Latest research in football - week 10 - 2020

#1 Player-surface interactions: perception in elite soccer and rugby players on artificial and natural turf
Reference: Sports Biomech. 2020 Mar 4:1-11. doi: 10.1080/14763141.2020.1720279. [Epub ahead of print]
Authors: Strutzenberger G, Edmunds R, Nokes LDM, Mitchell ID, Mellalieu SD, Irwin G
Summary: Artificial turf (AT) is common at all levels of soccer and rugby. Employing an interdisciplinary design, this study aimed to examine the extent to which the negative attitude commonly expressed by players concerning AT is based on the difference in technique between AT and natural turf (NT), or due to pre-existing biases. Thirty professional soccer and rugby players performed a defined set of movements with masked and normal perception conditions on NT and AT. Two-dimensional kinematic analysis (100 Hz) of characteristics in parallel to a psychological assessment of the impact of cognitive bias for a playing surface was assessed. No significant interaction effects between the level of perception and surface type were found. For AT, contact time (CT) was shorter across conditions, while for NT rugby players had longer CT during acceleration/deceleration phases and shorter flight times. Pre-existing negative bias against AT was found during the normal perception trials in the technology acceptance model (Usefulness and Ease of Use) and the general preference questions on how much the athlete would like to play a game on it. The results suggest that opinion was not driven by surface characteristics, but by a cognitive bias, players brought with them to the pitch.


#2 Chronic Beetroot Juice Supplementation Accelerates Recovery Kinetics following Simulated Match Play in Soccer Players
Reference: J Am Coll Nutr. 2020 Mar 3:1-9. doi: 10.1080/07315724.2020.1735571. [Epub ahead of print]
Authors: Daab W, Bouzid MA, Lajri M, Bouchiba M, Saafi MA, Rebai H
Summary: The purpose was to assess the effect of beetroot juice (BET) on recovery kinetics of physical performance, muscle damage and perceived muscle soreness after simulated soccer match play in soccer players. In a randomized, double-blind, crossover design, thirteen soccer players completed the Loughborough Intermittent Shuttle Test LIST. Players received either BET or placebo (PLA) (2*150) for 7 days (3 days pre-exercise, on the day trial, and 3 days post-exercise). Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 meters sprint: SP), blood markers of muscle damage (creatine kinase: CK, Lactate dehydrogenase: LDH), inflammatory parameter (C-reactive protein: CRP) and perceived muscle soreness (DOMS) were assessed at baseline, 0 h, 24 h, 48 h and 72 h following the exercise. Following the LIST, a decrease was observed in CMJ, MVC and SP at 0 h, 24 h, 48 h in both conditions (p < 0.05). However, compared to PLA session, this decrease was significantly attenuated with BET for CMJ at 24 h and at 48 h and for MVC at 0 h, 24 h, 48 h and for SP at 48 h after the LIST (p < 0.05). Likewise, DOMS values were significantly lower with BET compared to PLA condition immediately and at 24 h after exercise.CK, LDH and CRP levels increased at 0 h and at 24 h post exercise in both conditions (p < 0.05), but without any significant difference between the two condition (p > 0.05). The results of the present study suggest that chronic beetroot juice supplementation reduces post exercise perceived muscle soreness and maintain better performance during the recovery period in soccer players.


#3 The physical demands of professional soccer goalkeepers throughout a week-long competitive microcycle and transiently throughout match-play
Reference: J Sports Sci. 2020 Mar 2:1-7. doi: 10.1080/02640414.2020.1736244. [Epub ahead of print]
Authors: White A, Hills SP, Hobbs M, Cooke CB, Kilduff LP, Cook C, Roberts C, Russell M
Summary: The physical demands of English Premier League soccer goalkeepers were quantified during training and match-play in a two-part study. Goalkeeper-specific micromechanical electrical systems (MEMS) devices, profiled training and match-day activities throughout one competitive week (n=8; part A). Changes in MEMS-derived outputs were also profiled throughout match-play (100 matches; n=8, 18±14 observations per goalkeeper; part B). In part A, goalkeeping-training elicited the most dives (51±11) versus all activities (all p≤0.030) except shooting-training (p=0.069). Small-sided games elicited the fewest (5±3) dives (all p≤0.012). High-speed distance covered in match (103±72 m) was similar to goalkeeping-training (p=0.484), while exceeding shooting-training, small-sided games, pre-match shooting, and pre-match warm-up (all p=0.012). Most changes of direction (34±12) and explosive efforts (70±18) occurred during goalkeeping-training, with values exceeding match (both p=0.012). In part B, between-half reductions in total distance, but increased high-speed changes of direction and explosive efforts, occurred (both p≤0.05). Excluding the number of high jumps, all variables differed from 0-15-min during at least one match epoch, with more dives (1.3±1.4 vs 1.0±1.1) and explosive efforts (2.5±2.4 vs 2.0±1.8) performed between 75-90-min versus 0-15-min (all p<0.05). These data highlight the differing physical demands of various activities performed by professional soccer goalkeepers throughout a competitive week.


#4 Psychometric Analysis and Effectiveness of the Psychological Readiness of Injured Athlete to Return to Sport (PRIA-RS) Questionnaire on Injured Soccer Players
Reference: Int J Environ Res Public Health. 2020 Feb 27;17(5). pii: E1536. doi: 10.3390/ijerph17051536.
Authors: Gómez-Piqueras P, Ardern C, Prieto-Ayuso A, Robles-Palazón FJ, Cejudo A, Baranda PS, Olmedilla A
Download link: https://www.mdpi.com/1660-4601/17/5/1536/pdf
Summary: The decision-making process about when an athlete may safely return to training and competition after an injury is a difficult decision. Safe return to training and competition is characterised by physical and psychological readiness to return to the sport. The objectives of this study are (1) to assess the measurement properties of the Psychological Readiness of Injured Athlete to Return to Sport questionnaire (PRIA-RS), and (2) to analyse the effectiveness which the PRIA-RS questionnaire possesses when applied during four consecutive seasons on professional soccer players. One hundred and nine male soccer players from the Albacete Soccer Club (Spain) were involved during four consecutive seasons for the current study: 2012-2013, 2013-2014, 2014-2015 and 2015-2016. Psychometric analysis (validity, reliability, internal consistency and effectiveness) and external psychometric analysis (evaluating measures of patient-reported outcomes (EMPRO)) were confirmed and supported. The main results of the study reveal that the psychometric properties of this questionnaire are optimum for their application in a professional sports context.


#5 Validity of Field Methods to Estimate Fat-Free Mass Changes Throughout the Season in Elite Youth Soccer Players
Reference: Front Physiol. 2020 Feb 12;11:16. doi: 10.3389/fphys.2020.00016. eCollection 2020.
Authors: Núñez FJ, Munguía-Izquierdo D, Suárez-Arrones L
Download link: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7029743/pdf/fphys-11-00016.pdf
Summary: The aim of this study was to determine the most effective anthropometric equations or bioelectrical impedance analysis (BIA) devices for quantifying the sensitivity to change in fat-free mass (FFM) in elite young soccer players, in comparison with measurements using dual-energy X-ray absorptiometry (DXA), between the pre- and mid-season. A total of 40 elite youth soccer players participated in this study. DXA values provided a criterion measure of FFM. Correlation coefficients, biases, limits of agreement, and differences were used as measures of sensitivity to change. All body density, skinfold, and anthropometric equations and BIA devices used to obtain FFM data showed positive and very large correlations (r from 0.70 to 0.89) with DXA. A significant increase in FFM was shown between time points using DXA, BIA, and all anthropometric equations (p < 0.01). The magnitudes of differences were small for DXA, BIA inbody and all anthropometric equations except those of Faulkner (1966), Durnin and Rahaman (1967), Brook (1971), and Sarría et al. (1998). Six anthropometric equations [Faulkner (1966), Durnin and Womersley (1974), Carter (1982), Slaughter et al. (1988), Reilly et al. (2009), and Munguia-Izquierdo et al. (2018)] and BIA Tanita showed no statistical differences compared to DXA, with a low bias. We concluded that the equations developed by Durnin and Womersley (1974), Carter (1982), Slaughter et al. (1988), Reilly et al. (2009), and Munguia-Izquierdo et al. (2018) showed the best sensitivity in assessing FFM changes between pre- and mid-season in elite youth soccer players.


#6 Psychometric properties of the standardized assessment of concussion in youth football: Validity, reliability, and demographic factors
Reference: Appl Neuropsychol Child. 2020 Mar 6:1-7. doi: 10.1080/21622965.2020.1726746. [Epub ahead of print]
Authors: Maerlender A, Smith E, Brolinson PG, Urban J, Rowson S, Ajamil A, Campolettano ET, Gellner RA, Bellamkonda S, Kelley ME, Jones D, Powers A, Beckwith J, Crisco J, Stitzel J, Duma S, Greenwald RM
Summary: The objective of this study was to determine the psychometrics (reliability, validity) of the original Standardized Assessment of Concussion (SAC) in a youth sample (ages 11 to 13). Demographic factors of race, level of vocabulary knowledge, mother's level of education were also considered. Over 150 youth football athletes completed the SAC and a brief battery of NIH Toolbox cognitive tests as part of a larger study on biomechanical factors in youth sport concussion. This was a within-subjects design (pre-season, post-season assessments), and correlational analysis of convergent and discriminant validity. Between groups analysis based on demographic differences was also employed. The pre-season SAC scores were not different by age; however, SAC scores were statistically different by race: t(155) = 3.162, p = .002, d = .519. Maternal level of education and participant vocabulary scores were related to racial group membership. Convergent and discriminant validity were established compared to NIH Toolbox tests of memory and speed. Pre-post-season tests for 108 participants established marginally acceptable test-retest reliability (ICC = .692). These data support the use of the original SAC in youth football although clinicians must be aware of racial differences in scores.


#7 Surgical excision of post-traumatic myositis ossificans of the adductor longus in a football player
Reference: BMJ Case Rep. 2020 Mar 3;13(3). pii: e233504. doi: 10.1136/bcr-2019-233504.
Authors: de Smet GHJ, Buijk SE, Weir A
Download link: https://casereports.bmj.com/content/bmjcr/13/3/e233504.full.pdf
Summary: A football player was diagnosed with myositis ossificans of his right adductor longus muscle after an acute injury. Conservative treatment failed and 1 year after the initial trauma the patient underwent surgical excision of a large ossification. Seven months postoperatively, the patient was fully recovered and returned to his preinjury activity levels. We present our approach to this case and discuss our considerations, referring to background information about this rare disease.


#8 Bone metabolism, bone mass and structural integrity profile in professional male football players
Reference: J Sports Med Phys Fitness. 2020 Feb 27. doi: 10.23736/S0022-4707.20.09913-2. [Epub ahead of print]
Authors: Filippella M, Altieri B, Falchetti A, Cosso R, Cena H, Musso C, Geronutti E, Rassat L, Cipriani G, Colao A, Di Somma C, Faggiano A
Summary: Physical exercise plays an important role in bone mineralization as well as factors involved in bone metabolism influence the athletic performance. In European countries, soccer is the most popular sport. The aim of the study was to investigate bone metabolism, bone mass and structural integrity profile in professional male adult football players. Sixteen professional male football players from a single team of the 2nd division Italian League (mean age 22.4±0.7 years) were enrolled. Bone biochemical parameters, including serum calcium, phosphorus, albumin, creatinine, alkaline phosphatase, intact plasma PTH, 25-hydroxy- vitamin D (25-OHD), 24-h urinary calcium and phosphorus, and calcaneal quantitative ultrasound (QUS), were evaluated at the beginning (October 2012) and at the end of the League (May 2013). 25-OHD levels were significantly lower at the end of the League compared to the beginning (27.1 ± 5.9 vs 36.6 ± 9.5 ng/ml, fold change (FC)=0.25, p=0.008), and the prevalence of 25-OHD deficiency increased from 25 to 73%. Moreover, higher rate of previous bone, cartilage or ligament injuries correlated with 25-OHD deficiencies (p=0.014). T-score and Z-score were at the upper limits of the normality ranges, without significant difference between the beginning and end of the League. Phosphaturia was slightly decreased at the end of the League [(691.0 ± 364.5 vs 934.0 ± 274.3 mg/24h, FC=0.26, p=0.06)]. A significant correlation was found between phosphaturia and BQI (R square=0.28, p=0.03), and both T-s and Z-s (R square=0.28, p=0.03) at the beginning of the League. With this pilot study, we demonstrated that vitamin D status significantly worsened at the end of the League. Therefore, vitamin D supplementation might be suggested in adult football players in order to prevent vitamin D deficiency and improve the athletic performance.


#9 Resisted Sprint Velocity in Female Soccer Players: Influence of Physical Capacities
Reference: Int J Sports Med. 2020 Mar 11. doi: 10.1055/a-1083-6724. [Epub ahead of print]
Authors: Loturco I, Jeffreys I, Kobal R, Reis VP, Fernandes V, Rossetti M, Pereira LA, McGuigan M
Summary: This study aimed to examine the effects of different sled overloads on maximum sprint velocity achieved by female soccer players with different strength, speed, and power levels. Twenty elite female soccer players from the same club participated. On the same day, athletes performed: linear and resisted-sprint tests with 30 and 60 % of body-mass over 5-, 10-, and 20-m; half-squat maximum bar-power output, and half-squat one-repetition maximum assessment. A median split analysis was used to divide players into two groups according to their velocity, half-squat one-repetition maximum, and half-squat power. Differences in percentage decreases between unresisted- and resisted-sprints comparing higher and lower groups were analyzed using magnitude-based inferences. Overall, the stronger, faster, and more powerful players were less affected by both loads, as demonstrated by their lower decreases in velocity over the different distances. However, half-squat power appeared to be more sensitive for indicating impairments in resisted-sprint performance, due to meaningful differences in percentage decreases observed between higher and lower power groups. Notably, overloads of 30 and 60% of body-mass provoked substantial reductions in resisted-sprint velocity (~22.9% for 30% and ~51.4% for 60% of body-mass, relative to unresisted-sprint velocity). Athletes with superior power levels are less affected by the progressive sled overloading.


#10 Genetic interplay with soccer ball heading
Reference: Nat Rev Neurol. 2020 Mar 9. doi: 10.1038/s41582-020-0334-6. [Epub ahead of print]
Authors: Smith DH, Stewart W
Download link: https://www.nature.com/articles/s41582-020-0334-6.pdf


#11 The Effects of a Mindfulness-Based Program on the Incidence of Injuries in Young Male Soccer Players
Reference: J Sport Exerc Psychol. 2020 Mar 9:1-11. doi: 10.1123/jsep.2019-0003. [Epub ahead of print]
Authors: Naderi A, Shaabani F, Gharayagh Zandi H, Calmeiro L, Brewer BW
Summary: The authors tested the effectiveness of a mindfulness-based program in reducing sport-injury incidence. A total of 168 young male elite soccer players were randomly assigned to mindfulness and control groups. The mindfulness group consisted of seven sessions based on the mindfulness-acceptance-commitment approach, while the control group consisted of seven presentations on sport-injury psychology. Athlete exposure and injury data were recorded during one season. State and trait mindfulness, sport anxiety, stress, and attention control of participants were assessed. Number of injuries, average of injuries per team, and days lost to injury in the mindfulness group were significantly lower than those in the control group. Mindfulness and attention control were lower and sport anxiety and stress were higher in injured players than in noninjured players. Psychological variables were associated with injury. Mindfulness training may reduce the injury risk of young soccer players due to improved mindfulness and attention control and reduced sport anxiety.