Latest research in football - week 38 - 2014

#1 Squad management, injury and match performance in a professional soccer team over a championship-winning season
Reference: Eur J Sport Sci. 2014 Sep 12:1-10. [Epub ahead of print]
Authors: Carling C, Le Gall F, McCall A, Nédélec M, Dupont G.
Summary:  Squad management, injury and physical, tactical and technical match performance were investigated in a professional soccer team across five consecutive league seasons (2008-2013, 190 league games) with specific focus on a championship-winning season (2010/11). For each player, match participation and time-loss injuries were recorded, the latter prospectively diagnosed by the team's physician. Defending and attacking tactical and technical performance indicators investigated included ball possession and possession in opponents' half, passes, forward passes, completed passes and forward passes, crosses and completed crosses, goal attempts and goal attempts on target, successful final third entries, free-kicks and 50/50 duels won/lost. Physical performance measures included total distance and distance covered at high-speeds (≥19.1 km/h). Results showed that during the 2010/11 season, squad utilisation was lowest potentially owing to the observed lower match injury occurrence and working days lost to injury thereby increasing player availability. In 2010/11, the team won both its highest number of points and conceded its lowest number of goals especially over the second half of this season. The team also won its highest number of games directly via a goal from a substitute and scored and conceded a goal first on the highest and lowest number of occasions, respectively. While multivariate analysis of variance (MANOVA) detected a significant difference in some attacking and defensive performance indicators across the five seasons, these were generally not distinguishing factors in 2010/11. Similarly, univariate ANOVAs showed a significant difference in running distances covered across seasons, but the trend was for less activity in 2010/11.


#2 Update: soccer injury and prevention, concussion, and chronic groin pain
Reference: Curr Sports Med Rep. 2014 Sep-Oct;13(5):319-25. doi: 10.1249/JSR.0000000000000085.
Authors: Jones NS.
Summary: Soccer, or football, as it is known in much of the world, is one of the most popular sports in the world. The purpose of this article was to provide a concise update on select soccer-specific medical issues published in the last year as they relate to soccer injury and prevention, concussions, and chronic groin pain. Both the Fédération Internationale de Football Association and the Union of European Football Associations published data from their longstanding injury tracking systems, providing foundation for further research. Concussion research continues to drive much interest, especially as it relates to heading and the controversy of subconcussive trauma. Lastly, our understanding of chronic groin pain continues to be refined as we try to understand the complexity of its pathophysiology and attempt to standardize a multispecialty approach of diagnosis and treatment.


#3 Measured and Estimated Energy Cost of Constant and Shuttle Running in Soccer Players
Reference: Med Sci Sports Exerc. 2014 Sep 10. [Epub ahead of print]
Authors: Stevens TG, de Ruiter CJ, van Maurik D, van Lierop CJ, Savelsbergh GJ, Beek PJ.
Summary: Players in team sports like soccer often make acceleration and deceleration movements, which are more energetically demanding than running at constant speed. The first aim of the present study was to estimate this difference in associated energy cost. To this end, we compared the actual energy cost of shuttle running to that of running at constant speed. In addition, since measuring oxygen consumption is not feasible during soccer, the study's second aim was to determine the validity of an indirect approach to estimate energy cost provided by di Prampero et al. (2005) using time-motion data obtained from a tracking system as input. Fourteen male amateur soccer players performed aerobic constant and continuous shuttle running at six different speeds (range 7.5-10.0 km[BULLET OPERATOR]h) on artificial turf. Measured energy cost was compared to the energy cost estimated with di Prampero's (2005) equation using data from a Local Position Measurement (LPM) system as input. As expected, measured energy cost was significantly higher (~30-50%) for shuttle running than for constant running (P < .001) and this difference increased with speed. For constant running, estimated energy cost was significantly higher (6 to 11%) than measured energy cost, while for shuttle running estimated energy cost was significantly lower (-13 to -16%) than measured energy cost. Shuttle running raised the player's energy cost of running compared to constant running at the same average speed. While for constant running actual energy cost was significantly overestimated by di Prampero's approach using LPM data as input, actual energy cost of shuttle running was significantly underestimated.


#4 The ECG of high-level junior soccer players: comparing the ESC vs. the Seattle criteria
Reference: Br J Sports Med. 2014 Sep 10. pii: bjsports-2013-093245. doi: 10.1136/bjsports-2013-093245. [Epub ahead of print]
Authors: Bessem B, de Bruijn MC, Nieuwland W
Summary: Sudden cardiac death in young athletes is a devastating event. The screening and detection of potentially life-threatening cardiac pathology by ECG is difficult due to high numbers of false-positive results, especially in the very young. The Seattle ECG criteria (2013) were introduced to decrease false-positive results. We compared the Seattle ECG criteria with the European Society of Cardiology (ESC) ECG criteria of 2005 and 2010 for cardiac screening in high-level junior soccer players. During the 2012-2013 season, all data from cardiovascular screenings performed on the youth division of two professional soccer clubs were collected. The total study population consisted of 193 male adolescent professional soccer players, aged 10-19 years. Five players dropped out of this study. Applying the ESC criteria of 2005 and 2010 to our population resulted in a total of 89 (47%) and 62 (33%) abnormal ECGs. When the Seattle ECG criteria were applied, the number of abnormal ECGs was 6 (3%). The reduction was mainly due to a reclassification of the long QT cut-off value and the exclusion of right atrial enlargement criteria. All ECG abnormalities using the Seattle criteria related to T-wave inversion criteria. The Seattle ECG criteria seem very promising for decreasing false-positive screening results for high-level junior soccer players.


#5 The Effect of Low-Volume Sprint Interval Training (SIT) on the Development and Subsequent Maintenance of Aerobic Fitness in Soccer Players
Reference: Int J Sports Physiol Perform. 2014 Sep 5. [Epub ahead of print]
Authors: Macpherson TW, Weston M.
Summary: The purpose was to examine the effect of low-volume sprint interval training (SIT) on the development (part one) and subsequent maintenance (part two) of aerobic fitness in soccer players. In part one, 23 players from the same semi-professional team participated in a 2-week SIT intervention (SIT, n = 14, age 25 ± 4 y, weight 77 ± 8 kg; control, n = 9, age 27 ± 6 y, weight 72 ± 10 kg). The SIT group performed six training sessions of 4-6 maximal 30-s sprints, in replacement of regular aerobic training. The control group continued with their regular training. Following this 2-week intervention, the SIT group were allocated to either intervention (n = 7, one SIT session per week as replacement of regular aerobic training) or control (n = 7, regular aerobic training with no SIT sessions) for a 5-week period (part two). Pre and post measures were the YoYo intermittent recovery test level 1 (YYIRL1) and maximal oxygen uptake (VO2max). In part one, the 2-week SIT intervention had a small beneficial effect on YYIRL1 (17%; 90% confidence limits ±11%), and VO2max (3.1%; ±5.0%), compared to control. In part two, one SIT session per week for 5 weeks had a small beneficial effect on VO2max (4.2%; ±3.0%), with an unclear effect on YYIRL1 (8%; ±16%). Two weeks of SIT elicits small improvements in soccer players' high-intensity intermittent running performance and VO2max, therefore representing a worthwhile replacement of regular aerobic training. The effectiveness of SIT for maintaining SIT-induced improvements in high-intensity intermittent running requires further research.


#6 Angle-Specific Eccentric Hamstring Fatigue Following Simulated Soccer
Reference: Int J Sports Physiol Perform. 2014 Sep 5. [Epub ahead of print]
Authors: Cohen DD, Zhao B, Okwera B, Matthews MJ, Delextrat A.
Summary: The purpose was to evaluate the effect of simulated soccer on the hamstrings eccentric torque-angle profile and angle of peak torque (APTeccH), and on the hamstrings:quadriceps torque ratio at specific joint angles (ASHecc:Qcon). We assessed dominant limb isokinetic concentric and eccentric knee flexion and concentric knee extension at 120°·s-1in nine semi-professional male soccer players immediately before and after completing the Loughborough Intermittent Shuttle Test (LIST). The LIST resulted in significant decreases in eccentric hamstrings torque at 60°, 50° and 10° and a significant (21.8%) decrease in ASHecc:Qconat 10° (P< 0.05). APTeccH increased from 7.1° ± 1.0° to 18.8° ± 4.2° (P< 0.05).Eccentric hamstring peak torque significantly declined from 185.1 ± 70.4 N·m pre-LIST to 150.9 ± 58.5 N·m post-LIST (P= 0.002) but there were no significant changes in hamstrings or quadriceps concentric peak torque (P = 0.312, 0.169, respectively). Conclusions: Simulated soccer results in a selective loss of eccentric hamstrings torque and hamstrings-to-quadriceps muscle balance at an extended joint position and a shift in the eccentric hamstring APT to a shorter length, changes that could increase vulnerability to hamstrings and anterior cruciate ligament injury. These findings suggest that injury risk screening could be improved by the evaluation of the eccentric hamstrings torque-angle profile and hamstrings strength-endurance and that the development of hamstrings fatigue resistance and long-length eccentric strength may reduce injury incidence.


#7 Velocity Thresholds for Women's Soccer Matches: Sex Specificity Dictates High-Speed Running and Sprinting Thresholds - Female Athletes in Motion (FAiM)
Reference: Int J Sports Physiol Perform. 2014 Sep 5. [Epub ahead of print]
Authors: Bradley PS, Vescovi JD.
Summary: There is no methodological standardization of velocity thresholds for the quantification of distances covered in various locomotor activities for women's soccer matches; especially for high-speed running and sprinting. Applying velocity thresholds used for motion analysis of men's soccer has likely created skewed observations about high-intensity movement demands for the women's game because these thresholds do not accurately reflect the capabilities of elite female players. Subsequently, a cohesive view of the locomotor characteristics of women's soccer does not yet exist. The aim of this commentary is to provide suggestions for standardizing high-speed running and sprint velocity thresholds specific to women's soccer. We also comment on utilizing generic versus individualized thresholds as well as age-related considerations to establishing velocity thresholds.


#8 Validity of the Session RPE for Monitoring Exercise Demands in Youth Soccer Players
Reference: Int J Sports Physiol Perform. 2014 Sep 5. [Epub ahead of print]
Authors: Rodríguez-Marroyo JA, Antoñan C.
Summary: The purpose of this study was to examine the concurrent and construct validity of the Borg (0-10) and children's OMNI scales for quantifying the exercise intensity and training load (TL) in youth soccer players. Twelve children (mean ± SD; age, 11.4 ± 0.5 yr; height, 154.3 ± 6.5 cm and body mass, 39.5 ± 5.4 kg) took part in this study. Exercise intensity and TL were calculated on the basis of the session rating of perceived exertion (sRPE) and HR (Edwards' method) during 20 technical-tactical training sessions. Players' sRPE were obtained from the Borg and OMNI scales. Low correlations between HR-based TL and sRPE TL based on the Borg (r = 0.17, P = 0.335) and OMNI (r = 0.34, P = 0.007) scales were obtained. Significant (P < 0.001) relationships in sRPE (r = 0.76) and TL (r = 0.79) between RPE scales were found. The present data do not support the relationship between the sRPE and HR methods for quantifying TL in youth soccer players. However, the sRPE method could be considered a better indicator of global internal TL, since sRPE is a measure of both physical and psychological stress. In addition, we have demonstrated the construct validity for OMNI scale to control exercise demands.


#9 Optimizing the prediction process: from statistical concepts to the case study of soccer
Reference: PLoS One. 2014 Sep 8;9(9):e104647. doi: 10.1371/journal.pone.0104647. eCollection 2014.
Authors: Heuer A, Rubner O.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4157759/pdf/pone.0104647.pdf
Summary: We present a systematic approach for prediction purposes based on panel data, involving information about different interacting subjects and different times (here: two). The corresponding bivariate regression problem can be solved analytically for the final statistical estimation error. Furthermore, this expression is simplified for the special case that the subjects do not change their properties between the last measurement and the prediction period. This statistical framework is applied to the prediction of soccer matches, based on information from the previous and the present season. It is determined how well the outcome of soccer matches can be predicted theoretically. This optimum limit is compared with the actual quality of the prediction, taking the German premier league as an example. As a key step for the actual prediction process one has to identify appropriate observables which reflect the strength of the individual teams as close as possible. A criterion to distinguish different observables is presented. Surprisingly, chances for goals turn out to be much better suited than the goals themselves to characterize the strength of a team. Routes towards further improvement of the prediction are indicated. Finally, two specific applications are discussed.


#10 Preventive Health Perspective in Sports Medicine: The Trend at the Use of Medications and Nutritional Supplements during 5 Years Period between 2003 and 2008 in Football
Reference: Balkan Med J. 2013 Mar;30(1):74-9. doi: 10.5152/balkanmedj.2012.090. Epub 2013 Mar 1.
Authors: Kavukcu E, Burgazlı KM
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4116030/pdf/bmj-30-1-74.pdf
Summary: The purpose was to assess the prevalence of medication and nutritional supplement use in male Football Super League players and to observe the long term changes of players' attitudes during 5 years period (4 seasons). Review and analysis of 4176 doping control forms -declaration reports- about players' medication intake including; Super League, UEFA Cup and the UEFA Champions League matches. Team physician was asked to document all medications and nutritional supplements taken by the Football Super League players in the last 72 hours before each match. A total intake of 5939 substances were documented, of which almost half 49.2% (n=2921) were classified as medications and 50.8% (n=3018) were nutritional supplements. The average consumption per player was 1.42 substance/match; 0.70 were medications and 0.72 of nutritional supplements. The supplements used most frequently were NSAIDs 24.6% (n=1460) accounting for almost one in four of all reported supplements. Diclofenac Sodium was the most frequently reported active pharmaceutical ingredient. Second most frequently used supplements were vitamins (22.2%). The average drug consumption reported per player has been increasing every passing year. It was 0.7 substance/match/player (0.4 medication; 0.3 nutritional supplement) in 2003-2004 season; was increased to 1.8 substance/match (0.8 medication; 1.0 nutritional supplement) in 2006-2007 season. The trends seen in this survey point to an overuse of NSAIDs and vitamins in comparison with other medications, amoung Turkish Super League football players (p<0.001). The use of NSAIDs has increased but the medication groups did not differ significantly between seasons, in terms of distribution. This increasing use of medications especially of non-steroidal anti-inflammatory drugs and nutritional supplements is alarming and needs to be argued.


#11 Analysis of body mass components in national club football players in Republic of Macedonia
Reference: Med Arh. 2014;68(3):191-4.
Authors: Nikolic S, Todorovskal L, Maleska V, Dejanova B, Efremova L, Zivkovic V, Pluncevic-Gligoroska J.
Summary: This study aims to analyze body composition in adult male football players and its changes during adulthood.  Adult male football players (n = 942, mean age 24.11 +/- 4.69 y), all members of national competitive clubs from Macedonia were included in the study. The absolute and the relative body components were calculated: lean body mass (LBMkg), muscle mass (MMkg; MM%), bone mass (BMkg; BM%) and fat components (FMkg; FM%), using the anthropometric protocol by Matiegka. Mean values of anthropometric measures for all included participants were as follows: height = 178.39 +/- 6.11 cm; weight = 77.02 +/- 7.57; LBM = 65.65 +/- 6.38; MM% = 53.23 +/- 2.78; BM% = 17.05 +/- 1.27; FM% = 14.58 +/- 1.48. Descriptive statistics for these parameters was made for age specific groups. The results obtained could be used as reference values for adult football players in Republic of Macedonia. In the examined age span (18-35 years) a slight increase of absolute values of all three body components has been registered with advancing age. The most significant increase in the absolute values was registered for the muscle component, followed by the fat and bone components, respectively. Regarding the relative values (%), the muscle and the fat components showed an equally slight positive correlation with the age increase of 1 year, whilst the bone component decreased with advancing age.