Latest research in football - week 37 - 2014

#1 Different endurance characteristics of female and male german soccer players
Reference: Biol Sport. 2014 Aug;31(3):227-32. doi: 10.5604/20831862.1111851. Epub 2014 Jul 15.
Authors: Baumgart C, Hoppe MW, Freiwald J.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4135068/pdf/JBS-31-1111851.pdf
Summary: The aims of the present study were to assess gender differences regarding lactate threshold and intermittent shuttle run performance in female and male soccer players as well as to investigate the relationships between both endurance characteristics in both genders. Fourteen female (1(st) division) and thirteen male (4(th) division) soccer players completed an incremental test (IT) to determine running velocities at 2 and 4 mmol · l(-1) blood lactate (v2 and v4) and maximum velocity (vmax) as well as an interval shuttle run test (ISRT) to determine running distance. Based on v2 and v4 and their percentages in relation to vmax, three intensity zones were calculated: a low lactate zone (<v2), a lactate accommodation zone (v2 to v4), and a lactate accumulation zone (>v4). Female soccer players have a lower v4 (8.2%), vmax (11.3%) and ISRT distance (31.6%). No gender difference was found in v2. In contrast to males, ISRT distance correlates with vmax as well as with v2 and v4 in female soccer players. The intensity zones <v2 and >v4 differ between genders. The present study revealed that gender differences increase when the running performance is intermittent including change of directions. In both genders, different relationships between lactate threshold and intermittent shuttle run performance exist. During incremental testing, the running performances of female and male players reflect different distributions of aerobic and anaerobic metabolic pathways. The revealed gender differences should be considered for soccer endurance training.


#2 Fractured Diaphyseal Tibiofibular Synostosis in an Adolescent Soccer Player
Reference: PM R. 2014 Aug 26. pii: S1934-1482(14)01357-4. doi: 10.1016/j.pmrj.2014.08.947. [Epub ahead of print]
Authors: Santa Maria DL1, Shaw T2, Allen M3, Marin J4.
Summary: Diaphyseal tibiofibular synostosis is a rare cause of symptomatic shin pain with exertion. In this case a 14 year old male soccer player presented with atraumatic right shin pain made worse with running. CT revealed heterotopic ossification, or synostosis, of the tibial-fibular syndesmosis. The patient's symptoms improved with rest without need for operative intervention.


#3 Is it better to be an English little pea than a Mexican little pea?: The role of the categorization process on the evaluation of football players
Reference: Int J Psychol. 2014 Oct;49(5):348-54. doi: 10.1002/ijop.12037. Epub 2014 Jan 17.
Authors: Puente-Diaz R1, Puente-Diaz S.
Summary: Two studies investigated the effects of manipulating team membership on the evaluation of a football player. We hypothesized that the evaluations of the same football player, Javier "Chicharito" Hernandez, would vary as a function of the categorization process. For study 1, participants were randomly assigned to one of three conditions: Manchester United, Mexican National team or control. Results showed that "Chicharito" obtained better evaluations when his membership to Manchester United was made salient. In study 2, participants were randomly assigned to one of two conditions: Manchester United and Mexican National team condition. We found support for the mediating role of team evaluation on the relationship between team membership and the evaluations of Chicharito. The theoretical and applied implications were discussed.


#4 Crystal structure of a symmetric football-shaped GroEL:GroES2 complex determined at 3.8Å reveals rearrangement between two GroEL rings
Reference: J Mol Biol. 2014 Aug 28. pii: S0022-2836(14)00460-4. doi: 10.1016/j.jmb.2014.08.017. [Epub ahead of print]
Authors: Koike-Takeshita A, Arakawa T, Taguchi H, Shimamura T
Summary: The chaperonin GroEL is an essential chaperone that assists in protein folding with the aid of GroES and ATP. GroEL forms a double ring structure, and both rings can bind GroES in the presence of ATP. Recent progress on the GroEL mechanism has revealed the importance of a symmetric 1:2 GroEL:GroES2 complex (the "football"-shaped complex) as a critical intermediate during the functional GroEL cycle. We determined the crystal structure of the "football" GroEL:GroES2 complex from Escherichia coli at 3.8Å, using a GroEL mutant that is extremely defective in ATP hydrolysis. The overall structure of the "football" complex resembled the GroES-bound GroEL-ring of the asymmetric 1:1 GroEL:GroES complex (the "bullet" complex). However, the two GroES-bound GroEL-rings form a modified interface by a ~7 ° rotation about the 7-fold axis. As a result, the inter-ring contacts between the two GroEL rings in the football complex differed from those in the bullet complex. The differences provide a structural basis for the apparently impaired inter-ring negative cooperativity observed in several biochemical analyses.


#5 Muscle fiber characteristics, satellite cells and soccer performance in young athletes
Reference: J Sports Sci Med. 2014 Sep 1;13(3):493-501. eCollection 2014.
Authors: Metaxas TI, Mandroukas A, Vamvakoudis E, Kotoglou K, Ekblom B, Mandroukas K
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4126283/pdf/jssm-13-493.pdf
Summary: This study is aimed to examine the muscle fiber type, composition and satellite cells in young male soccer players and to correlate them to cardiorespiratory indices and muscle strength. The participants formed three Groups: Group A (n = 13), 11.2 ± 0.4yrs, Group B (n=10), 13.1 ± 0.5yrs and Group C (n = 9), 15.2 ± 0.6yrs. Muscle biopsies were obtained from the vastus lateralis. Peak torque values of the quadriceps and hamstrings were recorded and VO2max was measured on the treadmill. Group C had lower type I percentage distribution compared to A by 21.3% (p < 0.01), while the type IIA relative percentage was higher by 18.1% and 18.4% than in Groups A and B (p < 0.05). Groups B and C had higher cross-sectional area (CSA) values in all fiber types than in Group A (0.05 < p < 0.001). The number of satellite cells did not differ between the groups. Groups B and C had higher peak torque at all angular velocities and absolute VO2max in terms of ml·min(-1) than Group A (0.05 < p < 0.001). It is concluded that the increased percentage of type IIA muscle fibers noticed in Group C in comparison to the Groups A and B should be mainly attributed to the different workload exercise and training programs. The alteration of myosin heavy chain (MHC) isoforms composition even in children is an important mechanism for skeletal muscle characteristics. Finally, CSA, isokinetic muscle strength and VO2max values seems to be expressed according to age. Key PointsFifteen years old soccer players have higher IIA percentage distribution than the younger players by approximately 18%.The age and the training status play a crucial role in muscle fibers co-expression.Specific training in young athletes seems to alter significantly the muscular metabolic profile.


#6 Return-to-play criteria after hamstring injury: actual medicine practice in professional soccer teams
Reference: J Sports Sci Med. 2014 Sep 1;13(3):721-3. eCollection 2014.
Authors: Delvaux F, Rochcongar P, Bruyère O, Bourlet G, Daniel C, Diverse P, Reginster JY, Croisier JL
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC4126316/pdf/jssm-13-721.pdf


#7 Maximal heart rate in soccer players: Measured versus age-predicted
Reference: Biomed J. 2014 Sep 2. doi: 10.4103/2319-4170.131397. [Epub ahead of print]
Author: Nikolaidis PT.
Summary: Although maximal heart rate (HRmax) is widely used to assess exercise intensity in sport training, and particularly in soccer, there are limited data with regards to the use of age-based prediction equations of HRmax in soccer players. The aim of this study was to compare the measured-HRmax with two prediction equations (Fox-HRmax = 220 - age and Tanaka-HRmax = 208 - 0.7 Χ age) in soccer players. Methods: Adolescent (n = 162, 15.8 ± 1.5 years) and adult players (n = 158, 23.4 ± 4.6 years), all members of competitive clubs, voluntarily performed a graded exercise field test (Conconi protocol) to assess HRmax. Results: The measured-HRmax (197.6 ± 9.4 bpm in total, 200.2 ± 7.9 bpm in adolescent players, and 195.0 ± 10.0 bpm in adult players) was explained by the formula HRmax = 212.3 - 0.75 Χ age (r = -0.41, standard error of the estimate = 8.6). In the total sample, Fox-HRmax overestimated measured-HRmax [mean difference (95% confidence intervals) = 2.8 bpm (1.6; 3.9)], while Tanaka-HRmax underestimated HRmax [-3.3 bpm (-4.5; -2.2)]. In adolescents, Fox-HRmax overestimated measured- HRmax [4.0 bpm (2.5; 5.5)] and Tanaka-HRmax underestimated HRmax [- 3.2 bpm (-4.7; -1.8)]. In adults, Tanaka-HRmax underestimated HRmax [-5.0 bpm (-5.3; -4.7)], while there was not any difference between Fox-HRmax and measured-HRmax [1.6 bpm (-3.4; 0.2)]. Conclusions: The results of this study failed to validate two widely used prediction equations in a large sample of soccer players, indicating the need for a sport-specific equation. On the other hand, the new equation that we presented should be investigated further by future studies before being adopted by coaches and fitness trainers.