and weekly competition might produce antagonistic changes between the knee flexor muscles.



#7 Evaluation of the impact of hot environmental conditions on physical activity among soccer players

Reference: Eur Rev Med Pharmacol Sci. 2022 Nov;26(22):8216-8223. doi: 10.26355/eurrev_202211_30353.

Authors: W-H Liu, Z-Y Li, Y C Loh

Summary: The aim of the study was to evaluate the effect of a hot environment on several physiological variables of soccer players and suggest feasible solutions to it. The study is of prospective design, considering 66 participants comprising professional soccer players. All the participants completed the Physical Activity Readiness Questionnaire (PARQ). The participants were assigned to 3 different groups. Each group was assigned 22 participants. They were made to play in three different chambers, maintained at cool, moderate and hot temperatures. Players were made to play and various variables were determined to assess the effect of hot temperature on them. Several variables were determined including absolute and relative oxygen uptake, heart rate, minute ventilation, the blood concentration of lactate and time to get exhausted. All the variables of players who played in hot temperatures have revealed higher heart rate, ventilation and increased lactate concentration. Players in a hot environment ran out faster. The study was concluded due to the players' dehydration and physiological deteriorated factors in a hot environment, leading to poor performances and also affecting the players' health in the long run. Further, the study suggested improving the environment around the game venues.



#8 Shuttle Running Within a Small-Sided Game: Effects on Internal and External Workloads, in Young Elite Soccer Players

Reference: Int J Sports Physiol Perform. 2022 Dec 2;1-8. doi: 10.1123/ijspp.2022-0203. Online ahead of print.

Authors: Marco Panascì, Vittoria Ferrando, Ambra Bisio, Luca Filipas, Piero Ruggeri, Emanuela Faelli

Summary: The aim was to compare the effects of 2 small-sided games (SSGs), shuttle running within the bout (SSG-S) versus possession play only (SSG-P) on acute physiological and metabolic responses, perception of effort, and performance. Ten young elite male soccer players (age 18.6 [1.9] y) performed two 5vs5 SSG formats (SSG-S and SSG-P) consisting of 4 × 4 minutes with 1 minute of passive recovery between bouts, 2 times each, once a week, and in a randomized order. Heart rate, blood lactate concentration, and rating of perceived exertion were assessed as indices of internal workload. Total and relative distances, distance at moderate and high speed, distances traveled in accelerations (≥2 m·s-2) and decelerations (≤-2 m·s-2; DDEC), and average metabolic power were chosen as indices of external workload and collected with a 10-Hz portable global positioning system device. Total distance, distances traveled in acceleration, distances traveled in deceleration, average metabolic power (always P < .01 and g > 1.62-large effect), and distance at moderate speed (P = .03 and g = 0.84-large effect) were significantly higher in SSG-S than in SSG-P. Moreover, the SSG-S showed higher blood lactate concentration (P = .0001, g = 12.58-large effect) and rating of perceived exertion (P = .03, g = 1.14-large effect) values than SSG-P. No significant differences in peak heart rate, relative distance, and distance at high speed were found. Our study showed, in young competitive male soccer players, the effectiveness of an SSG format that includes shuttle running within each bout in the development of more relevant internal and external workloads. These experimental data should encourage coaches to use this new SSG regimen within the traditional weekly training program.



#9 Effects of speed, agility and quickness training programme on cognitive and physical performance in preadolescent soccer players

Reference: PLoS One. 2022 Dec 1;17(12):e0277683. doi: 10.1371/journal.pone.0277683. eCollection 2022.

Authors: Athos Trecroci, Luca Cavaggioni, Alessio Rossi, Andrea Moriondo, Giampiero Merati, Hadi Nobari, Luca Paolo Ardigò, Damiano Formenti

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Summary: The aim of the present study was to investigate the effect of a short-term (4 weeks) non-soccer-specific training programme based on speed, agility and quickness (SAQ) and a soccer-specific training programme based on small-sided games (SSG) on cognitive and physical performance in preadolescent soccer players. Twenty-one participants were randomly assigned to SAQ group (n = 11) or SSG group (n = 10). They were tested pre and post interventions on physical (5 m sprint, 20 m sprint and sprint with turns of 90°) and cognitive (inhibitory control by means of the Flanker task and perceptual speed by means of the visual search task) performances. Although no significant time x group interactions were observed, the main effect of time was significant for cognitive performance and 5 m and 20 m sprint, showing improvements after both SAQ and SSG. These findings highlight that 4 weeks of SAQ training programme induced comparable improvements in cognitive and physical performance with respect to a soccer-specific training programme based on SSG in preadolescent soccer players. Non-sport-specific activities targeting speed, agility and quickness combined with cognitive engagement (i.e., SAQ) should be useful strategies as soccer-specific activities to be included within a soccer training programme for promoting both physical and cognitive domain in preadolescent individuals.



#10 Dominant and Nondominant Leg Kinematics During Kicking in Young Soccer Players: A Cross-Sectional Study

Reference: Motor Control. 2022 Nov 29;1-11.  doi: 10.1123/mc.2022-0017. Online ahead of print.

Authors: Francesco Frontani, Marco Prenassi, Viviana Paolini, Giovanni Formicola, Sara Marceglia, Francesca Policastro

Summary: The goal of the study is to analyze the kinematics and provide an EMG analysis of the support limb during an instep kick in adolescent players. We set a video camera, two torque transducers on the knee, and EMG sensors. A sample of 16 adolescent soccer players between 10 and 12 years old performed kicks. The kinematics shows a p = .039 on frontal plane (dominant 15.4 ± 1.8, nondominant 18.8 ± 1.7); the EMG analysis shows a p = .04 on muscular activation timing for the vastus medialis. A difference between the legs on the frontal plane emerges. Moreover, a huge difference on sagittal plane between the adolescent pattern and adult pattern exists (15° in adolescent population, 40° in adult population). The result shows a greater activation of the vastus medialis in the nondominant leg; probably, in this immature pattern, the adolescents use this muscle more than necessary.



#11 Quadratus lumborum muscle strain in a youth soccer player: a case report

Reference: Radiol Case Rep. 2022 Nov 24;18(2):499-502. doi: 10.1016/j.radcr.2022.10.084. eCollection 2023 Feb.

Authors: Kota Tanaka, Hiroki Funasaki, Daisuke Kubota, Yusuke Murayama, Mitsuru Saito, Yuta Iguchi

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Summary: We report a case of quadratus lumborum muscle strain that occurred in a 16-year-old soccer player during a game. According to a video recording of the game, the injury occurred when the leg landed just after kicking the ball with the same leg while dribbling. The mechanism was suspected to be right lateral flexion of the trunk while the pelvis was simultaneously forced to tilt backward. The injury healed and he was able to return to competition 3 weeks later. This is the first report of a sports-related quadratus lumborum muscle strain.



#12 The effect of the perceived social support on mental health of Chinese college soccer players during the COVID-19 lockdown: The chain mediating role of athlete burnout and hopelessness

Reference: Front Psychol. 2022 Nov 11;13:1001020. doi: 10.3389/fpsyg.2022.1001020. eCollection 2022.

Authors: Liangyu Zhao, Zongyu Liu, Liguo Zhang

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Summary: The isolation and blockade during the COVID-19 pandemic have a great impact on the mental health of Chinese college soccer players. This study aimed to explore the effect of perceived social support on mental health of college soccer players, as well as the mediating role of athlete burnout and hopelessness during the COVID-19 lockdown. Based on a sample of 674 college soccer players from several universities in China, the study used the Perceived Social Support Scale (PSSS), Kessler Psychological Distress Scale (K10), Athlete Burnout Questionnaire (ABQ) and Beck Hopelessness Scale (BHS). The results indicated that: (1) there was a significant positive correlation between perceived social support and mental health of college soccer players; (2) the athlete burnout played a mediating role between perceived social support and mental health of college soccer players; (3) the hopelessness also played a mediating role between perceived social support and mental health of college soccer players; (4) the athlete burnout and hopelessness played a chain mediating role between perceived social support and mental health. These findings could contribute to insight into the mechanisms by which perceived social support affects the mental health of college soccer players and provide important practical guidance for protecting and promoting their mental health.



#13 Match Loads May Predict Neuromuscular Fatigue and Intermittent-Running Endurance Capacity Decrement after a Soccer Match

Reference: Int J Environ Res Public Health. 2022 Nov 21;19(22):15390. doi: 10.3390/ijerph192215390.

Authors: Diego Marqués-Jiménez, Julio Calleja-González, Iñaki Arratibel-Imaz, Nicolás Terrados

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Summary: How the match-derived load metrics relate to post-match fatigue in soccer is scarcely researched. Thus, the aim of this study was to determine the associations between soccer match-related internal and external loads, neuromuscular performance decrease and intermittent-running endurance capacity decrement immediately post-match. Vertical jump (countermovement jump), straight-line sprinting (10- and 20-m sprint), change of direction ability (T-test) and intermittent-running endurance capacity (YO-YO intermittent recovery level 2) were measured one day before and immediately after a friendly match in male soccer players. During the match, players' internal and external loads were also monitored, including heart rate-derived indices, total distance at various speed thresholds, average running velocity, maximal running velocity, number of sprints and number of accelerations and decelerations at various intensity thresholds. The results show that match-induced fatigue was reflected on neuromuscular performance and intermittent-running endurance capacity immediately post-match (p &lt; 0.05). The quantification of percentage change of match external-load metrics, particularly accelerations and decelerations, provides a useful non-invasive predictor of subsequent neuromuscular fatigue status in soccer players immediately post-match (p &lt; 0.05). However, only internal load metrics present a practical application for predicting intermittent-running endurance capacity impairment (p &lt; 0.05). In summary, internal and external load metrics may allow for predicting the extent of acute fatigue, and variability between halves may represent a valuable alternative to facilitate the analysis of match-related fatigue both for research and applied purposes.



#14 Evaluation of Neuromuscular Fatigue in a Repeat Sprint Ability, Countermovement Jump and Hamstring Test in Elite Female Soccer Players

Reference: Int J Environ Res Public Health. 2022 Nov 16;19(22):15069. doi: 10.3390/ijerph192215069.

Authors: Estrella Armada-Cortés, José A Benítez-Muñoz, Alejandro F San Juan, Javier Sánchez-Sánchez

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Summary: The straight-line run is the most frequent action in soccer goal scoring situations, and it deserves considerable attention. The objective of this study was to evaluate the neuromuscular fatigue produced by an independent repeat sprint ability (RSA) test, a countermovement jump (CMJ) and a hamstring test (HT) in elite female soccer players. Twenty-four elite female soccer players participated in the study. The evaluation protocol included hamstring and CMJ tests before an RSA test (6 × 40 m 30 s rest), and hamstring and CMJ post-tests. Significant differences were found between pre-post HT measurements in the maximum angulation of the right leg (p = 0.012 Effect Size (ES) = 0.27), and the maximum velocity was higher in the left leg after RSA (p = 0.023 ES = 0.34). CMJ height after RSA was significantly lower than before the RSA test (p &lt; 0.001 ES = 0.40). The sprint total time (SprintTT) and percentage difference (%Dif) increased throughout the RSA (p &lt; 0.001, and ES = 0.648 and ES = 0.515, respectively). In elite female soccer players, it seems that the fatigue induced by an RSA test can be assessed through the loss of CMJ height and the different performance variables extracted from the RSA itself (e.g., SprintTT, Ideal Sprint). These findings could contribute to better performance management and injury prevention for elite female soccer players.



#15 Effects of video-based training on anticipation and decision-making in football players: A systematic review

Reference: Front Hum Neurosci. 2022 Nov 10;16:945067. doi: 10.3389/fnhum.2022.945067. eCollection 2022.

Authors: Jie Zhao, Qian Gu, Shuo Zhao, Jie Mao

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Summary: The training of athletes' anticipation and decision-making skills has received increasing attention from researchers, who developed and implemented training programs to achieve this. Video-based training (VBT) has become a popular method in anticipation and decision-making skills training. However, little is known about the benefits of implementing VBT in soccer. This systematic review considered the results of studies on VBT aiming to develop decision-making and anticipation skills in football players, and analyzed its effects. Literature published up to March 2022 was systematically searched on the scientific electronic databases Web of Science, PubMed, Scopus, SportDiscus, and Google Scholar. In total, 5,749 articles were identified. After screening the records according to the set exclusion and inclusion criteria, ten articles were considered eligible, including six longitudinal studies and four acute studies. Eight of the ten included studies (80%) showed that VBT group performance in anticipation or decision-making skills was significantly better at post-test than at pre-test, as evidenced by improvements in response accuracy (RA), response times (RT), mean distance scores (MDS) and passing decision-making performance. In six studies that included the no video-based training (NVBT) group, results showed that athletes in the VBT group performed better in anticipation or decision-making skills than in the NVBT group, as evidenced by improvements in RA and RT performance. The studies used different methods for VBT, both explicit and implicit training effectively improved participants' anticipation and decision-making skills. In addition, the implementation of the "first-person" perspective (i.e., the player's perspective) and virtual reality (VR) improved the presentation of video stimuli, effectively improving anticipation and decision-making. The findings of this review suggest that VBT is beneficial in developing anticipation and decision-making judgments in football players. However, some findings were inconsistent with previous studies due to differences in intervention duration and experimental protocols, and further studies are needed. Furthermore, future research should actively seek to design appropriate retention tests and transfer tests to truly understand the benefits of VBT for athletes.



#16 Adductor Strengthening Programme is successfully adopted but frequently modified in Norwegian male professional football teams: a cross-sectional study

Reference: BMJ Open. 2022 Sep 7;12(9):e060611. doi: 10.1136/bmjopen-2021-060611.

Authors: Joakim Stensø, Thor Einar Andersen, Joar Harøy

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Summary: Groin injuries represent a substantial problem in male football, with the Adductor Strengthening Programme (ASP) being the only exercise programme demonstrated to significantly reduce the risk of groin problems. We aimed first, to use the Reach Adoption Effectiveness Implementation Maintenance (RE-AIM) framework to investigate attitudes, beliefs and behaviour to the ASP among primary delivery agents of injury prevention exercises in Norwegian male professional football teams. Second, we aimed to identify a real-world application of the ASP protocol used in a professional team setting. A descriptive cross-sectional survey, using a questionnaire designed to cover all five dimensions of the RE-AIM framework and the top two divisions of Norwegian male professional football was used. Primarily, the proportion of respondents being aware of the ASP and its effect; having adopted it; having implemented it as intended; and considering maintaining using it. Secondary, the most often used ASP modifications. Twenty-nine (91%) participants responded. All (100%) respondents were aware of the ASP and its injury preventive effect. The two most stated reasons for using the ASP were its injury preventive effect and that it does not require equipment. The ASP was adopted by all (100%) delivery agents, but only 10% used it in accordance with the original protocol. The main modifications were that the players in 72% of the teams were instructed to perform a non-progressive number of repetitions during pre-season, and in 86% of the teams instructed to perform more sets, but fewer repetitions per set, during in season. In total, 97% of the delivery agents planned to continue using the ASP. The delivery agents have positive attitudes and beliefs to the ASP, but they frequently modify it. We identified and reported a real-world application of the ASP protocol.



#17 Do Serum 25-Hydroxyvitamin D Concentrations Affect Body Composition, Physical Fitness, Bone Strength and Bone Biomarkers in Female Children and Adolescent Football Players? A One-Season Study

Reference: Int J Environ Res Public Health. 2022 Nov 21;19(22):15394. doi: 10.3390/ijerph192215394.

Authors: Gabriel Lozano-Berges, Ángel Matute-Llorente, Alejandro Gómez-Bruton, Alex González-Agüero, Germán Vicente-Rodríguez, José A Casajús

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Summary: The aim was to compare changes in body composition, physical fitness, and bone biomarkers in female children and adolescent football players with different Vitamin D levels. Twenty-two players were classified into two groups according to 25(OH)D concentrations: 11 with deficient/insufficient 25(OH)D levels (IVD; &lt;30 ng/mL) and 11 with sufficient 25(OH)D levels (SVD; ≥30 ng/mL). Body composition parameters were measured using dual-energy X-ray absorptiometry and a peripheral quantitative computed tomography scanner. The following physical fitness tests were applied: maximal isometric knee extension (MIF), long jump, 30-m sprint, and 20-m shuttle run test (VO2max). Electrochemiluminescence immunoassays were used to analyze bone biomarkers and 25(OH)D. All variables were registered at the beginning and the end of the football season. The increase in subtotal bone mineral density (BMD) was higher in players with SVD than those with IVD (p = 0.030). Only players with SVD improved their MIF of the left leg (p = 0.005); whereas, only players with IVD decreased their 30-m sprint performance (p = 0.007) and VO2max (p = 0.046). No significant between- and within-group differences were found for bone biomarkers. SVD might cause an extra improvement of subtotal BMD in female children and adolescent football players. Moreover, it seems that the 25(OH)D concentration could be an important parameter for physical fitness improvement in this population.



#18 "Football- It's in Your Blood"-Lived Experiences of Undertaking Recreational Football for Health in Older Adults

Reference: Int J Environ Res Public Health. 2022 Nov 10;19(22):14816. doi: 10.3390/ijerph192214816.

Authors: Sophie Mowle, Emma Eyre, Mark Noon, Jason Tallis, Michael J Duncan

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Summary: Physical inactivity is prevalent in older adults and contributes to age-related decline in function, health, well-being, and quality of life. Recreational football for older adults has shown promise for promoting health benefits. This study explores the lived experiences of older adults engaging in a walking and recreational football intervention and identifies factors that affect behaviours and can encourage change in this population. A purposive sample (n = 14; aged 67 ± 5 years) of the lived experiences of those participating in a recreational football intervention took part in two focus groups. The participants' responses were grouped into three-time reflecting specific points in their lives: what stopped them from playing football, what got them playing, and what is needed for them to continue playing in the future. Within each of these time points in their lives, themes were identified. The key findings and practical recommendations were that football needs to be adapted and local, that the priority to play football changes over time, and that football itself is a fundamentally intrinsic motivator; 'it's in your blood'. The findings can be used to inform future interventions, encourage participation, and advise on the best practices for key stakeholders in the physical activity domain.



#19 Effects of Fatigue Induced by Repeated Sprints on Sprint Biomechanics in Football Players: Should We Look at the Group or the Individual?

Reference: Int J Environ Res Public Health. 2022 Nov 8;19(22):14643. doi: 10.3390/ijerph192214643.

Authors: Valentin Romero, Johan Lahti, Adrián Castaño Zambudio, Jurdan Mendiguchia, Pedro Jiménez Reyes, Jean-Benoît Morin

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Summary: The aim of this study was to analyse the influence of fatigue on sprint biomechanics. Fifty-one football players performed twelve maximal 30 m sprints with 20 s recovery between each sprint. Sprint kinetics were computed from running speed data and a high-frequency camera (240 Hz) was used to study kinematic data. A cluster analysis (K-mean clustering) was conducted to classify individual kinematic adaptations. A large decrease in maximal power output and less efficiency in horizontally orienting the ground reaction force were observed in fatigued participants. In addition, individual changes in kinematic components were observed, and, according to the cluster analysis, five clusters were identified. Changes in trunk, knee, and hip angles led to an overall theoretical increase in hamstring strain for some players (Cluster 5, 20/51) but to an overall decrease for some others (Cluster 1, 11/51). This study showed that the repeated sprint ability (RSA) protocol had an impact on both kinetics and kinematics. Moreover, fatigue affected the kinematics in a different way for each player, and these individual changes were associated with either higher or lower hamstring length and thus strain.



#20 The congested International Match Calendar in football: views of 1055 professional male players

Reference: BMC Sports Sci Med Rehabil. 2022 Nov 29;14(1):200. doi: 10.1186/s13102-022-00597-w.

Authors: L Pillay, D Burgess, D C Janse van Rensburg, G M Kerkhoffs, V Gouttebarge

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Summary: The International Match Calendar congestion affects players recovery. The views of a worldwide cohort of professional football players is shared in this communication. A cross-sectional observational study recruited players through Fédération Internationale des Associations de Footballeurs Professionnel's national members. An electronic survey was shared in English, French, Italian and Spanish with 1055 players consenting and completing it anonymously in November 2021. A total of 42% of respondents believe back-to-back matches should be limited to three. Most respondents (69%) felt off or in season breaks are infringed by clubs or national teams and 83% believe regulations should protect them. A total of 55% of players believed they sustained one or more injuries due to the overload and it has affected 52% of respondents' mental state. ‡The congested International Match Calendar poses a risk to professional footballers physical and mental health. Poor recovery between matches may affect player availability and performance. Players should be represented by active players when International Match Calendar scheduling decisions are made. Administrators should seek medical guidance regarding the effects of overload on performance prior to making decisions. This study allows the opportunity for a larger national team player sample to be studied.



#21 Construct Validity and Test-Retest Reliability of Hip Load Compared With Playerload During Football-Specific Running, Kicking, and Jumping Tasks

Reference: Int J Sports Physiol Perform. 2022 Dec 1;1-8. doi: 10.1123/ijspp.2022-0194. Online ahead of print.

Authors: Erik Wilmes, Bram J C Bastiaansen, Cornelis J de Ruiter, Riemer J K Vegter, Michel S Brink, Hidde Weersma, Edwin A Goedhart, Koen A P M Lemmink, Geert J P Savelsbergh

Summary: The aim was to determine the test-retest reliability of the recently developed Hip Load metric, evaluate its construct validity, and assess the differences with Playerload during football-specific short-distance shuttle runs. Eleven amateur football players participated in 2 identical experimental sessions. Each session included 3 different shuttle runs that were performed at 2 pace-controlled running intensities. The runs consisted of only running, running combined with kicks, and running combined with jumps. Cumulative Playerload and Hip Loads of the preferred and nonpreferred kicking leg were collected for each shuttle run. Test-retest reliability was determined using intraclass correlations, coefficients of variation, and Bland-Altman analyses. To compare the load metrics with each other, they were normalized to their respective values obtained during a 54-m run at 9 km/h. Sensitivity of each load metric to running intensity, kicks, and jumps was assessed using separate linear mixed models. Intraclass correlations were high for the Hip Loads of the preferred kicking leg (.91) and the nonpreferred kicking leg (.96) and moderate for the Playerload (.87). The effects (95% CIs) of intensity and kicks on the normalized Hip Load of the kicking leg (intensity: 0.95 to 1.50, kicks: 0.36 to 1.59) and nonkicking leg (intensity: 0.96 to 1.53, kicks: 0.06 to 1.34) were larger than on the normalized Playerload (intensity: 0.12 to 0.25, kicks: 0.22 to 0.53). The inclusion of Hip Load in training load quantification may help sport practitioners to better balance load and recovery.



#22 Evaluation of the Playing Time Benefits of Foreign Players in the Big-5 European Football Leagues

Reference: J Hum Kinet. 2022 Nov 8;84:238-249. doi: 10.2478/hukin-2022-000072. eCollection 2022 Oct.

Authors: Hui Zhang, Junxian Jiang

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Summary: The aim was to explore the benefits that foreign players bring to their clubs, this study used foreign players in the Big-5 European leagues (2013/2014-2017/2018 seasons) as samples and constructed a benefit model based on playing time and game points to evaluate the contribution of foreign players to their clubs in different leagues. The results showed the following: 1) from the 2013/2014 season to the 2017/2018 season, foreign players in the Bundesliga had the highest playing time benefits (PTBs) (0.526 ± 0.012), followed by foreign players in La Liga (0.523 ± 0.014), the Premier League (0.518 ± 0.011), Serie A (0.500 ± 0.012) and Ligue 1 (0.486 ± 0.011); 2) foreign players from South America had the highest PTBs in the Big-5 leagues, while those from Africa had the lowest PTBs. However, among the different leagues, there were no significant differences in the PTBs of foreign players from the same continent; 3) PTBs of foreign players in the forward position were lower than those of foreign players in the defender position; 4) the country that produced foreign players in the Big-5 leagues with the highest total PTBs was Brazil, followed by Argentina, Spain and France. Additionally, the top 15 countries by total PTBs qualified for either the 2014 or the 2018 World Cup Final.


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