Latest research in football - week 46 - 2013

Latest research in football

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 Relationship between Repeated Sprint Ability and Aerobic Capacity in Professional Soccer Players
Authors: Jones RM, Cook CC, Kilduff LP, Milanović Z, James N, Sporiš G, Fiorentini B, Fiorentini F, Turner A, Vučković G.
Reference: ScientificWorldJournal. 2013 Oct 1;2013:952350. doi: 10.1155/2013/952350.
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Summary: The aim of the present study was to investigate the relationship between maximal aerobic capacity (VO2 max) and repeated sprint ability (RSA) in a group of professional soccer players. Methods. Forty-one professional soccer players (age 23 ± 4 yrs, height 180.0 ± 5.3 cm, weight 79.6 ± 5.3 kg) were required to perform tests to assess RSA and VO2 max on two separate days with at least 48 hr rest between testing sessions. Each player performed a treadmill test to determine their VO2 max and a test for RSA involving the players completing 6 × 40 m sprints (turn after 20 m) with 20 s active recovery between each sprint. Results. There was a significant negative correlation between body mass normalised VO2 max and mean sprint time (RSAmean) (r = -0.655; P < 0.01) and total sprint time (RSAtotal) (r = -0.591, P < 0.01). Conclusion. Results of the current study indicate that VO2 max is one important factor aiding soccer players in the recovery from repeated sprint type activities.

#2 Nutritional practices of national female soccer players: analysis and recommendations
Authors: Martin L, Lambeth A, Scott D.
Reference: J Sports Sci Med. 2006 Mar 1;5(1):130-7.
Summary: The aim of the study was to establish the nutritional practices and activity patterns of elite female soccer players. The nutritional intake of 16 female England Soccer players was self-reported over a seven-day period. Participants were provided with written and verbal guidelines for the completion of the diaries. Training details were also recorded, and used in combination with BMR predictions to calculate daily energy expenditure. Energy, macronutrient and micronutrient intakes were determined using DietMaster 4.0 software. Results suggest that energy intake was low (1904 ± 366.3 kcal) in relation to previous recommendations for soccer players. Energy expenditure (2153.5 ± 596.2 kcal) was not significantly different (p > 0.05) from intake, suggesting energy balance was achieved. Carbohydrate (53.8 ± 6.8%), protein (16.8 ± 2.1%) and fat (28.8 ± 6.6%) intakes were in line with recommendations. Fluid intake (2466 ± 1350.5ml·day(-1)) was sufficient to meet baseline recommendations, but would need to be higher to meet the additional requirement of training and competition. With the exception of vitamin A and iron, all micronutrient intakes were higher than the DRI. In conclusion, recommendations for female soccer players are to encourage consumption of carbohydrate-electrolyte beverages to enhance carbohydrate intake and increase fluid intake, and ensure sufficient iron rich foods are included in the diet to meet the DRI. Key pointsFemale soccer players demonstrate a low energy intake in relation to predicted requirements, but were in energy balance in this study.Increased carbohydrate intake may be beneficial to both training and competition performance of elite female soccer playersFluid requirements should be addressed on an individual basis and matched to player requirements.The iron status of female soccer players may be compromised due to insufficient dietary intake to meet the DRV.

#3 Soccer players have a better standing balance in nondominant one-legged stance
Authors: Barone R, Macaluso F, Traina M, Leonardi V, Farina F, Di Felice V.
Reference: Open Access J Sports Med. 2010 Dec 16;2:1-6. doi: 10.2147/OAJSM.S12593.
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Summary: The purpose of this study was to analyze the differences in standing balance during dominant and nondominant one-legged stance among athletes of different sports and sedentary subjects. The right-footed subjects of four groups (sedentary, n = 20; soccer, n = 20; basketball, n = 20; windsurfer n = 20) underwent 5-sec unipedal (left and right foot) stabilometric analysis with open eyes and closed eyes to measure center of pressure (COP) sway path and COP velocity (mean value, anteroposterior, and laterolateral in millimeters per second). The soccer group showed better standing balance on the left leg than the sedentary group (P < 0.05). No other significant differences were observed within and amongst groups. The soccer players have a better standing balance on the nondominant leg because of soccer activity.

#4 Are There Differences in Neurocognitive Function and Symptoms Between Male and Female Soccer Players After Concussions?
Authors: Covassin T, Elbin RJ, Bleecker A, Lipchik A, Kontos AP.
Reference: Am J Sports Med. 2013 Nov 6. [Epub ahead of print]
Summary: Researchers have suggested that there are sex differences in outcomes after sport-related concussions. Factors such as sport type/rules, age, and body mass index (BMI) may influence these differences. The purposes of this study were (1) to examine neurocognitive performance after concussions between male and female soccer players and (2) to compare concussion symptoms between male and female soccer players. We hypothesized that female concussed soccer players would report more concussion symptoms and worse cognitive performance compared with male concussed soccer players.A total of 39 male (mean BMI, 22.21 ± 2.34 kg/m2; mean age, 17.69 ± 2.10 years) and 56 female (mean BMI, 23.47 ± 2.66 kg/m2; mean age, 17.78 ± 2.30 years) concussed soccer players participated in this study. Participants were similar in age, history of concussion, sport, and time since injury. Participants completed computerized neurocognitive tests and symptom reports at baseline and 8 days after injury. Body mass index served as a covariate in all analyses. After adjusting for BMI, results from a repeated-measures analysis of covariance (ANCOVA) revealed a group by time interaction for visual memory (F1,82 = 5.50; P = .021). Specifically, female concussed soccer players (mean score, 68.7 ± 15.2) performed worse at 8 days after a concussion compared with male concussed athletes (mean score, 77.2 ± 8.9). Results of another ANCOVA for total concussion symptoms indicated an interaction for group by time (F1,82 = 4.26; P = .04). Specifically, female concussed soccer players (mean score, 11.9 ± 15.7) reported more total concussion symptoms at 8 days compared with male concussed athletes (mean score, 5.3 ± 7.4). There were significant main effects for sex on verbal (F1,82 = 5.98; P = .017) and visual (F1,82 = 4.65; P = .034) memory, with female athletes reporting lower scores than male athletes. Female athletes also reported more symptoms on the migraine-cognitive-fatigue (F1,82 = 10.8; P = .001) and sleep (F1,82 = 9.2; P = .003) clusters than male athletes. In contrast to recent studies, after controlling for BMI, female athletes exhibited lower performance on visual memory composite scores and higher scores on total symptoms than male athletes after concussions.

#5 Effect of a Novel Movement Strategy in Decreasing ACL Risk Factors in Female Adolescent Soccer Players: A Randomized Controlled Trial
Authors: Celebrini RG, Eng JJ, Miller WC, Ekegren CL, Johnston JD, Depew TA, Macintyre DL.
Reference: Clin J Sport Med. 2013 Oct 31. [Epub ahead of print]
Summary: To determine the effect of a novel movement strategy incorporated within a soccer warm-up on biomechanical risk factors for anterior cruciate ligament injury during 3 sport-specific movement tasks. Twenty top-tier female teenage soccer players participated in this study. Subjects were randomized to the Core Position and Control movement strategy (Core-PAC) warm-up or standard warm-up, which took place before their regular soccer practice over a 6-week period. The Core-PAC focuses on getting the centre of mass closer to the plant foot or base of support.  Peak knee flexion angle and abduction moments during a side-hop (SH), side-cut, and unanticipated side-cut task after the 6 weeks with (intervention group only) and without a reminder to use the Core-PAC strategy were used as main outcome measures. The Core-PAC group increased peak flexion angles during the SH task [mean difference = 6.2 degrees; 95% confidence interval (CI), 1.9-10.5 degrees; effect size = 1.01, P = 0.034] after the 6-week warm-up program without a reminder. In addition, the Core-PAC group demonstrated increased knee flexion angles for the side-cut (mean difference = 8.5 degrees; 95% CI, 4.8-12.2 degrees; ES = 2.02; P = 0.001) and SH (mean difference = 10.0 degrees; 95% CI, 5.7-14.3 degrees; ES = 1.66; P = 0.001) task after a reminder. No changes in abduction moments were found. The results of this study suggest that the Core-PAC may be one method of modifying high-risk soccer-specific movements and can be implemented within a practical, team-based soccer warm-up. The results should be interpreted with caution because of the small sample size.

#6 Watching soccer is not associated with an increase in cardiac events
Authors: Niederseer D, Thaler CW, Egger A, Niederseer MC, Plöderl M, Niebauer J.
Reference: Int J Cardiol. 2013 Oct 25. pii: S0167-5273(13)01910-4. doi: 10.1016/j.ijcard.2013.10.066. Summary: It remains controversial, whether spectators of soccer matches are exposed to an increased risk of cardiac events. In 2006, the Soccer World Cup (SWC) took place in Germany and provided an excellent opportunity to assess the effects of emotional stress on cardiac events in a large cohort of soccer enthusiasts in the region of Bavaria. We analyzed data from the Bavarian Council for Statistics and Data Management for the period of SWC (June 9-July 9, 2006) and reference periods (SWCRef; May 1-July 31, 2005; May 1-June 8, 2006 and July 10-31, 2006) for the following diagnoses: myocardial infarction; myocardial re-infarction; cardiac arrest; paroxysmal tachycardia; atrial fibrillation, atrial flutter; all remaining tachyarrhythmias. Data were compared to the seven days during the tournament, on which the German team played (SWCGerman), the rest of the SWC period (i.e. the days the German team did not play, 24days, SWCRest) and SWCRef (61days). There was neither a significant increase (p>0.433) in total cardiac events in Bavaria per day during SWCGerman (161.1±46.7) or SWCRest (170.5±52.3) as compared to the SWCRef (176.2±51.8), nor in any investigated diagnosis. After controlling for age, gender, loss of a match, outside temperature and nitric-dioxide air pollution levels the results remained essentially unchanged. Watching soccer was not associated with an increased incidence of cardiac events, regardless of whether the home team played or not. These data further support the hypothesis that spectators of sporting events are not exposed to an increased risk of cardiac events.

#7 Effect of an Injury Prevention Program on Muscle Injuries in Elite Professional Soccer
Authors: Owen AL, Wong Del P , Dellal A, Collie S
Reference: Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1519/JSC.0b013e318290cb3a
Summary: Due to the continual physical, physiological and psychological demands of elite level soccer increasing the incidence and risk of injuries, preventative training programs have become a common feature of soccer players training schedule. The aim of the current investigation was to examine the effectiveness of a structured injury prevention program on the number of muscle injuries as well as the total number of injuries within elite professional soccer. The present study was conducted over two consecutive seasons, of which the first (2008-2009) being the intervention season and the second the control season (2009-2010). In total, 26 and 23 elite male professional soccer players competing within the Scottish Premier League and European competition participated. The training programme was performed twice weekly for the entirety of the season (58 prevention sessions). The results revealed an increase in the total number of injuries within the intervention season (88 vs. 72), however this was largely due to the greater number of contusion injuries sustained within the intervention season (n=44) when compared to control season (n=23). Significantly less muscle injuries were observed during the intervention season (moderate effect) and this occurred concomitant with a bigger squad size (large effect, p<0.001). The findings from this study identify a multi component injury prevention training program may be appropriate for reducing the number of muscle injuries during a season but may not be adequate to reduce all other injuries.

#8 Possibility of SSC training using a jump rope
Authors: Miyaguchi K, Demura S
Reference: Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1519/JSC.0b013e3182a0c9a5
Summary: Although jumping rope has been said to be a typical Stretch-Shortening Cycle movement (SSC) from the dynamic analysis of muscle contraction, there are few research reports that focus on this point. Recently, the function of SSC of the legs with respect to the jumping movement has been evaluated using the rebound jump index (RJ-index). This study aimed to examine the possibility of using rope jumping in SSC training by comparing the RJ-index of the rebound jump (standard value) and the two different methods of rope jumping. The subjects included 76 healthy young men. Most subjects were involved in routine sports training 2-3 times per week. They performed the rebound jump (five consecutive vertical jumps) and both a basic and a double-under jump with the jump rope, according to each participant’s individual style (rhythm or timing). The RJ-index was calculated using the ground contact time and the jump height. The reliabilities of the RJ-index in the basic (ICC: 0.85) and double-under jump (0.92) were high, and the RJ-index of the latter (1.34±0.24) was significantly higher than that of the former (0.60±0.21). In the case of a group with inferior SSC ability, the RJ-index of the rebound jump only showed a significant correlation with the double-under, but not with the basic jump. When using the RJ index (1.97±0.38) of the rebound jump as a criterion, the double-under—using about 70% of the SSC ability—may be effective for reinforcement of SSC ability.

#9 The use of MRI to evaluate posterior thigh muscle activity and damage during Nordic Hamstring exercise
Authors: Mendiguchia J, Los Arcos A, Aranzazu Garrues M, Myer G, Yanci J, Idoate F.
Reference: Journal of Strength and Conditioning Research Publish Ahead of Print DOI: 10.1519/JSC.0b013e31828fd3e7
Summary: The aim of this study was to investigate the effects of the Nordic hamstring exercise on the biceps femoris long head (BFlh), biceps femoris short head (BFsh), semitendinosus (ST) and semimembranosus (SM) muscles. The Nordic hamstring strengthening exercise has been widely used in injury prevention, yet not much is known about the site specific activation of this exercise on different muscles of the thigh. Eight male national level referees were assigned to a Nordic hamstring exercise protocol (5 sets of 8 repetitions). Magnetic resonance imaging (MRI) of the subjects’ thighs were performed before, within three minutes after and repeated again 72 hours after the exercise intervention. Fifteen axial scans of the thigh interspaced by a distance of 1 / 15 right femur length were obtained from the level of 1/15 Lf to 15/15 Lf. The MRI data were analyzed for signal intensity changes. After 72 hrs, significant changes in transverse (spin-spin) relaxation time signal intensity and CSA were maintained distally at Biceps Femoris short head (BFsh) cranial portion; concretely at the non-dominant limb, while no significant changes were observed in transverse (spin-spin) relaxation time signal intensity at BFlh, SMM or SMT . The present study demonstrated that the Nordic hamstring exercise did not result in a uniform response (training stimulus) neither inter (dominant vs non-dominant) or intra hamstring muscles (same leg) and was better suited for loading proximal BFsh.

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