Mon

28

Oct

2013

Latest research in football - week 44 - 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 Effects of sport involvement in assets, attitudes and enjoyment in youth soccer players
Authors: Santos A, Carvalho H, Gonçalves C.
Reference: Br J Sports Med. 2013 Nov;47(17):e4. doi: 10.1136/bjsports-2013-093073.7.
Summary: Sport involvement by youths is generally seen as positive for the youth development. Nevertheless, group norms, competition pressures and winning can lead to the adoption of anti-social and risk behaviours. A lack of enjoyment in sport is associated with burnout and dropout and consequently with lower levels of physical activity. We : a) observed the effect of sport involvement in youth soccer players during a season; b) observed the age effects in the developmental assets, attitudes and enjoyment in youth sport; c) explored the correlation between enjoyment, sport attitudes and developmental assets. This study comprised 135 male players aged 12-18 years (M=15, SD=2). A multilevel analysis and Pearson correlation was performed. The magnitude of the changes during a season were modest. There were negative effects of a season involvement in soccer program, with increased cheating and reductions in commitment and some developmental assets. The negative attitudes are correlated with other-referenced sources and positive values. The findings suggest that a proper environment and postive role models can foster the maintenance in sport and a positive development.


#2 Youth soccer athletes' involvement in different sport practice contexts
Authors: Santos A, Carvalho H, Gonçalves C.
Reference: Br J Sports Med. 2013 Nov;47(17):e4. doi: 10.1136/bjsports-2013-093073.25.
Summary: The sport can serve as an informal educational context, helping the youth development positive values and healthy habits. The ecological theories give importance to the contexts where the individual are inserted and to the involvement time on those, through the Process-Person-Context-Time model. The orientation to performance or to socialization and healthy habits can promote different values and behaviors in the youth athletes. We aim to: a) examine the contextual effects in youth soccer players; b) observe the effects of a season involvement in the developmental assets, attitudes and enjoyment; c) examine the sport involvement effects according to age in the developmental assets, attitudes and enjoyment in sport. The participants (n=135) were male soccer players aged 12-18 years (M=15, SD=2) from three different contexts: Professional Club (n=45), Amateur Urban Club (n=46), Amateur Rural Club (n=44). They fulfilled the Sources of enjoyment in youth sport questionnaire, Developmental Assets Profile and to Sport Attitudes Questionnaire. A multilevel analysis was performed. The Professional Club athletes reveal lower levels of assets, enjoyment and sport attitudes than the other contexts athletes, suggesting a disadvantage context for positive development. The sport involvement during a soccer season has negative effects in the athletes' enjoyment and attitudes, revealing that a season exposure leads to athletes perceive less interest in being involved in those sport contexts. This findings reinforces the solicitudes of sport contexts influences in athletes development, as well the need to promote enjoyable and pro-social practice environment to augment the interest in being involved in sport.


#3 The physiological response, time-motion characteristics and reproducibility of various speed endurance drills in elite youth soccer players: small sided games vs generic running
Authors:  Ade J, Harley J, Bradley P.
Reference: Br J Sports Med. 2013 Nov;47(17):v-e4. doi: 10.1136/bjsports-2013-093073.3.
Summary: The aim of the study was to quantify the physiological responses, time-motion characteristics and reproducibility of various speed endurance production (SEP) and speed endurance maintenance (SEM) drills. Twenty-one elite male youth soccer players completed four drills: (1) SEP 1 v 1 small sided game, (2) SEP running drill, (3) SEM 2 v 2 small sided game and (4) SEM running drill. The SEP drills consisted of eight bouts of 30 s with 120 s recovery (1:4 exercise to rest ratio) whilst SEM drills encompassed eight bouts of 60 s with 60 s recovery (1:1 exercise to rest ratio). Heart rate response, blood lactate concentration, rating of perceived exertion and time-motion characteristics were recorded for each drill. The SEP and SEM running drills elicited greater (P<0.05) heart rate responses, blood lactate concentrations and subjective ratings of perceived exertion than the equivalent small sided games (ES: 1.1-1.4 & 1.0-3.2). Players covered less (P<0.01) total distance, high-, very high-speed running and sprint distance in the SEP and SEM small sided game's compared to the equivalent running drills (ES: 6.0-22.1 & 3.0-18.4). Greater distances (P<0.01) were covered in high and maximum acceleration/deceleration bands during the SEP and SEM small sided game's compared to the equivalent running drills (ES: 2.6-4.6 and 2.3-4.8). Small-moderate test-retest variability was observed for heart rate response (CV: 0.9-1.9%), ratings of perceived exertion (CV: 2.9-5.7%) and blood lactate concentration (CV: 9.9-14.4%); Moderate-large test-retest variability was observed for high-intensity running parameters (CV: >11.3%) and the majority of acceleration/deceleration distances (CV: >9.8%) for all small sided games and running drills. The data demonstrate the differential response of SEP and SEM training for taxing various energy systems and the superior acceleration/deceleration profiles of small sided games compared to generic running drills.


#4 Effects of One Versus Two Games a Week on Physical and Subjective Scores of Sub-Elite Soccer Players
Authors: Rollo I, Impellizzeri FM, Zago M, Iaia FM.
Reference: Int J Sports Physiol Perform. 2013 Oct 23. [Epub ahead of print]
Summary: The physical performance profiles of sub-elite male footballers were monitored during 6 weeks of a competitive season. The same squad of players played either one (1G, n=15) or two (2G, n=15) competitive matches per week. On week, 0, 3 and 6, 48 h post-match, players completed: i) countermovement jump (CMJ), ii) 10 and 20 m sprints, iii) Yo-Yo IR1, iv) subjective questionnaire (REST-Q 52). Both groups undertook two weekly training sessions. The 2G showed after 6 weeks lower Yo-Yo IR1 (-11-3%, 90% CI -15.8 to -6.8%; p<0.001) and CMJ performances (-18.7%, -21.6 to -15.9%; p=0.007), and higher 10-m (4.4%, 1.8% to 6.9%; p=0.007) and 20-m sprints values (4.7%, 2.9% to 6.4%; p<0.001). No differences were found at three weeks (0.06 < p < 0.99). No changes over time (0.169 < p < 0.611) and no differences Time x Group interactions (0.370 < p < 0.550) were found for the Stress, Recovery and the Stress:Recovery Index. In conclusion players' ability to sprint, jump and perform repeated intense exercise was impaired when playing two competitive matches a week over 6 weeks.


#5  Abnormal hip physical examination findings in asymptomatic female soccer athletes
Authors: Prather H, Hunt D, Rho M, Yemm T, Fong K, Brophy RH.
Reference: Knee Surg Sports Traumatol Arthrosc. 2013 Oct 23. [Epub ahead of print]
Summary: Examination of the hip provides information regarding risk for pre-arthritic hip disorders, knee injuries, and low back pain. The purpose of this study was to report a hip screening examination of asymptomatic female soccer athletes and to test the hypothesis that these findings vary by competition experience. Asymptomatic females from a youth soccer club, a college, and a professional team were evaluated. Passive hip range of motion, hip abduction strength, and hip provocative tests were assessed. Data were compared for the grade/middle school, high school, college, and professional athletes. One hundred and seventy-two athletes with a mean age of 16.7 ± 5 years (range 10-30) participated. Professional athletes had less flexion (HF) for both hips (p < 0.0001) and less internal rotation (IR) for the preferred kicking leg (p < 0.05) compared to all other groups. Grade/middle school athletes had more external rotation in both hips as compared to all other groups (p < 0.0001). For the preferred kicking leg, collegiate athletes had less hip abduction strength as compared to other groups (p < 0.01). Positive provocative hip tests were found in 22 % of all players and 36 % of the professionals. In professionals, a positive provocative test was associated with ipsilateral decreased HF (p = 0.04). Asymptomatic elite female soccer athletes with the most competition experience had less bilateral hip flexion and preferred kicking leg IR than less-experienced athletes. Positive provocative hip tests were found in 22 % of athletes. Future studies are needed to show whether these findings link to risk for intra-articular hip or lumbar spine and knee disorders.


#6 The influence of professional status on maximal and rapid isometric torque characteristics in eliter soccer referees
Reference: J Strength Cond Res. 2013 Oct 21. [Epub ahead of print]
Authors: Palmer TB, Hawkey MJ, Smith DB, Thompson BJ.
Summary: The purpose of the present study was to examine the effectiveness of maximal and rapid isometric torque characteristics of the posterior muscles of the hip and thigh and lower body power to discriminate between professional status in full-time and part-time professional soccer referees. Seven full-time (mean±SE: age=36±2yr; mass=82±4kg; and height=179±3cm) and 9 part-time (age=34±2yr; mass=84±2kg; and height=181±2cm) professional soccer referees performed two isometric maximal voluntary contractions (MVCs) of the posterior muscles of the hip and thigh. Peak torque (PT) and absolute and relative rate of torque development (RTD) were calculated from a torque-time curve that was recorded during each MVC. Lower body power output was assessed via a vertical jump test. Results indicated that the rapid torque characteristics were greater in the full time compared to the part time referees for absolute RTD (P=0.011) and relative RTD at 1/2 (P=0.022) and 2/3 (P=0.033) of the normalized torque-time curve. However, no differences were observed for PT (P=0.660) or peak power (Pmax, P=0.149) between groups. These findings suggest that rapid torque characteristics of the posterior muscles of the hip and thigh may be sensitive and effective measures for discriminating between full-time and part-time professional soccer referees. Strength and conditioning coaches may use these findings to help identify professional soccer referees with high explosive strength-related capacities and possibly overall refereeing ability.


#7 Validation of the Loughborough Soccer Passing Test in young soccer players
Authors: Le Moal E, Rué O, Ajmol A, Ben Abderrahman A, Hammami MA, Ben Ounis O, Kebsi W, Zouhal H.
Reference: J Strength Cond Res. 2013 Oct 21. [Epub ahead of print]
Summary: The aim of this study was to examine the validity and reliability of the Loughborough Soccer Passing Test (LSPT) in adolescent soccer players. Eighty-seven players, aged 14-17 years, were recruited according to playing level: elite (n=44), sub-elite (n=22) and non-elite (n=21). Two attempts of the LSPT were performed at baseline. Players then completed 10 attempts over three weeks to familiarize themselves with the test. Subsequently, two main trials, separated by one week, were performed; the mean of two attempts was recorded as the performance score. Following familiarization, the performance scores showed significant differences (p<0.01) between elite (40.3 ± 8.3 s), sub-elite (58.1 ± 10.2 s) and non-elite players (66.6 ± 11.7 s). There was low to moderate reliability between trials with sub-elite (r=0.35, p<0.05) and non-elite players (r=0.47, p<0.05), but very good for elite players (r=0.96, p<0.05). Scores at baseline were better (p<0.05) for elite players (51.0 ± 9.3 s) compared to sub-elite (60.8 ± 8.2 s) and non-elite players (69.0 ± 11.1 s). The LSPT seems to be a valid and reliable protocol to assess differences in soccer skill performance in adolescent players and can distinguish players according to their playing level. The LSPT was able to distinguish different abilities without players undergoing any familiarization with the test, thus enabling it to be used for talent identification purposes.


#8 The effects of interday rest on adaptation to 6-weeks of plyometric training in young soccer players
Authors: Ramírez-Campillo R, Meylan CM, Alvarez-Lepín C, Henriquez-Olguín C, Martinez C, Andrade DC, Castro-Sepúlveda M, Burgos C, Baez EI, Izquierdo M.
Reference:  J Strength Cond Res. 2013 Oct 21. [Epub ahead of print]
Summary: The purpose of this study was to determine the effects of short-term plyometric training interposed with 24 hours or 48 hours of rest between training sessions on explosive and endurance adaptations in young soccer players. A total of 166 players, between 10 and 17 years of age were randomly divided into 3 groups: control (CG; n=55), plyometric training with 24 h (PT24; n=54), and 48 h (PT48; n=57) of rest between training sessions. Before and after intervention, players were measured in squat jump (SJ), countermovement jump (CMJ), 20 (RSI20) cm drop jump reactive strength index, broad long jump (BLJ), 20-m sprint time, 10 x 5-m agility time, 20-m multi-stage shuttle run test (MST), and sit and reach test (SR). The plyometric training program was applied during 6 weeks, 2 sessions per week, with a load from 140 to 260 jumps per session, replacing some soccer-specific drills. After intervention, the CG did not show significant performance changes. PT24 and PT48 groups showed a small to moderate significant improvement in all performance tests (p<0.001), with no differences between treatments. Although it has been recommended that plyometric drills should not be conducted on consecutive days, the study shows that plyometric training applied twice weekly on consecutive or non-consecutive days result in similar explosive and endurance adaptations in young male soccer players.


#9 Effects of a 12 Week SAQ Training Programme on Agility with and without the Ball among Young Soccer Players
Authors: Milanović Z, Sporiš G, Trajković N, James N, Samija K.
Reference: J Sports Sci Med. 2013 Mar 1;12(1):97-103.
Summary: The purpose of this study was to determine the effects of a 12 week conditioning programme involving speed, agility and quickness (SAQ) training and its effect on agility performance in young soccer players. Soccer players were randomly assigned to two groups: experimental group (EG; n = 66, body mass: 71.3 ± 5.9 kg; body height: 1.77 ± 0.07 m) and control group (CG; n = 66, body mass: 70.6 ± 4.9 kg; body height: 1.76 ± 0.06 m). Agility performance was assessed using field tests: Slalom; Slalom with ball; Sprint with 90° turns; Sprint with 90° turns with ball; Sprint with 180° turns; Sprint with backward and forward running; Sprint 4 x 5 m. Statistically significant improvements (p < 0.05) between pre and post training were evident for almost all measures of agility, with and without the ball, with the exception being the Sprint with backward and forward running. This suggests that SAQ training is an effective way of improving agility, with and without the ball, for young soccer players and can be included in physical conditioning programmes. Key pointsSAQ training appears to be an effective way of improving agility with and without the ball in young soccer playersSoccer coaches could use this training during pre-season and in-season trainingCompared with pre-training, there was a statistically significant improvement in all but one measure of agility, both with and without the ball after SAQ training.


#10 Monitoring external and internal loads of brazilian soccer referees during official matches
Authors: Costa EC, Vieira CM, Moreira A, Ugrinowitsch C, Castagna C, Aoki MS.
Reference: J Sports Sci Med. 2013 Sep 1;12(3):559-64.
Download link: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3772602/pdf/jssm-12-559.pdf
Summary: This study aimed to assess the external and internal loads of Brazilian soccer referees during official matches. A total of 11 field referees (aged 36.2 ± 7.5 years) were monitored during 35 matches. The external (distance covered, mean and maximal speed) and internal load parameters (session ratings of perceived exertion [RPE] training load [TL], Edwards' TL, and time spent in different heart rate [HR] zones) were assessed in 3-4 matches per referee. External load parameters were measured using a wrist Global Positioning System (GPS) receiver. No differences in distance covered (5.219 ± 205 vs. 5.230 ± 237 m) and maximal speed (19.3 ± 1.0 vs. 19.4 ± 1.4 km·h(-1)) were observed between the halves of the matches (p > 0.05). However, the mean speed was higher in the first half of the matches (6.6 ± 0.4 vs. 6.4 ± 0.3 km·h(-1)) (p < 0.05) than in the second half. The mean HR during the matches was ~89% of HRmax. In ~95% of the matches, the referees demonstrated a HR ≥ 80% of HRmax. Nonetheless, the time spent at 90-100% of HRmax was higher in the first half (59.9 vs. 52.3%) (p < 0.05). Significant correlations between session RPE TL and distance covered at 90-100% of HRmax (r = 0.62) and session RPE TL and maximal speed (r = 0.54) (p < 0.05) were noted. Furthermore, there was a positive correlation between session RPE TL and Edwards' TL (r = 0.61) (p < 0.05). Brazilian soccer referees demonstrated high external and internal load demands during official matches. The portable GPS/HR monitors and session RPE method can provide relevant information regarding the magnitude of the physiological strain during official matches. Key PointsHigh external and internal loads were imposed on Brazilian soccer referees during official matches.There was a high positive correlation between a subjective marker of internal load (session RPE) and parameters of external load (distance covered between 90-100% of HRmax and maximal speed).There was a high positive correlation between session RPE method and Edwards' method.Session RPE seems to be a reliable marker of internal load.The portable GPS/HR monitors and the session RPE method can provide relevant information regarding the magnitude of external and internal loads of soccer referees during official matches.


#11 Effects of the 11+ and Harmoknee Warm-up Programs on Physical Performance Measures in Professional Soccer Players
Authors: Daneshjoo A, Mokhtar AH, Rahnama N, Yusof A.
Reference: J Sports Sci Med. 2013 Sep 1;12(3):489-96.
Summary: The purpose of this study was to examine the effects of the 11+ and HarmoKnee warm-up programs on performance measures in professional soccer players. Thirty-six male professional soccer players (age: 18.9 ± 1.4 years) were divided into 3 groups, the 11+, HarmoKnee and control group (n = 12 per group). The experimental groups performed the programs 3 times per week for 2 months (24 sessions), whereas the control group only performed their regular soccer training. The performance tests carried out were: 10m speed tests with and without a ball, 20m single sprint, vertical jump, Wall-Volley and Illinois agility tests. The 11+ group demonstrated significant increases from pre-to-post time points in the vertical jump (3.7%), Wall- Volley (5.4%) and Illinois agility tests (1.7%), while the HarmoKnee group showed a significant increase in Wall-Volley test, with a 5.2% increase. The repeated measures analysis revealed differences between the groups (large effect size) in the 11+ and HarmoKnee groups, compared to the control group, in 10m speed tests with and without a ball, 20m single sprint and Illinois agility tests (p < 0.05). Thus 8-weeks performing the 11+ warm-up program can enhance jump height, agility and soccer skill while the HarmoKnee program generally only improves soccer skill in young professional male soccer players. Key PointsThe 11+ improves performance by means of Illinois agility, vertical jump and Wall-Volley tests whereas HarmoKnee improves Wall-Volley test. Incorporating 11+ as a part of the warm-up program by the young teams would be beneficial in agility, leg power and soccer skill respectively.Further modification of both programs may be required to fully realize the players' speed performance potential.Data from this research can be helpful for soccer trainers in choosing programs to enhance performances in young male professional soccer players.


#13 Gender differences in match performance characteristics of soccer players competing in the UEFA Champions League
Authors: Bradley PS, Dellal A, Mohr M, Castellano J, Wilkie A.
Reference: Hum Mov Sci. 2013 Oct 16. pii: S0167-9457(13)00109-7. doi: 10.1016/j.humov.2013.07.024. [Epub ahead of print]
Summary: The aim of this study was to examine gender differences in match performance characteristics of elite soccer players. Fifty-four male and fifty-nine female soccer players were tracked during UEFA Champions League matches using a multi-camera system (Amisco, Nice, France). Male players covered more (P<.01) distance than female players in total during a match (Effect Size [ES]: 0.5) and at higher speed thresholds (>15, >18, 18-21, 21-23, 23-25 and >27kmh-1; ES: 0.7-1.4). Decrements in the second versus first half (P<.01) were only evident in female players for the distance covered in total and at selected speed thresholds (12-15, >12 and >15kmh-1; ES: 0.6). Male central midfielders covered more (P<.01) total distance during a match than female central midfielders and at selected speed thresholds (15-23kmh-1; ES: 1.3-2.2). Male full-backs and wide midfielders covered a greater distance (P<.01) than female players in the same positions at higher speed thresholds (>15, 21-23, 23-25, 25-27 and >27kmh-1; ES: 1.5-3.1). The distance covered during the most intense 5min period of the match (>15kmh-1) was higher (P<.01) in male compared to female players (ES: 1.0) but no distance deficit in the next versus the average 5min period was observed for either gender (ES: 0.1-0.2). No gender differences were found for technical events such as the number of ball touches, time in possession of the ball or total duels won during both halves and the entire match (ES: 0.1-0.3). However, female players lost the ball more often (P<.05) and displayed lower pass completion rates than male players during both halves and the entire match (ES: 0.5-0.9). The data demonstrate that large gender differences exist for match performance characteristics of players competing at the highest competitive standard of European soccer. Such detailed analyses could be useful for gender-specific training information for optimal preparation. However, more research is warranted to establish gender-specific speed thresholds for elite soccer players.


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