Latest research in football - week 49 - 2018

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 Football Compared with Usual Care in Men with Prostate Cancer (FC Prostate Community Trial): A Pragmatic Multicentre Randomized Controlled Trial
Reference: Sports Med. 2018 Dec 1. doi: 10.1007/s40279-018-1031-0. [Epub ahead of print]
Authors: Bjerre ED, Brasso K, Jørgensen AB, Petersen TH, Eriksen AR, Tolver A, Christensen JF, Poulsen MH, Madsen SS, Østergren PB, Borre M, Krustrup P, Johansen C, Rørth M, Midtgaard J
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Summary: Physical activity has been shown to mitigate the unwanted psychological and physiological side effects of prostate cancer treatments, but sustainable exercise possibilities are limited. Our objective was to examine whether football in a real-world setting (i.e., local football clubs) was safe and feasible in practice and could improve quality of life, mitigate decline in muscle mass and bone density, and increase fat mass in patients with prostate cancer. In this pragmatic, multicentre, parallel randomized controlled trial, men diagnosed with prostate cancer were recruited from five Danish urological departments. Men (N = 214) diagnosed with prostate cancer were randomly allocated, using random generated lists (block size 4-8) stratified for center and androgen-deprivation therapy status, to either 1 h of football twice weekly in a local football club or to usual care, which was a 15- to 30-min telephone session covering their options for physical activity or free-of-charge rehabilitation delivered as standard in Denmark. Allocation was concealed from the trial investigator performing the randomization, but-given the nature of the intervention-this was not possible for personnel and participants. Assessments were performed at baseline, 12 weeks, and 6 months. The primary outcome was mean change difference in prostate cancer-specific quality of life at 12 weeks. Secondary outcomes were body composition, 12-Item Short Form Health Survey (SF-12) physical and mental health, and safety-reported as fractures, falls, and serious adverse events. Attrition was 1 and 3% at 12 weeks, and 5% and 5% at 6 months for the usual care and football groups, respectively. Prostate cancer-specific quality of life was equal between groups at 12 weeks (mean difference + 1.9 points, 95% confidence interval [CI] -1.0-4.8; P = 0.20) and at 6 months (+ 0.5 points, 95% CI -2.8-3.8; P = 0.76). Fractures were equally distributed, with two fractures in the usual care group and one in the football group. Likewise, body composition outcomes were equal. Mental health improved after 6 months of football (mean difference + 2.7 points, 95% CI 0.8-4.6; P = 0.006). In this trial, community-based football was a feasible exercise strategy for men with prostate cancer. Football did not improve prostate cancer-specific quality of life but did improve mental health; the clinical significance of this is unclear.

#2 Faster physical performance recovery with cold water immersion is not related to lower muscle damage level in professional soccer players
Reference: J Therm Biol. 2018 Dec;78:184-191. doi: 10.1016/j.jtherbio.2018.10.001. Epub 2018 Oct 12.
Authors: Bouzid MA, Ghattassi K, Daab W, Zarzissi S, Bouchiba M, Masmoudi L, Chtourou H
Summary: The aim of the present study was to assess the effects of cold water immersion (CWI) after an intermittent test on the recovery kinetic of physical performance, muscle damage and perceived muscle soreness in professionals soccer players. In a randomized design, eight soccer players completed the Loughborough Intermittent Shuttle Test followed by 10 min of either CWI (10C°) or thermoneutral water immersion (TWI) (28C°). Physical performance (Squat jump: SJ, countermovement jump: CMJ, maximal voluntary contraction: MVC, and 20 m sprint: SP), muscle damage parameter (creatine kinase: CK) and perceived muscle soreness were assessed at baseline, 0 h, 24 h, 48 h and 72 h after the intermittent test. After the test, a decrease was observed in SJ and in CMJ at 0 h, 24 h, 48 h and 72 h with TWI (p < 0.05) and only at 0 h for SJ with CWI (p < 0.05). SP decreased at 24 h and 48 h after the test with TWI (p < 0.05) and only at 24 h with CWI (p < 0.05). MVC, CK activity and perceived muscle soreness increased in both condition after the test and returned to baseline levels 72 h after the test with TWI (p < 0.05) and at 48 h with CWI (p < 0.05). For the correlation between physical performance and muscle damage parameters in CWI session, the statistical analysis didn't reveal any significant link between CK and SJ, CMJ, MVC or SP values (p > 0.05). The results suggest that CWI immediately after an intermittent test reduces muscle damage and perceived muscle soreness, and accelerate recovery of physical performance in professional soccer players. However, the faster recovery of physical performance seems not be related to the lower level of muscle damage induced by CWI.

#3 Use of Individual Relative Thresholds to Assess Acceleration in Young Soccer Players According to Initial Speed
Reference: J Strength Cond Res. 2018 Nov 29. doi: 10.1519/JSC.0000000000002902. [Epub ahead of print]
Authors: Martínez-Cabrera FI, Núñez-Sánchez FJ, Losada J, Otero-Esquina C, Sánchez H, De Hoyo M
Summary: The aims of the current study were (a) to analyze the characteristics of acceleration efforts using individual relative thresholds according to the initial speed during official matches in elite young soccer players according to player position and (b) to compare the differences between absolute and relative thresholds in assessing high-intensity acceleration. Player acceleration profiles were assessed using an individual relative threshold based on their acceleration capacity at different initial speeds (standing, 6, 10.8, and 15 km·h), and the number of accelerations (>75% of the maximal acceleration) performed during soccer matches was divided into 3 categories attending to the initial speed. (S1 = 0-7 km·h; S2 = 7.1-14 km·h; and S3 = ≥14.1 km·h). Within-group analyses showed that the number of accelerations performed in each category was higher when the effort started from a static or walking position than at moderate- or high-intensity running (S1 > S2 > S3; very likely to almost certain). Between-group analyses revealed substantial differences between some playing positions according to initial speed. In S1 and S3, central defenders had the lowest number of accelerations (likely to almost certain), whereas midfielders had the greatest number of high-intensity accelerations in S1 and S2. There were also substantial differences between the other playing positions (possibly to almost certain). Regarding relative and absolute thresholds (>3 m·s), the results showed that absolute threshold overestimated the number of high-intensity accelerations compared with the individual relative threshold in S1 and underestimated the results in S2 and S3 (almost certain). The use of an individual relative threshold to measure acceleration demands allows to distinguish between the numbers of accelerations in function of the initial speed and playing positions. In addition, the absolute acceleration threshold could overestimate or underestimate the acceleration demands in young soccer players as a function of the initial speed. Then, the absolute acceleration thresholds should be taken with caution in the assessment of acceleration activities.

#4 Ingesting a 12% Carbohydrate-Electrolyte Beverage Before Each Half of a Soccer-Match Simulation Facilitates Retention of Passing Performance and Improves High-Intensity Running Capacity in Academy Players
Reference: Int J Sport Nutr Exerc Metab. 2018 Dec 3:1-28. doi: 10.1123/ijsnem.2018-0214. [Epub ahead of print]
Authors: Rodriguez-Giustiniani P, Rollo I, Witard OC, Galloway SDR
Summary: This study investigated the influence of ingesting a 12% carbohydrate plus electrolyte (CHO-E) solution providing 60 g of carbohydrate before each half of a 90-min soccer match simulation (SMS) protocol on skill performance, sprint speed and high-intensity running capacity. Eighteen elite academy (age 18±2 y) soccer players ingested two 250 mL doses (pre-exercise and at half-time) of a 12% CHO-E solution or electrolyte placebo administered in a double-blind randomised cross-over design. During an indoor (artificial grass pitch) SMS, dribbling, passing and sprint performance were assessed, and blood was drawn for glucose and lactate analysis. High-intensity running capacity was assessed following the SMS. Dribbling speed/accuracy and sprint speed remained unchanged throughout the SMS. Conversely, passing accuracy for both dominant (mean % difference (95% CI): 9 (3-15)) and non-dominant (mean % difference (95% CI): 13 (6-20)) feet was better maintained during the SMS on CHO-E (p<0.05), with passing speed better maintained in the non-dominant foot (mean % difference (95% CI): 5.3 (0.7 to 9.9), p=0.032). High-intensity running capacity was greater in CHO-E vs. placebo (mean % difference (95% CI): 13 (6 to 20), p=0.010). Capillary blood glucose concentration was higher in CHO-E than placebo at half-time (CHO-E: 5.8±0.5 mM vs. placebo: 4.1±0.4 mM, p=0.001) and following the high-intensity running capacity test (CHO-E: 4.9±0.4 mM vs. placebo: 4.3±0.4 mM, p=0.001). Ingesting a 12% CHO-E solution before each half of a match can aid in the maintenance of soccer-specific skill performance, particularly on the non-dominant foot, and improves subsequent high-intensity running capacity.

#5 Ruptured Extensor Pollicis Longus Tendon After a Nondisplaced Distal Radius Fracture in a Young Adult Soccer Player
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000708. [Epub ahead of print]
Authors: Bogart R, Vidlock K
Summary: Forearm fractures of the distal radius are one of the most common fractures seen in the upper extremity, and they represent approximately 1/6 of fractures treated in the emergency department. Forearm fractures are associated with a rare but known complication of a delayed ruptured extensor pollicis longus (EPL) tendon. This sequela is more commonly seen in adults after a nondisplaced distal radius fracture, with much variability in the incidence ranging from 0.07% to 5%. By contrast, this complication in the pediatric population is almost exclusively seen after a displaced or unstable fracture necessitating surgical correction with open reduction and internal fixation.

#6 Postural Control Deficits After Repetitive Soccer Heading
Reference: Clin J Sport Med. 2018 Dec 13. doi: 10.1097/JSM.0000000000000709. [Epub ahead of print]
Authors: Caccese JB, Buckley TA, Tierney RT, Rose WC, Glutting JJ, Kaminski TW
Summary: The objective was to determine the acute effects of repetitive soccer heading on postural control. One hundred sixty participants, including youth (age = 13.0 ± 0.8 years), high school (age = 17.2 ± 1.0 years), and collegiate (age = 20.2 ± 1.3 years) male and female soccer players, participated in this study. Participants in the soccer heading group performed 12 soccer headers (initial velocity = 11.2 m/s). Postural control testing was performed both before (PRE) and immediately after (POST) the purposeful soccer headers. Control participants performed postural control testing PRE and POST a 15-minute wait period. During postural control testing, participants were asked to stand on the MobileMat (Tekscan Inc, Boston, Massachusetts) for two 2-minute intervals with their hands on their hips and their feet together with one eyes-open and one eyes-closed trial. Using the center-of-pressure data, 95% area, sway velocity, and ApEn were calculated. Multilevel linear models were used to analyze the effects of age, sex, group, condition, and concussion history simultaneously. Participants in the soccer heading group had significantly higher sway velocity POST than participants in the control group after controlling for age, sex, concussion history, condition, and PRE (t = -3.002; P = 0.003; 95% confidence interval, -0.482 to -0.100). There were no significant differences from PRE to POST for 95% area, M/L ApEn, and A/P ApEn. Repetitive soccer heading does not affect most postural control measures, even among youth athletes. However, sway velocity increased after heading relative to control participants independent of age, sex, and concussion history.

#7 A Match-Derived Relative Pitch Area Facilitates the Tactical Representativeness of Small-Sided Games for the Official Soccer Match
Reference: J Strength Cond Res. 2018 Dec 13. doi: 10.1519/JSC.0000000000002978. [Epub ahead of print]
Authors: Olthof SBH, Frencken WGP, Lemmink KAPM
Summary: Small-sided games (SSGs) are a promising training format in soccer to replicate (situations of) the official match across all age groups. Typically, SSGs are played on a smaller relative pitch area (RPA; i.e., <150 m) than the match (320 m RPA), which results in different tactical demands. To create a more precise replication of tactical match demands in SSGs with less than 11 players per team, a match-derived RPA (320 m) may be considered because this affords a similar playing area per player. In addition, subgroup analysis is necessary to deal with the different number of players in match and SSGs. Therefore, this study aims to investigate tactical demands of matches and various SSGs-with a different number of players and played on 320 m RPA-in talented youth soccer players. Twelve elite soccer teams in 4 age categories (under-13, under-15, under-17, and under-19) played official matches and 4 vs. 4 + goalkeepers (GKs), 6 vs. 6 + GKs, and 8 vs. 8 + GKs. Positional data were collected to calculate tactical variables (interpersonal distances, length, width, and surface areas) for all players and for 2- and 4-player subgroups. Corresponding tactical variability (coefficients of variation expressed as percentages) was determined for all players. Results demonstrated that in each age category, with an increase in number of players, team distances increased and tactical variability decreased. Subgroup analyses revealed similar team distances in matches and SSGs with the exception of larger interpersonal distances in 4 vs. 4 + GKs than the match in under-13, under-15, and under-17. Match-derived RPA in SSGs facilitates the tactical representativeness for the match. Soccer coaches can use such SSGs for an optimal tactical match preparation.This is an open-access article distributed under the terms of the Creative Commons Attribution-Non Commercial-No Derivatives License 4.0 (CCBY-NC-ND), where it is permissible to download and share the work provided it is properly cited. The work cannot be changed in any way or used commercially without permission from the journal.

#8 A 9-months multidisciplinary rehabilitation protocol based on early post-operative mobilization following a chronic-degenerative patellar tendon rupture in a professional soccer player: a case report
Reference: Eur J Phys Rehabil Med. 2018 Dec 14. doi: 10.23736/S1973-9087.18.05479-5. [Epub ahead of print]
Authors: Vitale JA, Banfi G, Belli E, Negrini F, La Torre A
Summary: Isolated patellar tendon rupture (PTR) is the final stage of a long-standing tendon chronic degeneration. PTR requires immediate repair in order to avoid important muscle retraction and tendon fibrosis. The aim was to describe the effects of a rehabilitation protocol after chronic-degenerative PTR on subjective functional outcomes, knee range of motion (ROM), size, and strength in a professional football player. A 26-years-old football player who experienced RPT after a 3-year history of proximal patellar tendinopathy. After early surgical repair of the tendon, the athlete underwent a 9-months multidisciplinary rehabilitation program, based on early post-operative mobilization. Early knee mobilization and gradual controlled load from the second week determined a large increase in flexion ROM, muscular strength and trophy over the weeks by the athlete. Early surgical repair of PTR together with an early knee mobilization program demonstrated excellent results after a 9-months follow-up.

#9 Comparative Analysis of Load Profile between Small-Sided Games and Official Matches in Youth Soccer Players
Reference: Sports (Basel). 2018 Dec 12;6(4). pii: E173. doi: 10.3390/sports6040173.
Authors: Gómez-Carmona CD, Gamonales JM, Pino-Ortega J, Ibáñez SJ
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Summary: The purposes of the present study are: (a) to characterize the external (eTL) and internal load (iTL) of official matches and small-sided games (SSGs) in relation to their objective, (b) to compare demands between SSG, and (c) to analyze the SSG requirements in relation to official matches during a one-month competition period. Twenty under-18 national-level soccer players were recorded using WIMUTM inertial devices (RealTrack Systems, Almeria, Spain) during four official matches and 12 training sessions where four SSGs with different objectives were performed: (SSG1) keeping the ball; (SSG2) keeping the ball and progressing; (SSG3) keeping the ball, progressing and ending in mini-goals; and (SSG4) keeping the ball, progressing and ending in an official goal with a goalkeeper. Statistical analysis included Kruskall-Wallis' H and Mann-Whitney's U with Cohen's d effect size. The SSGs presented walking and jogging intensity movements (0.7⁻7 to 7⁻14 km/h), with a 5-to-8 %HIA (high intensity activity, >16 km/h), where low intensity accelerations, decelerations and impacts were predominant (1⁻2.5 m/s²; 5⁻7 G), and %HRMAX (maximum heart rate percentage) was between 70⁻90%. Only SSG4 presented similar demands to competition, finding differences between SSGs (p < 0.05; d = 1.40 - 0.36). In conclusion, the objective of the SSGs directly influenced the demands on the players in training sessions. For this reason, it is important to monitor demands for designing specific training sessions.

#10 Spatiotemporal and Kinetic Determinants of Sprint Acceleration Performance in Soccer Players
Reference: Sports (Basel). 2018 Dec 9;6(4). pii: E169. doi: 10.3390/sports6040169.
Authors: Murata M, Takai Y, Kanehisa H, Fukunaga T, Nagahara R
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Summary: We aimed to elucidate spatiotemporal and kinetic determinants of sprint acceleration performance in soccer players. Thirty-seven male soccer players performed 60-m sprints. The spatiotemporal variables and ground reaction impulses were calculated over a 50-m distance. When controlling the influence of stature and body mass, change in running speed was correlated with the step length at the 1st⁻4th step section (r = 0.695), step frequency from the 9th to 20th step sections (r = 0.428 to 0.484), braking impulse during the 17th⁻20th step section (r = 0.328), propulsive impulse from the 1st to 8th step sections (r = 0.738 and 0.379), net anteroposterior impulse for all step sections (r = 0.384 to 0.678), and vertical impulse from the 9th⁻12th step section and thereafter (r = -0.355 to -0.428). These results confirmed that an effective acceleration is probably accomplished by a greater step length originated in greater propulsive impulse during the initial acceleration phase (to the 8th step), a higher step frequency through smaller vertical impulse and smaller braking impulse during the middle and later acceleration phases (from the 9th step), as well as greater net anteroposterior impulse during the entire acceleration phase.

#11 Positional Differences in GPS Outputs and Perceived Exertion During Soccer Training Games and Competition
Reference: J Strength Cond Res. 2018 Nov;32(11):3222-3231. doi: 10.1519/JSC.0000000000002387.
Authors: Abbott W, Brickley G, Smeeton NJ
Summary: Soccer training games are popular training modalities, allowing technical, tactical, and physical aspects to be trained simultaneously. Small (SSGs), medium (MSGs), and large training games (LSGs) elicit differing physical demands. To date, no research has investigated physical and perceived demands of training games on soccer playing positions relative to competitive demands. In addition, previous research has referenced average competitive intensities, ignoring peak demands of competition. The current aim was to investigate the effect of training game formats on average and peak physical outputs produced by soccer playing positions. Physical and perceptual data from 22 competitive matches and 39 training game sessions were collected for 46 U23 professional players using 10-Hz global positioning system (GPS) and 100-Hz accelerometer devices (MinimaxX version 4.0; Catapult Innovations, Melbourne, Australia). Data analyzed included GPS-derived distance, speed, acceleration, deceleration, and rating of perceived exertion (RPE). Two-way between-subjects analyses of variance were used to compare average and peak GPS metrics, and RPE, between training games and competition for playing positions. Despite eliciting significantly higher average total distances compared with competition (p < 0.01), LSGs produced significantly lower peak total distance relative to the competition (p < 0.01). For very high-speed running and sprinting, LSGs elicited similar average intensities to competition; however, peak intensities were significantly lower than competition (p < 0.01). Medium training games and LSGs produced significantly higher average and peak moderate-intensity explosive distances than competition (p < 0.01). Results indicate the importance of analyzing relative to peak competitive demands, instead of focusing solely on average demands. The study demonstrates that specific game formats can overload the competitive demands of playing positions and provide an individualized training stimulus.

#12 Pre-season Fitness Level and Injury Rate in Professional Soccer - A Prospective Study
Reference: Sports Med Int Open. 2018 Aug 22;2(3):E84-E90. doi: 10.1055/a-0631-9346. eCollection 2018 Jun.
Authors: Eliakim E, Doron O, Meckel Y, Nemet D, Eliakim A
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Summary: The aim of the present study was to assess prospectively the effect of pre-season fitness on injury rate during the competitive season among professional soccer players. Thirty-one players participated in the study during two consecutive competitive seasons (2015-16 and 2016-17; a squad of 22 players in each season). During the 6-week pre-season training period (8 training sessions and a friendly match every week, 14-18 training hours/week) there was a significant improvement in VO 2 max, a significant increase in ideal and total sprint time and no change in vertical jump, flexibility and repeated sprint-test performance decrement. During the two consecutive seasons, 28 injuries were recorded. Ten injuries were classified as mild (missing 3-7 days of practice/match), 8 as moderate (missing 8-28 days) and 10 as severe (missing >28 days). The rate of match injuries was higher (9.4 per 1000 match hours) compared to practice injuries (4.7 per 1000 training hours). Most injuries were overuse injuries (72%) of the lower limbs (71%). Most of match injuries occurred during the last 15 min of each half. There were no differences in fitness characteristics in the beginning of pre-season training between injured and non-injured players. However, improvements in VO 2 max during the pre-season training period were significantly lower among injured players (0.9±5.5%) compared to non-injured players (10.4±6.5%, p<0.05). Our results emphasize the importance of pre-season training in professional soccer players not only for improvement in fitness but also for injury prevention during the following competitive season.

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