Latest research in football - week 10 - 2019

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 Lateral foot pain due to os vesalianum pedis in a young football player; a case report and review of the current literature
Reference: Skeletal Radiol. 2019 Feb 27. doi: 10.1007/s00256-019-03190-4. [Epub ahead of print]
Authors: Aykanat F, Vincenten C, Cankus MC, Kose O, Sindel M
Summary: Os vesalianum pedis is a rare accessory ossicle located at the 5th metatarsal base. This anatomic variation is typically asymptomatic and usually detected incidentally on routine foot radiographs. However, it may be a source of lateral foot pain and rarely become symptomatic following traumatic ankle injuries such as an inversion ankle sprain. To date, seven symptomatic os vesalianum pedis cases that required surgical treatment have been reported in the current literature. Herein, a 17-year-old professional football player with a symptomatic os vesalianum pedis was presented. The ossicle was surgically removed upon failure of conservative treatment. At the sixth month, the patient returned to sport without any restriction or pain. Clinical presentation, diagnosis, and treatment options of symptomatic os vesalianum pedis were discussed with an extensive literature review.

#2 Applying the New Teaching Methodologies in Youth Football Players: Toward a Healthier Sport
Reference: Front Physiol. 2019 Feb 13;10:121. doi: 10.3389/fphys.2019.00121. eCollection 2019.
Authors: García-Angulo A, García-Angulo FJ, Torres-Luque G, Ortega-Toro E
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Summary: At early ages (6-12 years), the levels of physical activity developed in sports initiation and Physical Education often fall short of optimal levels. Ecological models of education seek, among other things, to make up for this deficit by modifying the structural elements of sport, bringing play closer to the child's developmental characteristics. In this sense, Nonlinear Pedagogy is a model of active pedagogy that seeks the integral development of young players through a sport more in line with their abilities, and that for this is based on a system of constraints on the environment, the task and the player himself. However, there are no studies that analyze the effects of these methodologies on the parameters of physical activity at such an early age. The aim of this study was to analyze the impact of a learning methodology based on Nonlinear Pedagogy on health-related levels of physical activity (heart rate) in young football players (U-11). A quasi-experimental study was developed in which three tasks were applied using structural modifications of the football elements related to Nonlinear Pedagogy (modification of the number of players related to situations of inferiority, equality and numerical superiority; dimensions of the field of play). The sample studied was composed of football players, U-11 n = 32), age: 10.35 ± 0.54 years; years of experience: 2.14 ± 0.768 years. The players carried out each task for 10 min. Physical activity levels were measured by controlling heart rate using heart rate monitors (Polar Team2). The results showed very high levels of vigorous and very vigorous physical activity in all the tasks designed. These data show that the use of these new teaching methodologies has an impact on levels of physical activity in accordance with the recommended parameters.

#3 A combination of oral L-citrulline and L-arginine improved 10-min full-power cycling test performance in male collegiate soccer players: a randomized crossover trial
Reference: Eur J Appl Physiol. 2019 Feb 16. doi: 10.1007/s00421-019-04097-7. [Epub ahead of print]
Authors: Suzuki I, Sakuraba K, Horiike T, Kishi T, Yabe J, Suzuki T, Morita M, Nishimura A, Suzuki Y
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Summary: The purpose of the study was to investigate Oral L-citrulline (Cit) that increases plasma L-arginine (Arg) concentration and the production of nitric oxide (NO). NO dilates blood vessels and potentially improves sports performance. The combination of oral Arg and Cit (Arg + Cit) immediately and synergistically increases plasma Arg and nitrite/nitrate (NOx) concentrations more than either Cit or Arg alone. This prompted us to assess the effects of oral Arg + Cit on 10-min cycling performance in a double-blind, randomized, placebo-controlled crossover trial. Twenty-four male soccer players ingested either Cit + Arg or placebo (both 1.2 g/day each) for 6 days. On day 7, they ingested Cit + Arg 1 h before performing a 10-min full-power pedaling test on a bicycle ergometer. Plasma NOx and amino acid levels were measured before and after the test, as well as the participants' subjective perception of physical exertion. Power output was significantly greater with Cit + Arg than in the placebo group (242 ± 24 vs. 231 ± 21 W; p < 0.05). Plasma concentrations of post-exercise NOx (p < 0.05), Cit (p < 0.01) and Arg (p < 0.01) were significantly higher in the Cit + Arg than in the placebo group, whereas exercise upregulated plasma NOx concentrations in both groups (p < 0.05). Cit + Arg also gave improved post-exercise subjective perception of "leg muscle soreness" and "ease of pedaling" (both p < 0.05). Seven days of oral Citrulline (1.2 g/d) and Arginine (1.2 g/d) ingestion improved 10-min cycling performance and the perception of physical exertion in male collegiate soccer players.

#4 Fat Oxidation Rates in Professional Soccer Players
Reference: Med Sci Sports Exerc. 2019 Mar 4. doi: 10.1249/MSS.0000000000001973. [Epub ahead of print]
Authors: Randell RK, Carter JM, Jeukendrup AE, Lizarraga MA, Yanguas JI, Rollo I
Summary: Large inter-individual variation exists in maximal fat oxidation rates (MFO) and the exercise intensity at which it occurs (FATMAX). However, there is no data describing the shape of the fat oxidation curve or, if individual differences exist when tested on separate occasions. Furthermore, there is limited data on fat metabolism in professional team sport athletes. Therefore, the aim of this study was to test-retest the concavity (shape) and intercept (height) of fat oxidation curves within a group of professional soccer players. On two occasions 16 professional male soccer players completed a graded exercise test in a fasted state (≥5 h). Rates of fat oxidation were determined using indirect calorimetry. Maximal oxygen uptake (VO2max) was measured to calculate FATMAX (%VO2max). The shape of the fat oxidation curves were modelled on an individual basis using third degree polynomial. Test-by-test differences, in the shape and vertical shift of the fat oxidation curves, were established to assess within-individual variability. Average absolute MFO was 0.69 ± 0.15 g[BULLET OPERATOR]min (range 0.45 - 0.99g[BULLET OPERATOR]min). On a group level, no significant differences were found in MFO between the two tests. No differences were found (p>0.05) in the shape of the fat oxidation curves in 13/16 players (Test1 vs. Test2). There were also no differences (p>0.05) in the vertical shift of the fat oxidation curves in 10 players. In general, the shape of the fat oxidation curve does not change within an individual however the vertical shift is more susceptible to change, which may be due to training status and body composition. Understanding a player's metabolism may be of value to practitioners working within sport, with regards to personalising nutrition strategies.

#5 Adolescent characteristics of youth soccer players: do they vary with playing status in young adulthood?
Reference: Res Sports Med. 2019 Mar 6:1-12. doi: 10.1080/15438627.2019.1586704. [Epub ahead of print]
Authors: Figueiredo AJ, Coelho-E-Silva MJ, Sarmento H, Moya J, Malina RM
Summary: Adolescent characteristics of young adult soccer players (n = 35) were compared with those of youth teammates (n = 124) no longer involved in soccer. Former U-13 players active in soccer as young adults were slightly later in maturation and performed better in several functional and soccer skills than youth teammates. Former U-15 players active in soccer as young adults did not differ in maturity status from youth teammates but were chronologically older and performed better in agility and ball control. Young adult regional and national players in both age groups were rated significantly higher on the potential for success by their youth coaches, and national players were rated significantly higher than regional players. The results highlight the need for study of interactions among coaches, youth training and playing environments and the growth, maturity, functional, skill and behavioural characteristics of youth players, and how these interactions may influence persistence in soccer and later playing status.

#6 Match Fatigue Time-Course Assessment Over Four Days: Usefulness of the Hooper Index and Heart Rate Variability in Professional Soccer Players
Reference: Front Physiol. 2019 Feb 19;10:109. doi: 10.3389/fphys.2019.00109. eCollection 2019.
Authors: Rabbani A, Clemente FM, Kargarfard M, Chamari K
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Summary: The aims of the present study were to (a) examine recovery time-course and (b) analyze the usefulness of the Hooper-Index (wellness index) and resting heart rate variability (HRV) in professional soccer players during an in-season phase. The Hooper-Index and resting HRV were collected on matchday and on the four following days in three consecutive in-season weeks in nine players (25.2 ± 4.3-years). The usefulness of monitoring variables was assessed by (a) comparing noise (typical error, TE) to the smallest worthwhile change (SWC) (TE/SWC) and (b) comparing match-related changes (i.e., signal) to TE (i.e., signal-to-noise ratio). Between-days standardized differences in the changes of Hooper-Index and HRV were compared to the SWC using magnitude-based inferences. The magnitudes of TE were small and moderate for the Hooper-Index and HRV, respectively. The Hooper-Index showed to be more useful than HRV for monitoring match-induced fatigue as having a lower TE/SWC (3.1 versus 4.4) and a higher signal-to-noise ratio (5.5 versus 1.5). Small-to-very large [range of effect sizes, 0.48; 2.43, confidence limits (0.22; 2.91)] and moderate-to-large [-1.71; -0.61 (-2.44; -0.03)] detrimental changes in Hooper-Index and HRV, respectively, were observed on the days following matchday. While group analyses showed a similar pattern for recovery time-course, more individual players responded, similarly when tracked using the Hooper -Index compared to when they were tracked using HRV. An inverse moderate within-individual relationship was observed between changes in the Hooper index and HRV [r = -0.41, (-0.60, 0.18)]. The Hooper index is an easy-to-use, no-cost, and non-invasive monitoring tool and seems promising for tracking match-induced fatigue during in the season in professional soccer.

#7 Epidemiological profile of soccer-related injuries in a state Brazilian championship: An observational study of 2014-15 season
Reference: J Clin Orthop Trauma. 2019 Mar-Apr;10(2):374-379. doi: 10.1016/j.jcot.2018.05.006. Epub 2018 May 14.
Authors: Gaspar-Junior JJ, Onaka GM, Barbosa FSS, Martinez PF, Oliveira-Junior SA
Summary: Soccer related injuries are often reported in studies, but epidemiological research on this theme is rare in Brazil, Furthermore, the conditions in which athletes have returned to sports practice, namely, either symptomatic or asymptomatic, have been neglected in research. The aim of this study was to describe the epidemiological features of injuries among professional Brazilian soccer players in relation to location, type, mechanism, severity, recurrence, treatment and, lastly, symptoms in return to sport. 116 male professional athletes of teams from a Brazilian state championship were interviewed and information about injuries was recorded using a retrospective reported morbidity questionnaire. Data were analyzed in mean ± SD for physical characteristics and sports practice history in absolute and relative frequencies (chi-square test with Bonferroni's correction) for characterization of soccer injuries in terms of type, location, severity, recurrence and symptoms in return to sport. The numbers of injuries per athlete and per injured athlete were 0.92 and 1.43 respectively. The injuries of muscle-tendon unit and the joint types localized on lower limbs constituted the most important clinical occurrences with significant difference both in relation to other types (p < 0.05). Moderate and severe injuries were the most frequent occurrences. In relation to mechanisms for each type of injury, body contact was at least three times more responsible for injury cases. This type of mechanism was associated with a significantly greater impairment of joint structures. Concerning occurrence and recurrence of cases, the number of recurrent injuries of the muscle-tendon unit reached about 7.5% of the first-time injuries, while the number of joint recurrent injuries integrated almost 40% of the first-time cases. Significant differences between first-time injuries and recurrent injuries were found only for muscle-tendon and joint structures (p < 0.05), while significant differences among the type of injuries within each type of occurrence (first-time or recurrent injuries) were also found between muscle-tendon and joint injuries (p < 0.05). In relation to athletes with symptoms, in return to sport, 77.6% of them were treated for their injuries but more than half of them returned with symptoms still present when compared to those who returned without any symptoms. Among athletes who did not receive treatment, a lower percentage (58.3%) returned to the sport with symptoms still present. Significant associations between treatment and symptomatology were not found.

#8 Looking for Complementary Intensity Variables in Different Training Games in Football
Reference: J Strength Cond Res. 2019 Mar 5. doi: 10.1519/JSC.0000000000003025. [Epub ahead of print]
Authors: Casamichana D, Castellano J, Gómez Díaz A, Martín-García A
Summary: The main aim of this study was to identify which combination of external intensity training load (iTL) metrics capture similar or unique information for different training game (TG) formats and official matches (OMs) in football using principal component (PC) analysis. Ten metrics of iTL were collected from 24 professional male football players using global positioning technology. A total of 348, 383, 120, 127, 148, and 207 individual files for small-sided possession games, medium-sided possession games, small-sided games, medium-sided games, large-sided games, and OMs, respectively, were studied. Principal component analysis was conducted on each game format. Extraction criteria were set at an eigenvalue of greater than one. Varimax rotation mode was used to extract more than one PC. Intensity training load metrics with PC "loadings" above 0.7 were deemed to possess well-defined relationships with the extracted PC. In each TG and OM, 3 PCs were identified. For the first PC, eigenvalues for each game format ranged from 3.89 to 4.45, which explained 39-44% of the information (i.e., variance) provided by the 10 iTL metrics. For the second PC, eigenvalues ranged from 2.17 to 2.47, explaining 22-26% of iTL information. For the third PC, eigenvalues ranged from 1.41 to 1.98, explaining 14-20% of iTL information. This would suggest that TG and OM have multidimensional demands; so, the use of only a single iTL could potentially lead to an underestimation of the physical demands. Consequently, a combination of 3 iTL metrics is required during professional football game formats.

#9 Assessing the Return on Investment of Injury Prevention Procedures in Professional Football
Reference: Sports Med. 2019 Mar 6. doi: 10.1007/s40279-019-01083-z. [Epub ahead of print]
Authors: Fuller CW
Summary: The aim of this study was to develop a quick and simple screening procedure for evaluating the return on investment provided by injury prevention programmes in professional football. Injury prevention in sport has usually been considered in isolation of other management responsibilities, and interventions are published irrespective of whether their impact is worthwhile and irrespective of the return on players' time investment in the programme. This approach is naive from a business perspective and is not an approach normally adopted by commercial organisations. In professional football, the overwhelming cost associated with implementing an injury prevention programme is the players' time commitment, and the major benefit is the players' increased availability, achieved through the reduction in the number of injuries. A comparison of these time-based costs and benefits provides the basis for the evaluation process presented. Applying the evaluation process to a number of published injury prevention programmes recommended for football demonstrates that they are unlikely to provide an adequate return on investment. Researchers should focus on developing injury prevention programmes that provide an adequate return on players' time investment, otherwise there is no incentive for clubs to implement the programmes. Reporting that an injury prevention programme produces a statistically significant reduction in the incidence of injury, for example, is insufficient information. Injury prevention programmes should focus on 'at risk' players to increase the return on investment, and researchers should evaluate and report on the utility of prevention programmes within the intended sports setting.

#10 Lifelong Football Training: Effects on Autophagy and Healthy Longevity Promotion
Reference: Front Physiol. 2019 Feb 19;10:132. doi: 10.3389/fphys.2019.00132. eCollection 2019.
Authors: Mancini A, Vitucci D, Randers MB, Schmidt JF, Hagman M, Andersen TR, Imperlini E, Mandola A, Orrù S, Krustrup P, Buono P
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Summary: Aging is a physiological process characterized by a progressive decline of biological functions and an increase in destructive processes in cells and organs. Physical activity and exercise positively affects the expression of skeletal muscle markers involved in longevity pathways. Recently, a new mechanism, autophagy, was introduced to the adaptations induced by acute and chronic exercise as responsible of positive metabolic modification and health-longevity promotion. However, the molecular mechanisms regulating autophagy in response to physical activity and exercise are sparsely described. We investigated the long-term adaptations resulting from lifelong recreational football training on the expression of skeletal muscle markers involved in autophagy signaling. We demonstrated that lifelong football training increased the expression of messengers: RAD23A, HSPB6, RAB1B, TRAP1, SIRT2, and HSBPB1, involved in the auto-lysosomal and proteasome-mediated protein degradation machinery; of RPL1, RPL4, RPL36, MRLP37, involved in cellular growth and differentiation processes; of the Bcl-2, HSP70, HSP90, PSMD13, and of the ATG5-ATG12 protein complex, involved in proteasome promotion and autophagy processes in muscle samples from lifelong trained subjects compared to age-matched untrained controls. In conclusion, our results indicated that lifelong football training positively influence exercise-induced autophagy processes and protein quality control in skeletal muscle, thus promoting healthy aging.

#11 The FIFA 11 programme reduces the costs associated with ankle and hamstring injuries in amateur Spanish football players: A retrospective cohort study
Reference: Eur J Sport Sci. 2019 Mar 4:1-7. doi: 10.1080/17461391.2019.1577495. [Epub ahead of print]
Authors: Nouni-Garcia R, Asensio-Garcia MR, Orozco-Beltran D, Lopez-Pineda A, Gil-Guillen VF, Quesada JA, Bernabeu Casas RC, Carratala-Munuera C
Summary: This study aimed to assess the cost-effectiveness of the "Fédération Internationale de Football Association (FIFA) 11" injury prevention programme for ankle and hamstring injuries. This retrospective cohort study included eighty-four male amateur football players aged 18-40 years. The exposed group performed the FIFA 11 protocol twice a week throughout the 2010-2011 and 2011-2012 seasons; the unexposed group performed the usual training during the 2008-2009 and 2009-2010 seasons. Lateral ankle ligament and hamstring injuries were recorded over the whole study period. We compared the mean costs associated with lateral ankle ligament and hamstring injuries in the two groups. The mean cost per player and lateral ankle injury was EUR 928 in the unexposed group versus EUR 647 in the exposed group (p = 0.19). The mean cost of hamstring injury per player was EUR 1271 in the unexposed group versus EUR 742 in the exposed group (p = 0.028). The mean total cost per player was EUR 2199 in the unexposed group versus EUR 1273 in the exposed group (p = 0.008). We concluded that the use of the FIFA 11 injury prevention programme reduced both the direct and indirect costs associated with lateral ankle ligament and hamstring injuries.

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