Latest research in football - week 23 - 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 The Impact of Jumping during Recovery on Repeated Sprint Ability in Young Soccer Players
Reference: Res Sports Med. 2015 Jun 3:1-13. [Epub ahead of print]
Authors: Padulo J, Tabben M, Attene G, Ardigò LP, Dhahbi W, Chamari K.
Summary: This study compared the effect of counter-movement-jump (CMJ)-based recovery on repeated-sprint-ability (RSA). Eighteen male footballers (16 ± 0 years, 65 ± 10 kg, 1.74 ± 0.10 m) performed three RSA-tests. RSA-1/-3 were performed according to standard procedures, while three CMJs (over 10″) - as a potential fatigue-determinant and/or running mechanics interference - were administered during RSA-2 recoveries. RSA performance, exercise effort (fatigue index [FI], rating of perceived exertion [RPE], blood lactate concentration [BLa]), simple kinematics (steps number), vertical-jump characteristics (stretch-shortening-cycle-efficiency [SSCE] assessed before/after RSA) were investigated. ANOVA showed no differences between RSA-1,-3. During RSA-2, performance was lower than RSA-1/-3, while steps number did not change. During RSA-2, FI, BLa, RPE were higher than RSA-1/-3 (FI +21.10/+20.43%, P<0.05; BLa +16.25/+13.34%, P<0.05; RPE +12.50/+9.57%, P<0.05). During RSA-2, SSCE, as the CMJ/squat-jump-height-ratio, was not significantly different from RSA-1/-3. Passive recovery RSA allows better performance. Yet, RSA CMJ-based recovery is effective in increasing training load (FI, BLa, RPE) without perturbing running mechanics (simple kinematics, SSCE).

#2 Hydration status and fluid intake of urban, underprivileged South African male adolescent soccer players during training
Reference: J Int Soc Sports Nutr. 2015 May 3;12:21. doi: 10.1186/s12970-015-0080-0. eCollection 2015.
Authors: Gordon RE1, Kassier SM1, Biggs C1.
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Summary: Poor hydration compromises performance and heightens the risk of heat stress which adolescents are particularly susceptible to as they produce comparatively larger amount of metabolic heat during exercise. This study determined the hydration status and fluid intake of socio-economically disadvantaged, male adolescent soccer players during training. A pilot study was conducted among 79 soccer players (mean age 15.9 ± 0.8 years; mean BMI 20.2 ± 2.1 kg/m(2)). Hydration status was determined before and after two training sessions, using both urine specific gravity and percent loss of body weight. The type and amount of fluid consumed was assessed during training. A self-administered questionnaire was used to determine the players' knowledge regarding fluid and carbohydrate requirements for soccer training. Players were at risk of developing heat illness during six of the 14 training sessions (60 - 90 minutes in length). Although on average players were slightly dehydrated (1.023 ± 0.006 g/ml) before and after (1.024 ± 0.007 g/ml) training, some were extremely dehydrated before (24%) and after (27%) training. Conversely some were extremely hyperhydrated before (3%) and after training (6%). The mean percent loss of body weight was 0.7 ± 0.7%. The majority did not consume fluid during the first (57.0%) and second (70.9%) training sessions. An average of 216.0 ± 140.0 ml of fluid was consumed during both training sessions. The majority (41.8%) consumed water, while a few (5.1%) consumed pure fruit juice. More than 90% stated that water was the most appropriate fluid to consume before, during and after training. Very few (5.0%) correctly stated that carbohydrate should be consumed before, during and after training. Approximately a quarter were severely dehydrated. Many did not drink or drank insufficient amounts. The players' beliefs regarding the importance of fluid and carbohydrate consumption did not correspond with their practices. A nutrition education programme is needed to educate players on the importance of fluid and carbohydrate to prevent dehydration and ensure appropriate carbohydrate intake.

#3 Soccer results affect subjective well-being, but only briefly: a smartphone study during the 2014 FIFA World Cup
Reference: Front Psychol. 2015 May 12;6:497. doi: 10.3389/fpsyg.2015.00497. eCollection 2015.
Authors: Stieger S, Götz FM, Gehrig F
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Summary: The current research examined the effects of soccer match results on spectators' subjective well-being. Across the group stage of the soccer World Cup 2014, German-speaking participants indicated their well-being three times per day through a smartphone-based science app. In line with proposed hypotheses, comparisons of data taken after the three matches of the German national team showed robust effects, revealing that well-being was higher among spectators than non-spectators, with effects increasing as a function of goal difference. Moreover, this gain in well-being was only found in spectators supporting the German soccer team, allowing us to rule out a general emotional contagion effect affecting all spectators. Although soccer results are associated with national identity and pride, their effects on subjective well-being were short-lived and only affected supporters.

#4 Recovery Kinetics of Knee Flexor and Extensor Strength after a Football Match
Reference: PLoS One. 2015 Jun 4;10(6):e0128072. doi: 10.1371/journal.pone.0128072.
Authors: Draganidis D, Chatzinikolaou A, Avloniti A, Barbero-Álvarez JC, Mohr M, Malliou P, Gourgoulis V, Deli CK, Douroudos II, Margonis K, Gioftsidou A, Fouris AD, Jamurtas AZ, Koutedakis Y, Fatouros IG
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Summary: We examined the temporal changes of isokinetic strength performance of knee flexor (KF) and extensor (KE) strength after a football match. Players were randomly assigned to a control (N = 14, participated only in measurements and practices) or an experimental group (N = 20, participated also in a football match). Participants trained daily during the two days after the match. Match and training overload was monitored with GPS devices. Venous blood was sampled and muscle damage was assessed pre-match, post-match and at 12h, 36h and 60h post-match. Isometric strength as well as eccentric and concentric peak torque of knee flexors and extensors in both limbs (dominant and non-dominant) were measured on an isokinetic dynamometer at baseline and at 12h, 36h and 60h after the match. Functional (KFecc/KEcon) and conventional (KFcon/KEcon) ratios were then calculated. Only eccentric peak torque of knee flexors declined at 60h after the match in the control group. In the experimental group: a) isometric strength of knee extensors and knee flexors declined (P<0.05) at 12h (both limbs) and 36h (dominant limb only), b) eccentric and concentric peak torque of knee extensors and flexors declined (P<0.05) in both limbs for 36h at 60°/s and for 60h at 180°/s with eccentric peak torque of knee flexors demonstrating a greater (P<0.05) reduction than concentric peak torque, c) strength deterioration was greater (P<0.05) at 180°/s and in dominant limb, d) the functional ratio was more sensitive to match-induced fatigue demonstrating a more prolonged decline. Discriminant and regression analysis revealed that strength deterioration and recovery may be related to the amount of eccentric actions performed during the match and athletes' football-specific conditioning. Our data suggest that recovery kinetics of knee flexor and extensor strength after a football match demonstrate strength, limb and velocity specificity and may depend on match physical overload and players' physical conditioning level.

#5 Tackling risky alcohol consumption in sport: a cluster randomised controlled trial of an alcohol management intervention with community football clubs
Reference: J Epidemiol Community Health. 2015 Jun 2. pii: jech-2014-204984. doi: 10.1136/jech-2014-204984. [Epub ahead of print]
Authors: Kingsland M, Wolfenden L, Tindall J, Rowland BC, Lecathelinais C, Gillham KE, Dodds P, Sidey MN, Rogerson JC, McElduff P, Crundall I, Wiggers JH
Summary: An increased prevalence of risky alcohol consumption and alcohol-related harm has been reported for members of sporting groups and at sporting venues compared with non-sporting populations. While sports clubs and venues represent opportune settings to implement strategies to reduce such risks, no controlled trials have been reported. The purpose of the study was to examine the effectiveness of an alcohol management intervention in reducing risky alcohol consumption and the risk of alcohol-related harm among community football club members. A cluster randomised controlled trial of an alcohol management intervention was undertaken with non-elite, community football clubs and their members in New South Wales, Australia. Risky alcohol consumption (5+ drinks) at the club and risk of alcohol-related harm using the Alcohol Use Disorders Identification Test (AUDIT) were measured at baseline and postintervention. Eighty-eight clubs participated in the trial (n=43, Intervention; n=45, Control) and separate cross-sectional samples of club members completed the baseline (N=1411) and postintervention (N=1143) surveys. Postintervention, a significantly lower proportion of intervention club members reported: risky alcohol consumption at the club (Intervention: 19%; Control: 24%; OR: 0.63 (95% CI 0.40 to 1.00); p=0.05); risk of alcohol-related harm (Intervention: 38%; Control: 45%; OR: 0.58 (95% CI 0.38 to 0.87); p<0.01); alcohol consumption risk (Intervention: 47%; Control: 55%; OR: 0.60 (95% CI 0.41 to 0.87); p<0.01) and possible alcohol dependence (Intervention: 1%; Control: 4%; OR: 0.20 (95% CI 0.06 to 0.65); p<0.01). With large numbers of people worldwide playing, watching and sports officiating, enhancing club-based alcohol management interventions could make a substantial contribution to reducing the burden of alcohol misuse in communities.

#6 Higher shoe-surface interaction is associated with doubling of lower extremity injury risk in football codes: a systematic review and meta-analysis
Reference: Br J Sports Med. 2015 Jun 2. pii: bjsports-2014-094478. doi: 10.1136/bjsports-2014-094478. [Epub ahead of print]
Authors: Thomson A, Whiteley R, Bleakley C
Summary: Turning or cutting on a planted foot may be an important inciting event for lower limb injury, particularly when shoe-surface traction is high. We systematically reviewed the relationship between shoe-surface interaction and lower-extremity injury in football sports. A systematic literature search of four databases was conducted up to November 2014. Prospective studies investigating the relationship between rotational traction and injury rate were included. Two researchers independently extracted outcome data and assessed the quality of included studies using a modified Downs and Black index. Effect sizes (OR+95% CIs) were calculated using RevMan software. Where possible, data were pooled using the fixed effect model. Three prospective studies were included (4972 male athletes). The methodological quality was generally good with studies meeting 68-89% of the assessment criteria. All studies categorised athletes into low (lowest mean value 15 nm) or high traction groups (highest mean value 74 nm) based on standardised preseason testing. In all cases, injury reporting was undertaken prospectively over approximately three seasons, with verification from a medical practitioner. Injury data focused on: all lower limb injuries, ankle/knee injuries or ACL injury only. There was a clear relationship between rotational traction and injury and the direction and magnitude of effect sizes were consistent across studies. The pooled data from the three studies (OR=2.73, 95% CI 2.13 to 3.15; χ2=3.19, df=2, p=0.21; I2=36.5%) suggest that the odds of injury are approximately 2.5 times higher when higher levels of rotational traction are present at the shoe-surface interface. Higher levels of rotational traction influence lower limb injury risk in American Football athletes. We conclude that this warrants considerable attention from clinicians and others interested in injury prevention across all football codes.

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