Latest research in football - week 16 -2014

#1 The Relationship Between Workloads, Physical Performance, Injury and Illness in Adolescent Male Football Players
Authors: Gabbett TJ, Whyte DG, Hartwig TB, Wescombe H, Naughton GA.
Reference: Sports Med. 2014 Apr 9. [Epub ahead of print]
Summary: The expectation that training enhances performance is well explored in professional sport. However, the additional challenges of physical and cognitive maturation may require careful consideration when determining workloads to enhance performance in adolescents. The objective of this study was to determine the state of knowledge on the relationship between workloads, physical performance, injury and/or illness in adolescent male football players.  A systematic review of workloads, physical performance, injury and illness in male adolescent football players was conducted. Studies for this review were identified through a systematic search of six electronic databases (Academic Search Complete, CINAHL, PsycINFO, PubMed, SPORTDiscus, and Web of Science). For the purpose of this review, load was defined as the cumulative amount of stress placed on an individual from multiple training sessions and games over a period of time, expressed in terms of either the external workloads performed (e.g., resistance lifted, kilometres run) or the internal response (e.g., heart rate, rating of perceived exertion) to that workload.  A total of 2,081 studies were initially retrieved from the six databases, of which 892 were duplicates. After screening the titles, abstracts and full texts, we identified 23 articles meeting our criteria around adolescent football players, workloads, physical performance, injury and/or illness. Seventeen articles addressed the relationship between load and physical performance, four articles addressed the relationship between load and injury and two articles addressed both. A wide range of training modalities were employed to improve the physical performance of adolescent football players, with strength training, high-intensity interval training, dribbling and small-sided games training, and a combination of these modalities in addition to normal football training, resulting in improved performances on a wide range of physiological and skill assessments. Furthermore, there was some (limited) evidence that higher workloads may be associated with the development of better physical qualities, with one study demonstrating enhanced submaximal interval shuttle run performance with each additional hour of training or game play. Of the few studies examining negative consequences associated with workloads, increases in training load led to increases in injury rates, while longer training duration was associated with a greater incidence of illness. The combined capacity for adolescent males to grow, train and improve physical performance highlights and underscores an exciting responsiveness to training in the football environment. However, the capacity to train has some established barriers for adolescents experiencing high workloads, which could also result in negative consequences. Additional research on stage-appropriate training for adolescent male footballers is required in order to address the knowledge gaps and enhance safe and efficient training practices.


#2 Physiological responses according to rules changes during 3 vs. 3 small-sided games in youth soccer players: stop-ball vs. small-goals rules
Authors: Halouani J, Chtourou H, Dellal A, Chaouachi A, Chamari K.
Reference: J Sports Sci. 2014 Apr 9. [Epub ahead of print]
Summary: Small-sided games (SSGs) are effective for soccer-specific aerobic endurance training. To date, no study has investigated the effect of stop-ball (SB-SSG) rule on the physiological responses to SSG. Therefore, the purpose of the present study was to examine the effects of SB-SSG vs. small-goals (SG-SSG) rules on physiological responses during a 3 vs. 3 SSG in young soccer players. Twelve male amateur young soccer players (age, 14.0 ± 0.7 years; body mass, 51.8 ± 8.0 kg; height, 164 ± 7 cm) randomly performed either SB-SSG or SG-SSG for 4 × 4 min separated by 2 min of recovery on a 20 × 15 m pitch. During the SB-SSG, participants were instructed to stop the ball with the soles of their boots in a 15 × 1 m surface behind the pitch bottom line; whereas during the SG-SSG, the participants were instructed to score to a mini-goal (i.e., 1 × 0.5 m). During each test session, the mean heart rate (HR), the post-SSG rating of perceived exertion (RPE) scores and blood lactate concentrations ([La-]) were recorded. Results showed that SB-SSG induced significantly higher mean HR (178 ± 3 vs. 174 ± 3 bpm; P < 0.05) and [La-] (4.66 ± 0.98 vs. 4.16 ± 1.02 mol · L-1; P < 0.05) than SG-SSG. However, there was no significant difference between SB-SSG and SG-SSG for the RPE scores. In conclusion, the present study demonstrates the effectiveness of SB-SSG in SSG training. Indeed, SB-SSG can influence the effort intensity in SSG (i.e., resulted in a higher intensity than SG-SSG). Therefore, coaches have the possibility to choose between SB-SSG and SG-SSG rules during training sessions according to their physical and technical objectives.


#3 Changing doping-related attitudes in soccer players: How can we get stable and persistent changes?
Authors: Horcajo J, De la Vega R.
Reference: Eur J Sport Sci. 2014 Apr 10. [Epub ahead of print]
Summary:  The aim of this experiment was to analyse the consequences of changing attitudes related to doping through thoughtful versus non-thoughtful processes. Participants were young soccer players. They received a persuasive message either against or in favour of the legalisation of several doping behaviours in soccer (e.g., the use of anabolic androgenic steroid - AAS), and participants' level of elaboration (i.e., deliberative thinking) was manipulated in two different experimental (high vs. low) conditions. Attitudes towards the legalisation proposal were assessed immediately following the message and one week later. Results showed attitude change was a function of message direction and was relatively equivalent for both high and low elaboration participants immediately after reading the message. That is, those who received the message against legalisation showed significantly more unfavourable attitudes towards the proposal than did those who received the message in favour of legalisation regardless of the extent of elaboration. However, attitude change was found to be persistent only for high elaboration participants one week after message exposure. In the present paper, we discuss implications of changing attitudes related to doping depending on whether the change occurred through psychological processes that require either extensive or small amounts of deliberative thinking and elaboration.


#4 Repeated change-of-direction test for collegiate male soccer players
Authors: Mizuguchi S, Gray HS, Calabrese LS, Haff GG, Sands WA, Ramsey MW, Cardinale M, Stone MH.
Reference: J Sports Med Phys Fitness. 2014 Apr 9. [Epub ahead of print]
Summary: The aim of the study was to investigate the applicability of a repeated change-of-direction (RCoD) test for NCAA Division-I male soccer players. The RCoD test consisted of 5 diagonal direction changes per repetition with a soccer ball to be struck at the end. Each player performed 15 repetitions with approximately 10 seconds to jog back between repetitions. Data were collected in two sessions. In the first session, 13 players were examined for heart rate responses and blood lactate concentrations. In the second session, 22 players were examined for the test's ability to discriminate the primary from secondary players (78.0 ± 16.1 and 10.4 ± 13.3 minutes per match, respectively). Heart rate data were available only from 9 players due to artifacts. The peak heart rate (200.2 ± 6.6 beats∙min1: 99.9 ± 3.0% maximum) and blood lactate concentration (14.8 ± 2.4 mmol∙L1 immediately after) resulted in approximately 3.5 and 6.4fold increases from the resting values, respectively. These values appear comparable to those during intense periods of soccer matches. In addition, the average repetition time of the test was found to discriminate the primary (4.85 ± 0.23 s) from the secondary players (5.10 ± 0.24 s) (p = 0.02). The RCoD test appears to induce physiological responses similar to intense periods of soccer matches with respect to heart rate and blood lactate concentration. Players with better average repetition times tend to be those who play major minutes.


#5 Effect of different seasonal strength training protocols on circulating androgen levels and performance parameters in professional soccer players
Authors: Koundourakis NE, Androulakis N, Spyridaki EC, Castanas E, Malliaraki N, Tsatsanis C, Margioris AN
Reference: Hormones (Athens). 2014 Jan;13(1):578-83.
Summary: The purpose was to examine the effects of three seasonal training programs, largely different in strength volume, on androgen levels and performance parameters in soccer players. Sixty-seven soccer players, members of three different professional teams, participated in the study. Strength intensity of the training programs were assessed as high (for Team-A, n=23), moderate (for Team-B, n=22), and low (for Team-C, n=22). Blood samples were analyzed for total-testosterone, free-testosterone, and the metabolic product of activate testosterone 3a-androstendiol glucuronade (3a-Diol-G). Players were tested for maximal oxygen consumption (VO2max), squad-jump (SJ), countermovement-jump (CMJ), 10m and 20m sprint performance prior at the beginning of the pre-season period, at the middle (mid-point), and at the end of the competition period (end-point). All performance parameters increased significantly until mid-point in all teams (p<0.001). However, performance was further increased only in Team-A only for jumping and sprinting ability between end-point vs mid-point (p<0.001). An effect of the training program of Team-A on TT levels was evident exhibiting significant differences between at all point-measurements (baseline/mid-point:p=0.024, baseline/end-point:p<0.001, mid/end-point:p=0.008), while a marginally significant effect (p=0.051) was detected within Team-B and a non-significant effect in Team-C. Similar results were obtained for 3a-Diol-G in Team-A (p=0.001) where significant differences were found between end-point to both baseline (p=0.001) and mid-point (p=0.038). No differences were detectable for FT. A borderline significant negative correlation was observed between 3a-Diol-G and VO2max in Team-B at mid-point. No other correlations were evident between performance and hormonal parameters. Our findings suggest that the volume of strength training combined with intensive soccer training caused an elevation of circulating TT and 3a-Diol-G levels in parallel to the induction of performance capacity. It is our opinion that the elevation of endogenous androgens as a result of the volume of strength training indicates that the only method to improve athletic performance is hard training. There are no substitutes or shortcuts. If the organism needs more androgens it will produce them endogenously.


#6 Psychophysiological Responses to Overloading and Tapering Phases in Elite Young Soccer Players
Authors: Freitas CG, Aoki MS, Franciscon CA, Arruda A FS, Carling C, Moreira A.
Reference: Pediatr Exerc Sci. 2014 Apr 10. [Epub ahead of print]
Summary: This study investigated the effect of a 2 week overloading training phase followed by a 2 week tapering phase on internal training load (ITL), salivary cortisol, stress tolerance, and upper respiratory tract infections symptoms (URTI) in 11 male young soccer players (16.0 ± 0.5 yrs). Ratings of perceived exertion (session-RPE) were taken after each training session (n=194) to determine ITL. Saliva sampling was conducted at the end of each week and cortisol concentration assessed by ELISA. DALDA and WURSS-21 questionnaires were administered every week to evaluate stress tolerance and severity of URTI respectively. The number of athletes reporting URTI symptoms was recorded. The overloading phase promoted greater ITL and a higher resting cortisol concentration than the tapering phase (p < 0.05). While no significant changes in stress tolerance or URTI severity were observed, the number of athletes reporting URTI symptoms was higher during the overloading phase. A significant correlation was observed between symptoms of stress and severity of URTI (rs=-0.71; p=0.01). The results indicate that an integrated approach using psychological measures (session-RPE and DALDA), self-reports of URTI symptoms, and endocrine responses (cortisol) to training are pertinent for monitoring young soccer players.