Latest research in football - week 18 - 2013

#1 Match Injury Rates in Professional Soccer Vary With Match Result, Match Venue, and Type of Competition
Authors: Bengtsson H, Ekstrand J, Waldén M, Hägglund M.
Reference: Am J Sports Med. 2013 Apr 30. [Epub ahead of print]
Summary: The purpose of the study was to investigate whether there are associations between injury rates and the match result, venue, and type of competition in male soccer. Twenty-six professional clubs from 10 countries were followed prospectively during 9 seasons (2001-2002 to 2009-2010). All matches, and injuries occurring in these matches, were registered by the team's medical staff. An injury was registered if it resulted in player absence from training or matches. Information about match result, venue, and type of competition for all reported matches was gathered by the authors from online databases. Injury rates in matches with varying match characteristics were compared by use of generalized estimating equations. Odds ratios (ORs) with 95% confidence intervals (CIs) were calculated. A total of 2738 injuries during 6010 matches were registered. There were no associations between odds of 1 injury occurrence and match result or type of competition, whereas the odds were decreased in matches played away compared with home matches (OR, 0.89). The odds of 2 or more injury occurrences in a match were increased in matches resulting in a draw (OR, 1.39) or loss (OR, 1.66) compared with matches won and were decreased in other cup matches compared with league matches (OR, 0.57) and in matches played away compared with home matches (OR, 0.70). Finally, injuries with more than 1 week's absence occurred more frequently in Champions League matches compared with league matches both for matches with 1 injury (OR, 1.26; 95% CI, 1.09-1.45) and matches with 2 or more injuries (OR, 1.57). The odds of 2 or more injury occurrences in professional soccer were higher in matches resulting in a loss or a draw compared with a win, whereas the odds of injury occurrences were lower in matches played away compared with home matches. The rate of moderate and severe injuries increased with the importance of the match.


#2 Injury surveillance in the World Football Tournaments 1998-2012
Authors: Junge A, Dvorak J.
Reference: Br J Sports Med. 2013 Apr 30. [Epub ahead of print]
Summary: The purpose was to analysis of the incidence, characteristics and changes of football injury during international top-level tournaments 1998-2012. All newly incurred football injuries during the FIFA tournaments and the Olympic Games were reported by the team physicians on a standardised injury report form after each match. The average response rate was 92%. A total of 3944 injuries were reported from 1546 matches, equivalent to 2.6 injuries per match. The majority of injuries (80%) was caused by contact with another player, compared with 47% of contact injuries by foul play. The most frequently injured body parts were the ankle (19%), lower leg (16%) and head/neck (15%). Contusions (55%) were the most common type of injury, followed by sprains (17%) and strains (10%). On average, 1.1 injuries per match were expected to result in absence from a match or training. The incidence of time-loss injuries was highest in the FIFA World Cups and lowest in the FIFA U17 Women's World Cups. The injury rates in the various types of FIFA World Cups had different trends over the past 14 years.
Changes in the incidence of injuries in top-level tournaments might be influenced by the playing style, refereeing, extent and intensity of match play. Strict application of the Laws of the Games is an important means of injury prevention.


#3 A spectral analysis of team dynamics and tactics in Brazilian football
Authors: Moura FA, Martins LE, Anido RO, Ruffino PR, Barros RM, Cunha SA.
Reference: J Sports Sci. 2013 Apr 30. [Epub ahead of print]
Summary: The purposes of this study were to characterise the total space covered and the distances between players within teams over ten Brazilian First Division Championship matches. Filmed recordings, combined with a tracking system, were used to obtain the trajectories of 277 players before and after half-time. The team surface area (the area of the convex hull formed by the positions of the players) and spread (the Frobenius norm of the distance-between-player matrix) were calculated as functions of time. A Fast Fourier Transform (FFT) was applied to each time series. The median frequency was then calculated. The results of the surface area time series median frequencies for the first half were significantly greater than the second-half values. Similarly, the spread variable median frequencies for the first half were significantly greater than the second-half values. The median frequencies allowed the characterisation of the time series oscillations that represent the speed at which players distribute and then compact their team formation during a match. This analysis can provide insights that allow coaches to better control the team organisation on the pitch.


#4 Vitamin D concentration in 342 professional football players and association with lower limb isokinetic function
Authors: Hamilton B, Whiteley R, Farooq A, Chalabi H.
Reference: J Sci Med Sport. 2013 Apr 23. pii: S1440-2440(13)00054-6. doi: 10.1016/j.jsams.2013.03.006.

Summary: The purpose was to evaluate both the epidemiology of Vitamin D deficiency in Qatar-based footballers originating from a variety of countries and the existence of any relationship between 25 hydroxy-cholecalciferol (25(OH)D) concentration and lower limb isokinetic performance in well trained professional football players. Three hundred and forty-two professional footballers based in Qatar were evaluated as part of their routine annual medical assessment. History, examination, blood tests and a lower limb isokinetic evaluation were performed. Association between 25(OH)D concentrations and lower limb isokinetic peak torque was assessed. Eighty four percent of players had 25(OH)D concentrations less than 30ng/ml; 12% were severely deficient (<10ng/ml) and there was a significant difference in 25(OH)D level depending on the country of origin of the player. Total body mass and lean mass was significantly higher in players with 25(OH)D levels greater than 20ng/ml, when compared with the less than 10ng/ml group. There was no consistent association found between lower limb isokinetic peak torque and 25(OH)D concentration. 25(OH)D deficiency is highly prevalent in Qatar based footballers. Severe 25(OH)D deficiency is associated with lower body mass, and lower lean mass, when compared with footballers with concentrations >20ng/ml. Vitamin D deficiency was not shown to have a consistent association with lower limb isokinetic peak torque and both the clinical and performance related significance of this high prevalence of Vitamin D deficiency remains unclear.