Latest research in football - week 14 - 2021

As previous literature updates, I have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases. 


Following studies were retrieved for this week:

#1 Does Warm-up Type Matter? A Comparison between Traditional and Functional Inertial Warm-up in Young Soccer Players 

Reference: J Funct Morphol Kinesiol. 2020 Nov 19;5(4):84. doi: 10.3390/jfmk5040084. 

Authors: Giovanni Fiorilli, Federico Quinzi, Andrea Buonsenso, Giulia Di Martino, Marco Centorbi, Arrigo Giombini, Giuseppe Calcagno, Alessandra di Cagno 

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Summary: Functional inertial training, a popular high-intensity training mode, provides high neuromuscular activation, developing proprioception, postural control, power, and sprint time. Aim of the study was to assess the acute effects of two types of warm-up (WU), inertial warm-up (IWU) vs. traditional warm-up (TWU), on explosive and reactive strength, sprint, and Change of Directions (COD) in young soccer players. In a randomized cross-over design study, twelve soccer players (aged 13.3 ± 0.7) performed 16 min of IWU and 16 min of TWU. IWU and TWU were spaced two weeks apart. Pre and post intervention tests, aimed at assessing explosive and reactive strength, sprint, and COD ability included: Squat Jump test (SJ), Countermovement Jump test (CMJ), Drop Jump test (DJ), Seven Repetition Hopping test (7R-HOP), 40 m-sprint test (40 m), and Illinois Agility Test (IAT). RM-ANOVA, used to compare differences between IWU and TWU effects (the level of significance set at ρ ≤ 0.05), showed enhanced performance after the IWU compared to the TWU. In addition, the effects of the IWU on performance lasted longer after the IWU than after the TWU. For IAT, the enhanced effects of IWU on performance lasted up to ten minutes after the administration of the IWU. Our results suggest that IWU affects functional changes displaying earlier adaptation in explosive and reactive strength with longer lasting effects compared to TWU and it could be recommended in young soccer athletes as a WU procedure. 



#2 Bioimpedance Vector References Need to Be Period-Specific for Assessing Body Composition and Cellular Health in Elite Soccer Players: A Brief Report 

Reference: J Funct Morphol Kinesiol. 2020 Oct 1;5(4):73. doi: 10.3390/jfmk5040073. 

Authors: Tindaro Bongiovanni, Gabriele Mascherini, Federico Genovesi, Giulio Pasta, Fedon Marcello Iaia, Athos Trecroci, Marco Ventimiglia, Giampietro Alberti, Francesco Campa

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Summary: Bioimpedance data through bioimpedance vector analysis (BIVA) is used to evaluate cellular function and body fluid content. This study aimed to (i) identify whether BIVA patters differ according to the competitive period and (ii) provide specific references for assessing bioelectric properties at the start of the season in male elite soccer players. The study included 131 male soccer players (age: 25.1 ± 4.7 yr, height: 183.4 ± 6.1 cm, weight: 79.3 ± 6.6) registered in the first Italian soccer division (Serie A). Bioimpedance analysis was performed just before the start of the competitive season and BIVA was applied. In order to verify the need for period-specific references, bioelectrical values measured at the start of the season were compared to the reference values for the male elite soccer player population. The results of the two-sample Hotelling T2 tests showed that in the bivariate interpretation of the raw bioimpedance parameters (resistance (R) and reactance (Xc)) the bioelectric properties significantly (T2 = 15.3, F = 7.6, p ≤ 0.001, Mahalanobis D = 0.45) differ between the two phases of the competition analyzed. In particular, the mean impedance vector is more displaced to the left into the R-Xc graph at the beginning of the season than in the first half of the championship. For an accurate evaluation of body composition and cellular health, the tolerance ellipses displayed by BIVA approach into the R-Xc graph must be period-specific. This study provides new specific tolerance ellipses (R/H: 246 ± 32.1, Xc/H: 34.3 ± 5.1, r: 0.7) for performing BIVA at the beginning of the competitive season in male elite soccer players. 



#3 Body Composition Changes over Multiple Academic Years in Female Collegiate Soccer Players

Reference: J Funct Morphol Kinesiol. 2020 Sep 28;5(4):72. doi: 10.3390/jfmk5040072. 

Authors: Austin Katona, Caroline Riewe, Angela Bruzina, Nicholas J Ollberding, Mary Ankrom, Jon Divine, Robert Mangine, Abigail Peairs

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Summary: Body composition plays a key role in overall health and sports performance and its assessment is an important part of many athletic programs. The purpose of this study was to describe longitudinal changes in body composition for collegiate female soccer players in order to provide data to inform future training and nutrition interventions for this population. A linear mixed-model (LMM) approach was used to analyze four years of pre- and post-season body composition data, including total mass, fat-free mass (FFM), fat mass, and body fat percentage (%BF) for 49 athletes. Athletes gained an average of 0.5 kg FFM during the season (p < 0.05) and increased total mass, FFM, fat mass, and %BF (2.5 kg, 1.1 kg, 1.7 kg, and 1.7%, respectively; p < 0.05) over four years. Freshmen experienced a 1.5 kg gain in total mass pre- to post-season (p < 0.05), while no changes in total mass or body composition were seen in other grade levels. Gains in %BF during the off season between Freshman and Sophomore years represented negative changes in body composition that should be addressed further. These results can help interdisciplinary athlete care teams optimize training programs in this population by understanding what changes are expected over multiple years. Normalizing these changes may also help the promotion of realistic body composition goals and the development of positive training and dietary habits. 



#4 Effects of Hoverboard on Balance in Young Soccer Athletes 

Reference: J Funct Morphol Kinesiol. 2020 Aug 6;5(3):60. doi: 10.3390/jfmk5030060. 

Authors: Stefano Moffa, Angelica Perna, Gabriele Candela, Alessandro Cattolico, Carmine Sellitto, Paolo De Blasiis, Germano Guerra, Domenico Tafuri, Angela Lucariello

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Summary: Hoverboards are always more popular among children. Hoverboards are to them like a game or a mean of transport, but they could be used as a valid and useful instrument in children's training programs to improve their performance. In this study, we compared the athletic performance of two groups of 12 children. A total of 24 children aged between 8 and 11 years followed a similar training program for five months, but the first group used a hoverboard (Hb+ group: Age: Standard Deviation (SD) = 1.15 Mean = 9.66; Weight: SD = 5.90 Mean = 32; Height: SD = 7.64 Mean = 135.08) for some of the training time, differently from the second group (Hb- group: Age: SD = 1.15 Mean = 9.66; Weight: SD = 5.82 Mean = 31.16; Height: SD = 7.66 Mean = 136.16), which never used it. All of the children were asked to complete three tests (one leg test, stork test and balance beam walking test) before starting their own training program and after five months, to evaluate how their performances changed in terms of time. Comparing the recorded time difference between T0 and T1 of the Hb+ group with the same difference measured in Hb- group, it was found that there was a statistically significant difference (p value < 0.05) between these data for all three tests. Children who used the hoverboard in their training program achieved better result than children who did not use it. In the future, the hoverboard could help athletes to improve their performances, possibly applying it not only in football training, but even in other sports. 



#5 Body Fat Assessment in International Elite Soccer Referees 

Reference: J Funct Morphol Kinesiol. 2020 Jun 6;5(2):38. doi: 10.3390/jfmk5020038. 

Authors: Cristian Petri, Francesco Campa, Vitor Hugo Teixeira, Pascal Izzicupo, Giorgio Galanti, Angelo Pizzi, Georgian Badicu, Gabriele Mascherini

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Summary: Soccer referees are a specific group in the sports population that are receiving increasing attention from sports scientists. A lower fat mass percentage (FM%) is a useful parameter to monitor fitness status and aerobic performance, while being able to evaluate it with a simple and quick field-based method can allow a regular assessment. The aim of this study was to provide a specific profile for referees based on morphological and body composition features while comparing the accuracy of different skinfold-based equations in estimating FM% in a cohort of soccer referees. Forty-three elite international soccer referees (age 38.8 ± 3.6 years), who participated in the 2018 Russian World Cup, underwent body composition assessments with skinfold thickness and dual-energy X-ray absorptiometry (DXA). Six equations used to derive FM% from skinfold thickness were compared with DXA measurements. The percentage of body fat estimated using DXA was 18.2 ± 4.1%, whereas skinfold-based FM% assessed from the six formulas ranged between 11.0% ± 1.7% to 15.6% ± 2.4%. Among the six equations considered, the Faulkner's formula showed the highest correlation with FM% estimated by DXA (r = 0.77; R2 = 0.59 p < 0.001). Additionally, a new skinfold-based equation was developed: FM% = 8.386 + (0.478 × iliac crest skinfold) + (0.395 × abdominal skinfold, r = 0.78; R2 = 0.61; standard error of the estimate (SEE) = 2.62 %; p < 0.001). Due to these findings, national and international federations will now be able to perform regular body composition assessments using skinfold measurements. 



#6 Injury prevention effects of stretching exercise intervention by physical therapists in male high school soccer players

Reference: Scand J Med Sci Sports. 2020 Nov;30(11):2178-2192. doi: 10.1111/sms.13777. Epub 2020 Aug 2. 

Authors: Nobuhide Azuma, Fujiko Someya

Summary: We aimed to examine the prevalence of injury after physical therapy intervention for muscle tightness and injury prevention in male high school soccer players. A randomized controlled trial was conducted. Participants comprised 124 players from two high schools who competed in national tournament soccer games held from April 2018 to March 2019. Players were randomly divided into intervention (with a 12-week stretching intervention by physical therapists) and control groups (without the intervention). Players and coaches provided written information regarding injuries and daily training and match times; physical therapists visited each team weekly to collect data and review documentation. Muscle tightness and injury incidence, number, type, location, circumstances, situations, severity, and contents during the 12-week intervention period and a subsequent 40-week observation period were compared between groups. Injuries were significantly lower with intervention during the 40-week observation period (P < .01) but not during the 12-week intervention period (P = .44). Injury types mainly included disorder, non-contact, lower-limb/trunk, and muscle/tendon injuries. Significant interactions were observed for all tightness-test measurement items. The intervention group showed significant improvements in heel-buttock distance, and straight leg-raise and hip rotation angles (pre-intervention < 12 weeks < 52 weeks), as well as significant improvements in ankle dorsiflexion angles at 12 and 52 weeks (relative to pre-intervention values). Instructed stretching exercises, personally designed by physical therapists to address muscle tightness, improved the range of motion and trunk flexibility, with a positive effect on the injury rate in male high school soccer players, especially for non-contact disorder injuries during training. 



#7 Associations of Body Composition, Maximum Strength, Power Characteristics with Sprinting, Jumping, and Intermittent Endurance Performance in Male Intercollegiate Soccer Players

Reference: J Funct Morphol Kinesiol. 2021 Jan 7;6(1):E7. doi: 10.3390/jfmk6010007. 

Authors: Ai Ishida, S Kyle Travis, Michael H Stone

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Summary: The purpose of this study was to determine the relationships between body composition, strength, power characteristics, sprinting, jumping, and intermittent endurance performance in collegiate male players. Twenty-three players participated (19.7 ± 1.6 yrs; 71.8 ± 7.1 kg; 176.5 ± 5.1 cm). Measurements of interest in body composition included body fat percentage (BF%), lean body mass (LBM), and body mass (BM). Power characteristics were measured with an unloaded squat jump (SJ0) and loaded SJ at 20 kg (SJ20) and 40 kg (SJ40), and unloaded countermovement jump (CMJ0). Power assessments included peak power (PP) and PP allometrically scaled (PPa). Strength characteristics were assessed using isometric mid-thigh pull. Strength assessment included isometric peak force (IPF) and IPF allometrically scaled (IPFa). Performance measures included 10m and 20 m sprint time, CMJ0 jump-height, and Yo-Yo intermittent endurance test level 1 distance. Significant correlations ranging from moderate to very large were found for LBM and CMJ jump height (CM0 JH) (p = 0.01, r = 0.50); BF% and sprint times at 10 m (p = 0.03, r = 0.44) and 20 m (p = 0.02, r = 0.50). PP and PPa from SJ0 and CMJ0 were significantly correlated to 10m sprint time (p < 0.05, r = -0.45 to -0.53) and 20 m sprint time (p < 0.05, r = -0.40 to -0.49). Our findings agree with previous literature in that body composition and power characteristics are directly related to soccer-related performance. 



#8 Cell integrity indicators in university athletes: comparison among playing positions in indoor football 

Reference: J Sports Med Phys Fitness. 2021 Jan 22. doi: 10.23736/S0022-4707.21.12008-0. Online ahead of print. 

Authors: Priscila C Martins, Paula DA Silva, Diego A Silva

Summary: The aim of this study was to compare cell integrity indicators according to the playing position in university indoor football athletes. The sample consisted of 34 university athletes (20 female and 14 male). Dependent variables were cell integrity indicators: total body water (TBW), intracellular water (ICW), extracellular water (ECW), ECW/ICW ratio, body cell mass (BCM), ECW/BCM ratio, phase angle (PhA), resistance (R), Xc (reactance) and impedance (Z), evaluated by the electrical bioimpedance method. Independent variable was the playing position: goalkeeper (a), defender (a), winger (left and right) and pivot collected through questionnaire. Control variables were age, time of sport practice, participation in competitions per year and training load obtained by applying the anamnesis form, and body fat and fat and bone-free mass were obtained through dual emission X-ray absorptiometry (DXA). Covariance analysis (ANCOVA) was used, with post-roc Tukey's test, to identify difference between groups, with p <0.05. In the adjusted analysis, female athletes in the defense position had BCM values (31.1 ±2.1) higher than those in the wing position (25.8 ±1.1) (p <0.01). In males, pivots showed higher ICW values (31.47 ±0.77) when compared to defenders (25.7 ±0.8) (p = 0.02). In addition, goalkeepers had higher TBW values (52.7 ±2.5) compared to wingers (42.3 ±1.2) (p = 0.03). Cell integrity indicators may vary according to the playing position in indoor football. 



#9 Reopening elite sport during the COVID-19 pandemic: Experiences from a controlled return to elite football in Denmark

Reference: Scand J Med Sci Sports. 2021 Jan 21. doi: 10.1111/sms.13915. Online ahead of print. 

Authors: Lars Pedersen, Jens Lindberg, Rune Rasmussen Lind, Hanne Rasmusen

Summary: As the SARS-CoV-2 infection rate decreased in spring 2020, phased reopening of Danish society began, including a reopening of elite football (soccer), adhering to a strict protocol. In this study, we report the consequences of resumption of competitive play in the two best football (soccer) leagues for men in Denmark measured by number of SARS-CoV-2 positive players. The players were tested weekly for SARS-CoV-2 for 11 consecutive weeks. The test protocol comprised 26 teams with 748 players. In total, 6511 tests were done with a positivity rate of 0.06%. The incidence rate of players testing positive for SARS-CoV-2 was 0.53% (4/748). There were no signs of a chain of infection. We found a low incidence rate of SARS-CoV-2, and based on this, a controlled reopening of professional football strictly following a detailed protocol appears safe for the players. 



#10 The Influence of Child-Related Factors on Caregiver Perceptions of Their Child's Sustained Participation in a Community Football Program: A Study of Children with and without Neurodevelopmental Disorders 

Reference: Int J Environ Res Public Health. 2021 Jan 19;18(2):831. doi: 10.3390/ijerph18020831. 

Authors: Carmel Sivaratnam, Bethany Devenish, Tayla Chellew, Nicole Papadopoulos, Jane McGillivray, Nicole Rinehart

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Summary: This study evaluated the influence of activity preference and involvement on season completion in a community-based football program for children with and without neurodevelopmental disorders. Caregivers (n = 1428) of 1529 children aged 4 to 17 (M = 7.27, SD = 1.85), with (n = 175) and without (n = 1354) neurodevelopmental disorders who were currently participating or had previously participated in a group-based NAB AFL Auskick football program completed an online survey. The survey collected information on their child's completion of any attempted seasons of the football program, level of involvement during the sessions and preference for football over other sports and activities. Eighty percent of children with a neurodevelopmental diagnosis had completed all seasons of Auskick, compared with 93% of children without a neurodevelopmental diagnosis. Results indicated that children with neurodevelopmental disorders (n = 135) were 3.71 times less likely to complete a football season than their typically developing peers (n = 903). Higher levels of involvement during football sessions and greater preference for football were linked to a higher football season completion rate, irrespective of neurodevelopmental disability diagnosis. This study highlights the influence of child-related factors, in particular, preference and involvement, on children's sustained participation in community football programs, regardless of neurodevelopmental disability status. 



#11 The effects of residential environment on the condition and fitness of soccer players in the summer 

Reference: J Exerc Rehabil. 2020 Dec 28;16(6):522-528. doi: 10.12965/jer.2040748.374. eCollection 2020 Dec. 

Authors: Jae-Hoon Jang, Chang-Hwa Joo

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Summary: Exercise performance is reduced in hot environments due to physiological responses caused by increased body temperature. A proper residential environment is important for improving the performance and maintaining physical condition of soccer players in the summer. The purpose of this study was to determine the effect of indoor temperature of the resting space during the summer on the fitness and condition of soccer players. A total of 12 K-3 League semiprofessional players without serious injuries in the last 3 months voluntarily participated in the study. Participants performed speed (10 m, 20 m, and 30 m), soccer-specific coordination skill (dribbling), agility, repeated sprints, Yo-Yo intermittent level 2, vertical jump, and questionnaire (fatigue, sleep quality, muscle soreness, stress, and mood) after staying indoor temperature at 20°C, 26°C, and 30°C for one night, respectively. There was no difference among groups in physical fitness (speed, agility, jump, coordination, Yo-Yo intermittent level 2, and repeated sprints). The differences in fatigue and sleep quality were not statistically significant among groups, but they tended to be different. Muscle soreness was similar among all groups. Significant differences were observed between the 20°C and 30°C groups in stress and mood levels. The present study concluded that, while the physical fitness did not differ among groups, the 30°C residential environment was shown to have a negative psychological effect. Considering that many diseases associated with hot weather occur in low residential temperatures, a room temperature of 26°C is recommended for elite soccer players in hot summer weather. 



#12 Effects of home confinement due to COVID-19 pandemic on eccentric hamstring muscle strength in football players 

Reference: Scand J Med Sci Sports. 2020 Oct;30(10):2010-2012. doi: 10.1111/sms.13768. 

Authors: Victor Moreno-Pérez, Juan Del Coso, Daniel Romero-Rodríguez, Luis Marcé-Hernández, Marcelo Peñaranda, Marc Madruga-Parera

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