Latest research in football - week 31 - 2014

#1 Half-time re-warm up increases performance capacity in male elite soccer players
Reference: Scand J Med Sci Sports. 2014 Apr 30. doi: 10.1111/sms.12236. [Epub ahead of print]
Authors: Edholm P, Krustrup P, Randers MB.
Summary: This study investigated the acute effects of a half-time re-warm up on performance and movement patterns in soccer match play. Using a crossover design, 22 professional male players performed traditional passive rest (CON) or a low-intensity re-warm up (RW) during the half-time period of two soccer matches. Before and after the first half and before the second half, maximal sprint and jump performance were evaluated. Time-motion analysis of the first 15 min of each half was conducted. Sprint and jump performance were reduced (P < 0.05) by 2.6% and 7.6%, respectively, during the half-time period in CON, whereas sprint performance was maintained and the decrement in jump performance (3.1%; P < 0.05) was lower after RW. No significant interaction for high-intensity running was observed, but less defensive high-intensity running was observed after RW than CON (0.14 ± 0.06 vs 0.22 ± 0.07 km; P < 0.01). Moreover, RW had more possession of the ball in the beginning of the second half. In conclusion, traditional passive half-time rest leads to impaired sprint and jump performance during the initial phase of the second half in professional soccer players whereas a re-warm up effectively attenuates such deteriorations. Less defensive high-intensity running and more ball possession were observed after RW, indicating a game advantage at the onset of the second half.


#2 Effects of anterior cruciate ligament reconstruction on neuromuscular tensiomyographic characteristics of the lower extremity in competitive male soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2014 Jul 22. [Epub ahead of print]
Authors: Alvarez-Diaz P, Alentorn-Geli E, Ramon S, Marin M, Steinbacher G, Rius M, Seijas R, Ballester J, Cugat R.
Summary: The purpose was to investigate the effects of anterior cruciate ligament (ACL) reconstruction on mechanical and contractile properties of the skeletal muscles of the lower extremities in soccer players through tensiomyography (TMG). All soccer players with acute ACL tear included underwent resting TMG assessment of muscles of both lower extremities before and 1 year after ACL reconstruction. The muscles assessed were vastus medialis (VM), vastus laterals (VL), rectus femoris (RF), semitendinosus (ST), biceps femoris (BF), gastrocnemius medialis (GM), and gastrocnemius lateralis (GL). The TMG parameters obtained for each muscle were maximal displacement (D m), delay time (T d), contraction time (T c), sustained time (T s), and half-relaxation time (T r). The injured leg had a significant decrease in VL-T c, ST-T c, GM-T c, GL-T r, and GL-T d, and a significant increase in VM-T r and GM-T s in the postoperative compared to preoperative period. The non-injured leg demonstrated significant preoperative-postoperative changes in the VL, RF, and BF, but not in VM, ST, GM, and GL The magnitude of preoperative-postoperative differences in the injured leg was significantly higher in RF-T c, ST-T c, BF-D m, and GL-T r, but lower in RF-T r and GM-T s, compared to the non-injured leg. Both groups improved their symmetry between the quadriceps and hamstring muscle groups in both sides. The quadriceps muscles improved their resistance to fatigue and contraction velocity in both sides, and the hamstring muscles improved their contraction velocity and muscle tone in both sides as well. Improvements in contraction velocity and muscle tone were more evident in the quadriceps and hamstrings of the injured compared to the uninjured side. In addition, the intervention increased the percentage of symmetry between both sides in the TMG of the quadriceps muscles and the balance between ACL-agonist (hamstrings) and ACL-antagonist (quadriceps) muscle groups in both sides. This study shows how ACL reconstruction (and subsequent rehabilitation) can positively impact neuromuscular characteristics of the quadriceps and hamstrings.


#3 Hamstring Muscle Fatigue and Central Motor Output during a Simulated Soccer Match
Reference: PLoS One. 2014 Jul 21;9(7):e102753. doi: 10.1371/journal.pone.0102753. eCollection 2014.
Authors: Marshall PW, Lovell R, Jeppesen GK, Andersen K, Siegler JC
Download links: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4105441/pdf/pone.0102753.pdf
Summary: The purpose was to examine changes in hamstring muscle fatigue and central motor output during a 90-minute simulated soccer match, and the concomitant changes in hamstring maximal torque and rate of torque development. Eight amateur male soccer players performed a 90-minute simulated soccer match, with measures performed at the start of and every 15-minutes during each half. Maximal torque (Nm) and rate of torque development (RTD; Nm.s-1) were calculated from maximal isometric knee flexor contractions performed at 10° of flexion. Hamstring peripheral fatigue was assessed from changes in the size and shape of the resting twitch (RT). Hamstring central motor output was quantified from voluntary activation (%) and normalized biceps femoris (BF) and medial hamstrings (MH) electromyographic amplitudes (EMG/M). Maximal torque was reduced at 45-minutes by 7.6±9.4% (p<0.05). RTD in time intervals of 0-25, 0-50, and 0-75 ms post-contraction onset were reduced after 15-minutes in the first-half between 29.6 to 46.2% (p<0.05), and were further reduced at the end of the second-half (p<0.05). Maximal EMG/M was reduced for biceps femoris only concomitant to the time-course of reductions in maximal torque (p = 0.007). The rate of EMG rise for BF and MH was reduced in early time periods (0-75 ms) post-contraction onset (p<0.05). No changes were observed for the size and shape of the RT, indicating no hamstring peripheral fatigue. Centrally mediated reductions in maximal torque and rate of torque development provide insight into factors that may explain hamstring injury risk during soccer. Of particular interest were early reductions during the first-half of hamstring rate of torque development, and the decline in maximal EMG/M of biceps femoris in the latter stages of the half. These are important findings that may help explain why the hamstrings are particularly vulnerable to strain injury during soccer.


#4 Nutrient intake and food habits of soccer players: analyzing the correlates of eating practice
Reference: Nutrients. 2014 Jul 18;6(7):2697-717. doi: 10.3390/nu6072697.
Authors: García-Rovés PM, García-Zapico P, Patterson AM, Iglesias-Gutiérrez E
Download link: http://www.mdpi.com/2072-6643/6/7/2697
Summary: Despite the impact and popularity of soccer, and the growing field of soccer-related scientific research, little attention has been devoted to the nutritional intake and eating habits of soccer players. Moreover, the few studies that have addressed this issue suggest that the nutritional intake of soccer players is inadequate, underscoring the need for better adherence to nutritional recommendations and the development and implementation of nutrition education programs. The objective of these programs would be to promote healthy eating habits for male and female soccer players of all ages to optimize performance and provide health benefits that last beyond the end of a player's career. To date, no well-designed nutrition education program has been implemented for soccer players. The design and implementation of such an intervention requires a priori knowledge of nutritional intake and other correlates of food selection, such as food preferences and the influence of field position on nutrient intake, as well as detailed analysis of nutritional intake on match days, on which little data is available. Our aim is to provide an up-to-date overview of the nutritional intake, eating habits, and correlates of eating practice of soccer players.


#5 Osteochondral Lesions of the Ankle Joint in Professional Soccer Players: Treatment With Autologous Matrix-induced Chondrogenesis
Reference: Foot Ankle Spec. 2014 Jul 17. pii: 1938640014539811. [Epub ahead of print]
Authors: Valderrabano V, Barg A, Alattar A, Wiewiorski M
Summary: Acute and recurrent ankle sprains and other trauma to the ankle joint are common injuries in soccer and can be accompanied by or result in osteochondral lesions of the ankle joint, majorly of the talus. Conservative treatment frequently fails. Several operative treatment techniques exist; however, the choice of the right procedure is difficult due to lack of literature with a high level of evidence. We present our treatment method for acute and chronic ankle osteochondral lesions with cystic formation approached by a new surgical technique combining bone plasty and a collagen matrix (autologous matrix-induced chondrogenesis).


#6 Dengue and the world football cup: a matter of timing
Reference: PLoS Negl Trop Dis. 2014 Jul 24;8(7):e3022. doi: 10.1371/journal.pntd.0003022. eCollection 2014.
Authors: Barcellos C, Lowe R
Download link: http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0003022


#7 Exercise training, lymphocyte subsets and their cytokines production: experience of an italian professional football team and their impact on allergy
Reference: Biomed Res Int. 2014;2014:429248. doi: 10.1155/2014/429248. Epub 2014 Jun 23.
Authors: Del Giacco SR, Scorcu M, Argiolas F, Firinu D, Del Giacco GS
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4094862/pdf/BMRI2014-429248.pdf
Summary: In recent years, numerous articles have attempted to shed light on our understanding of the pathophysiological mechanisms of exercise-induced immunologic changes and their impact on allergy and asthma. It is known that lymphocyte subclasses, cytokines, and chemokines show modifications after exercise, but outcomes can be affected by the type of exercise as well as by its intensity and duration. Interesting data have been presented in many recent studies on mouse models, but few studies on humans have been performed to check the long-term effects of exercise over a whole championship season. Methods. This study evaluated lymphocyte subsets and their intracellular IL-2, IL-4, TNF-α, and IFN-γ production in professional football (soccer) players, at three stages of the season, to evaluate if alterations occur, particularly in relation to their allergic status. Results and Conclusion. Despite significant mid-season alterations, no significant lymphocyte subclasses count modifications, except for NKs that were significantly higher, were observed at the end. IL-2 and IL-4 producing cells showed a significant decrease (P = 0.018 and P = 0.001, but in a steady fashion for IL-4), confirming the murine data about the potential beneficial effects of aerobic exercise for allergic asthma.


#8 Structured neuromuscular warm-up for injury prevention in young elite football players
Reference: Rev Esp Cir Ortop Traumatol. 2014 Jul 18. pii: S1888-4415(14)00112-X. doi: 10.1016/j.recot.2014.05.008. [Epub ahead of print]
 [Article in English, Spanish]
Authors: Mayo M, Seijas R, Alvarez P
Summary: The purpose was to gather evidence about the outcomes of structured neuromuscular warm-up programs without additional equipment, as prevention of non-contact injuries in young professional soccer players. A literature search was conducted during March and April 2013 (PubMed, Cochrane Library, The American Journal of Sports Medicine, The British Journal of Sports Medicine and the search engine Trip Database). After applying the inclusion and exclusion criteria, a total of 6 studies were obtained (3 clinical trials, one cohort study and 2 systematic reviews). «FIFA 11+» program showed a reduction of injuries of between 33% and 57%. These included 52% in knee, 22% in ankle, 40% in medial tibial stress syndrome, 50% in posterior thigh, and 21% in the anterior, and 12% in the groin area. «FIFA 11» program showed a 58% reduction in ankle sprains and 27% in anterior cruciate ligament (ACL) injuries. Other specific programs to prevent ACL injuries reduced them by 74% and «Knäkontroll, SISU Idrottsböcker©» by 64%. «HarmoKnee» program reduced knee injuries by 78%. Several methodological weaknesses were observed, but it seems that there is a trend toward a warm-up that contains basic stretching, strengthening and balance exercises, which performed for more than three months and regularly, could prevent injuries. «FIFA 11 +» program might be a good preventive measure of injuries by implementing its program of structured warm- up. In any event new, better designed, studies are needed to assess this evidence.


#9 Cardiac arrest in spectators in German football stadiums : Precautionary measures, frequency and short-term outcome
Reference: Anaesthesist. 2014 Jul 23. [Epub ahead of print]
 [Article in German]
Authors: Luiz T, Preisegger T, Rombach D, Madler C.
Summary: Provision of medical care is an important element of safety precautions for visitors of sports arenas. The organizational requirements are especially high if cardiac arrest occurs; how this scenario is managed may thus serve as the ultimate indicator of the quality of stadium medical care. The objectives of this study were to analyze the structures and the resources available for the medical care of spectators in German professional soccer stadiums and to identify the frequency and the primary resuscitation success of cardiac arrest. In 2011 a questionnaire-based survey was performed among the clubs of the first and second German soccer leagues regarding medical care of spectators during the seasons 2008/2009 and 2009/2010. The focus was on the qualifications of emergency teams, the equipment and the incidence of cardiac arrest. A total of 15 stadiums were included (38 %) in the survey. The mean number of physicians and emergency medical technicians on site was 0.6/10,000 seats and 16/10,000 seats, respectively. Of the latter, a mean of 82 % (minimum 20 % and maximum 100 %) had received training with automatic external defibrillators. In 87 % of the stadiums regular advanced life support training (ALS) was required. The mean number of defibrillators per stadium was 2.8/10,000 seats (minimum 1.3 and maximum 3.8) including 1.7 automatic defibrillators (minimum 0.4 and maximum 2.8). For patient transport, a mean of 0.65 ALS ambulance vehicles per 10,000 seats (minimum 0.14 and maximum 1.46) were available on site. In all stadiums staff members were connected via mobile radio communication with the stadium medical control room. A total of 52 cardiac arrests (= 0.25/100,000 spectators) were recorded of which 96 % of the patients were transported to hospitals with spontaneous circulation. Cardiac arrests are not a rare occurrence in German soccer stadiums. The participating stadiums are overall well prepared for such incidents in terms of organization, staff and technology and due to short response times, the resuscitation success by far surpasses that of the standard emergency medical services. These findings may in addition serve as a motivational example to start resuscitation early in public information campaigns.