Latest research in football - week 11 - 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 Center backs work hardest when playing in a back three: The influence of tactical formation on physical and technical match performance in professional soccer

Reference: PLoS One. 2022 Mar 17;17(3):e0265501. doi: 10.1371/journal.pone.0265501. eCollection 2022.

Authors: Leon Forcher, Leander Forcher, Darko Jekauc, Alexander Woll, Timo Gross, Stefan Altmann

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Summary: The purpose of this study was to investigate whether tactical formation affects the physical and technical match performance of professional soccer players in the first German Bundesliga. From official match data of the Bundesliga season 2018/19, physical (total distance, high-intensity distance, sprinting distance, accelerations, maximum velocity) and technical performance (short/middle/long passes, dribblings, ball-possessions) of players were analyzed. Players were categorized into five playing positions (center back, full back, central midfielder, wide midfielder, forward) and teams into eight different tactical formations (4-4-2, 4-4-2 diamond, 4-2-2-2, 4-3-3, 4-5-1, 4-2-3-1, 3-4-3, 3-5-2). Results revealed that the degree to which tactical formation affects match performance is position dependent. In terms of physical performance, center backs and full backs showed highest sprinting distances when playing in a formation with only three defenders in the back row (3-4-3, 3-5-2) compared to all other formations (ES range: 0.13≤ES≤1.27). Regarding technical performance, all positions except forwards displayed fewer short passes, middle passes and ball-possessions in the formations 4-3-3 and 4-2-3-1 compared to all other formations (0.02≤ES≤1.19). In conclusion, physical and technical performance of center backs, full backs and wide midfielders differed markedly between the tactical formations. Conversely, the physical and technical performance of central midfielders and forwards only showed small differences between the different tactical formations. These findings can help coaches scheduling their practice. For example, if a coach wants to change the playing formation, he can anticipate the physical and technical match performance changes depending on the respective playing position.



#2 The Effect of Intensity Soccer Training Sessions on Marked Biochemical Indicators of Blood Acidity of Saudi Young Soccer Players

Reference: Open Access J Sports Med. 2022 Mar 10;13:17-23. doi: 10.2147/OAJSM.S356075. eCollection 2022.

Authors: Ghareeb O Alshuwaier, Hadeel Ali Ghazzawi, Abdulrahman I Alaqil, Yahya R Alsharif, Mohammed Shaab Alibrahim, Khalid S Aljaloud

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Summary: The purpose was to assess the effect of low-to-moderate-intensity exercise on specific blood biomarkers and blood acidity in young Saudi Arabian professional soccer players. A total of 43 professional soccer players participated in the current study. A cross-sectional research method was used to compare the changes in the following blood biomarkers: calcium, magnesium, glucose, anion-gap metabolic acidosis, and carbon dioxide, after a range of low-to-moderate intensity training sessions. Measurements were taken in two soccer training sessions (Day 1, and Day 2). The exercise intensity was estimated by heart rate percentage of maximal heart rate. Wilcoxon signed-rank testing was used to analyze the results. Significant differences were found between and pre-and post-training sessions for anion-gap metabolic acidosis: Day 1: 12.55 vs 15.4 mmol/L; Day 2: 14.15 vs 16.35 mmol/L; and magnesium: Day 1: 0.82 vs 0.74 mmol/L; Day 2: 0.85 vs 0.74 mmol/L. Exercise caused anion-gap metabolic acidosis concentrations to rise post-training; magnesium levels decreased after training sessions on Day 1 and Day 2. The concentrations of anion-gap metabolic acidosis and magnesium were significantly affected by exercise intensity in the subjects, the former rose post-training while the latter fell. More studies are required to investigate the effects of different exercise intensities on other blood biomarkers in soccer players.



#3 The incidence and burden of injuries in elite English youth female soccer players

Reference: Sci Med Footb. 2022 Mar 17. doi: 10.1080/24733938.2022.2051730. Online ahead of print.

Authors: Jake Beech, Ben Jones, Ryan King, Pippa Bennett, Stephanie Young, Sean Williams, Keith Stokes, Stacey Emmonds

Summary: This study aimed to investigate the incidence, severity, and burden of injury in English elite youth female soccer players. Qualified therapists at six English girls' academies prospectively recorded all injuries that required medical attention or caused time loss for matches and training in 375 elite youth female soccer players (under-10 , U12, U14 and U16) during the 2019/2020 season. One hundred- and eleven time-loss injuries (52 from training, 59 from matches) were sustained, resulting in 1,946 days absent (779 days from training injuries, 1,167 days from match injuries) from soccer activities. The injury incidence for matches (9.3/1000 hours, 95% CIs: 7.2-11.9) was significantly greater than training (1.1/1000 hours, 95% CIs: 0.9-1.5, p<0.001). Additionally, the injury burden for matches (183 days lost/1000 hours, 95% CIs: 142-237) was significantly greater than training (17 days lost/1000 hours, 95% CIs: 13-22, p<0.001). Injury incidence and burden were greatest in the U16 age group, and were found to increase with age. Whilst injury incidence and burden are greater in matches than training, a large proportion of preventable injuries, soft-tissue and non-contact in nature, were sustained in training. Findings provide comparative data for elite youth female soccer players.



#4 Exploring interactions between maturity status and playing time with fluctuations in physical fitness and hormonal markers in youth soccer players

Reference: Sci Rep. 2022 Mar 16;12(1):4463. doi: 10.1038/s41598-022-08567-5.

Authors: Ebrahim Eskandarifard, Hadi Nobari, Mustafa Sogut, Filipe Manuel Clemente, António José Figueiredo

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Summary: The purpose of this study was to determine the differences in functional capacities and hormonal indices according to biological maturity and seasonal playing time status in young soccer players. Twenty-three male under-15 players (14.6 ± 0.2 years) were divided into two groups, based on their maturity status and seasonal playing time. They were measured for anthropometrics, Yo-Yo intermittent recovery level 1 (YYIR1), seven repeated sprint test (7RST), countermovement jump (CMJ), skeletal age, growth hormone, and insulin-like growth factor-1 (IGF-1) level. Age at peak height velocity (APHV) was determined to estimate the maturity timing. The results revealed that players who advanced in maturation were significantly heavier (p = 0.029) and had higher values in skeletal age (p < 0.001), sitting height (p = 0.005), CMJ (p = 0.038), and IGF-1 (p = 0.013). Players given greater playing time exhibited significantly lower fatigue index (p = 0.012), but higher CMJ (p = 0.003) and IGF-1 (p = 0.001) values. The overall results highlighted that early-maturing players and players with greater playing time obtained higher values in both CMJ and IGF-1. The findings may provide an insight on the coaches' evaluation of players and on the possible factors that may affect the future playing status of young male soccer players.



#5 Did the Absence of Crowd Support During the Covid-19 Pandemic Affect the Home Advantage in Brazilian Elite Soccer?

Reference: J Hum Kinet. 2022 Feb 10;81:251-258. doi: 10.2478/hukin-2022-0047. eCollection 2022 Jan.

Authors: Lucas de Castro Ribeiro, Fabiano de Souza Fonseca, Gustavo De Conti Teixeira Costa, Henrique de Oliveira Castro, João Paulo Victor da Silva Santos, Lucas Savassi Figueiredo

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Summary: This study aimed to investigate the impact of crowd absence due to the COVID-19 pandemic on home advantage in Series A and B of professional Brazilian male soccer. Moreover, we sought to compare the home advantage between different competitive levels. Data from 2018 to 2020 Brazilian professional soccer championships (Series A and B) were analyzed, consisting of 2280 matches. The effect of home advantage was calculated in relation to the number of points won, the number of wins, goals scored and goals conceded. Our results indicated that home advantage was reduced in Serie A. Specifically, the 2020 (absence of the crowd) and 2019 seasons showed smaller home advantage compared to the 2018 season. On the other hand, Serie B analyses indicated no changes in home advantage over the seasons analyzed. The comparison of home advantage between competitive levels indicated higher home advantage in Serie A, exclusively in the 2018 season. In addition to the absence of fans, other changes occurred in elite sports due to the pandemic, such as changes in rules and the calendar. Considering that home advantage is affected by multiple interacting factors, it is important to investigate specific sports leagues across the world to determine which factors had the greatest impact on the advantage of playing home matches.



#6 Variations in Internal and External Training Load Measures and Neuromuscular Performance of Professional Soccer Players During a Preseason Training Period

Reference: J Hum Kinet. 2022 Feb 10;81:149-162. doi: 10.2478/hukin-2022-0012. eCollection 2022 Jan.

Authors: Lucas A Pereira, Tomás T Freitas, Vinicius Zanetti, Irineu Loturco

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Summary: We described the internal and external training loads (TLs) experienced by soccer players over a 4-week preseason, examined their effects on vertical jump (VJ) performance, and investigated the relationships between different TL variables. Eighteen professional soccer players performed 17 training sessions and 1 friendly-match (FM) over the preseason. The internal TL was obtained using the session-rating of perceived exertion method. The external TL variables collected were total and high-intensity distances, body-load, and high-metabolic power distance via the GPS system. VJ performance was assessed 13 times throughout the study. Moreover, total quality recovery and delayed onset muscle soreness were assessed before every training session as a measure of recovery status. Players were divided, using a median split analysis, into two groups, according to their VJ performance (i.e., "lower" and "higher" VJ). External TL variables displayed similar variations across training sessions and were significantly interrelated (r ranging from 0.48 to 0.88). In periods where higher internal TLs were detected, impaired recovery status was noticed. Notably, the higher VJ group exhibited decreased jump performance at post-test and higher internal and external TLs across the entire preseason (compared to the lower VJ group). From our results it is suggested that professional soccer players with higher VJ performance are potentially more susceptible to concurrent training effects.



#7 Ultrasound Shear Modulus and Thickness of Lateral Abdominal Muscles in Different Contractile States in Relation To Self- Reported Hip/Groin Problems in Youth Soccer Players

Reference: J Hum Kinet. 2022 Feb 10;81:97-108. doi: 10.2478/hukin-2022-0009. eCollection 2022 Jan.

Authors: Pawel Linek, Nadine Booysen, Maria Stokes

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Summary: To date, no studies have assessed lateral abdominal muscles' (LAM) elasticity and thickness in relation to hip and groin symptoms in any population. The objectives were to a) assess the relationship between LAM ultrasound measurements (elasticity and thickness) and self-reported subscales of the Copenhagen Hip and Groin Outcome Score (HAGOS) and b) compare LAM elasticity and thickness between asymptomatic and symptomatic sides. Shear modulus and thickness of the oblique external (OE), internal (OI) and transversus abdominis (TrA) muscles in 25 young soccer players were assessed at rest and during isometric contraction using ultrasound shear wave elastography. HAGOS subscales were used to assess self-reported hip/groin problems. There was a significant (p < 0.05) moderate correlation between allometric-scaled OI resting thickness (mean of right and left) and the Activities of Daily Living (r = 0.40), Sport (r = 0.57) and Quality of Life (QOL) (r = 0.41) HAGOS subscales. Also, a moderate significant correlation was found between allometric-scaled TrA resting thickness and the QOL subscale (r = 0.47). Moderate correlations were found between resting OI shear modulus and the QOL (r = 0.44), between right TrA shear modulus during contraction and Symptoms (r = 0.57), and between the left TrA shear modulus during contraction and Physical Activity (r = 0.41) subscales. No differences were found between the symptomatic and asymptomatic side in thickness and elasticity measurements among soccer players with unilateral symptoms (p > 0.05). The relationships found between LAM and hip/groin problems in youth male soccer players indicate that muscles are thinner and more elastic (less stiff) in more symptomatic athletes.



#8 Energy Requirements and Nutritional Strategies for Male Soccer Players: A Review and Suggestions for Practice

Reference: Nutrients. 2022 Feb 4;14(3):657. doi: 10.3390/nu14030657.

Authors: Andrew T Hulton, James J Malone, Neil D Clarke, Don P M MacLaren

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Summary: Soccer is a high intensity intermittent sport, featuring critical events completed at high/maximal intensity which is superimposed onto an aerobic base of lower intensity activities and rest. Due to these varying energic demands and the duration of competition the need for optimal nutritional strategies to offset and delay fatigue are paramount. Over the last 50 years, several investigations have been reported on aspects of soccer be they nutrition-focused or those concerning the demands of the sport. Emanating from these scientific papers, observations have been made on the likely factors which result in the fatigue during match-play. Factors such as muscle glycogen depletion and hypoglycaemia are discussed. Studies on the energy demands of soccer have employed a variety of methodologies which are briefly reviewed and vary between the use of heart rate telemetry to the use of global positioning systems (GPS). Moving on from observations of the energy demands of the sport leads to the major focus of this review which highlights key nutritional strategies to support the preparation and recovery of male soccer players to enhance performance, or at least to enable players to perform adequately. This review examines relevant methodologies in assessing training and competitive energy costs as well as the concomitant energy intakes demanded for successful performance outcomes. In order to bring an applied aspect to the overall findings from areas discussed, some practical ideas of feeding strategies are presented.



#9 Match-Related Statistics Differentiating Winning and Losing Teams at the 2019 Africa Cup of Nations Soccer Championship

Reference: Front Sports Act Living. 2022 Feb 25;4:807198. doi: 10.3389/fspor.2022.807198. eCollection 2022.

Authors: Alliance Kubayi, Paul Larkin

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Summary: This study investigated game-related statistics differentiating the winning and losings teams of matches during the 2019 African Cup of Nations (AFCON) soccer tournament. The sample consisted of 38 games, with the data obtained from the InStat Scout platform. Data were analyzed using mean (M), SD, effect size (ES), structure coefficients (SCs), and the Wilcoxon signed-rank test. The results showed that the winning teams performed significantly better than the losing teams in terms of shots (M = 12.13, SD = 4.67, Z = -2.26, ES = 0.62), shots on target (M = 5.05, SD = 2.54, Z = -4.22, ES = 1.13), and shots from counter-attacks (M = 2.24, SD = 1.42, Z = -2.48, ES = 0.57). Shots on target (SC = 1.22), shots (SC = -0.73), fouls (SC = 0.60), total passes (SC = 0.44), and yellow cards (SC = -0.32) presented the highest discriminatory power. These findings highlight the key match performance variables which influence the game results and may assist coaches in developing and implementing team strategies to improve the likelihood of winning the AFCON championship.



#10 Small-Sided Soccer Games with Larger Relative Areas Result in Higher Physical and Physiological Responses: a Systematic and Meta-Analytical Review

Reference: J Hum Kinet. 2022 Feb 10;81:163-176. doi: 10.2478/hukin-2022-0013. eCollection 2022 Jan.

Authors: Gibson Moreira Praça, Mauro Heleno Chagas, Sarah da Glória Teles Bredt, André Gustavo Pereira de Andrade

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Summary: This study aimed to systematically review the influence of the relative area on athletes' physical and physiological responses (outcomes) during small-sided games of soccer which were not matched to the relative area. It also presents a meta-analysis comparing standard small-sided games protocols with different relative areas. We searched the Web of Science and Scopus electronic databases for literature published up to March 2020 following all PRISMA guidelines for selecting articles for a qualitative and quantitative synthesis. As a result, eleven articles matched the inclusion criteria. For the quantitative synthesis, a pooled random-effects model was used to make pairwise comparisons between protocols with larger or smaller areas in each selected study. Prediction intervals were used to assess the heterogeneity. We found positive effects of larger relative areas per player on their total distance (d = 0.73; 95% CI = 0.12-1.34; p = 0.006; medium to large effect), distance covered at high speed (d = 0.93; 95% CI = 0.22-1.65; p = 0.001; large effect), and mean heart rate (d = 0.52; 95% CI = 0.17-0.88; p = 0.008; medium effect). In other words, larger relative areas were found to induce higher physical and physiological responses in players. Future studies should consider the relative area per player when comparing data for different small-sided games configurations to avoid confounding variables. Also, coaches can use relative area per player calculations to easily predict increases and decreases in expected training loads for different versions of SSGs during training.



#11 Seasonal Training Load Monitoring Among Elite Level Soccer Players: Perceived Exertion and Creatine Kinase Variations Between Microcycles

Reference: J Hum Kinet. 2022 Feb 10;81:85-95. doi: 10.2478/hukin-2022-0008. eCollection 2022 Jan.

Authors: Bruno Mendes, Filipe Manuel Clemente, Francisco Calvete, Sandro Carriço, Adam Owen

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Summary: The primary aim of the investigation was to determine the daily load variations between the microcycles of an entire season of an elite group of professional soccer players. The second aim of this study was to determine the relationships between Foster's rating of perceived exertion (RPE), the Hooper index (HI) and CK levels over the weekly microcycles of the season. Thirty-five male professional soccer players participated in this study (3 goalkeepers, 6 wide defenders, 4 central defenders, 9 midfielders, 8 wide midfielders and 4 forwards) (25.7 ± 5.0 years, 182.3 ± 6.4 cm; 79.1 ± 7.0 kg). Significant differences between months in the variables of HI (p = 0.001; ES = 0.052), minT (p = 0.001; ES = 0.066), IL (p = 0.001; ES = 0.052, minimum effect) and CK (p = 0.002; ES = 0.031) were found. Comparison of the HI (p = 0.044; ES = 0.002), minT (p = 0.001; ES = 0.045), and IL (p = 0.001; ES = 0.045) revealed significant differences between microcycles. No significant differences were found in CK (p = 0.710; ES = 0.001) across the period. A significantly higher internal training load and fatigue perception in microcycles with only one official match was found. The greater load occurred 3 to 4 days before the game. In addition, it can be concluded that the first quarter of the season seemed to induce a greater physical demand on elite professional players.



#12 The maturity status but not the relative age influences elite young football players' physical performance

Reference: Sci Med Footb. 2022 Mar 15;1-8. doi: 10.1080/24733938.2022.2053338. Online ahead of print.

Authors: Iván Peña-González, Alejandro Javaloyes, Eduardo Cervelló, Manuel Moya-Ramón

Summary: Talent identification and selection process in young football is based on coaches' decisions regarding the players' performance at early ages. The aim of this study was to show how the maturity status and the relative age impact on young football players' physical performance and their coaches' efficacy expectations. The physical performance (1RM, Peak power output [PPO], 30-m sprint and t-test) of 118 young football players (U13 to U15; and their coaches' efficacy expectations were assessed. Relative age was calculated according to the players' date of birth within their selection year. The maturity status was estimated as the years from/to their peak height velocity (PHV). Linear regression analyses showed a significant relationship between players' physical performance and their maturity status but not with their relative age. In contrast, the maturity status of players only was associated to the coaches' efficacy expectations in the 1RM and PPO tests, whereas the relative age was a predictor of the coaches' expectations about players' performance in the t-test. These findings may be important for coaches and managers in young football academies since inter-individual differences in the maturity status but not in the relative age are related to physical performance despite the coaches' expectations.



#13 Time to change direction in training load monitoring in elite football? The application of MEMS accelerometers for the evaluation of movement requirements

Reference: Sci Med Footb. 2022 Mar 15;1-10. doi: 10.1080/24733938.2022.2053337. Online ahead of print.

Authors: Matthew Green, Patrick Ward, Matthew Bickley, Mark Gillett, Andy O'Boyle, Barry Drust

Summary: In elite football, the emphasis is placed on monitoring the output from the Global Positioning Systems (GPS) component of a Micro-Electro-Mechanical Systems (MEMS) device; however, this does not comprehensively overview the total demands due to the intermittent multidirectional nature. The aim of the study was to investigate the application of accelerometer data provided by MEMS, to evaluate movement requirements in elite football. A two-staged research approach, involving an effectiveness and efficacy stage, was deployed. The effectiveness stage examined two MEMS-accelerometer variables (PlayerLoadTM (PL) and PlayerLoadTM per meter (PL.m-1)) for four years and four months. Ninety-nine English Premier League outfield football players' participated. In the efficacy stage, 26 elite outfield football players completed three different training modalities (running, possession and dribbling) and a range of MEMS-accelerometer variables were analysed. In the effectiveness stage, the mean difference in PL for all training activities other than Set Pieces were similar to Matches (-283 to -246au). Model coefficients for PL.m-1 were smallest in Team Shape (-0.00114au), Attacking (0.00025au) and Games (0.00196au), and largest for Possession (0.03356AU), Defending (0.03182au) and Skills Games (0.03106au) compared to Matches. The findings suggest that PL.m-1 but not PL may be effective at describing differences in movement requirements. In the efficacy stage, PL.m-1 and inertial movement analysis (IMA) efforts were the only variables that had greater mean differences in the smaller conditions, confirming PL.m-1's suitability in evaluating movement requirements of different training activities and pitch dimensions. The findings suggest such a variable offers value in a monitoring strategy in football.



#14 The influence of exposure, growth and maturation on injury risk in male academy football players

Reference: J Sports Sci. 2022 Mar 14;1-10. doi: 10.1080/02640414.2022.2051380. Online ahead of print.

Authors: David M Johnson, Sean P Cumming, Ben Bradley, Sean Williams

Summary: Adolescence is a period of increased injury risk in youth footballers; however, no studies have considered the influence of growth-related factors and exposure time upon injury risk. Forty-nine elite male youth footballers were prospectively monitored for growth, lower-limb growth, maturation, training volume and injury for one season. Generalised linear mixed-effects models were used to model growth rate, lower-limb growth rate, maturation, and smoothed week-to-week changes in exposure on time-loss injury risk. The relationship between growth rate and injury incidence was linear (P = 0.031) and injury burden was non-linear (P = 0.019). The relationship between lower-limb growth rate and injury incidence was linear and positive (P = 0.098). A non-linear relationship was observed between lower-limb growth rate and injury burden (P = 0.001). A non-linear relationship between Percentage of Predicted Adult Stature and both injury incidence and injury burden were found, with peak risk occurring at 92% and 95% , respectively. There was a positive linear relationship between week-to-week changeand injury incidence (P = 0.001), and a non-linear relationship between week-to-week change and injury burden (P = 0.01). Practitioners should monitor the timing and rate of the growth spurt and exposure time to identify players at greater injury risk.



#15 Sports Injuries Among Players of The Polish National Team in Amputee Football in The Annual Training Cycle

Reference: J Hum Kinet. 2022 Feb 10;81:211-219. doi: 10.2478/hukin-2022-0021. eCollection 2022 Jan.

Authors: Zofia Kasińska, Piotr Kazimierz Urbański, Tomasz Tasiemski

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Summary: The aim of the study was to determine the frequency, type and origin of the occurrence of injuries in amputee football. The studied group comprised all members of the Polish national amputee football team (n = 25). During the 9-month observation period, 13 players incurred 22 injuries. The incidence proportion was 48.0 per 100 athletes (95% Cl, 28.4-67.6) and the incidence rate was 5.73 per 1000 athlete-days (95% Cl, 3.33-8.12). The study showed that 32.8% of the injuries were to the thigh, 13.6% to the ankle, and 9.1% to the knee. The obtained results indicate that amputee football players rather frequently incur play-related injuries, but a single athlete incurs relatively few of them, with the lower limb being most commonly injured.



#16 Effect of support foot placement on football instep kick performance

Reference: Sci Med Footb. 2022 Mar 24;1-7. doi: 10.1080/24733938.2022.2055781. Online ahead of print.

Authors: Yu-Cheng Ou, Man Kit Lei, Kuangyou B Cheng

Summary: Although the support foot plays an important role in kicking a football, there has been a paucity of research exploring the effect of the placement of the support foot on kicking performance. To investigate the kick performance under different support foot positions, ten male footballers were recruited to participate in two experiments: one determining the maximum ball speed and the second determining accuracy. The participants were instructed to plant their support foot on one of nine different spots marked in the form of a 3 × 3 shape on a piece of artificial grass and asked to kick the ball. In the first (maximum speed) test, the participants tried their best to kick the ball at the maximum ball speed from nine different support foot positions. In the second (accuracy) test, the participants kicked the ball toward the target area without restricting the support foot position. The ball speed, as well as the success rate, were recorded from each support foot position. Significantly higher ball speed and accuracy were obtained at medial positions than was the case at lateral positions from the nine spots. It was concluded that although footballers may choose different positions for support foot placement, the maximum ball speed and better accuracy could be expected when the support foot was next to or slightly in front of the ball centre without too much side-by-side separation (27-37 cm).



#17 Estimation of maximal oxygen uptake using the heart rate ratio method in male recreational football players

Reference: Eur J Appl Physiol. 2022 Mar 17;1-8. doi: 10.1007/s00421-022-04928-0. Online ahead of print.

Authors: Carlo Castagna, Peter Krustrup, Susana Póvoas

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Summary: Maximal oxygen uptake (VO2max) is associated with cardiovascular and metabolic health in the general population. The heart rate (HR) ratio method (HRratio) is a valid, easy and accessible method for estimating VO2max in well-trained subjects. This study examined the validity of using the HRratio to estimate VO2max in recreational football players in the untrained and trained states. Sixty-six participants (age 39.3 ± 5.8 years) were tested pre-training and 28 after 12 weeks, for VO2max assessment, running on a treadmill alternating speed (1 km h-1) and inclination (1%) increments every 30 s until exhaustion. Maximal HR (HRmax) was assessed directly with a multiple approach and estimated with selected equations. Resting HR (HRrest) was measured in supine position, after 15 min of rest. The HRratio method considers the product of HRmax/HRrest ratio by a theoretical proportionality factor (15 ml kg-1 min-1, TPF) to estimate VO2max. This population-specific proportionality factor (SPF) was 14.6 ± 2.6 ml kg-1 min-1. In the untrained state (n = 66), participants' actual VO2max (41.3 ± 6.2 ml kg-1 min-1) was moderately lower (~ 2 ml kg-1 min-1) than the estimated VO2max using the TPF. A nonsignificant difference (0.7 ml kg-1 min-1) was found when the VO2max was estimated using the SPF. When using HRmax equations and the TPF, a small nonsignificant difference (~ 1.5 ml kg-1 min-1) was reported between actual and estimated VO2max. In the trained state (n = 28), the estimated VO2max values were not significantly different from the actual VO2max (44.2 ± 5.2 ml kg-1 min-1), with large effect sizes when considering TPF and estimated HRmax. The results of this study provide evidence of the applicability of HRratio in estimating VO2max in male adult/middle-aged recreational football players.



#18 Deficits in eccentric antagonist/concentric agonist strength ratios: a comparative study of football players with and without osteitis pubis

Reference: Eur Rev Med Pharmacol Sci. 2022 Mar;26(5):1559-1564. doi: 10.26355/eurrev_202203_28221.

Authors: W S Mohammad, W M Elsais

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Summary: Dynamic hip stabilizers are essential for optimal performance in football players, particularly during kicking. Although the muscle strength deficits of hip muscles as an etiology of osteitis pubis (OP) in football players have not yet been well investigated, previous assessments give more attention to the concentric mode of strength for both hip flexor and extensor muscles. Functionally, the hip muscles interact in an eccentric/concentric pattern. This study aimed to compare the concentric, eccentric, and eccentric antagonist/concentric agonist ratios for hip flexor and extensor strength between football players with OP and healthy athletes. Thirty-four male footballers with OP and eighteen healthy footballers were tested using an isokinetic dynamometer at a speed of 180°/s. Football players with osteitis pubis demonstrated a significantly lower eccentric extensor/concentric flexor ratio and higher eccentric hip flexor/extensor ratio (p < 0.05) when compared with healthy participants. The present study demonstrated that football players with OP had a reduced capability to produce eccentric hip extension torque compared to healthy athletes. Consequently, the eccentric rather than the concentric weakness of hip extensors could be suggested as one of the intrinsic contributing factors for OP. Incorporating findings of the current study in clinical practice could afford critical information while evaluating the hip muscles in football players with OP for pre-screening, developing rehabilitation programs, and guiding the decision to return to sports after injury.



#19 Ramadan Nutritional Strategy: Professional Soccer Player Case Study

Reference: Nutrients. 2022 Jan 21;14(3):465. doi: 10.3390/nu14030465.

Authors: Alejandro Martínez-Rodríguez, Laura Miralles-Amorós, Manuel Vicente-Martínez, Nuria Asencio-Mas, Rodrigo Yáñez-Sepúlveda, María Martínez-Olcina

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Summary: The period of Ramadan induces changes in the usual eating patterns of individuals. During this period, Muslims must abstain from drinking and eating from dawn to dusk. Therefore, some research conducted on professional soccer players has observed that during and/or after Ramadan, performance, running speed, agility, dribbling speed, and endurance and/or skill performance in athletic events may be negatively affected by Ramadan intermittent fasting (RIF). The objective of this study was to analyze the influence of a dietary plan during RIF on performance and body composition in a professional soccer player. A 20-year-old elite player (86.0 kg, 188.5 cm) followed a dietary-nutritional plan with an isocaloric diet and was supplemented with glycerol. The athlete's strength and power in the lower limbs was assessed by performing a countermovement jump (CMJ) and Abalakov vertical jump (ABK) before and after Ramadan. After nutritional planning, the patient's body composition improved in terms of fat loss (6.61 to 5.70%) and muscle mass gain (50.26 to 51.50%). In addition, this translated into improvements in performance tests, both in the CMJ (36.72 to 40.00 cm) and ABK (39.16 to 49.34 cm). In conclusion, during a period of fasting, personalised nutritional planning and an appropriate supplementation and rest protocol can improve the body composition and performance of soccer players.



#20 Molecular Hydrogen Mitigates Performance Decrement during Repeated Sprints in Professional Soccer Players

Reference: Nutrients. 2022 Jan 25;14(3):508. doi: 10.3390/nu14030508.

Authors: Michal Botek, Deepesh Khanna, Jakub Krejčí, Michal Valenta, Andrew McKune, Barbora Sládečková, Iva Klimešová

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Summary: Hydrogen-rich water (HRW) supplementation has been shown to have an antifatigue effect across different modes of exercise. However, its effect on repeated sprint performance is unknown. The aim of this study was to assess the effect of pre-exercise HRW consumption on repeated sprint performance, lactate, and perceptual responses using a repeated sprint protocol. This randomized, double blinded, placebo controlled, crossover study included 16 professional, male soccer players aged 18.8 ± 1.2 years. Athletes performed two indoor tests, particularly 15 × 30 m track sprints interspersed by 20 s of recovery, separated by a 1-week washout period. Sprint time was measured at 15 m and 30 m. Ratings of perceived exertion were assessed immediately after each sprint, and post-exercise blood lactate concentration was measured after the last sprint. There were significantly faster sprint times after HRW consumption compared with placebo at 15 m for the 14th and 15th sprints, representing improvements in time of 3.4% and 2.7%, respectively. Sprint time at 30 m also significantly improved by 1.9% in the HRW group in the last sprint. However, neither lactate concentrations nor ratings of perceived exertion were significantly different between HRW and placebo. Pre-exercise HRW supplementation is associated with an increased ability to reduce fatigue, especially during the later stages of repeated sprint exercise.



#21 Changes of 25(OH)D Concentration, Bone Resorption Markers and Physical Performance as an Effect of Sun Exposure, Supplementation of Vitamin D and Lockdown among Young Soccer Players during a One-Year Training Season

Reference: Nutrients. 2022 Jan 25;14(3):521. doi: 10.3390/nu14030521.

Authors: Joanna Jastrzębska, Maria Skalska, Łukasz Radzimiński, Guillermo F López-Sánchez, Katja Weiss, Lee Hill, Beat Knechtle

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Summary: The main purpose of this research was to demonstrate the changes in 25(OH)D concentration, bone resorption markers, and physical fitness along the one-year training season in young soccer players. A total of 24 young soccer players (age: 17.2 ± 1.16 years, mass: 70.2 ± 5.84, height: 179.1 ± 4.26 cm) were tested at four different time points across one year (T1-September 2019; T2-December 2019; T3-May 2020; T4-August 2020). After T2 (during COVID-19 lockdown), players were divided into a supplemented (GS) group and a placebo group (GP). Variables such as 25(OH)D, calcium (Ca), phosphorus (P), parathyroid hormone (PTH), aerobic capacity, speed, and explosive power were measured. Analyses performed for all participants indicated significant changes in all selected blood markers and running speed. The highest values in 25(OH)D were noted during summertime in T1 and T4. After individuals were split into two groups, a two-factorial ANOVA demonstrated a significant time interaction for 25(OH)D, Ca, P, PTH, 30 m sprint, and counter-movement jump. Significant time x group effect was calculated for aerobic capacity. This study confirmed that 25(OH)D concentration varies between four seasons, with the greatest decreases in the low sunlight periods. Vitamin D supplementation did not cause a preventive and long-lasting effect of increasing the 25(OH)D concentration in the young soccer players.


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