Latest research in football - week 34 - 2015

#1 Repeated sprint ability related to recovery time in young soccer players
Reference: Res Sports Med. 2015 Aug 14:1-12. [Epub ahead of print]
Authors: Padulo J, Tabben M, Ardigò LP, Ionel M, Popa C, Gevat C, Zagatto AM, Dello Iacono A.
Summary: This study aimed to describe the influence of recovery duration during a repeated sprint ability (RSA) test (6 × 40 m) by investigating a number of variables, such as general performance, metabolic demand, and muscular stretch-shortening performance. Seventeen male soccer outfield players (16 ± 0 years, 66 ± 10 kg) performed three field shuttle-running tests with 15, 20, and 25-sec recoveries. In addition to specific shuttle test's variables, blood lactate concentration and vertical jump height were assessed. Resulting measures were highly reliable (intra-class correlation coefficient up to 0.86). 25-sec recovery improved test performance (-3% total time from 15-sec to 25-sec recovery), vertical jump height (+7% post-test height from 15-sec to 25-sec recovery), and decreased blood lactate accumulation (-33% post-test from 15-sec to 25-sec recovery). Study findings suggest that metabolic acidosis plays a role in worsening performance and fatigue development during the shuttle test. A 25-sec recovery duration maximized performance, containing metabolic-anaerobic power involvement and muscular stretch-shortening performance deterioration during a RSA test.


#2 Tensiomyography parameters and jumping and sprinting performance in Brazilian elite soccer players
Reference: Sports Biomech. 2015 Aug 14:1-11. [Epub ahead of print]
Authors: Gil S, Loturco I, Tricoli V, Ugrinowitsch C, Kobal R, Cal Abad CC, Roschel H.
Summary: Tensiomyography has been suggested as an indirect marker of muscle stiffness, which is associated with strength/power performance. Therefore, it is reasonable to suggest that tensiomyography parameters could be associated with power-related motor tasks. The purpose of this study was to investigate the association between tensiomyography parameters (from rectus and biceps femoris) and jumping and sprinting abilities in elite soccer players. In addition, we used tensiomyography parameters to compare the lateral symmetry between dominant and non-dominant legs. Twenty elite soccer players (age: 23.3 ± 4.8 years; height: 183.5 ± 6.6 cm; weight: 77.8 ± 7.5 kg) volunteered to participate in the study. Significant moderate negative correlations between biceps femoris displacement and contact time (r = -0.5, p = 0.03), rectus femoris displacement and contact time (r = -0.51, p = 0.02), and a significant moderate correlation between biceps femoris displacement and reactive strength index (r = 0.5, p = 0.03) were found. There were no correlations between tensiomyography parameters and power-related motor tasks. In addition, no differences in tensiomyography parameters between dominant and non-dominant legs were found. Our data suggest that tensiomyography parameters are not associated with power-related motor tasks performance in elite soccer players.


#3 Why the Three-Point Rule Failed to Sufficiently Reduce the Number of Draws in Soccer: An Application of Prospect Theory
Reference: J Sport Exerc Psychol. 2015 Jun;37(3):316-26. doi: 10.1123/jsep.2015-0018.
Authors: Riedl D, Heuer A, Strauss B.
Summary: Incentives guide human behavior by altering the level of external motivation. We apply the idea of loss aversion from prospect theory (Kahneman & Tversky, 1979) to the point reward systems in soccer and investigate the controversial impact of the three-point rule on reducing the fraction of draws in this sport. Making use of the Poisson nature of goal scoring, we compared empirical results with theoretically deduced draw ratios from 24 countries encompassing 20 seasons each (N = 118.148 matches). The rule change yielded a slight reduction in the ratio of draws, but despite adverse incentives, still 18% more matches ended drawn than expected, t(23) = 11.04, p < .001, d = 2.25, consistent with prospect theory assertions. Alternative point systems that manipulated incentives for losses yielded reductions at or below statistical expectation. This provides support for the deduced concept of how arbitrary aims, such as the reduction of draws in the world's soccer leagues, could be more effectively accomplished than currently attempted.


#4 Myositis ossificans of the quadriceps femoris in a soccer player
Reference: BMJ Case Rep. 2015 Aug 11;2015. pii: bcr2015210545. doi: 10.1136/bcr-2015-210545.
Authors: Marques JP, Pinheiro JP, Santos Costa J, Moura D
Summary: A young soccer player was diagnosed with myositis ossificans 6 weeks after a muscle strain in the right thigh. Radiographic and sonographic investigations initially helped to confirm diagnosis and later supported clinical improvement. We present our approach to the case and discuss pathophysiology, prevention and treatment of this rare condition.


#5 Prevalence of dehydration before training in professional Chilean soccer players
Reference:  Nutr Hosp. 2015 Jul 1;32(1):308-11. doi: 10.3305/nh.2015.32.1.8881. [Article in Spanish]
Authors: Castro-Sepúlveda M, Astudillo S, Álvarez C, Zapata-Lamana R, Zbinden-Foncea H, Ramírez-Campillo R, Jorquera C
Download link: http://www.aulamedica.es/nh/pdf/8881.pdf
Abstract in English, Spanish
Summary: There is a lack of studies concerning hydration status before training in professional soccer player. The aim of the study was to describe hydration status before regular training practices in professional soccer players. A total of 156 male soccer players (age 25.4 ± 5.2 y) from six professional Chilean clubs were included. No hydration or food intake recommendations were made before experiment, with the aim to assess hydration status under athlete's regular "real" conditions. Body mass, height and urine specific gravity (USG) measurements were performed before training practices. 98% of athletes showed dehydration (between moderate and severe) before regular training practices. Dehydration is the most prevalent hydration status in professional Chilean soccer players before training, which may negatively affect athlete´s performance and may increase their risk of heat-related injuries.


#6 Skeletal Maturation and Aerobic Performance in Young Soccer Players from Professional Academies
Reference: Int J Sports Med. 2015 Aug 10. [Epub ahead of print]
Authors: Teixeira AS, Valente-Dos-Santos J, Coelho-E-Silva MJ, Malina RM, Fernandes-da-Silva J, Cesar do Nascimento Salvador P, De Lucas RD, Wayhs MC, Guglielmo LG
Summary: The contribution of chronological age, skeletal age (Fels method) and body size to variance in peak velocity derived from the Carminatti Test was examined in 3 competitive age groups of Brazilian male soccer players: 10-11 years (U-12, n=15), 12-13 years (U-14, n=54) and 14-15 years (U-16, n=23). Body size and soccer-specific aerobic fitness were measured. Body composition was predicted from skinfolds. Analysis of variance and covariance (controlling for chronological age) were used to compare soccer players by age group and by skeletal maturity status within of each age group, respectively. Relative skeletal age (skeletal age minus chronological age), body size, estimated fat-free mass and performance on the Carminatti Test increased significantly with age. Carminatti Test performance did not differ among players of contrasting skeletal maturity status in the 3 age groups. Results of multiple linear regressions indicated fat mass (negative) and chronological age (positive) were significant predictors of peak velocity derived from the Carminatti Test, whereas skeletal age was not a significant predictor. In conclusion, the Carminatti Test appears to be a potentially interesting field protocol to assess intermittent endurance running capacity in youth soccer programs since it is independent of biological maturity status.


#7 Anthropometric Injury Risk Factors in Elite-standard Youth Soccer
Reference: Int J Sports Med. 2015 Aug 10. [Epub ahead of print]
Authors: Kemper GL, van der Sluis A, Brink MS, Visscher C, Frencken WG, Elferink-Gemser MT
Summary: The aim of the study was to investigate whether an increased risk of injury occurrence can be determined through frequent anthropometric measurements in elite-standard youth soccer players. Over the course of one season, we followed 101 male elite-standard youth soccer players between 11 and 19 years of age. Height and body mass were monitored at monthly measurement intervals and fat percentage was assessed every 3 months by use of the sum of skinfold method. Growth in height (cm), alternations in body mass index (kg/m2), fat percentage and fat-free mass index (kg/m2) were calculated. Injuries were recorded in accordance with the recommendations of the FIFA Consensus Model for Injury Registration. Odds ratio scores and 95% confidence intervals were calculated using binary logistic regression analyses. The following anthropometric injury risk factors were identified: ≥ 0.6 centimeter growth per month (p=0.03; OR=1.63; 95% CI: 1.06-2.52), ≥ 0.3 kg/m2 increase of body mass index value per month (p=0.03; OR=1.61; 95% CI: 1.04-2.49) and low fat percentage; i. e., < 7% for players aged 11-16 and < 5% for players over 16 years (p=0.01; OR=1.81; 95% CI: 1.18-2.76). Individual monitoring of anthropometrics provides useful information to determine increased risk of injury occurrence in elite-standard youth soccer.


#8 Effects of soccer vs swim training on bone formation in sedentary middle-aged women
Reference: Eur J Appl Physiol. 2015 Aug 9. [Epub ahead of print]
Authors: Mohr M, Helge EW, Petersen LF, Lindenskov A, Weihe P, Mortensen J, Jørgensen NR, Krustrup P.
Summary: The present study examined the effects of 15 weeks of soccer training and two different swimming training protocols on bone turnover in sedentary middle-aged women. Eighty-three premenopausal mildly hypertensive women [age: 45 ± 6 (±SD) years, height: 165 ± 6 cm, weight: 80.0 ± 14.1 kg, body fat: 42.6 ± 5.7 %, systolic blood pressure/diastolic blood pressure: 138 ± 6/85 ± 3 mmHg] were randomized into soccer training (SOC, n = 21), high-intensity intermittent swimming (HS, n = 21), moderate-intensity swimming (MS, n = 21) intervention groups, and a control group (C, n = 20). The training groups completed three sessions per week for 15 weeks. DXA scans were performed and resting blood samples were drawn pre- and post-intervention. In SOC, plasma osteocalcin, procollagen type I N propeptide and C-terminal telopeptide increased (P < 0.05) by 37 ± 15, 52 ± 23 and 42 ± 18 %, respectively, with no changes in MS, HS and C. The intervention-induced increase in SOC was larger (P < 0.05) than in MS, HS and C. In SOC, leg BMC increased (P < 0.05) by 3.1 ± 4.5 %, with a larger increase in SOC than in C. Femoral shaft and trochanter bone mineral density (BMD) increased (P < 0.05) by 1.7 ± 1.9 and 2.4 ± 2.9 %, respectively, in SOC, with a greater (P < 0.05) change in SOC than in MS and C, whereas total body and total leg BMD did not change in any of the groups. In conclusion, 15 weeks of soccer training with sedentary middle-aged women caused marked increases in bone turnover markers, with concomitant increases in leg bone mass. No changes in bone formation and resorption markers were seen after prolonged submaximal or high-intensity intermittent swimming training. Thus, soccer training appears to provide a powerful osteogenic stimulus in middle-aged women.