Latest research in football - week 6 - 2015

As previous literature updates, we have performed a PubCrawler search looking for football articles in NCBI Medline (PubMed) and GenBank databases.

Following studies were retrieved for this week:

#1 Comparison of the postural control between football players following ACL reconstruction and healthy subjects
Reference: Med J Islam Repub Iran. 2014 Sep 21;28:101. eCollection 2014.
Authors: Pahnabi G, Akbari M, Ansari NN, Mardani M, Ahmadi M, Rostami M
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Summary: Rupture of the Anterior Cruciate Ligment (ACL) is a common knee injury. The purpose of this study was to determine the balance control in football players with and without ACL reconstruction in posture of injury. Sway of the center of gravity of 15 patients with ACL reconstruction was compared with 15 healthy, age and sex-matched subjects as the control group. All tests were done unilaterally in the posture of injury, using a kistler force plate with the open and -closed eye conditions. The knee of the operated side of the case group showed more displacement of the center of gravity when compared to the non-operated side in the same subject for all variables of the force plate. The operated side of the case group showed more displacement of the center of gravity for all variables of the force plate in comparison with the dominant side of knees in control group. There were significant differences between the non-operated side in the case group and the dominant side of the control group. All together, postural control in the operated side of the case group was weaker than the nonoperated side of the same group and the dominant limb of the control group, which might have resulted from poor proprioception. The postural control was even weaker in the non-operated side of the case group as compared with the dominant limb of the control group, which can justify the hypo mobility of limb for several months after the surgery.

#2 'You'll never walk alone': Supportive social relations in a football and mental health project
Reference: Int J Ment Health Nurs. 2015 Feb 11. doi: 10.1111/inm.12122. [Epub ahead of print]
Authors: McKeown M, Roy A, Spandler H.
Summary: Football can bring people together in acts of solidarity and togetherness. This spirit is most evocatively illustrated in the world renowned football anthem 'You'll Never Walk Alone' (YNWA). In this paper, we argue that this spirit can be effectively harnessed in nursing and mental health care. We draw on data from qualitative interviews undertaken as part of evaluating a football and mental health project to explore the nature of supportive social relations therein. We use some of the lyrics from YNWA as a metaphor to frame our thematic analysis. We are especially interested in the interactions between the group facilitators and group members, but also address aspects of peer support within the groups. A contrast is drawn between the flexible interpersonal boundaries and self-disclosure evident in the football initiative, and the reported, more-distant relations with practitioners in mainstream mental health services. The findings suggest scope for utilizing more collective, solidarity-enhancing initiatives and attention to alliances and boundaries to maximize engagement and therapeutic benefits within routine practice.

#3 The Role of Instability with Plyometric Training in Sub-elite Adolescent Soccer Players
Reference: Int J Sports Med. 2015 Feb 9. [Epub ahead of print]
Authors: Granacher U, Prieske O, Majewski M, Büsch D, Muehlbauer T
Summary: The purpose of this study was to investigate the effects of plyometric training on stable (SPT) vs. highly unstable surfaces (IPT) on athletic performance in adolescent soccer players. 24 male sub-elite soccer players (age: 15±1 years) were assigned to 2 groups performing plyometric training for 8 weeks (2 sessions/week, 90 min each). The SPT group conducted plyometrics on stable and the IPT group on unstable surfaces. Tests included jump performance (countermovement jump [CMJ] height, drop jump [DJ] height, DJ performance index), sprint time, agility and balance. Statistical analysis revealed significant main effects of time for CMJ height (p<0.01, f=1.44), DJ height (p<0.01, f=0.62), DJ performance index (p<0.05, f=0.60), 0-10-m sprint time (p<0.05, f=0.58), agility (p<0.01, f=1.15) and balance (p<0.05, 0.46≤f≤1.36). Additionally, a Training group×Time interaction was found for CMJ height (p<0.01, f=0.66) in favor of the SPT group. Following 8 weeks of training, similar improvements in speed, agility and balance were observed in the IPT and SPT groups. However, the performance of IPT appears to be less effective for increasing CMJ height compared to SPT. It is thus recommended that coaches use SPT if the goal is to improve jump performance.

#4 A Preliminary Examination of Neurocognitive Performance and Symptoms Following a Bout of Soccer Heading in Athletes Wearing Protective Soccer Headbands
Reference: Res Sports Med. 2015 Feb 10:1-12. [Epub ahead of print]
Authors: Elbin RJ, Beatty A, Covassin T, Schatz P, Hydeman A, Kontos AP.
Summary: This study compared changes in neurocognitive performance and symptom reports following an acute bout of soccer heading among athletes with and without protective soccer headgear. A total of 25 participants headed a soccer ball 15 times over a 15-minute period, using a proper linear heading technique. Participants in the experimental group completed the heading exercise while wearing a protective soccer headband and controls performed the heading exercise without wearing the soccer headband. Neurocognitive performance and symptom reports were assessed before and after the acute bout of heading. Participants wearing the headband showed significant decreases on verbal memory (p = 0.02) compared with the no headband group, while the no headband group demonstrated significantly faster reaction time (p = 0.03) than the headband group following the heading exercise. These findings suggest that protective soccer headgear likely does not mitigate the subtle neurocognitive effects of acute soccer heading.

#5 Muscle injuries of the lower extremity: a comparison between young and old male elite soccer players
Reference: Knee Surg Sports Traumatol Arthrosc. 2015 Feb 11. [Epub ahead of print]
Authors: Svensson K, Alricsson M, Karnebäck G, Magounakis T, Werner S.
Summary: The purpose of the study was to make a comparison between players in two age groups in an elite male soccer team regarding injury localisation within the muscle-tendon unit, injury size and muscle group in terms of muscle injuries of the lower extremity. Cohort study based on data collected from a Swedish elite male soccer team during the seasons 2007-2012. In total, 145 muscle injuries were included. Injury localisation to the tendon or muscle, the size of haematoma and the affected muscle group were assessed using ultrasound. Age comparison was made between younger players (≤23 years) and older players (>23 years). No difference regarding injury localisation to either the tendon or the muscle, or the size of haematoma between the two age groups was found. However, the older group of players suffered a significantly higher number of injuries to the triceps surae than the younger players (p = 0.012). In a Swedish team of male soccer players at elite level, there was no difference between players 23 years or younger and players older than 23 years, in terms of injury distribution to muscles or tendons. Players older than 23 years sustained more injuries to triceps surae when compared with players 23 years or younger. The clinical relevance is to pay attention to muscle function of triceps surae in older players and to screen those players who may need an injury prevention programme.

#6 Two-year changes in anthropometric and motor ability values as talent identification indexes in youth soccer players
Reference: J Sci Med Sport. 2015 Jan 23. pii: S1440-2440(15)00007-9. doi: 10.1016/j.jsams.2015.01.004. [Epub ahead of print]
Authors: Hirose N, Seki T
Summary: The present study examined 2-year changes in anthropometric variables and motor abilities in elite male youth soccer players to identify potential talent identification indexes. Height, weight, 40-m sprint speed, muscular power (5-step bounding), and change of direction (COD) ability (10 m×5 COD) were measured in 12- and 14-year-old soccer players and repeated after 2 years (at 14 and 16 years of age). Correlations and changes in ranking between the two measurements were determined. Both groups had small ranking changes in height (12-14-year-olds: r=0.80, 14-16-year-olds: r=0.89; p<0.01), weight (r=0.94, r=0.80; p<0.01), 40-m sprint speed (r=0.81, r=0.90; p<0.01), and muscular power (r=0.48, r=0.64; p<0.05), with a statistically significant correlation between the initial values and those obtained 2 years later. However, 10m×5 COD ability had a large ranking change, with no statistically significant correlation observed between the first- and second-year values. Because of the minimal ranking change in sprint speed in normal circumstances of soccer practice, linear sprint speed has the potential to be a useful talent identification index for youth soccer players. On the other hand, muscular power and COD ability is changeable during growth period suggests that these parameters is not useful for talent identification index.

#7 Injuries of Veteran Football (Soccer) Players in Germany
Reference: Res Sports Med. 2015 Feb 11:1-12. [Epub ahead of print]
Authors: Hammes D, Aus Der Fünten K, Kaiser S, Frisen E, Dvorák J, Meyer T.
Summary: There is a lack of injury data for the population of veteran football players. Therefore, a prospective study was conducted to investigate injury incidences and characteristics. Over one season, injuries and exposure of 18 teams (n = 265 players, age: 44.2±7.3 years, BMI: 26.6±3.2 kg/m2) were documented. Sixty-three players sustained a total of 88 injuries during the season. The incidence of training injuries (4.5 per 1000 hours) was significantly lower than of match injuries (24.7 per 1000 hours). The majority of injuries (n = 73; 83%) were located at the lower extremities, 52 (47%) were muscle injuries. The injury incidence of veteran football players is similar to other male football players of different skill levels and age groups, indicating a need for the implementation of preventive measures. Prevention programmes should consider the specific injury characteristics, with more muscle injuries in this population compared with younger football players.

#8 Factors Influencing Perception of Effort (Session-RPE) During Elite Soccer Training
Reference: Int J Sports Physiol Perform. 2015 Feb 11. [Epub ahead of print]
Authors: Gaudino P, Iaia FM, Strudwick AJ, Hawkins RD, Alberti G, Atkinson G, Gregson W
Summary: The aim of the present study was to identify the external training load markers that are most influential of session rating of perceived exertion (RPE) training load (RPE-TL) during elite soccer training. Twenty-two elite players competing in the English Premier League were monitored. Training load data (RPE and 10 Hz GPS integrated with a 100 Hz accelerometer) were collected during 1892 individual training sessions over an entire in-season competitive period. Expert knowledge and a colinearity r<0.5 were used initially to select the external training variables for the final analysis. A multivariate-adjusted within subjects model was employed to quantify the correlations between RPE and RPE-TL (RPE x Duration) and various measures of external training intensity and training load respectively. Total high-speed running distance (HSR; >14.4 km·h-1), number of impacts and accelerations >3 m·s-2 remained in the final multivariate model (p<0.001). The adjusted correlations with RPE were r=0.14, r=0.09 and r=0.25 for HSR, impacts and accelerations respectively. For RPE-TL, the correlations were r=0.11, r=0.45 and r=0.37 respectively. The external load measures that were found to be moderately predictive of RPE-TL in soccer training were HSR distance, and the number of impacts and accelerations. These findings provide new evidence to support the use of RPE-TL as a global measure of training load in elite soccer. Furthermore, understanding the influence of characteristics impacting RPE-TL may serve to help coaches and practitioners enhance training prescription and athlete monitoring.

#9 Eating and nutrition habits in young competitive athletes: a comparison between soccer players and cyclists
Reference: Transl Med UniSa. 2014 Dec 19;11:44-7.
Authors: Galanti G, Stefani L, Scacciati I, Mascherini G, Buti G, Maffulli N
Summary: The study evaluated the dietary habits in two groups of young athletes, practicing two different sports: soccer players and cycling. The dietary habits of 47 athletes were investigated by questionnaire. Body Mass Index, Fat Mass, Free Fat Mass, Total Body, Intracellular, Extracellular Water and Phase Angle were measured by bioimpedance. The t-Student test for unpaired data was used. Significance was set at P < 0.05. Body Mass Index was similar between the groups, while total body water and extracellular water were significantly higher in the soccer player group (soccer players: 63.8±1.96%; cyclists : 59.8 ± 8.7%; and soccer players 43.9±3.1%, cyclists 43.8 ±2.1%, respectively). Fatty mass of the soccer player group (14.5±2.9%) was significantly lower than that of the cyclist group (19.5±3.6%). Daily food intake was similar between the two groups (2844 kCal/die for soccer players /2630 kcal/die for cyclists), and lower than recommended. There was a low intake of Calcium (soccer players 1120±128.9 mg/die, cyclists 718±309 mg/die) for both groups, and a low intake of Potassium for soccer player (2576 mg/die ± 52.4) The caloric intake of adolescent athletes is lower than recommended. Body composition is significantly different between soccer players and cyclists.

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