Latest research in football - week 47 - 2013

#1 Activity profiles of soccer players during the 2010 world cup
Authors: Clemente FM, Couceiro MS, Martins FM, Ivanova MO, Mendes R.
Reference: J Hum Kinet. 2013 Oct 8;38:201-11. doi: 10.2478/hukin-2013-0060.
Summary: The main objective of this study was to analyse the distance covered and the activity profile that players presented at the FIFA World Cup in 2010. Complementarily, the distance covered by each team within the same competition was analysed. For the purposes of this study 443 players were analysed, of which 35 were goalkeepers, 84 were external defenders, 77 were central defenders, 182 were midfielders, and 65 were forwards. Afterwards, a thorough analysis was performed on 16 teams that reached the group stage, 8 teams that achieved the round of 16, 4 teams that reached the quarter-finals, and 4 teams that qualified for the semi-finals and finals. A comparison of the mean distance covered per minute among the playing positions showed statistically significant differences (F(4,438) = 559.283; p < 0.001; 2 = 0.836; Power = 1.00). A comparison of the activity time among tactical positions also resulted in statistically significant differences, specifically, low activity (F(4,183.371) = 1476.844; p < 0.001; 2 = 0.742; Power = 1.00), medium activity (F(4,183.370) = 1408.106; p < 0.001; 2 = 0.731; Power = 1.00), and high activity (F(4,182.861) = 1152.508; p < 0.001; 2 = 0.703; Power = 1.00). Comparing the mean distance covered by teams, differences that are not statistically significant were observed (F(3,9.651) = 4.337; p < 0.035; 2 = 0.206; Power = 0.541). In conclusion, the tactical positions of the players and their specific tasks influence the activity profile and physical demands during a match.


#2 Performance consistency of international soccer teams in euro 2012: a time series analysis
Authors: Shafizadeh M, Taylor M, Peñas CL.
Reference: J Hum Kinet. 2013 Oct 8;38:213-26. doi: 10.2478/hukin-2013-0061.
Summary: The purpose of this study was to examine the consistency of performance in successive matches for international soccer teams from Europe which qualified for the quarter final stage of EURO 2012 in Poland and Ukraine. The eight teams that reached the quarter final stage and beyond were the sample teams for this time series analysis. The autocorrelation and cross-correlation functions were used to analyze the consistency of play and its association with the result of match in sixteen performance indicators of each team. The results of autocorrelation function showed that based on the number of consistent performance indicators, Spain and Italy demonstrated more consistency in successive matches in relation to other teams. This appears intuitive given that Spain played Italy in the final. However, it is arguable that other teams played at a higher performance levels at various parts of the competition, as opposed to performing consistently throughout the tournament. The results of the cross-correlation analysis showed that in relation to goal-related indicators, these had higher associations with the match results of Spain and France. In relation to the offensive-related indicators, France, England, Portugal, Greece, Czech Republic and Spain showed a positive correlation with the match result. In relation to the defensive-related indicators, France, England, Greece and Portugal showed a positive correlation with match results. In conclusion, in an international soccer tournament, the successful teams displayed a greater degree of performance consistency across all indicators in comparison to their competitors who occasionally would show higher levels of performance in individual games, yet not consistently across the overall tournament. The authors therefore conclude that performance consistency is more significant in international tournament soccer, versus occasionally excelling in some metrics and indicators in particular games.


#3 Calculating Home Advantage in the First Decade of the 21th Century UEFA Soccer Leagues
Authors: García MS, Aguilar OG, Marques PS, Tobío GT, Fernández Romero JJ.
Reference: J Hum Kinet. 2013 Oct 8;38:141-50. doi: 10.2478/hukin-2013-0054.
Summary: Home advantage has been studied in different sports, establishing its existence and its possible causes. This article analyzes the home advantage in soccer leagues of UEFA countries in the first part of the 21st century. The sample of 52 countries monitored during a period of 10 years allows us to study 520 leagues and 111,030 matches of the highest level in each country associated with UEFA. Home advantage exists and is significant in 32 of the 52 UEFA countries, where it equals 55.6%. A decrease can be observed in the tendency towards home advantage between the years 2000 and 2010. Values between 55 and 56 were observed for home advantage in the top ten leagues in Europe. It has also been observed that home advantage depends on the level of the league evaluated using UEFA's 2010/11 Country coefficients. The home advantage is calculated taking into account the teams' position and the points obtained in each of the leagues. A direct relationship was observed with the number of points gained and an inverse relationship was observed with the team position.


#4 Cardiovascular responses, perceived exertion and technical actions during small-sided recreational soccer: effects of pitch size and number of players
Authors: Aslan A.
Reference: J Hum Kinet. 2013 Oct 8;38:95-105. doi: 10.2478/hukin-2013-0049.
Summary: The aim of this study was to determine the cardiovascular, perceived exertion and technical effects of altering pitch size and number of players in recreational soccer match-play. The further aim was to evaluate to what extent exercise intensity during various game formats corresponds to the recommended intensity level for cardiovascular fitness improvement. Ten male recreational players aged 31.7±7.6 years (mean ± SD) completed four variations of small-sided games (except for goalkeepers, 5-a-side and 7-a-side on small and large pitches) during which heart rate, perceived exertion and technical actions were evaluated. Two-way analysis of variance on repeated measures was applied to collected data. The results indicated that an average workload expressed as heart rate and percentage of heart rate reserve during 5-a-side games was higher than for 7-a-side games. The rate of perceived exertion values were moderate and similar for all formats of games. The players performed more dribbling and successful passes, but fewer unsuccessful passes during 5-a-side games. Furthermore, the number of ball possessions and unsuccessful passes was higher on a small pitch than on a large one. Consequently, the current findings suggest that, independent of pitch size, the cardiovascular demands imposed on participants increase when the game is played with fewer players. However, all formats of recreational soccer can be used as an effective activity to promote cardiovascular fitness. Finally, participants may have more chance to perform basic technical actions during 5-a-side games on small and large pitches.


#5 An evaluation of the levels of vitamin d and bone turnover markers after the summer and winter periods in polish professional soccer players
Authors: Kopeć A, Solarz K, Majda F, Słowińska-Lisowska M, Mędraś M.
Reference: J Hum Kinet. 2013 Oct 8;38:135-40. doi: 10.2478/hukin-2013-0053.
Summary: Vitamin D is synthesised in the skin during exposure to sunlight. The fundamental roles of vitamin D are the regulation of calcium and phosphate metabolism and bone mineralisation. Low vitamin D levels in athletes may adversely affect their exercise capabilities. The aim of our study was to investigate changes in serum levels of 25(OH)D3, calcium and bone turnover markers in football players in two training periods differing in the exposure to sunlight (after the summer period and after the winter period). We investigated 24 Polish professional soccer players. Serum levels of the following parameters were determined: 25(OH)D3, calcium, osteocalcin (OC), parathormone (PTH), procollagen type I N - terminal peptide (P1NP), and beta - CrossLaps (beta - CTx). We showed significantly higher levels of 25(OH)D3 and calcium and lower levels of PTH after the summer period versus the winter period. No significant differences in the levels of bone turnover markers were found. Furthermore, we did not observe any significant correlations between the levels of 25(OH)D3 and other parameters. Normal levels of 25(OH)D3 were observed in 50% of the players after the summer period and only in 16.7% of the players after the winter period. It is justified to measure the levels of 25(OH)D3, calcium and PTH in soccer players, especially after the winter period, when the exposure to sunlight is limited.


#6 Soccer Boots Elevate Plantar Pressures in Elite Male Soccer Professionals
Authors: Carl HD, Pauser J, Swoboda B Prof, Jendrissek A, Brem M.
Reference: Clin J Sport Med. 2013 Nov 13. [Epub ahead of print]
Summary: The present study measured the difference in peak plantar pressure between running shoes and soccer shoes in male soccer professionals [mean (SD): age, 23 (4) years; height, 184 (7) cm; weight, 81 (6) kg]. Fifteen right and left steps with sensor-loaded insoles (99 sensors, 50 Hz) while running (3.3 m/s) in running shoes and then chosen soccer shoes (12-stud profile). The players were equipped with running shoes from the supplier without any medical supervision. Changes of peak plantar pressure for 9 defined foot portions between soccer boots and running shoes were used as outcome measures. A statistically significant increase of peak plantar pressure was found for the lateral midfoot (P < 0.001 for preferred and nonpreferred foot), the first metatarsal head (preferred foot: P < 0.001; nonpreferred foot: P = 0.002), the metatarsal heads 4/5 (preferred foot: P = 0.001, nonpreferred foot: P = 0.002), and the big toe (preferred foot: P = 0.001, nonpreferred foot: P < 0.001), but not for the lateral and medial hindfoot, the medial midfoot, and lesser toes. In running, soccer boots generate excessive foot loadings predominantly under the lateral midfoot, as compared with running shoes. Players should be trained with a thoughtfully designed workout regimen that allows performing as many straight running exercises as possible in running shoes instead of soccer boots. This may help to prevent fifth metatarsal stress fractures in elite male soccer players.


#7 Arthroscopic Meniscus Allograft Transplantation in Male Professional Soccer Players: A 36-Month Follow-up Study
Authors: Marcacci M, Marcheggiani Muccioli GM, Grassi A, Ricci M, Tsapralis K, Nanni G, Bonanzinga T, Zaffagnini S.
Reference: Am J Sports Med. 2013 Nov 8. [Epub ahead of print]
Summary: Meniscus allograft transplantation (MAT) is an option for symptomatic patients who have undergone subtotal meniscectomy and can potentially result in pain relief and increased function. HYPOTHESIS:Professional soccer players would benefit from arthroscopic MAT in terms of pain, knee function, and return to play at 36-month follow-up. Twelve male patients who had undergone MAT (6 medial, 6 lateral) were prospectively evaluated at 12- and 36-month follow-up. The mean age at the time of surgery was 24.5 ± 3.6 years (range, 19-29 years), and the mean time from meniscectomy to surgery was 37 ± 31 months (range, 2-82 months). The transplantation was performed in patients who had undergone subtotal meniscectomy using an arthroscopic bone plug-free technique with a single tibial tunnel plus "all-inside" meniscus sutures. The anterior horn of the transplanted meniscus was sutured to the capsule and to the remnant of the anterior horn of the native meniscus. Seven patients (58%) underwent concurrent procedures. All patients were evaluated at follow-up by the Tegner, Lysholm, International Knee Documentation Committee (IKDC) subjective, IKDC objective, Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC), and visual analog scale (VAS) for pain scores. Information regarding rehabilitation, return to play, and return to official competition was recorded. Eleven of the 12 patients (92%) returned to play soccer. At 36-month follow-up, 9 patients (75%) were still playing as professionals (Tegner score of 10), whereas 2 patients (17%) were playing as semiprofessionals (Tegner score of 9). The mean time from surgery to the end of rehabilitation was 7.5 ± 2 months, whereas the mean time to official competition was 10.5 ± 2.6 months. Patients demonstrated significant improvements on the median Tegner score from 8 (interquartile range, 3-10) to 10 (interquartile range, 9-10) (P = .0391); the mean Lysholm score from 67 ± 14 to 92 ± 10 (P = .0021); the mean IKDC subjective score from 61.8 ± 16.3 to 85.3 ± 9.8 (P = .0026); the mean IKDC objective score from 1 A, 8 B, 1 C, and 2 D to 7 A and 5 B (P = .0077); the mean WOMAC score from 77.1 ± 15.9 to 92.2 ± 9.1 (P = .0242); and the mean VAS score from 61 ± 16 to 29 ± 32 (P = .0029) at 12-month follow-up. There were no significant improvements in these outcomes at 36-month follow-up. One patient developed a knee infection after MAT plus anterior cruciate ligament allograft reconstruction. This complication was successfully treated, but the patient stopped playing soccer (Tegner score of 3 at 36-month follow-up), and this was considered a failure (8%). Arthroscopic MAT in professional soccer players allowed a return to play at the same level (Tegner score of 10) in 75% of the cases at 36-month follow-up.


#8 Locomotor Performance in Highly-Trained Young Soccer Players: Does Body Size Always Matter?
Authors: Buchheit M, Mendez-Villanueva A, Mayer N, Jullien H, Marles A, Bosquet L, Maille P, Morin JB, Cazorla G, Lambert P.

Reference: Int J Sports Med. 2013 Nov 7;. [Epub ahead of print], PMID: 24203798 [PubMed - as supplied by publisher]
Summary: To examine the effects of body size on locomotor performance, 807 15-year-old French and 64 Qatari soccer players participated in the present study. They performed a 40-m sprint and an incremental running test to assess maximal sprinting (MSS) and aerobic speeds, respectively. French players were advanced in maturity, taller, heavier, faster and fitter than their Qatari counterparts (e.g., Cohen's d=+1.3 and + 0.5 for body mass and MSS). However, when adjusted for body mass (BM), Qatari players had possibly greater MSS than French players (d=+0.2). A relative age effect was observed within both countries, with the players born in the first quarter of the year being taller, heavier and faster that those born during the fourth quarter (e.g., d=+0.2 for MSS in French players). When directly adjusted for BM, these MSS differences remained (d=+0.2). Finally, in both countries, players selected in National teams were taller, heavier, faster and fitter than their non-selected counterparts (e.g., d=+0.6 for MSS in French players), even after adjustments for body size (d=+0.5). Differences in locomotor performances between players with different phenotypes are likely mediated by differences in body size. However, when considering more homogeneous player groups, body dimensions are unlikely to substantially explain the superior locomotor performances of older and/or international players.


#9 Improving the Value of Fitness Testing for Football
Authors: Pyne DB, Spencer M, Mujika I.
Reference: Int J Sports Physiol Perform. 2013 Nov 13. [Epub ahead of print]
Summary: One of the challenges for the sports scientist working in football is to balance the needs for routine fitness testing with daily fatigue and well-being monitoring to best manage the physical preparation of players. In this commentary we examine contemporary issues of fitness testing in football to identify ways of improving the value of routine testing and monitoring. A testing program must be well planned and organised to ensure the results are useful. Different tests can be employed for younger and older players. A rigorous approach to analysis and interpretation of results is desirable, and database management must address both short- and long-term requirements of players, staff and programs.

#10 Injuries in professional football: current concepts
Authors: Olson D, Sikka RS, Labounty A, Christensen T.
Reference: Curr Sports Med Rep. 2013 Nov-Dec;12(6):381-90. doi: 10.1249/JSR.0000000000000015.
Summary: Professional football is one of the most popular sports in the United States. There is a common constellation of injuries that are seen frequently. Much attention has been focused on concussions and their long-term outcomes in this population. Other common causes of morbidity include cervical spine injuries, knee injuries including anterior cruciate ligament and other ligamentous injuries, ankle sprains, and medical issues including cardiac and sickle trait. Several recent studies have focused on hip impingement and hamstring injuries, among others, as sources of missed playing time as well. This review describes some of the frequently seen injuries and medical issues in professional football players. Proper management of both medical disease and on-field injuries can reduce morbidity and may lead to faster return to play and reduced risk of future injury.

#11 Side-to-side differences in the lower leg muscle-bone unit in male soccer players
Authors: Anliker E, Sonderegger A, Toigo M.
Reference: Med Sci Sports Exerc. 2013 Aug;45(8):1545-52. doi: 10.1249/MSS.0b013e31828cb712.
Summary: To characterize side-to-side differences in the lower leg muscle-bone unit between the nondominant leg (NL) and the dominant leg (DL) using maximum voluntary forefoot ground reaction force (Fm1LH) during multiple one-legged hopping (m1LH) and tibial bone mass and geometry measured by peripheral quantitative computed tomography (pQCT). Sixty-six male high-level soccer players (age range = 12-18 yr) performed m1LH to determine Fm1LH acting on the forefoot during landing for the NL and DL separately. pQCT scans were obtained to assess bone structural variables at 4%, 14%, 38%, and 66% tibia length and calf muscle cross-sectional area at the 66% site. First, participants displayed significant (P < 0.05) side-to-side differences in bone mass and geometry at 4%, 14%, and 38% (but not at the 66% site) of tibia length, with higher values in NL relative to DL (+0.7% to +5.6%), most evident at the 14% site. Second, no asymmetries were found for Fm1LH between the two legs (P = 0.442). Third, the relationship between Fm1LH and vBMC 14% was strong for both NL and DL (R2 = 0.48 and R = 0.54, respectively), but side-to-side differences in Fm1LH (ΔFm1LH) and side-to-side differences in vBMC 14% (ΔvBMC 14%) were not related (R2 = 0.04). Contrary to expectations from the mechanostat theory, ΔFm1LH and ΔvBMC 14% did not differ in proportion to each other. It seems that playing soccer is a well-balanced activity with respect to Fm1LH. However, the NL contributes to the supporting of the action of the DL, meaning that the loading experienced by the tibia might be more pronounced for the NL relative to the DL, leading to the observed higher bone strength values for the NL.