Latest research in football - week 48 - 2013

#1 Psychosocial stress as a predictor of injury in elite junior soccer: A latent growth curve analysis
Authors: Ivarsson A, Johnson U, Lindwall M, Gustafsson H, Altemyr M.
Reference: J Sci Med Sport. 2013 Oct 31. pii: S1440-2440(13)00473-8. doi: 10.1016/j.jsams.2013.10.242. [Epub ahead of print]
Summary: The purpose was to investigate by use of a latent growth curve analysis framework whether athletes' individual levels and changes in hassle and uplift levels over a 10-week period could predict injury outcome in an elite junior soccer population. Participants were 101 Swedish elite junior soccer players (67 males and 34 females). Ten sets of measures were taken on a weekly basis during which participants completed the Hassles and Uplifts Scale (HUS). Latent growth curve models were used to examine whether the level and change in psychological stress could predict the frequency of injury over the 10-week period. The results show that injury occurrence was significantly associated with both the initial level of daily hassle and the change in daily hassle. High initial daily hassle levels and a smaller decrease in daily hassles were associated with injury occurrence. Moreover, injury occurrence was significantly associated with a greater decrease in daily uplift. The findings highlight the importance of focusing on state variables using prospective designs and appropriate analysis of within-person change to detect complex and dynamic associations across time in injury-prediction research.


#2 The Relationship between Trunk Function and Injury among Junior High School Soccer Players
Authors: Nakazawa R, Endo Y, Sakamoto M.
Reference: J Phys Ther Sci. 2013 Jul;25(7):775-777. Epub 2013 Aug 20.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3820415/pdf/jpts-25-775.pdf
Summary: The purpose of this study was to examine the relationship between trunk stability and injury among young soccer players. The subjects were 19 male soccer players in junior high school. The presence of injury was noted, and trunk stability was measured by using the bench test and sideways bench test, which were modified from "The 11+" exercises. There was no significant difference in endurance time in the bench test or sideways bench test between the injury group (n=9) and non-injury group (n=10). Comparison within each group revealed no significant difference in endurance time between the right and left sideways bench tests in the non-injury group; however, the time in the left sideways bench test was significantly longer than that in the right in the injury group. This study suggests that there is a relationship between asymmetric trunk stability and injury. Further research investigating the relationship between asymmetric trunk function and balance skills is necessary.


#3 Does soccer cleat design influence the rotational interaction with the playing surface?
Authors: Galbusera F, Tornese DZ, Anasetti F, Bersini S, Volpi P, La Barbera L, Villa T.
Reference: Sports Biomech. 2013 Sep;12(3):293-301.
Summary: Non-contact injuries in soccer players may be related to the interplay between cleat type and playing surface, and bladed shoes were often blamed for non-contact injuries with no research support. The aim of this study was to compare the rotational resistance (stiffness and peak sustainable torque) among three types of soccer cleats (metal studs, molded rubber studs, and bladed) in a controlled laboratory environment. The shoes were tested on both natural and artificial turfs under a compressive preload of 1000 N and with internal and external rotations. The three shoe models showed comparable performances with a good repeatability for each individual test on both playing surfaces. A less stiff behavior was observed for the natural turf. A tendency toward highest peak torque was observed in the studded model on natural surface. The bladed cleats provided peak torque and rotational stiffness comparable to the other models. Studded and bladed cleats did not significantly differ in their interaction with the playing surface. Therefore, soccer shoes with bladed cleats should not be banned in the context of presumed higher risk for non-contact injuries.


#4 Variability and typical error in the kinematics and kinetics of the maximal instep kick in soccer
Authors: Lees A, Rahnama N.
Reference: Sports Biomech. 2013 Sep;12(3):283-92.
Summary: The purpose of this paper was to establish the variability and typical error of kinematic and kinetic variables representing the maximal instep kick in soccer for both the kicking and support legs. Ten skilled (good amateur or semi-professional) soccer players performed 20 maximal instep kicks of a stationary ball into a goal mouth. Motion of the kicking and support legs was recorded by an optoelectronic motion analysis system, and a six degrees of freedom model was used to compute kinematic and kinetic variables. Participants repeated the kicks on a second day at least 1 week later. The mean within-subject coefficient of variation across the kinematic and kinetic variables, trials, and days was 16% and did not change substantially as trial number increased or between day of test. Increasing trial number reduced the typical error (as determined by the standard error of the mean) such that for 20 trials 75% of the variables were below an arbitrary 5% threshold. It was concluded that for kicking investigations, 10-15 trials could be used and typical errors of 5% should be expected.


#5 Concomitant Effects of Ramadan Fasting and Time-Of-Day on Apolipoprotein AI, B, Lp-a and Homocysteine Responses during Aerobic Exercise in Tunisian Soccer Player
Authors: Hammouda O, Chtourou H, Aloui A, Chahed H, Kallel C, Miled A, Chamari K, Chaouachi A, Souissi N.
Reference: PLoS One. 2013 Nov 11;8(11):e79873. doi: 10.1371/journal.pone.0079873.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3823586/pdf/pone.0079873.pdf
Summary: To examine the time-of-day and Ramadan fasting (RF) effects on serum apolipoprotein-AI (Apo-AI) and B (Apo-B), lipoprotein particles-a (Lp-a), high-sensitive C-reactive-protein (hs-CRP), and homocysteine (Hcy) during the Yo-Yo intermittent recovery test (YYIRT). Performance and biochemical measures were completed at two times-of-day (07:00 and 17:00 h), 1-week before RF (BR), the second week of RF (SWR), and the fourth week of RF (ER). For each session, subjects performed the YYIRT, and blood samples were taken before and 3-min after the test for biochemical measures. Fifteen soccer players participated in this study and were measured on total distance during the YYIRT, core temperature, body composition, dietary intakes, lipid (HDL-C, LDL-C, Apo-AI, B and Lp-a) and inflammatory (hs-CRP and Hcy). Performances during the YYIRT were higher in the evening than the morning BR (P < 0.05), but this fluctuation was not observed during RF. Moreover, LDL-C, ApoB, and Lp-a were stable throughout the daytime BR. However, during RF, they decreased at 17:00 h (P < 0.05). Likewise, HDL-C and Apo-AI increased after the exercise and were higher at 17:00 h BR (P < 0.001). Moreover, these parameters increased during RF (P < 0.01). Furthermore, Hcy and hs-CRP increased during the exercise (P < 0.01) with higher evening levels BR. During ER, the diurnal pattern of Hcy was inversed (P < 0.001). This study concluded that caloric restriction induced by RF seems to ameliorate lipid and inflammatory markers of cardiovascular health during intermittent exercise performed in the evening.


#6 Medical examinations undertaken by Dutch professional football clubs
Authors: Gouttebarge V, Sluiter JK.
Reference: Occup Med (Lond). 2013 Nov 21. [Epub ahead of print]
Summary: During their career, professional football players undergo periodic medical examinations intended to screen and monitor their fitness and health. In the Netherlands, information about the content of these examinations is lacking and it is not known whether they comply with current Dutch occupational medicine guidelines. To explore the content of medical examinations undertaken in Dutch professional football clubs, and assess whether they comply with current Dutch occupational medicine guidelines. An observational study conducted among physicians working for all clubs in the Dutch first- and second-tier professional football leagues, using an electronic questionnaire Cardiovascular assessment based on different instruments was used in all clubs and respiratory assessment based on different instruments was used in most (87%). Other assessments such as mental health (7%), neurological (27%) or urinary (22%) assessments were only undertaken in some clubs. Seven out of the 26 clubs met some of the relevant aspects of current Dutch occupational medicine guidelines. The medical examinations currently undertaken in Dutch professional football clubs are diverse in nature and not consistent from one club to another. Only a limited number of clubs meet Dutch guidelines for periodic medical examinations of workers.


#7 Impact of the 2010 FIFA (Federation Internationale de Football Association) World Cup on Pediatric Injury and Mortality in Cape Town, South Africa
Authors: Zroback C, Levin D, Manlhiot C, Alexander A, van As AS, Azzie G.
Reference: J Pediatr. 2013 Nov 16. pii: S0022-3476(13)01237-7. doi: 10.1016/j.jpeds.2013.10.009. [Epub ahead of print]
Summary: To examine how a mass-gathering event (the Federation Internationale de Football Association World Cup, 2010, South Africa) impacts trauma and mortality in the pediatric (≤18 years) population. We investigated pediatric emergency visits at Cape Town's 3 largest public trauma centers and 3 private hospital groups, as well as deaths investigated by the 3 city mortuaries. We compared the 31 days of World Cup with equivalent periods from 2007-2009, and with the 2 weeks before and after the event. We also looked at the World Cup period in isolation and compared days with and without games in Cape Town. There was significantly decreased pediatric trauma volume during the World Cup, approximately 2/100 000 (37%) fewer injuries per day, compared with 2009 and to both pre- and post-World Cup control periods (P < .001). This decrease occurred within a majority of injury subtypes, but did not change mortality. There were temporal fluctuations in emergency visits corresponding with local match start time, with fewer all-cause emergency visits during the 5 hours surrounding this time (-16.4%, P = .01), followed by a subsequent spike (+26.2%, P = .02). There was an increase in trauma 12 hours following matches (+15.6%, P = .06). In Cape Town, during the 2010 Federation Internationale de Football Association World Cup, there were fewer emergency department visits for traumatic injury. Furthermore, there were fewer all-cause pediatric emergency department visits during hometown matches. These results will assist in planning for future mass-gathering events.


#8 Serum paraoxonase activity and lipid hydroperoxide levels in adult football players after three days football tournament
Author: Atli M.
Reference: Afr Health Sci. 2013 Sep;13(3):565-70. doi: 10.4314/ahs.v13i3.6.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3824444/pdf/AFHS1303-0565.pdf
Summary: It has been suggested that physical activity is an important factor in the prevention and treatment of cardiovascular diseases. Low serum paraoxononase-1 (PON1) activity is with an associated risk of atherosclerotic disease. In this study, we aimed to investigate serum PON1 activity and lipid hydroperoxide (LOOH) levels in adult football players after three days football tournament. Twenty-three adult male football players and 23 sedentary male subjects after three days football tournament were enrolled. Serum paraoxonase, arylesterase activities and LOOH levels were determined. Serum paraoxonase and arylesterase activities were signiûcantly higher in football players than sedentary subjects (all, p<0.05), while LOOH levels were significantly lower (p< 0.05). Serum LOOH levels were inversely correlated with paraoxonase and arylesterase activities (r=-0.552, p<0.001; r=-0.812, p<0.001; respectively) in adult football players. Our data show, for the first time, that physical activity is associated with increased PON1 activity and decreased oxidative stress after three days football tournament. In addition, physical activity for a healthy life is important in increasing serum PON1 activity, and this may play a role in the prevention of atherosclerosis.


#9 Selection, de-selection and progression in German football talent promotion
Author: Güllich A.
Reference: Eur J Sport Sci. 2013 Nov 19. [Epub ahead of print]
Summary:  This study explored to which extent the development of German professional football players is based on early talent identification (TID) and long-term nurture in talent promotion (TP) programmes or on their emergence in the course of repeated procedures of player selection and de-selection in these programmes through childhood and youth. The annual turnover of squad members in national junior teams (2001-2013) and youth elite academies was calculated; national U-team members were followed up with regard to nominations through subsequent seasons and to their success level eventually achieved at senior age; and all current Bundesliga players were analysed retrospectively regarding their earlier involvement in TID/TP programmes. Analyses revealed that the mean annual turnover of squad members was 24.5% (youth academies) and 41.0% (national U-teams), respectively. At any age, the probability of persisting in the programme three years later was <50%. Among current Bundesliga players, the age of recruitment into the TID/TP programme was widely evenly distributed across childhood and youth, respectively. Accordingly, the number of (future) Bundesliga players who were involved in TID/TP was built up continuously through all age categories. The observations suggest that the collective of professional players emerged from repeated procedures of selection and de-selection through childhood and youth rather than from early selection and long-term continuous nurture in TID/TP programmes. The findings are discussed with regard to the uncertainty of TID and of interventions applied to the selected players, and they are related to the individualistic and collectivistic approach in TP.


#10 Physiological Characteristics of International Female Soccer Players
Authors: Manson SA, Brughelli M, Harris NK
Reference: Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1519/JSC.0b013e31829b56b1
Summary: The purpose of this study was to investigate the physiological characteristics of FIFA eligible international female soccer players aged 14 to 36 yrs, and to determine if measures were significantly different for players selected (i.e. starters) to the starting line up for a FIFA tournament as compared to those not selected (i.e. non-starters). Fifty-one (N=18 Under 17; N=18 Under 20; N=15 Senior) international female soccer players participated in this study. Subjects underwent measurements of anthropometry (height and body mass), lower body strength (isokinetic testing), sprint kinetics and kinematics (non-motorized treadmill), leg power (unilateral jumping) and maximal aerobic velocity (30:15 intermittent fitness test) during the final preparatory stage for a FIFA event. Outcomes of the age group data indicate that differences in physiological capacities are evident for the Under 17 players as compared to the Under 20 and Senior caped international players, suggesting a plateau in the acquisition of physical qualities as players mature. Starters tended to be faster (ES = 0.55-1.0, p<0.05) and have a higher maximal aerobic velocity (ES = 0.78-2.45, p<0.05), along with greater eccentric leg strength (ES = 0.33-1.67, p<0.05). Significant differences were detected between starters and non-starters for isokinetic leg strength (ES = 0.54-1.24, p<0.05) and maximal aerobic velocity (ES = 0.87, p<0.05) for Under 17 players, where maximal aerobic velocity was the primary difference between starters and non-starters (ES = 0.83-2.45, p<0.05) for the Under 20 and Senior players. Coaches should emphasize the development of speed, maximal aerobic velocity and leg strength in developing female soccer players


#11 Effect of gene ACTN3 on strength and endurance in soccer players
Authors: Pimenta, E.M., Coelho, D.B., Coelho, E.J.B., Cruz, I.R., Morandi, R.F., Pussieldi, G.d.A., Carvalho, M.R.S., Silami-Garcia, E., and de Paz Fernandez, J.A.
Reference: Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1519/JSC.0b013e3182915e66
Summary: Sports efficiency in activities in which strength and speed are determining factors has been associated to the ACTN3 gene, which is responsible for the expression of α- actinin-3. Soccer is a mainly aerobic sport due to its long duration, but the acute actions that define the game demand a lot of strength and speed. The purpose of the present study is to compare the performance capacity of soccer players with different genotype groups of ACTN3 (XX, RX and RR) in strength, speed and endurance tests. Two hundred professional players of Brazilian soccer first division teams participated in this study. Speed, jump and endurance tests results were compared to the polymorphisms of the ACTN3 gene. It was noticed that RR individuals spent less time to run a 10m path, compared to XX individuals (p<0.05). The RR individuals also presented lower time rates at the 20 and 30m path, compared to RX and XX individuals (p<0.05). In jump tests, RR individuals presented higher rates, compared to RX and XX individuals (p<0.05). As for aerobic tests, the XX individuals presented higher rates of VO2 maximum, compared to the RR group (p<0.05) and did not differ from the RX group. The main conclusion of this study is that soccer players of genotype ACTN3/RR are the fastest in short distances and present higher jump potential. ACTN3/XX individuals presented the highest aerobic capacity. These findings can be used in training load adjustment and can influence the development of tactical schemes in soccer matches