Latest research in football - week 39 - 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 The Effect of External Dissociative Stimuli on Plank Duration Performed by Male Collegiate Soccer Players

Reference: J Strength Cond Res. 2022 Oct 12. doi: 10.1519/JSC.0000000000004371. Online ahead of print.

Authors: Michele N D'Agata, Jason P Staub, Daniel J Scavone, Gregory M Kane

Summary: Individuals commonly use music as an external auditory stimulus to divert their attention away from aerobic endurance exercise tasks. Music generally results in lower ratings of perceived exertion, which may be the mechanism by which it increases aerobic exercise task duration. However, less is known regarding how music affects the performance of other forms of exercise, such as isometric exercise. Moreover, the effects of different external stimuli on isometric task duration, such as the use of virtual reality (VR), have yet to be investigated. Therefore, the purpose of this study was to investigate the effects of self-selected music (SSM) and VR on isometric exercise task duration using a forearm plank. We hypothesized that both SSM and VR would effectively increase plank duration compared with no external stimuli. Seventeen male collegiate soccer players (19 ± 1 year) completed 3 planks to failure on 3 separate days, with 48-72 hours between the trials. The ordering of each exercise condition (SSM, VR, or None) was randomized for a total of 6 potential orders. A one-way repeated-measures analysis of variance was used to evaluate differences in plank duration and average heart rate (HRavg) between each trial, and significance was set at p < 0.05. There were no differences in plank duration (SSM: 200 ± 44, VR: 173 ± 38, None: 177 ± 37 seconds) or HRavg (SSM: 96 ± 18, VR: 92 ± 21, None: 87 ± 18 beats per minute) between the conditions. We conclude that there was no effect of external stimuli (SSM or VR) on isometric exercise task duration and the use of these modalities should be based on exerciser preference.



#2 Individualized reference ranges for markers of muscle recovery assessment in soccer

Reference: Eur J Sport Sci. 2022 Oct 13;1-44. doi: 10.1080/17461391.2022.2134052. Online ahead of print.

Authors: Sabrina Skorski, Werner Pitsch, Vanessa Barth, Max Walter, Mark Pfeiffer, Alexander Ferrauti, Michael Kellmann, Anne Hecksteden, Tim Meyer

Summary: Recently an individualization algorithm has been developed and shown to significantly improve diagnostic accuracy of creatine kinase (CK) and urea in endurance sports and Badminton. In this study, applicability and benefit of this algorithm was evaluated using repeated measures data from 161 professional German soccer players monitored during the 2015-2017 seasons. Venous blood samples were collected after a day off (recovered state) and after a minimum of two strenuous training sessions within 48 h (non-recovered state) and analyzed for CK and urea. Group-based reference ranges were derived from that same dataset to ensure a best possible reference for comparison. A z-Test was conducted to analyse differences in error rates between individualized and group-based classifications. CK values for the individualized approach showed significantly lower error rates in the assessment of muscle recovery compared to both a population-based (p<0.001; z-value: -17.01; test-pass error rate: 21 vs. 67%; test-fail: 19 vs. 64%) and a group-based cut-off (p<0.001; z-value: -15.29; test-pass error rate: 65%; test-fail: 67%). It could be concluded that the assessment of muscle recovery in soccer using individualized interpretations of blood-borne markers may offer higher diagnostic accuracy as compared to a population-based as well as a sample specific group-based approach.Key points: Assessing muscle recovery via CK using individualized ranges seems to offer a higher diagnostic accuracy compared to a sample-specific group-based analysis.Using an individualized algorithm seems to be a promising approach to overcome diagnostic problems arising from large inter- and intraindividual variability in blood parameters as it significantly improved the diagnostic accuracy of CK as a recovery marker.As recovery assessment in elite soccer ultimately aims at the accurate detection of differences in the individual player this algorithm seems to offer coaches and sport scientists a more sensitive approach compared to group-specific evaluations.



#3 Kinetic Effects of 6 Weeks' Pilates or Balance Training in College Soccer Players with Chronic Ankle Instability

Reference: Int J Environ Res Public Health. 2022 Oct 8;19(19):12903.  doi: 10.3390/ijerph191912903.

Authors: Quan Jiang, Yonghwan Kim, Moonyoung Choi

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Summary: Lateral ankle sprain (LAS) is a common sports injury that frequently occurs in active individuals. LAS is characterized by a high recurrence rate, with a large proportion of patients progressing to chronic ankle instability (CAI). Pilates exercises have provided positive results in health care and in rehabilitation. This study compared Pilates training (PT) with traditional balance training (BT) in patients with CAI. Fifty-one college football players with CAI, divided into PT (n = 26) and BT (n = 25) groups, were included in the study. The groups performed PT or BT training as assigned, three times per week for 6 weeks. Isokinetic ankle strength, one-leg hop tests, Y-balance test (YBT), and foot and ankle outcome score (FAOS) were evaluated before and after training. There were considerable improvements in both the PT and BT groups after training. Group and time comparisons revealed that the PT group achieved better triple hop test results than the BT group, whereas the BT group exhibited a greater improvement in YBT posteromedial and posterolateral reach distances. In athletes with CAI, both PT and BT effectively improved symptoms and function. These findings suggest that ankle strength, balance, and core stability should be comprehensively evaluated and targeted in CAI rehabilitation programs.



#4 Exploring the Effects of a Neck Strengthening Program on Purposeful Soccer Heading Biomechanics and Neurocognition

Reference: Int J Sports Phys Ther. 2022 Oct 2;17(6):1043-1052. doi: 10.26603/001c.38327. eCollection 2022.

Authors: Katelyn M Waring, Edward R Smith, Gary P Austin, Thomas G Bowman

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Summary: Cervical (neck) strengthening has been proposed as an important factor in concussion prevention. The purpose of the study was to determine if a six-week cervical strengthening program affected neurocognition and purposeful soccer heading biomechanics. The hypothesis was that the neck strengthening program would improve strength, maintain neurocognition, and alter purposeful soccer heading biomechanics. Twenty collegiate soccer athletes (8 males, 12 females, age=20.15±1.35 years, height=171.67±9.01 cm, mass=70.56±11.03 kg) volunteered to participate. Time (pre, post) and group (experimental, control) served as the independent variables. Four composite scores from the CNS Vital Signs computer based neurocognitive test (CNSVS; verbal memory, visual memory, executive function, reaction time) and aspects of heading biomechanics from inertial measurement units (xPatch; peak linear acceleration, peak rotational acceleration, duration, Gadd Severity Index [GSI]) served as the dependent variables. Each athlete completed a baseline measure of neck strength (anterior neck flexors, bilateral anterolateral neck flexors, bilateral cervical rotators) and CNSVS after heading 10 soccer balls at two speeds (11.18 and 17.88 m/s) while wearing the xPatch. The experimental group completed specific cervical neck strengthening exercises twice a week for six weeks using a Shingo Imara™ cervical neck resistance apparatus while the control group did not. After six weeks, the participants completed the same heading protocol followed by measurement of the same outcome variables. The alpha value was set to p<0.05 a priori. The interaction between time and group was significant for visual memory (F1,17=5.16, p=0.04, η2=0.23). Interestingly, post hoc results revealed visual memory decreased for the control group from pretest (46.90±4.46) compared to posttest (43.00±4.03; mean difference=3.90, 95% CI=0.77-7.03, p=0.02). Interactions for all other dependent variables were not statistically significant (p>0.05). The cervical neck strengthening protocol allowed maintenance of visual memory scores but did not alter other neurocognitive measures or heading biomechanics. The link between cervical neck strengthening and concussion predisposition should continue to be explored.



#5 Non-header impact exposure and kinematics of male youth soccer players 

Reference: Biomed Sci Instrum. 2021 Apr;57(2):106-113. doi: 10.34107/yhpn9422.04106.

Authors: Declan A Patton, Colin M Huber, Susan S Margulies, Christina L Master, Kristy B Arbogast

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Summary: Previous studies have investigated the head impact kinematics of purposeful heading in youth soccer; however, less than a third of all head injuries in youth soccer have been found to involve ball contact. The aim of the current study was to identity the head impact kinematics and exposure not associated with purposeful heading of the ball in male youth soccer. Headband-mounted sensors were used to monitor the head kinematics of male junior varsity and middle school teams during games. Video analysis of sensor-recorded events was used to code impact mechanism, surface and site. Junior varsity players had non-header impact rates of 0.28 per athlete-exposure (AE) and 0.37 per player-hour (PH), whereas middle school players had relatively lower non-header impact rates of 0.16 per AE and 0.25 per PH. Such impact rates fell within the large range of values reported by previous studies, which is likely affected by sensor type and recording trigger threshold. The most common non-header impact mechanism in junior varsity soccer was player contact, whereas ball-to-head was the most common non-header impact mechanism in middle school soccer. Non-header impacts for junior varsity players had median peak kinematics of 31.0 g and 17.4 rad/s. Non-header impacts for middle school players had median peak kinematics of 40.6 g and 16.2 rad/s. For non-header impacts, ball impacts to the rear of the head the highest peak kinematics recorded by the sensor. Such data provide targets for future efforts in injury prevention, such as officiating efforts to control player-to-player contact.



#6 Sports Injuries of a Portuguese Professional Football Team during Three Consecutive Seasons

Reference: Int J Environ Res Public Health. 2022 Oct 2;19(19):12582. doi: 10.3390/ijerph191912582.

Authors: Francisco Martins, Cíntia França, Adilson Marques, Beatriz Iglésias, Hugo Sarmento, Ricardo Henriques, Andreas Ihle, Helder Lopes, Rui T Ornelas, Élvio Rúbio Gouveia

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Summary: Professional football players are exposed to high injury risk due to the physical demands of this sport. The purpose of this study was to characterize the injuries of a professional football team in the First Portuguese League over three consecutive sports seasons. Seventy-one male professional football players in the First Portuguese Football League were followed throughout the sports seasons of 2019/2020, 2020/2021, and 2021/2022. In total, 84 injuries were recorded. Each player missed an average of 16.6 days per injury. Lower limbs were massively affected by injuries across all three seasons, mainly with muscular injuries in the quadriceps and hamstrings and sprains in the tibiotarsal structure. Overall, the injury incidence was considerably higher in matches than in training. The two times of the season that proved most conducive to injuries were the months of July and January. Our results emphasize the importance of monitoring sports performance, including injury occurrence, and assisting in identifying risk factors in professional football. Designing individualized training programs and optimizing prevention and recovery protocols are crucial for maximizing this global process.



#7 Injury incidence rates in women's football: a systematic review and meta-analysis of prospective injury surveillance studies

Reference: Br J Sports Med. 2022 Oct 13;bjsports-2021-105177. doi: 10.1136/bjsports-2021-105177.

Authors: Dan Horan, Fionn Büttner, Catherine Blake, Martin Hägglund, Seamus Kelly, Eamonn Delahunt

Summary: The aim was to review the literature to establish overall, match and training injury incidence rates (IIRs) in senior (≥18 years of age) women's football (amateur club, elite club and international). Databases such as MEDLINE via PubMed; EMBASE via Ovid; CINAHL via EBSCO and Web of Science were searched from earliest record to July 2021. Studies were elected if 1) football players participating in a senior women's football league (amateur club or elite club) or a senior women's international football tournament; (2) the study had to report IIRs or provide sufficient data from which this outcome metric could be calculated through standardised equations; (3) a full-text article published in a peer-reviewed journal before July 2021; (4) a prospective injury surveillance study and (5) case reports on single teams were ineligible. 17 articles met the inclusion criteria; amateur club (n=2), elite club (n=10), international (n=5). Overall, match and training 'time-loss' IIRs are similar between senior women's elite club football and international football. 'Time-loss' training IIRs in senior women's elite club football and international football are approximately 6-7 times lower than their equivalent match IIRs. Overall 'time-loss' IIRs stratified by injury type in women's elite club football were 2.70/1000 hours (95% CI 1.12 to 6.50) for muscle and tendon, 2.62/1000 hours (95% CI 1.26 to 5.46) for joint and ligaments, and 0.76/1000 hours (95% CI 0.55 to 1.03) for contusions. Due to the differences in injury definitions, it was not possible to aggregate IIRs for amateur club football. Lower limb injuries incurred during matches are a substantial problem in senior women's football. The prevention of lower limb joint, ligament, muscle and tendon injuries should be a central focus of injury prevention interventions in senior women's amateur club, elite club and international football.



#8 Fitness Soccer Athletes Training at the University of Limpopo, South Africa: Are the Macronutrients Intake and Anthropometric Status of These Athletes Optimal?

Reference: Int J Environ Res Public Health. 2022 Oct 3;19(19):12650. doi: 10.3390/ijerph191912650.

Authors: Masodi Makhafola, Hendrick Makhubela, Sylven Masoga, Sefora Hazel Makuse

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Summary: Dietary practices of the University of Limpopo soccer team athletes have been reported. However, the practices of those engaging in soccer for general fitness from different non-competitive teams remain unknown. To respond to this gap, the researchers investigated the energy, macronutrient intake, and BMI status and further correlated the two variables of the fitness non-competitive soccer athletes registered at the University of Limpopo in South Africa. A quantitative study design was undertaken to conveniently sample 60 out of 90 fitness soccer athletes from the four non-competitive soccer teams at the University of Limpopo sports grounds. Ethics approval was obtained from the University of Limpopo Research and Ethics Committee, and permission was given by the university sports management and team coaches. Athletes signed the informed consent form before participating in the study. Data were collected at the soccer fields during the afternoons before the start of training. Macronutrient intake data were collected using multiple (two) 24-h recall questionnaires on different days, which were validated by the food frequency questionnaire. Weight and height were measured using a digital scale (Seca 813 electronic flat scale) and stadiometer (Seca 213 portable stadiometer) for BMI calculations, respectively. The average energy and macronutrient intakes were calculated through the SAMRC FoodFinder software (3.0). The nutrient averages, together with the BMI results, were loaded into SPSS (26.0) for further analysis. Descriptive statistics were used to report the energy, macronutrient intake, and BMI statuses of athletes using percentages, means, and standard deviations (±SD). A one-way ANOVA test was used to determine the association between the latter variables. A p-value of ≤ 0.05 was the criterion used to correlate the variables. All (100%) athletes were males, most of whom played soccer for 2-3 years while at the university. Almost half (48%) of athletes consumed energy (39.6 kcal/kg) below the recommendations. About 92% and 53% of athletes consumed carbohydrates (5.0 g/kg) and fat (1.2 g/kg) below the recommended values; while 43% consumed protein (1.4 g/kg) optimally. The majority (&gt;80%) had a normal BMI (21.6 ± 2.6 kg/m2) status. However, there were no relationships between the energy (p = 0.383), CHO (p = 0.261), protein (p = 0.543), and fat (p = 0179) intake and the BMI status of athletes. The macronutrient intake of fitness soccer athletes at the University of Limpopo is, on the whole, suboptimal. However, the athletes had normal body weights. There was no association between both the energy and macronutrient intake and the anthropometric (BMI) status of soccer athletes.



#9 Are sprint accelerations related to groin injuries? A biomechanical analysis of adolescent soccer players

Reference: Sports Biomech. 2022 Oct 19;1-13. doi: 10.1080/14763141.2022.2133740. Online ahead of print.

Authors: Thomas Dupré, Wolfgang Potthast

Summary: Groin injuries have one of the highest incidences in soccer and can be career threatening, especially for adolescents, due to their high recurrence rate. Quick accelerations have been connected to groin injuries along with kicking and change of directions. Purpose of this study was to examine the hip joint kinematics, kinetics and the muscle forces of adductor longus and gracilis during first ground contact of a linear sprint acceleration performed by adolescent soccer players. Twenty-two male participants were investigated with 3D motion capture and two force plates. Inverse dynamics were used to calculate the kinematics, kinetics and muscle forces. The kinematics show a constant extension during the stance phase and a quick transition from an abduction to an adduction movement at 90% stance, which coincides with the highest forces in adductor longus and gracilis. This indicates a high load on the adductor muscles due to eccentric contractions combined with high muscle forces in the adductors. Compared to previously investigated inside passing and change of direction movements, adductor muscle forces and angular velocities are higher in this study. Therefore, it is suggested that sprint accelerations are likely to be connected to the development of groin injuries in adolescent soccer players.



#10 Finite Element Analysis of Soccer Ball-Related Ocular and Retinal Trauma and Comparison with Abusive Head Trauma

Reference: Ophthalmol Sci. 2022 Feb 20;2(2):100129. doi: 10.1016/j.xops.2022.100129. eCollection 2022 Jun.

Authors: Matthew R Lam, Pengfei Dong, Yasin Shokrollahi, Linxia Gu, Donny W Suh

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Summary: Trauma to the eye resulting from a soccer ball is a common sports-related injury. Although the types of ocular pathologic features that result from impact have been documented, the underlying pathophysiologic mechanics are not as well studied. The purpose of this study was to evaluate the biomechanical events after the collision of a soccer ball with the eye to better understand the pathophysiology of observed ocular and retinal injuries and to compare them with those observed in abusive head trauma (AHT). A finite element model of the eye was used to investigate the effects of a collision of a soccer ball on the eye. Intraocular pressure and stress were used as outcome measures. Impact of the soccer ball with the eye generated a pressure wave that traveled through the vitreous, creating transient pockets of high and negative pressure. During the high-frequency phase, pressure in the vitreous near the posterior pole ranged from 39.6 to -30.9 kPa. Stress in ocular tissue was greatest near the point of contact, with a peak of 66.6 kPa. The retina experienced the greatest stress at the vasculature, especially at distal branches, where stress rose to 15.4 kPa. On average, retinal stress was greatest in the subretinal layer, but was highest in the preretinal layer when considering only vascular tissue. The high intraocular pressure and stress in ocular tissue near the point of soccer ball impact suggest that injuries to the anterior segment of the eye can be attributed to direct transmission of force from the ball. The subsequent propagation of a pressure wave may cause injuries to the posterior segment as the positive and negative pressures exert compressive and tractional forces on the retina. The linear movement of the pressure wave likely accounts for localization of retinal lesions to the posterior pole or superior temporal quadrant. The primarily linear force in soccer ball trauma is the probable cause for the more localized injury profile and lower retinal hemorrhage incidence compared with AHT, in which repetitive angular force is also at play.



#11 Comprehensive training load monitoring with biomarkers, performance testing, local positioning data, and questionnaires - first results from elite youth soccer

Reference: Front Physiol. 2022 Oct 3;13:1000898. doi: 10.3389/fphys.2022.1000898. eCollection 2022.

Authors: Nils Haller, Julia C Blumkaitis, Tilmann Strepp, Anna Schmuttermair, Lorenz Aglas, Perikles Simon, Elmo Neuberger, Christina Kranzinger, Stefan Kranzinger, James O'Brien, Bernd Ergoth, Stefan Raffetseder, Christian Fail, Manfred Düring, Thomas Stöggl

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Summary: Load management, i.e., prescribing, monitoring, and adjusting training load, is primarily aimed at preventing injury and maximizing performance. The search for objective monitoring tools to assess the external and internal load of athletes is of great interest for sports science research. In this 4-week pilot study, we assessed the feasibility and acceptance of an extensive monitoring approach using biomarkers, neuromuscular performance, and questionnaires in an elite youth soccer setting. Eight male players (mean ± SD: age: 17.0 ± 0.6 years, weight: 69.6 ± 8.2 kg, height: 177 ± 7 cm, VO2max: 62.2 ± 3.8 ml/min/kg) were monitored with a local positioning system (e.g., distance covered, sprints), biomarkers (cell-free DNA, creatine kinase), questionnaires, neuromuscular performance testing (counter-movement jump) and further strength testing (Nordic hamstring exercise, hip abduction and adduction). Feasibility was high with no substantial impact on the training routine and no adverse events such as injuries during monitoring. Adherence to the performance tests was high, but adherence to the daily questionnaires was low, and decreased across the study period. Occasional significant correlations were observed between questionnaire scores and training load data, as well as between questionnaire scores and neuromuscular performance. However, due to the small sample size, these findings should be treated with caution. These preliminary results highlight the feasibility of the approach in elite soccer, but also indicate that modifications are needed in further large-scale studies, particularly in relation to the length of the questionnaire.



#12 Effects of playing 1 vs 3 matches in a one-week period on physical performance in young soccer players

Reference: Biol Sport. 2022 Oct;39(4):819-823. doi: 10.5114/biolsport.2022.108700. Epub 2021 Oct 25.

Authors: Jose Luis Hernández-Davo, Víctor Moreno Pérez, Pedro Moreno Navarro

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Summary: The aim of this study was to analyse the effects of playing 1 vs 3 matches in a one-week period on physical performance in young soccer players. Twelve youth soccer players completed a battery of physical tests (countermovement jump [CMJ], 25 m sprint, 5-0-5 agility test, ankle dorsiflexion range of motion [AD ROM]) 72 h after a match. These tests were performed on two different occasions: during a week with 1 competitive match, and during a week in which 3 matches were played. Three matches in a week caused from most likely to very likely impairments in CMJ (ES = 0.81), the 5-0-5 agility test (ES = 1.03), and in AD ROM (ES = 0.46-0.63) compared with the 1 match in a week. For the 25 m sprint test, performance impairments were found in the split times for 10-15 m (ES = 0.72), 15-20 m (ES = 0.52) and 20-25 m (ES = 0.90) compared with 1 match in a week. Jumping, sprinting, change of direction (COD) performance and AD ROM are significantly affected during congested calendars in young soccer players. The monitoring of these variables is a useful tool to assess players' recovery and may help in determining players' readiness for the next matches.



#13 Movement Regularity Differentiates Specialized and Nonspecialized Athletes in a Virtual Reality Soccer Header Task

Reference: J Sport Rehabil. 2022 Oct 20;1-8. doi: 10.1123/jsr.2021-0432. Online ahead of print.

Authors: Christopher D Riehm, Scott Bonnette, Michael A Riley, Jed A Diekfuss, Christopher A DiCesare, Andrew Schille, Adam W Kiefer, Neeru A Jayanthi, Stephanie Kliethermes, Rhodri S Lloyd, Mathew W Pombo, Gregory D Myer

Summary: Young athletes who specialize early in a single sport may subsequently be at increased risk of injury. While heightened injury risk has been theorized to be related to volume or length of exposure to a single sport, the development of unhealthy, homogenous movement patterns, and rigid neuromuscular control strategies may also be indicted. Unfortunately, traditional laboratory assessments have limited capability to expose such deficits due to the simplistic and constrained nature of laboratory measurement techniques and analyses. To overcome limitations of prior studies, the authors proposed a soccer-specific virtual reality header assessment to characterize the generalized movement regularity of 44 young female athletes relative to their degree of sport specialization (high vs low). Participants also completed a traditional drop vertical jump assessment. During the virtual reality header assessment, significant differences in center of gravity sample entropy (a measure of movement regularity) were present between specialized (center of gravity sample entropy: mean = 0.08, SD = 0.02) and nonspecialized center of gravity sample entropy: mean = 0.10, SD = 0.03) groups. Specifically, specialized athletes exhibited more regular movement patterns during the soccer header than the nonspecialized athletes. However, no significant between-group differences were observed when comparing participants' center of gravity time series data from the drop vertical jump assessment. This pattern of altered movement strategy indicates that realistic, sport-specific virtual reality assessments may be uniquely beneficial in exposing overly rigid movement patterns of individuals who engage in repeated sport specialized practice.



#14 Differences in lower leg kinetics of soccer instep kicking between female and male players

Reference: Sports Biomech. 2022 Oct 20;1-12. doi: 10.1080/14763141.2022.2133738. Online ahead of print.

Authors: Tsuyoshi Iitake, Maya Hioki, Hitoshi Takahashi, Hiroyuki Nunome

Summary: We aimed to clarify the difference in lower leg segment kinetics of soccer instep kicking between female and male players. Instep kicking motions of seven female and seven male university soccer players were captured at 500 Hz. Lower leg angular velocity, knee joint moment and the interaction moment acting on the lower leg were calculated. Discrete variables were compared using two sample-t-test, and statistical parametric mapping were used to compare the time-series changes between the two groups. Although female players maintained a comparable magnitude of lower leg angular velocity, they exhibited significantly lower knee extension moment in the latter part of kicking and significantly smaller forward angular impulse due to that moment. In contrast, female players were found to have a comparable magnitude of angular impulse due to forward component of interaction moment to that of male players. Eventually, female players come to have significantly larger ratio of angular impulses (forward interaction moment/knee extension moment) than male players. It can be considered that the forward component of interaction moment acting on the lower leg of female players may compensate their reduced exertion of knee extension moment, thereby achieving a comparable lower leg angular velocity to that of male players.



#15 Influence of the COVID-19 lockdown on Spanish professional soccer teams' external demands according to their on-field ranking

Reference: Biol Sport. 2022 Oct;39(4):1081-1086. doi: 10.5114/biolsport.2022.113294. Epub 2022 Feb 18.

Authors: Javier Raya-González, Tomás García-Calvo, Ana Rubio-Morales, Roberto López Del Campo, Ricardo Resta, José Carlos Ponce-Bordón

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Summary: The main objective of this study was to analyse the changes in external demand parameters (e.g., total distance, high-speed running distance, accelerations/decelerations) in Spanish professional soccer teams after the COVID-19 lockdown considering their on-field ranking (i.e., teams whose ranking worsened after the COVID-19 lockdown [WRS] vs. teams that improved their ranking after the COVID-19 lockdown [IMP]). A total of 23,527 individual match observations were collected on players competing during the 2019/20 season in the First Spanish Professional soccer League (LaLiga). Goalkeepers and players who participated for less than 10 minutes in each match were excluded. Relative total distance (TD/min), distance covered at 21-24 km · h-1 (HIRD/min) and > 24 km · h-1 per minute (VHIRD/min), high metabolic load distance (HMLD), and the number of accelerations (3 m/s2) and decelerations (< 3 m/s2) performed were analysed by the ChryonHego video-tracking system. These variables were analysed during two differentiated periods, before the COVID-19 lockdown (i.e., 27 matches) and after the COVID-19 lockdown (i.e., 11 matches), and teams were classified into two groups according to their ranking (i.e., WRS vs. IMP). R-Studio was employed for data analysis and a mixed linear model was conducted. A decrease in external demands in all teams after the COVID-19 lockdown was observed, and this decrease was greater in WRS. These results suggest that, after an inactive period (i.e., the COVID-19 lockdown), teams that return with better physical performance, mainly related to high-intensity actions, have more possibilities of improving their final qualifying position.



#16 A novel multifactorial hamstring screening protocol: association with hamstring muscle injuries in professional football (soccer) - a prospective cohort study

Reference: Biol Sport. 2022 Oct;39(4):1021-1031. doi: 10.5114/biolsport.2022.112084. Epub 2021 Dec 30.

Authors: Johan Lahti, Jurdan Mendiguchia, Pascal Edouard, Jean-Benoit Morin

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Summary: The aim of this pilot study was to analyze the potential association of a novel multifactorial hamstring screening protocol with the occurrence of hamstring muscle injuries (HMI) in professional football. 161 professional male football players participated in this study (age: 24.6 ± 5.36 years; body-height: 180 ± 7.07 cm; body-mass: 77.2 ± 7.70 kg). During the pre- and mid-season, players performed a screening protocol consisting of 11 tests aimed to evaluate their performance in regards to four main musculoskeletal categories: posterior chain strength, sprint mechanical output, lumbopelvic control and range of motion. Univariable cox regression analysis showed no significant association between the isolated test results and new HMI occurrence during the season (n = 17) (p > 0.05). When including injuries that took place between the pre- and mid-season screenings (~90 days), maximal theoretical horizontal force (F0) was significantly associated with higher HMI risk between pre- and mid-season evaluations (n = 14, hazard ratio; 4.02 (CI95% 1.08 to 15.0, p = 0.04). This study identified that 1) no single screening test was sufficient to identify players at risk of HMI within the entire season, while 2) low F0 was associated with increased risk of HMI when occurring closer to the moment of screening. The present results support the potential relevance of additionally including frequent F0 testing for HMI risk reduction management. Replication studies are needed in larger cohorts for more accurate interpretations on "univariable and multivariable levels levels. Finally, future studies should explore whether improving F0 is relevant within a multifactorial HMI risk reduction approach.



#17 Effects of mental fatigue on the psychophysiological responses, kinematic profiles, and technical performance in different small-sided soccer games

Reference: Biol Sport. 2022 Oct;39(4):965-972. doi: 10.5114/biolsport.2022.110746. Epub 2021 Dec 30.

Authors: Yusuf Soylu, Fikret Ramazanoglu, Ersan Arslan, Filipe Manuel Clemente

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Summary: The purpose of this study was to assess the effects of mental fatigue (MF) on the psychophysiological responses, kinematic profiles, and technical performance of young soccer players in small-sided games (SSGs). Twenty-four young soccer players (age: 15.9 ± 1.0 years) played 2vs2, 3vs3, and 4vs4 SSGs consisting of four bouts (with two-minute passive rest periods between bouts) under two different playing conditions: MF+SSGs and SSGs. The heart rate, total distance covered, and technical performance of each player were monitored during all SSGs, and the rating of perceived exertion, visual analogue scale, and Rating Scale Mental Effort values were determined after each bout. The Physical Activity Enjoyment Scale (PACES) and Brunel Mood Scale (BRUMS) were also determined at the end of each SSG. The results demonstrated that all MF+SSGs induced higher psychophysiological responses (p ≤ 0.05) than SSGs, except regarding the PACES responses. By contrast, the SSGs group covered a greater total distance (p ≤ 0.05) than the MF+SSGs group. During SSGs, the players' technical performances (in terms of lost balls and unsuccessful passes) were negatively affected after MF (p ≤ 0.05). The results of this study indicate that both PACES scores and mood responses were negatively affected after the MF intervention. Coaches could use the MF intervention before SSGs to improve soccer-specific technical and decision-making performances in young soccer players.



#18 Perception and application of flywheel training by professional soccer practitioners

Reference: Biol Sport. 2022 Oct;39(4):809-817. doi: 10.5114/biolsport.2022.109457. Epub 2021 Oct 25.

Authors: Kevin L de Keijzer, Stuart A McErlain-Naylor, Thomas E Brownlee, Javier Raya-González, Marco Beato

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Summary: Growing evidence supports use of eccentric methods for strength development and injury prevention within elite soccer, yet uncertainty remains regarding practitioners' application of flywheel (isoinertial) methods. The aims of this study were to investigate how the flywheel training literature is perceived and applied by elite soccer practitioners, highlight gaps in knowledge and develop industry-relevant research questions. Fifty-one practitioners completed an electronic questionnaire. Fourteen Likert scale statements were grouped into topics: strength and performance; post-activation performance enhancement and methodological considerations; chronic strength; chronic performance; injury prevention. Three general questions followed, allowing more detail about flywheel training application. A Majority of the participants reported ≥ 2 years' experience of programming flywheel training. Nearly all participants agreed that familiarisation is needed. Practitioners agree that flywheel training can improve sport performance, strength and likelihood of non-contact injury outcomes. Most practitioners prescribe 2 weekly sessions during pre- and in-season periods. Flywheel sessions mostly consist of squats but a variety of exercises (lunge, hip hinge, and open kinetic chain) are also frequently included. Practitioners are mostly unsure about differences between flywheel and traditional resistance training equipment and outcomes, practicality of flywheel equipment, and evidence-based guidelines. The investigation provides valuable insight into the perspectives and application of flywheel training within elite soccer, highlighting its perceived efficacy for strength and injury prevention.


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