The 21st annual congress of the European College of Sport Science is about to start on the 6th of July. The congress is going to be at Vienna and will last until the 9th.
I was able to collect the abstracts published on the ECSS website with regards to a football context.
Please find the abstracts below (and I hope I have not forgotten some).
Believes and attitudes among youth and professional football players regarding injury prevention
Authors: Zech, A., Wellmann K.
Summary: Although injury prevention strategies can be successfully promoted among team coaches and physiotherapists (Junge et al. 2011) it is still unknown which of these measures are generally accepted and regularly used by athletes. The objective of this study was to collect first data on perceptions on injury mechanisms and risk factors as well as used prevention strategies among professional and youth football players. The study was a cross-sectional survey among professional and youth football players in one German high-level football club. 139 youth (n=115) and professional players (n=24) between age 13 and 35 years completed a standardized questionnaire. It included categories with history of injuries and perceptions regarding the influence of intrinsic and extrinsic factors on lower extremity football injuries. Athletes were also asked to report which of several prevention strategies they regularly use for injury prevention. Pearson’s Chi-Square test was used to test whether these injury rates, perceptions on potential risk factors and preventive measures were differently distributed between teams or between injured and non-injured players. The response rate of returned questionnaires was at 98%. 84.2% of respondents reported a previous injury in the lower extremities. Most injuries of players between U17 and the first team occurred at the ankle joint whereas the younger teams (U16 and U15) reported more injuries at the thigh / groin. 47.5% of respondents believed that physical contact with other players is a risk factor for lower extremity injuries, followed by physical fatigue (38.1%), environmental factors (including equipment, 25.9%), muscle impairments (25.7%) and previous injuries (21.7%) The majority of respondents consider injury prevention important or very important. 91.5% of all players declared regularly to use stretching exercises in order to prevent injuries. About half of all respondents (54.0%) perform specific warm up exercises and one third (33.1%) specific strength exercises. External measures used regularly by players are taping (27.3%), shoe insoles (27.0%) and bracing (11.5%). The results show that athletes in general are positively disposed towards injury prevention. Nearly all athletes perform stretching in order to prevent injuries although no scientific evidence exists for this measure. Thus, effective transfer measures are needed to promote use of research evidence in football practice.
“FIFA 11+ Kids” a warm-up program to prevent injuries in children’s football: Cluster randomised controlled trial
Authors: Rössler, R., Bizzini, M., Dvorak, J., Chomiak, J., aus der Fünten, K., Verhagen, E., Lichtenstein, E., Beaudouin, F., Junge, A., Faude, O.
Summary: The prevention of football injuries should start at a young age (Rössler et al., 2014). Based on epidemiological data (Rössler et al., 2016b), the injury prevention program FIFA 11+ Kids was developed (Rössler et al., 2016a). The objective of the present study was to assess the effectiveness of FIFA 11+ Kids with regard to injury prevention. Children’s football teams (under-11 and under-13 age groups) from Switzerland, Czech Republic, The Netherlands, and Germany were recruited. Clubs were randomised to an intervention (INT) and a control group (CON), and followed for one season. INT performed FIFA 11+ Kids during their warm-up, while CON warmed-up as usually. Data was collected using an internet-based registration platform. Time-to-injury data were analysed, and hazard ratios (HR) calculated using extended Cox models to account for correlations on team- and intra-person-level. In total, 3,895 player seasons and 292,749 hours of football exposure were recorded. Mean age of players was 10.8 (SD 1.4) years. During the study period 374 (INT=139; CON=235) injuries occurred. Overall injury rate in INT was reduced by 48% compared to CON (HR 0.52; 95%-CI 0.32–0.86), P=0.01). Further reductions of injury rates were found with regard to match (49%, (HR 0.51; 0.27–0.94), P=0.03), to training (42%, (HR 0.58; 0.38–0.89), P=0.01), to severe (74%, (HR 0.26; 0.10–0.64), P=0.003) and to lower extremity injuries (55%, (HR 0.45; 0.24–0.84), (P=0.01). FIFA 11+ Kids is effective in reducing injuries in children’s football. Considerable effects were found for overall, match, training, lower extremity, and specifically severe injuries. The present overall injury reduction is comparable to studies in older youth football players (Rössler et al., 2014). The reduction of injury incidence might be due to improved motor performance (Rössler et al., 2016a). A broad implementation may help to reduce injuries and to support the health benefits of playing football in the long term. The authors gratefully acknowledge the financial support of FIFA.
Questioning the role of blue versus red uniforms in football’s penalty kicks
Authors: Krenn, B., Handsteiner, M.
Summary: Past research revealed an impact of uniform colour in sports: Most notably, beneficial effects of the colour red in combat sports were reported (Hill & Barton, 2005). However, also Greenlees Eynon and Thelwell (2013) found a benefit in football’s penalty kicks: Penalty takers succeeded less often when facing a goalkeeper wearing a red instead of blue or green jersey. By deepening the approach of their field study, the current experiments were aimed at particularise our understanding of the impact of goalkeepers’ but also of penalty takers’ uniform colour. Twenty-four video clips showing a football player taking a penalty kick from the perspective of a goalkeeper (experiment 1) and 25 clips showing a goalkeeper preparing himself for saving a penalty from the perspective of the penalty taker (experiment 2) were recorded. Uniform colour of the players/goalkeepers were chromatically changed to red and blue. Each clip lasted four seconds and ended when the player kicked the ball. Thus, ball’s trajectory was not shown. Participants rated each clip twice: Once in a red condition, once in a blue condition. The order of the videos was randomized. Thirty-nine experienced male football players (25.64 ± 4.90 years) participated in experiment 1 and rated the level of players’ resoluteness from 1 (minor) to 9 (high) and the position where the ball should hit the goal by using a 23-in. touch-screen. In experiment 2, 118 students of sport science (63 m/55 f, 22.25 ± 2.87 years) judged the videos following the same criteria as in experiment 1 but also rated the probability of success for saving the penalty kick from 1 (minor) to 9 (high). Paired t-tests did not reveal significant differences for penalty takers wearing red versus blue in resoluteness and anticipated lateral position of the ball. However, for ball’s anticipated height a small effect was observed (T(38) = 2.42, p = .02, d = .16): The kicks of red-glad penalty takers were judged to be shot lower at the goal (M = 109,52 ± 12.75) than those of the blue-glad players (M = 111.69 ± 13.52). In experiment 2, no impact of goal keepers’ uniform colour was found for resoluteness, probability of success and the anticipated position of the ball. Both experiments did not find any impact of uniform colour on ratings of resoluteness and probability of success in penalty kicks. Thus, an experimental corroboration of the results of Greenlees et al. (2013) failed. However, a rather small effect was observed for the height of the anticipated ball position. Further research is needed to clarify the origin and significance of this effect more comprehensively.
Investigation of Relationship Between Organizational Commitment and Job Satisfaction in Youth Team Football Coaches in Turkey
Authors: Yasar, M.O., Sunay, H.
Summary: To develop qualified football players, youth team process has a critical importance. During this process youth team coaches is the key factor. In this point of view the job satisfaction and organizational commitment levels of the youth team coaches are significant to achieve success (Topkaya, 2013). Job satisfaction is, an emotional reaction towards, comparison of the job expectation and what has been acquired the job (Sarminah, 2006). Organizational commitment is definition of employees psychological point of view and relationship between employee and organization. Both of these factors directly influences efficiency of the job. The sample of the study is consisted of 212 youth team coaches who work in Turkey. Coaches were selected by purpose sampling method. The job satisfaction survey which was developed by Spector (1985) and the organizational commitment survey which was developed by Porter et al. (1974) was used. The Cronbach Alpha value of job satisfaction survey was .80 calculated. In addition, non-parametric tests which are Kruskall-Wallis and Mann Whitney-U were used. Job satisfaction and organizational commitment levels of the coaches who participated in this study was found average.There are two remarkable results in this study. When coaches are compared by their education status, it was seen that, higher educated coaches’ job satisfaction levels were detected lower. Moreover, when coaches are compared by their football club types, it was found that, professional club coaches, job satisfaction and organizational commitment levels were reached higher than amateur club coaches. It was seen that when age gets older, job satisfaction and organizational commitment levels increase. Also Hickson and Obsehgemi(1999)were found that there was a positive relationship between job satisfaction. According to Ketchan(2001), age and organizational commitment also has a positive relationship.In financial parameters, unexperienced and young coaches satisfaction levels were higher than older experienced coaches. But general results about experience parameter; as the experience gets more the job satisfaction levels increase. In Orhan’s study same results were found. In parallel to these results, when experience is more, the organizational commitment level also increases.
An analysis of the comminication skills of coaches according to the perception of athletes who participated in interclollegiate football competition
Authors: Sunay, H., Cengiz, R., Yasar, O.M.
Summary: Football clubs are a part of system of communication and interaction. The qualification of the athletes are parallel with the trainers qualification. According to this fact, it is very important that trainers to improve their communication skills which are basics of learning and teaching process. The purpose of the study is determined to communication skills of trainers according to athletes perspective who have participated intercollegiate football tournament. The sampling of the study is made of 117 football players who are attended to intercollegiate football tournament during 30 April-4 May 2013. In investigation random sampling method was used. During the study basic personal information form was utilized. In addition to this Trainer communication skill survey’ which was developed by Yılmaz (2008). The Levene test was used to figure out normalization of data. During the analyze of data independent T test and one way Anova test were used besides descriptive statistical techniques. SPSS 16.0 statistic program were used to analyze to data. According to study there were no significant differences between trainers communication skills and training age, position on field, educational department of football players. However, football players thoughts towards trainers communication skills are that their skills are effective but need improvement. In the study of Yılmaz, et.al. which was researched on 739 athletes showed that individual sport trainers have more effective communication skills than team sports trainers. But also team sports trainers have sufficient communication skills however they need to work on their communication skills. Bayrak and Nacar studied on 209 athletes and they investigated trainers communication skills and results were that trainers mostly have adequately communication skills. According to Chih-Ming Yu (2016) in the organizations which have positive organizational climate, effects the communication skills of trainers. In contrary trainers should spend more time to develop on their communications skills.
Passing and shooting in football – Playing with the ball….and the others
Authors: Vicente, A., Lopes, H., Fernando, C.
Summary: Winning in football is about scoring more goals than the opponent. To do so, players must master a set technologies that, together with other technical, tactical, psychological and physiological (among others) factors will allow them to be successful. Although it is common to believe that in football the key is to play with the ball, master the ball at high speeds and in small spaces, studies that we have been developing in recent years on isolated situations (e.g. Vicente et al. 2015) showed that there is time relations with the opponents that players must not ignore to succeed. The aim of this study was to verify whether a correlation exists between the velocity of the stimulus in passing and shooting situations in football and the attacking and defending player’s responses. We’ve used a software (MeSiR2.2) designed to measure the relation between the velocity of the stimulus and the time to respond it. Four tests were used: Test 1 had a goalkeeper that moved from the center of the goal to each side (left or right) at different velocities (1 and 3 m/s) randomly; Test 2 had a striker that kicked a ball from the penalty kick spot to each side of the goal (left or right) at different ball velocities (±40km/h and ±90 km/h) randomly; Test 3 consisted on a defender that moved 3 meters in a real football field to each side (left or right) at different velocities (5 and 1 m/s) randomly; Test 4 consisted on a player with a ball that kicked it to the left or right at different ball velocities (±10km/h and ±50 km/h) randomly. 40 university football players and 25 semi-professional footballers had to perform each test for 20 trials and respond to each situation by moving their body towards the ball side (tests 2 and 4) or shooting a ball in the opposite direction to the movement of the player (tests 1 and 3). From the 5200 trials performed from the 4 tests, results showed that players took the right decision in 83% of the situations. Data also showed that for the fastest stimulus in tests 2 and 4 the average response time was also higher (test 2=378ms / test 4=399ms) than the slowest stimulus situations (test 2=427ms / test 4=473ms). The same trend was obtained on tests 1 and 3. Participants tended to kick the ball at lower speeds in response to slower opponents movements (73% in test 1 and 68% in test 3) than in higher opponents movements. Data showed that the stimulus velocity tend to influenced the response and the time to respond. As the stimulus was faster or slower the response was also faster or slower. The results tend to corroborate previous studies and other ecological studies we’re still performing. This suggest that in passing and shooting situations in football, where players are permanently exchanging stimulus with opponents and teammates, players must be prepared to relate with the opponents and teammates being aware that they can influence their actions and response times to take advantage and increase success chances.
The sweating response and fluid intake of elite professional football players during training at different exercise intensities in hot and cool environments
Authors: Rollo, I., Carter, J.M., Randell, R.K., Jeukendrup, A.E., Lizarraga, M.A., Medina, D.
Summary: Sweat rate and sweat composition vary between individual players of a team. To date no data is available on the fluid and sodium [Na+] losses or ad-libitum carbohydrate (CHO) or fluid intake of elite professional players in response to exercise at different intensities and in diverse environmental conditions. Data were collected from 12 male professional football players on four separate training occasions under the following conditions: cool (15 ± 7° C, 66 ± 6 RH) low/moderate intensity (RPE 1-5) (CL); cool high intensity (RPE 6-10) (CH); hot (29 ± 1° C, 52 ± 7 RH) low/moderate intensity (HL); hot high intensity (HH). Training sessions were 75 ± 15 min involving intermittent running and football specific play. Before and after the first training session of the day all players were weighed in minimal clothing. During training players had free access to sport drink (Gatorade Thirst Quencher) and water. Each player was allocated their own drinks bottles which were weighed before and after training. Any urine produced was also collected and measured during the training session. Sweat samples were collected from regional absorbent patches during exercise on the thigh and back of each player. Sweat was subsequently analysed for sodium concentration [Na+] (compact Horiba B-722). Results, mean ± SD (range). Urine specific gravity prior to exercise; CL: 1.024 ± 1.005 (1.016-1.032), CH: 1.014 ± 1.004 (1.014-1.028), HL: 1.023 ± 1.006 (1.011-1.030), HH: 1.026 ± 1.005 (1.017-1.034): F(3,33) = 2.0, P = 0.157. Sweat rate (L/h); CL: 0.66 ± 0.14 (0.40-0.87, CH: 0.88 ± 0.24 (0.70-1.50), HL: 0.99 ± 0.23 (0.60-1.37), HH: 1.56 ± 0.43 (1.08-2.70), F(3,33) = 22.7, P = 0.000. Sweat Na+ loss (mg/h); CL: 558 ± 230 (198-978), CH: 739 ± 420 (288-1846), HL: 889 ± 355 (435-1482), HH: 1493 ± 458 (979-2272), F(3,30) = 14.9, P = 0.00 (n.=11). Fluid intake (ml/h); CL: 351 ± 159 (0-552), CH: 427 ± 261 (81-1058), HL: 551 ± 174 (330-791), HH: 650 ± 282 (266-1257), F(3,33) = 5.3, P = 0.04. Percentage dehydration; CL: 0.5 ± 0.3 (0.0-0.9), CH: 0.8 ± 0.4 (0.2-1.6), HL: 0.6 ± 0.4 (0.2-1.4), HH: 1.3 ± 0.3 (0.8-1.9), F(3,33) = 22.7, P = 0.00. CHO intake (g/h); CL: 10 ± 7 (0-24), CH: 12 ± 11 (0-35), HL: 17 ± 10 (4-35), HH: 14 ± 11 (0-38), F(3,33) = 1.6, P = 0.195. Elite football players’ fluid loss, Na+ loss, ad-libitum fluid intake varies significantly in response to different exercise intensities in different environmental conditions. Ad-libitum CHO intake varies widely between players. These results may inform programs aimed to personalize player nutrition.
Injury Patterns among Elite Football Players: A Media-based Analysis over Six Seasons with Emphasis on Playing Position
Authors: Leventer, L., Eek, F., Lames, M., Hofstetter, S.
Summary: The study objective was to describe types, localizations and severity of injuries among first division Bundesliga football players, and to study the effect of playing positions on injury incidence and severity based on information from public media. Information about exposure and injuries from 1673 players over 6.4 seasons were collected from a media-based register. The knee was the most frequent localization and had the longest recovery time (p<0.001). Recovery following ligament injuries was significantly longer than muscle injuries. Significant differences between the playing positions were found in injury incidence and injury burden (lay-off time per incidence-rate), with wing-defenders sustaining significantly lower incidence-rates of groin injuries compared to forwards (rate ratio: 0.46, 95% CI: 0.21-0.99). Wing-midfielders had the highest incidence-rate and injury burden from match injuries while centre-defenders sustained the highest incidence-rate and injury burden from training injuries. There were also significant differences in match availability due to an injury across the playing positions, with midfielders sustaining the highest unavailability rates from a match and training injury. Injury-risk and patterns seem to vary substantially between different playing positions. Identifying positional differences in injury-risk may be of major importance to medical practitioners when considering preventive measures.
Development of strength and balance abilities during one competitive season in high level female football players of different age groups
Authors: Roth, R., Donath, L., Zahner, L., Faude, O.
Summary: Isokinetic assessment of thigh muscle strength is frequently applied to assess the risk of injury. Similarly, trunk muscle strength and a well-developed dynamic balance are considered beneficial with regard to sports performance and injury prevention. The aim of the present study was to assess leg and trunk muscle strength as well as dynamic balance in high-level female football players of different age groups over the course of a competitive season. 45 female soccer players of a high-level Swiss football club (under-16: N=19; age = 15.0 (SD 0.7) years; body mass = 54.6 (5.8) kg; under-18: N=15; age = 16.8 (0.6) y; body mass = 59.9 (8.0) kg; body fat = 18.4 (8.8)%; adult players: N=11; age = 21.2 (2.4) y; body mass = 61.1 (6.1) kg) participated. 26 (58%) of these players were tested twice (under-16: N=10; under-18: N=10; adults: N=6), at the end of the pre-season (November 2014) as well as at the end of the second leg of the season (May 2015). Hamstrings (H) and quadriceps (Q) strength was measured on an isokinetic device (IsoMed 2000) at a speed of 60°/sec, 240°/sec and -30°/sec (eccentric). H:Q-ratio was calculated at 60°, 240° and -30°/240° (Croisier et al., 2003). Ratios between flexion/extension and rotation were calculated for trunk strength measures. Dynamic balance performance was assessed by means of the Y-balance test. Quadriceps strength in the preferred leg was higher in all age-categories for flexion (60°, under-16: +11% (p=0.004); under-18: +10% (p=0.004); adults: +10% (p=0.007) and extension (i.e. 60°, under-16: +4% (p=0.31); under-18: +7% (p=0.09); adults: +3% (p=0.27)) as compared to the non-preferred leg. H:Q-ratio also showed higher values in the preferred leg. Trunk strength and flexion-to-extension-ratios rose with age (under-16: 1.59 (0.28); under-18: 1.68 (0.21); adults: 1.86 (0.14)). Balance performance showed no differences between age groups and legs (p>0.75). An increase from pre- to post-season was found for knee extension peak torque (60°, preferred leg: +12% (p=0.001); non preferred leg: +10% (p=0.08)) in the under-16 players. Our results show an inconsistent development in leg and trunk strength over age categories. However, players showed only small differences from pre- to post- season. H:Q ratios as well as the balance score developed differently in preferred and non-preferred leg. Whether strength and balance imbalances are potentially harmful cannot be clarified by our data. However, in order to prevent injuries and to detect maldevelopment timely, regular strength and balance assessment is advisable.
Re-warm-up prior to football matches – Is it beneficial for physical performance?
Authors: Abade, E., Gonçalves, B., Baptista, J., Sampaio, J., Alves, A., Viana, J.
Summary: Warm-up (WU) routines are widely explored and commonly accepted for optimizing performance and preventing injury. However, official international pre-match protocols may require players to passively rest for approximately 15 minutes in the time-course between WU and the beginning of the match. Therefore, the aim of this study was to assess the contribution of different re warm-up (re-WU) strategies on the physical performance of football players. Twenty-two Portuguese elite under-19 football players participated in the study conducted during the competitive season. 4 protocols (WU + re-WU) were tested in 4 consecutive days. The protocols differed only in the re-WU strategy applied after the standardized WU: without re-WU (CON), eccentric re-WU (ECC), plyometric re-WU (PLY) and repeated changes of direction re-WU (RCOD). Vertical jump (counter movement, CMJ; and abalakov, AJ) and Sprint capacity (10-m and 20-m) were tested immediately after WU and 12 minutes after WU. The re-WU strategies were performed 6 minutes after WU. Magnitude-based inferences and precision of estimation were employed in data analysis. Both CMJ and AJ performances presented a likely/very likely improvement after PLY intervention (~3.8% in CMJ and ~4.8% in AJ) when compared to CON. PLY also showed a moderate very likely beneficial effect in 10-m (Cohen d; ±90%CL, -0.7; ±0.3) and a moderate most likely beneficial effect in 20-m (ES=-0.9; ±0.3) performances. The RCOD presented a likely/possible beneficial effect to CMJ and AJ, and a moderate likely/most likely beneficial effect to 10-m and 20-m sprint performances. Different practical implications may be taken from the ECC since there was a -5.1±5.6% decrease in CMJ height from post-WU to re-WU which suggests a possible harmful effect when compared to CON. The absence of re-WU activities in the time-course between the WU and the beginning of the match may be detrimental to players’ physical performance. However, the inclusion of re-WU exercises prior to match is a very delicate issue, since the manipulation of volume, intensity and recovery may positively or negatively affect the subsequent performance (Robbins, 2005). In fact, our research shows that eccentric exercise prior a football match may be harmful for physical performance. However, plyometric and repeated changes of direction exercises seem to be efficient active strategies to attenuate losses in vertical jump and sprint capacity after WU.
Indicators of fatigue in football – effects of fatigue status and subject identity
Authors: Skorski, S., Hecksteden, A., Rauber, C., Walter, M., Meyer, T.
Summary: Large variability has been reported for indicators of exercise induced physical fatigue (1,2). This obviously impedes on their diagnostic accuracy. However, despite the practical importance of monitoring fatigue, not much data about the sources of this variability is currently available. Therefore, this study aims to analyse the inter- and intra-individual variabilities in indicators of physical fatigue during in-season training phases in football players. 41 male football players (4th League Germany, 26.5 ± 4.2 y) participated in the study. Within a period of 3 months in the regular football season venous blood samples (analysed for CK and UREA) and counter movement jump (CMJ) performances were collected repeatedly in ‘fatigued’ and ‘recovered’ states. Players were defined as fatigued after performing >2 training sessions within 48h and as recovered when they had at least 1 day off. Training load was documented throughout data collection. A minimum of 3 observations per fatigue status was necessary to be included for analysis (n = 35 included). Standard error of measurement expressed as a percentage of the groups mean score (coefficients of variation (CV)) for CK, UREA and CMJ was calculated. Variability was analysed using a mixed effects model (fixed factor: fatigue status, random factor: subject ID and fatigue status-by-subject ID interaction). CV for fatigued values was: CK: 52.3%, UREA: 14.6%, CMJ: 4.3%; and for recovered values: CK: 45.2%, UREA: 14.0%, CMJ: 4.5%. The fixed effect of fatigue status was highly significant for CK and UREA (p < 0.001) but not significant for CMJ (p = 0.49). The proportion of total variability attributable to subject ID was 37.9% for CK, 54.7% for UREA and 64.8% for CMJ. Fatigue status-by-subject ID interaction accounted for only 1.1% of total variability for CK and 0.5% for UREA. The current analysis indicates a high inter- as well as intra-individual variation in fatigue induced changes of CK, UREA and CMJ. By contrast status-by-subject ID interaction (‘individual response’) is negligible. Regarding the large between subject variability individualised interpretation using baseline measurements might lead to greater accuracy in the monitoring of the fatigue status in footballers.
Reliability of a fatigue response in elite youth football players
Authors: Fitzpatrick, J.F., Russell, M., Hayes, P.R.
Summary: In football, reliable and time-efficient methods of player monitoring are desirable as the effects of prior football-specific exercise may dictate the programming of subsequent training loads. Therefore, this study aimed to assess the reliability of different methods of assessing the fatigue response to a standardised exercise bout. In 12 elite youth football players and for two consecutive weeks, subjective ratings of wellness (fatigue, sleep quality, muscle soreness, stress and mood), indices of jump height (countermovement jump; CMJ, squat jump; SQJ, and drop jump; DJ-H), drop jump contact time (DJ-CT), drop jump reactive strength index (DJ-RSI), as well as locomotor profile recorded during a sub-maximal run, requiring players to complete a 20 m shuttle run at a speed of 12 km.h-1, whilst wearing a 100-Hz tri-axial accelerometer (Kionix: KXP94, Minimax S4, Catapult Sports). Accelerometer data collected was analysed for PlayerLoad (PL) in the anteroposterior (Fwd), mediolateral (Side) and vertical (Up) planes with the percent contribution of each plane retrospectively analysed. Testing took place over four consecutive days, leading up to and following a standardised football training session including; a repeated sprint protocol, possession drills and small sided games. A magnitude based inference approach (>75% likelihood of the effect size; ES, being greater than or equal to ± 0.2 pre-post exercise) determined the effect of training. Using data collected 24 h post exercise for two consecutive weeks the reliability of the fatigue response was expressed as a coefficient of variation (CV; %) and intraclass correlation (ICC). Substantial changes 24 h post exercise existed for sleep quality, muscle soreness, total wellness, DJ-H, DJ-RSI and all locomotor profile variables except PL (ES -1.27 - 0.46). However, when comparing the response 24 h post exercise over both weeks of testing, a reliable fatigue response was only found for DJ-H (CV 7.0%, ICC 0.84), DJ-RSI (CV 8.6%, ICC 0.93), PL Fwd (CV 10.9%, ICC 0.85), PL Side (CV 6.1%, ICC 0.84), PL %Fwd (CV 5.1%, ICC 0.90) and PL %Up (CV 4.6%, ICC 0.76). Drop jump height, reactive strength index and a number of locomotor profile variables, in particular PlayerLoad Side and % Fwd were reliably able to detect a training induced fatigue response in elite youth football players. These specific variables could therefore be employed prior to training to assess residual fatigue in an applied environment.
Subjective indicators of fatigue in football - effects of fatigue status and subject identity
Authors: Noor, D., Hecksteden, A., Howle, K., Duffield, R., Skorski, S., Meyer, T.
Summary: Current athlete monitoring approaches in many sport settings use a mix of subjective and objective indicators of fatigue. Whilst, there is recent evidence to suggest subjective measures reflect training load with greater sensitivity and consistency than objective measures (1,2), the appropriateness of a fatigue indicator will ultimately be determined by its long-term diagnostic accuracy, along with its potential sources of variability and bias. Thus, this study aims to analyse the inter- and intra-individual variability of football players’ subjective ratings of wellness during the seasonal competition phase. 35 male football players (1st League Australia, 25.3 ± 4.8 y) participated in the study. Individual perceptual ratings of wellness (fatigue (F), sleep quality (SQ), muscle soreness (MS), stress (S) and mood (M)) were repeatedly collected during the competition phase of a football season using a previously published questionnaire (3). Individual’s ratings were retrospectively classified into ‘fatigued’ and ‘recovered’ states according to recent physical load. Players were defined as fatigued after performing >30 match-day minutes and as recovered when they had >1 post-match rest/recovery day. A minimum of 6 observations per fatigue and subsequent recovery status was necessary to be included for analysis (n=14). Variability was then analysed using a mixed effects model (fixed factor: fatigue status, random factor: subject ID and fatigue status-by-subject ID interaction). The fixed effect of fatigue status was highly significant for all fatigue parameters (p < 0.001). The proportion of total variability attributable to fatigue status-by-subject ID was: W (40.7%), F (34.2%), SQ (19.4%), MS (21.8%), S (18.5%), and M (17.6%). Between-subject variabitity (random effect subject ID) was calculated to be redundant for F, SQ and W and very small for M (4.6%) and S (9.1%). The current study indicates that fatigue status-by-subject ID interaction (‘individual response’) explains a substantial proportion of variability in subjective ratings of fatigue in elite football players. By contrast, between-subject variability in fatigued and recovered ratings was small. Thus, when longitudinally examining the fatigue status of a footballer it is relevant to consider inter-individual differences in the magnitude of fatigue induced changes in ratings of subjective wellness.
Influence of the number of players during same- vs. mixed-gender football sessions on heart rate for 12 to 16-year-old children
Authors: Póvoas, S., Randers, M. Soares, D., Faria, G., Santos, T., Silva, P., Krustrup, P.
Summary: Recently, football has been established as a health promoting and performance enhancing activity in several populations (1). Nevertheless, the physiological demands of football played as small or large-sided games in school children is not known, as well as the intensity of various types of small-sided games played as same gender or mixed genders for girls and boys. This study aim was to compare the physiological demands of football sessions for 12-16-year-old school children using small-sided (2v2 and 4v4) and large-sided games (12v12) in same gender and mixed gender game formats. A total of 134 pupils (50 girls and 84 boys) were randomly assigned to same gender and mixed genders game formats, and each of the gender groups played 2x15 min artificial turf football games 2v2, 4v4 and 12v12, on separate days in a random order, using the same area per player and length to width ratio. Heart rates (HR) were determined for all game formats. Higher mean HR was found in 2v2 and 4v4 games compared to 12v12 for girls in mixed gender games (77±10% (±SD) and 73±12% vs. 63±11%HRpeak; p<0.01), as well as for boys playing same gender (81±6% and 79±5% vs. 73±9%HRpeak; p<0.05) and mixed gender games (76±9% and 77±8% vs. 69±8%HRpeak; p<0.05). Correspondingly, more time was spent with HR above 80%HRmax in 2v2 and 4v4 games compared to 12v12 for girls in mixed gender games (42±34% and 37±36% vs. 9±19%; p<0.01), as for boys playing same gender (50±27% and 43±24% vs. 24±29%; p<0.05) and mixed gender games (38±35% and 38±32% vs. 20±19%; p<0.05). In accordance with previous studies (2-4), these study results showed that HRs are high for school children playing small-sided games. Furthermore, the present study revealed that when girls are playing mixed gender games and when boys are playing mixed as well as same gender games, the aerobic exercise intensity is much higher during small-sided games 2v2 and 4v4 compared to large-sided games (12v12).
Fat Oxidation Rates in Professional Football Players
Authors: Randell, R.K., Rollo, I., Medina, D., Lizarraga, M.A., Jeukendrup, A.E., Carter, J.M.
Summary: The rates of maximal fat oxidation (MFO) and the exercise intensity at which it occurs (FATMAX), has been reported in obese, sedentary, lean and endurance trained populations. To date there are no data available describing fat oxidation rates in professional football players. During pre-season medical testing (2014 – 2015 season) 28 players (age 24 ± 4 y; body mass 74.3 ± 6.1 kg; stature 178.8 ± 7.0 cm; body fat 13.8 ± 2.6 %) from the professional football team at FC Barcelona completed a FATMAX test. Performed in a fasted state (> 5 h) on a treadmill, the test started at 5 km/h at a gradient of 1% for 3 min. The speed increased to 8 km/h and, thereafter, increased by 2 km/h until a respiratory exchange ratio (RER) of 1 was reached. The speed then remained constant and the gradient was increased by 1% every 1 min to determine peak oxygen uptake (VO2peak). Respiratory gas measurements (VO2 and VCO2) and heart rate (HR) were measured continuously. Stoichiometric equations  were used to calculated fat oxidation rates during each 3 min stage of the test to determine MFO. Heart rate max (HRmax) and VO2peak were measured in order to calculate FATMAX. The average MFO of professional football players was 0.75 g∙min-1 ± 0.18. The lowest absolute MFO rate was 0.45 g∙min-1, whereas the highest MFO measured was 1.18 g∙min-1. FATMAX occurred at an average exercise intensity of 51 ± 7% VO2peak (range 27 – 60% VO2peak), equating to 66% ± 5 of maximal HR (range 56 – 77% maximal HR). Our results show that, on average, professional football players have a high capacity to oxidise fat during exercise. However, there is a wide range in MFO and the exercise intensity at which it occurs, potentially emphasizing the importance of personalized nutrition strategies. Further investigation is required to determine the importance and the implications of accounting for substrate oxidation rates, and their interaction with exercise intensity, with regard to football specific training, performance and nutrition recommendations.
Reflections from a Female Sport Psychologist Working in Elite Level Professional Football
Authors: Francesca, C., Nesti, M.S., Tod, D., Littlewood, M.A.
Summary: The introduction of the Elite Player Performance Plan (EPPP) by the English Premier League in 2011 has resulted in more opportunities for sport psychology practitioners within Academy football. It is anticipated that more female sport psychology practitioners will join the sport and deliver psychological support at youth levels. However, few practitioners are currently writing about their experiences, and the challenges they have faced within this culture. The aim of the study was to outline a range of experiences that shaped the identity of a female sport psychology practitioner working in elite level professional football. An ethnographic study was conducted over a 24-month period (3-4 days per week) within an elite level professional football club. The first author’s role within the club was a practitioner-researcher, delivering sport psychology support to Academy footballers and support staff. Data was collected via participant observation, and field interviews (Hammersley & Atkinson, 1995). Data is presented in a series of progressive vignettes based upon critical moments that shaped the researcher’s development as a neophyte sport psychology practitioner. The findings from this study fall within the following themes; “Where it all began”, “11 months on; The same old story”, and finally “Learning to cope”. The first two themes outline challenges that the practitioner faced in developing a relationship with a senior member of staff in a culture where power, dominance, and control are paramount. A number of encounters left the practitioner questioning her belonging at the club, and more importantly her identity and future as a sport psychology practitioner. The final theme “Learning to cope” outlines how after 12 months the practitioner started to navigate her way through these challenges. An existential perspective is used to frame the experiences. The practitioner’s feelings of isolation were related to a lack of understanding, and an estrangement of meaning from the situations encountered. However, existentialists take a positive stance on this, and believe that recognition of the feelings associated with isolation are a pre-requisite for inner growth, and attaining greater self-knowledge (Kierkegaard, 1983). It was through reflection, frequent supervisory meetings and professional training that the practitioner began to feel more comfortable with her experiences, and began to understand the individual’s behaviour.
High intensity events and post-match fatigue in football
Authors: Wiig, H., Luteberget, L., Raastad, T., Spencer, M.
Summary: Football matches produce post-match fatigue and time until full recovery may take several days (Nedelec et al., 2012). The slow recovery, probably related to muscle damage, has been associated to the high intensity activities during the match (e.g. Russel et al., 2016). However, the role of accelerations and decelerations in this relationship is not well understood. Therefore, the aim of this study was to investigate high intensity events (HIE) in football matches using Inertial Measurements Units (IMU) and its interaction on post-match fatigue and indicators of muscle damage. Six Norwegian 2. division teams (n=81) were recruited to play three matches. IMUs (Catapult Optimeye S5, Australia) with 100Hz accelerometer, magnetometer, and gyroscope were worn in a vest placed on the upper back. HIE, the sum of accelerations, decelerations, change of directions efforts and jumps (>2.5 m·s-1), were quantified and expressed as counts per minute. Players were divided into keepers (KE;n=6), central defenders (CD;n=13), full backs (FB;n=13), central midfielders (CM;n=23), wide midfielders (WM;n=16) and attackers (AT;n=10). Countermovement jumps (CMJ;n=56) and Creatine Kinase (CK;n=35) were measured 1 hour pre and 1, 24, 48 and 72 hours’ post-match (KE excluded). Differences were deemed likely (L), very likely (VL) and most likely (ML) when there was a likelihood of > 75%, 95% and 99% of the difference exceeding an effect size of 0.2 respectively. The interaction of HIE on fatigue was investigated using mixed model analysis (fixed effects: time·HIE and random effects: subjects + teams). On average, HIE occurred 2.1±0.7 times per minute (mean±SD) including 0.3±0.1 accelerations, 0.5±0.2 decelerations, 1.3±0.5 changes of direction and 0.05±0.03 jumps and were position depended: WM (2.5±0.5), CM (2.4±0.5), AT (2.2±0.5), FB (2.0±0.6), CD (1.8±0.5) and KE (0.8±0.2). Differences ranged from L to VL. The percent changes from pre to +1h, +24h, +48, and +72h were -6.6 (VL), -6.2 (VL), -6.6 (VL) and -4.7 (L) for CMJ height and 69 (ML), 112 (ML), 42 (L), 4.1 (unclear) for CK respectively. Lastly, our model showed no interaction of HIE on neither CMJ nor CK for any of the time points. HIE were found to be position depended and thus, players from different positions are loaded differently in matches. The match load produced neuromuscular fatigue lasting for 72 hours. However, a direct interaction of total HIE on fatigue or muscle damage was missing, suggesting that the match load and fatigue relationship is more complex. Player fitness, pre-match fatigue, and match effort could possibly interact in this relationship.
Fitness parameters in professional football players among different divisions
Authors: Michaelides, M, Koulla, P, Evripidoy, D, Zacharia, A. Petousis, C.
Summary: The purpose of the study was to determine aspects of fitness that differentiate first division professional football players from players of second and third divisions in Cypriot football leagues. Four hundred and twenty seven professional male football players (age =25 ± 5 years) performed an isokinetic knee test using the Humac Norm dynamometer at two angular velocities (60°s-1, 300°s-1). On a different occasion, they performed an incremental cardiopulmonary exercise testing (CPET) on a treadmill. Furthermore, anthropometric and flexibility (sit and reach) measurements were recorded. Results were analyzed using one-way ANOVA, between subjects design revealing significant effects for division. Tukey’s HSD tests demonstrated that players from division 1 scored significant higher on maximal oxygen consumption (VO2 max) and lasted significantly longer on the treadmill than participants of division 2 and 3 (p<0.05). Similar findings were demonstrated when division 2 was contrasted against division 3 players. Marginal or no significant differences were recorded among players from the three different divisions on anthropometric measurements, flexibility and isokinetic parameters (muscular strength and muscular endurance). The marginal differences observed were mainly between first and third division players. The findings of this study clearly demonstrated that cardiovascular fitness as determined by CPET is the most important fitness parameter that differentiates professional football players who play at a more advanced championships. Although, strength and muscular endurance of the knee joint as well as low back- hamstring flexibility parameters are crucial for performance and injury prevention in football, they appear to be similar in players from smaller divisions too.
Searching tactical patterns in soccer game play by unsupervised machine learning
Authors: Leser, R., Hoch, T., Tan, X., Moser, B., Baca, A.
Summary: Location systems in game sports provide a wealth of data, which is capable of reconstructing game play from a tactical point of view. Precise position measurements up to 50 times per second/player during an entire soccer game enable in depth analyses of individual and collective game behavior. Small sided games (SSGs) are used in soccer training to simulate specific game situations. By the given constraints (smaller pitch size, lower number of players) SSGs are used to provoke intended player behavior with a higher rate than it occurs in the full size game. Due to these properties SSGs are also suited to analyse successful/unsuccessful tactical patterns in a reasonable framework. The research described in this paper aims to identify behavioral patterns in soccer SSGs based on the players’ positional data. The approach is demonstrated by a 3vs2-SSG (3 attackers playing versus 2 defenders), which is often used in soccer training to acquire collective and individual goal scoring skills against a shorthanded opponent. Based on expert information the SSG is temporally segmented and for each defined key moment and temporal phase a couple of parameters are derived from the position data. Statistical methods (e.g., the laplacian score for feature selection) reduce the high dimensional parameter space to a manageable number of variables. This resulted in the 3vs2 analyses in 9 parameters describing the shot and the assist (last past) situations. For each of the two situations unsupervised pattern recognition was performed by spectral clustering. For the shot as well as for the assist situation three different patterns were identified. The goal ratios for the assist patterns range from 0 to 29%, the goal ratios for the shot patterns from 8 to 24%. By a fuzzification of the quantitative parameters into linguistic variables the outcome of the pattern recognition process becomes understandable and interpretable for experts like coaches. The results give evidence that the most efficient assist is a middle distance to goal pass from the side to the centre, whereas rear-faced passes are far more successful than forward-faced passes (47 to 8% goal rate). Shots with the highest success rate are performed from a middle distance to the goal in the centre of the field. The findings of our study give data based hints for successful tactical principles in soccer, which are likely valid also for the 11-a-side game. For the 3vs2 test case we can support the common coaches’ assumption that ball possession at the wing moves the defenders to the side, which creates space in the centre field. This enables opportunities with the highest goal scoring probability.
Identifying tactical patterns in soccer game play by means of an explanatory computational model
Authors: Hoch, T., Leser, R., Tan, X., Baca, A., Moser, B.A.
Summary: The tactical analysis of player behaviour in team sports like association football is of great interest. The increasing availability of position data allows for an in-depth analysis of tactical behaviours of individual players (Leser et al., 2015). The high complexity of player interactions, however, makes the assessment of individual tactic skills based on time-continues position data difficult. We address the problem of designing an explanatory computational model for player assessment by fusing fuzzy human-like knowledge related to tactical behaviour with unsupervised feature extraction based on time-continuous position data from a tracking system. Our hierarchical model architecture consists of two layers. The first layer provides an abstract representation of the time domain via temporal segmentation of the data into game-situation specific temporal phases. Conceptually the coarsened view on the time domain is modelled via a Markov chain where transitions between states represent meaningful events. In a second step we then identify different behaviour patterns hidden in the data with unsupervised machine learning technics. The main focus of this layer is to provide the trainer with a qualitative description of the key differences of the behaviour patterns based on key performance indicators. We show how to reduce the high dimensionality of the input space using unsupervised dimensionality reduction methods and how to provide a meaningful explanatory model for the trainer using natural language expressions. We illustrate our approach by means of three different kinds of small sided games in association football with increasing complexity. Starting with a 1vs1 situation with low complexity, we show the principals of our modelling approach. Next we show that for 3vs2 and 5vs5 situations our approach is able to identify the underlying dynamical patterns of player interactions. With the multifactorial statistical analysis, as presented in this paper, we are able now to present the complex interaction between the automatically selected measurement variables in a qualitative way that is suitable for the trainer.
Functional semantics embedded in the assessment of self organization in soccer
Authors: Lopez-Felip, M.
Summary: To date, much of the research on coordination dynamics in team sport has benefitted from concepts and tools from Dynamical Systems Theory (DST). However, while DST provides suitable techniques for modeling living systems, it makes no direct claims about their status nor provides a theoretical basis for understanding the principles of their behavior. The aim of this study was to develop a method of analysis to measure the self-organization of teams based on a recently developed ecological ontology of perception and action in soccer . This framework applies DST to the functional semantics of the game, where, for example, self-organizing behaviors in the defensive team are defined by the relations between the position of the possessor of the ball relative to the goal as a function of time. Twenty-two elite soccer players from La Liga played a practice game during a training session. Player position data were collected via GPS (10 Hz) for an entire match (two halves of thirty minutes). We analyzed the degree of synchronization in the defensive team in terms of the Kuramoto order parameter (cluster amplitude) r, (high synchronization = 1) by measuring location data (x,y coordinates on the pitch) over time . Team synchronization was measured in 4 blocks of 5 minute time-epochs. For block 1 (r = 0.978 ± 0.014); block 2 (0.962 ± 0.033); block 3 (0.981 ± 0.026); and block 4 (0.968 ± 0.046). However, while mean synchronization across blocks was fairly consistent, F(1, 8) = 0.22, p = 0.65, the overall degree of synchronization ranged between 0.84 and 0.99. To account for this drastic changes we compared our synchronization time series of all blocks to corresponding events in the match. Visual inspection of these time series revealed five instances when r decreased by more than 0.20. These dramatic decreases in the defensive team’s synchrony corresponded with scoring opportunities of their opponent. Our analysis by means of the Kuramoto order parameter revealed that the synchronization measure was able to distinguish between periods of low and high group synchronization. Using this approach as a foundation, we are building a preliminary model that captures systematic changes in coordination between defensive players at the local (one-on-one) and global (team-wide) scales—quantifying breakdowns in the stability of the defensive team’s coordination and showing how they anticipate scoring opportunities for an opponent. This approach promises to address gaps in this literature by taking DST measures related to group coordination and synchrony and integrating them with measures that capture the functional, qualitative aspects of the game.
Training in the matrix – Introducing a combined program for youth soccer players development
Authors: Zago, M., Sforza, C., Giuriola, M.
Summary: High-intensity technical actions heavily influence the outcome of soccer matches. While performance factors are traditionally trained separately, we proposed a program combining technique and agility (combination of strength, speed, balance and coordination, (Sheppard and Young (2006)) for youth players’ development. We assessed the effect of this program on motor and technical skills. The program was structured on a 14x12-m matrix of elastic tapes (lifted at 25 cm) that provides a constraints-driven reference for movement timing and techniques. Practices were aimed to develop game-like high-intensity technical actions with the ball. Twenty U12 sub-elite male soccer players (41.8±7.1 kg, 1.55±0.08 m) from to the same club were randomly assigned to an experimental (EG) and a control group (CG). A repeated-measures design was used: the EG was exposed to 20-40 min/session of differentiated training (22 weeks, 38 sessions) while the CG continued the traditional training. Shuttle Dribbling Test (SDT, Huijgen et al. (2010)) and the Loughborough Soccer Passing Test (LSPT, Ali (2011)) were performed before and after the differentiated training. Medians and interquartile ranges (IQR) of percentage change between measurements, correlation coefficients (r) with individuals’ stature increments and Cohen’s d effect size were computed. The stature increment between measurements was 3.5 (IQR 0.1) cm for the CG and 3.8 (0.2) cm for the EG (d=0.11). In the SDT, the EG improved by 4.1%, while the CG performance decreased by 0.6% (d=0.97); in the LSPT, EG improved by 6.8% while the CG by 0.3% (d=0.78). Performance and stature changes were moderately-to-low correlated (CG vs. EG): r=0.35 vs. -0.17 (SDT); r=0.41 vs. 0.18 (LSPT). The matrix was designed to stress dynamic balance, quick changes-of-direction, and specific agility/coordination skills: the program produced higher performance improvements, compared to traditional training, in 180°-changes-of-direction and in a controlling and passing dynamic task. It seemed to balance the losses in coordination caused by the adolescent motor awkwardness (Quatman-Yates et al., 2012). The program acts simultaneously on the physical, technical and perceptual corners of soccer performance, thus optimizing the training process. Despite more age/proficiency levels have to been considered, the methodological implications of this study could be beneficial for youth training effectiveness.
Soccer players and coaches’ perspectives towards ergogenic aids and supplement use in the eThekwini region
Authors: Kisten, T., Naidoo, R.
Summary: Doping is regarded as a form of cheating where athletes use substances that are on the prohibited list, predominantly for gaining an edge over their competitors. Where sports participation was previously seen as recreational activity, it is now an intense environment for the adolescent athlete, placing high demands for performance in order to get drafted into professional sports. There is increased pressure on athletes to perform. This leads to increase use of performance enhancing substances and supplements to achieve increased performance levels and cope with the heavy demands that are placed on the player. The aim of this study was to determine the perspectives of U-19 soccer players and their coaches towards the use of ergogenic aids and supplements in the eThekwini region, KwaZulu-Natal. The study was a mixed-methods design. Both quantitative and qualitative designs were employed. The sample comprised of participants playing first team U-19 soccer from clubs in the eThekwini region and their respective coaches. A questionnaire was administered to players to assess the knowledge, attitudes and practices towards doping in sport, to determine their source of information and to determine which supplement was most frequently used. An interview was conducted with the coaches to assess his/her knowledge, attitude and beliefs about supplementation, and where do they get their information from about supplements. Both descriptive and inferential statistics were employed to analyse and report the data. The U-19 soccer players and coaches believed that consuming prohibited substances in sport is unethical. Majority of the U-19 soccer players (73.9% either agreed or strongly agree) and coaches believed that doping in soccer is on the increase. Almost a quarter (24.7%) of the U-19 soccer players consumed performance enhancing substances (PES), cannabis, alcohol and/or smoke. Coaches believed that there players do not consume PES or substances. Majority (84.4%) of the U-19 soccer players and majority of coaches stated that educational programmes are needed. The U-19 soccer players and coaches believe that doping is prevalent in soccer. Players and coaches believe that sport organisations need to implement more educational programmes about doping and on how to consume PES.
Effects of strength and conditioning on critical velocity in running and soccer
Authors: Karsten, B.
Summary: A regular strength training should be an integral part of the coaching process in team sports such as football. To-date no research has investigated the effects of such training on the velocity-duration relationship of Critical Velocity (CV). Objectives: To examine the effects of a moderate intensity strength training on changes in CV and sprint performances in recreationally trained football players. Methods: two football teams were divided in a football training only group (FO; n = 13 : 19 ± 1 127 yr., height 177.3 ± 5.2 cm, body mass 73.2 ± 7 kg). and a strength and football training group (ST; n=13: 18 ± 1 yr., 126 height 174.8 ± 5.4 cm, body mass 72.4 ± 6.6 kg). Both groups were tested for values of CV and 30-m sprint time prior and post training intervention. The ST group performed a concurrent 6-week upper and lower body strength and football training, whilst the FO group performed a football only training. Results: after the re-test of all variables, the ST demonstrated significant improvements for CV values by 0.32 m/s (95% C.I. = 0.16 233 to 0.48; p=0.000) after completing the specific training, with no significant changes in the SO group. 30-m sprint performance were slightly improved in the ST group (p=0.078, 0.12 m/s, 95% CI = -0.25 to 0.15) with FO players significantly worsening their performance (p=0.000) by about 0.98 m/s (95% CI = -1.11 to -0.84). Conclusions: combining a 6-week moderate strength training with football training significantly improves CV, whilst moderately improving 30-m sprint performances in non-previously resistance trained male football players. An integrated regular strength training can consequently be recommended to coaches to enhance critical velocity and sprint performances in football.
Levels of adiposity and other anthropometric parameters in soccer players with intellectual disability participants in adapted sport competition
Authors: Lizondo, V., Escrivá, D., Pérez-Encinas, C., Barrios, C.
Summary: Obesity and/or overweight in adolescents and adults with intellectual disabilities (such as Down syndrome) are well described in the literature (González-Agüero et al., 2011). There are few data on body composition in athletes with intellectual disabilities participating in competitive sports (Pitetti et a., 2013). The aim of this work was to determine the anthropometric characteristics and body composition of a group of soccer players with intellectual disabilities, with special reference to the levels of adiposity. The study sample consisted of 38 adolescents and young adults with mental disabilities enrolled in competitive sport (soccer): 24 suffered consequences of infantile cerebral palsy (CP) and 14 had Down syndrome (DS). The average age was 25.4±8.6. Anthropometric measurements including skinfold thickness (biceps, triceps, subscapular, abdominal, suprailiac, thigh and leg) were performed following the ISAK recommendations. The percentage of body fat (%BF) was calculated from measurements of skinfold equations as proposed by Faulkner, Reilly et al., and Yuhasz. The somatotype was assessed by the technique of Carter and Heath. Differences were established by groups of etiology of disability. As compared to subjects with CP, individuals with DS were smaller (158.3±7.7 vs. 168.5±9.4 cm, p<0.01), and had an increased %BF (Juhasz: 18.7±7.8 vs. 13.5%±5.0%, p<0.01) (Faulkner: 20.9±7.8% vs. 16.8±6.2%, p<0.01). The skinfolds of the leg, thigh and abdomen were also significantly thicker in patients with DS than patients with CP. Muscle weight was higher in subjects with CP (55.2±10.2 kg) than with DS (48.8±13.9 kg), but without statistically significant differences. Regarding somatotype, there were only significant differences between the two groups in the endomorphic component, being higher in subjects with DS (6.24±2.46 versus 4.54±2.16, p<0.05). This research shows for the first time evidence that adolescents and young adults with Down syndrome involved in competitive sport have higher levels of total and regional fat (trunk and lower extremities) than the disabled athletes with cerebral palsy. This high adiposity together with the lower levels of cardiovascular and strength capacities describes in this population (Guerra et al., 2003), can result in a high risk of adverse events when performing competitive sports. Particular attention could be considered in future research to the limits and implications for their health and possible intervention through sport.
Adding fish oil and natural antioxidants to whey protein improves eccentric-exercise recovery in soccer players
Authors: Philpott, J.D., Donnelly, C., Walshe, I.H., Dick, J., McKinlay, E., Galloway, S.D., Tipton, K.D., Witard, O.C.
Summary: The physical demands of soccer match-play is known to involve changing speed and direction, repeated sprints and explosives jumps, that predominantly requires eccentric type muscle contractions. Such movements often result in the phenomenon termed muscle damage. Protein feeding has been shown to preserve the functional capacity of skeletal muscle after eccentric exercise. Since fish oil derived n-3 polyunsaturated fatty acids (n-3PUFA) exhibit anti-inflammatory properties, combining ingestion of fish oil with protein may facilitate recovery. Therefore, the primary aim of the present study was to assess the influence of 6 wk supplementation with a juice-based antioxidant-rich drink containing a combination of n-3PUFA, whey protein and vitamin D on muscle function and soreness, inflammation and soccer performance during exercise recovery. Competitive soccer players (n=27) were assigned to one of three conditions. Drink-A contained n-3PUFA (550 mg DHA, 550 mg EPA), whey protein (15 g) and vitamin D (3 µg). Drink-B contained whey protein (15 g) and vitamin D (3.9 µg) and Drink-C was an isocaloric carbohydrate control. Eccentric exercise consisted of 12 sets of unilateral knee extension/flexion contractions on both legs separately. Statistical analyses included conventional p-value and magnitude-based inferential approaches. Eccentric exercise impaired maximal force and increased ratings of muscle soreness (p<0.05). Post supplementation, blood %n-3PUFA/total PUFA was greater in Drink-A (36 ± 6) vs. Drink-B (24 ± 3, p<0.05) or Drink-C (23 ± 2, p<0.05). Maximum force loss during recovery tended (p = 0.10) to be less in Drink-A (-19 ± 22%) vs. Drink-C (-30 ± 10%). Muscle soreness (dominant leg), expressed as AUC during 72 h exercise recovery, tended to be less in Drink-A (791 ± 549 mm × 72 h) vs. Drink-B (1403 ± 779 mm × 72 h, p=0.08) and Drink-C (1298 ± 621 mm × 72 h p=0.10). The blood concentration of c-reactive protein tended (p=0.09) to be lower in Drink-A (AUC: 42 ± 11 mg/L × 72 h) vs. Drink-C (AUC: 83 ± 42 mg/L × 72 h, p < 0.05). Drink-A elicited a very likely (79-96%) beneficial effect on agility t-test performance vs. Drink-B and Drink-C. A juice-based antioxidant-rich drink, containing n-3PUFA, whey protein and vitamin D, appears to mediate a reduced feeling of muscle soreness after eccentric exercise and translates into improved muscle function and soccer-specific performance during acute recovery. Hence, the benefit of whey protein ingestion to exercise recovery may be enhanced by the addition of n-3PUFA and natural antioxidants in competitive soccer players.
The organization of cognitive representation of group-specific tactics in soccer
Authors: Lex, H.
Summary: Scientific protocols describing tactical performance usually investigate indicators (e.g., running distances, maximum running speed etc.) derived from post-hoc video analyzes (Garganta, 2009). However, the results of a novel scientific approach showed that more experienced soccer players possess a functional cognitive re-presentation of team-specific tactics in soccer. More experienced soccer players end up with faster decisions, because of their functional representation structure allowing to coordinate their gaze behavior aligned to tactical needs (Lex, Essig, Knoblauch, & Schack, 2015). In soccer, performance is not only determined by team-specific tactics. Thus, the present study investigates the cognitive representation of group-specific tactics in soccer. The present study investigated whether cognitive representations are established for group-specific tactics in defense (i.e. defense triangle, four-man backfield defense, golden zone defense) and offense (i.e., give and go pass, overlap, two players crossing) with regard to players expertise. Participants (N = 45) made similarity judgments of 2 x 9 match situations displayed on a tactic board (i.e., 144 decisions) in a successive splitting procedure regarding the required tactical behavior. The de-cisions informed about the proximity between the match situations, and formed the basis for an unweighted average cluster analysis (p = .01,dcrit = 4.48) complemented by an invariance measure testing structural homogeneity (λcrit = .68). Experienced soccer players possess, in contrast to less experienced players (λ = 0.0), a structural invariant cognitive representation for offense and defense tactics identical with the representation structure of experienced coaches (λ = 1.0) and players from the Bundesliga (λ = 1.0). We found no differences between players specialized for defense and offense tactics. However, players with a coaching license showed as well a functional cognitive representation of group-specific tactics (λ = 1.0). This innovative experimental approach measuring individual cognitive representations of group-specific tactics in soccer reveals a well-integrated network of single match situations that each corresponds to functional meaningful group-specific tactics based on soccer specific playing experiences. The cognitive representations of group-specific tactics form an individual profile of each player, which allows to refer to tactical decision making on the pitch.
Effects of stress-level on hand-movement behavior with focus on Self-touch in female pre-and post-pubertal soccer players
Authors: Densing, K., Konstantinidis, I., Seiler, M.
Summary: Self-touch (ST) may serve for arousal regulation, both of hyper- and hypoarousal, as it may be observed in presence as well as absence of external stimulation. It remains unclear if ST with varying structural features occurs in different contexts, and if this potentially regulatory mechanism is learned or inherent. The aim of this study was to discover if the rate of ST increases with higher stress-levels, to identify structurally different forms of ST used in different contexts, and to find out if there are age differences in stress processing between pre- and post-pubertal female soccer players. We compared hand movements of 10 pre- (11.9±0.72 y.) and 10 post-pubertal (21.6±1.73 y.) soccer girls in non-stress (NS) and stress (S) settings. As NS setting we used an interview about a positive experience, whilst the arithmetic part of the Trier social stress test (TSST) was used as S-inducing setting. All settings lasted 5 minutes and were filmed. All hand movements as well as structural components of ST were analyzed with the NEUROGES-ELAN system by two independent raters. A decrease in repetitive ST was found (right hand (rh): 1.47±1.54 s/min vs. 0.11±0.24 s/min, p=0.023; left hand (lh): 3.81±3.72s/min vs. 0.92±2.53 s/min, p=0.007) in the post-pubertal girls in the S situation compared to the NS situation. The post-pubertal girls displayed less hand movements, including phasic (rh: 9.89±6.76 s/min vs. 0.73±0.97 s/min, p=0.000; lh: 8.7±4.57 s/min vs. 1.61±1.93 s/min, p=0.000) and repetitive (rh: 2.13±2.75 s/min vs. 0.03±0.09 s/min, p=0.002; lh: 1.35±1.26 s/min vs. 0±0 s/min, p=0.000) movements in space in the S setting. Pre-pubertal girls showed no change in hand movements in NS and S. The post-pubertal group displayed a stronger decrease in activation (rh: 1.58±13.79 s/min vs. -19.29±12.79 s/min, p=0.004; lh: -3.42±8.05 s/min vs. -17.09±14.31 s/min, p=0.043) and phasic movements (rh: -2.25±1.57 s/min vs. -9.17±6.88 s/min, p=0.001; lh: -0.93±1.92 s/min vs. -7.1±4.28 s/min, p=0.000) in the S situation compared to the pre-pubertal girls. The puberty seems to influence regulatory mechanisms for stress-regulation and structurally different groups of ST are used in different contexts. This is unlike earlier studies which show an increase of ST movements with increasing the complexity of a test, which might be due to the cognitive complexity or the stress level of the test. Our results suggest that there are differences in stress processing between younger and older female soccer players, which should be accounted in training situations.
Morningness/eveningness effects on autonomic function during a high intensity interval training protocol in soccer players. A randomized cross-over study
Authors: Bonato, M., Vitale, A., Mancuso, G., Merati, G., La Torre, A.
Summary: The 4x4 min of interval running proposed by Helgerud et al., (2001) is one of the widely used methods that have been demonstrated to improve soccer performance. For this reason, monitoring the effects of this type of training could provide useful information to make evidence based decisions on appropriate loading schemes to enhance team performance and reduce injuries. Therefore, the aim of this study was to assess the acute effects on heart rate variability (HRV) of this training protocol performed at different times of the day (8.00 am vs 8.00 pm). In a cross-sectional study, 30 male recreational soccer players, age 20±2 y-o, were randomized to morning (MG=15) or evening group (EG=15). Subjects performed an aerobic interval training protocol consisted of four times 4 min at 90–95% of maximal heart rate (assessed during a Yo-Yo IR1 test) with a 3-min jog in between. HRV was measured at REST, PRE, POST-12h and POST-24h the 4x4 protocol. HR variability indexes in time, Root Mean Square of the Successive Differences (RMSSD) and the standard deviation of NN intervals (SDNN), frequency (Low Frequencies, between 0.04 and 0.15 Hz [LF], and High Frequency, between 0.15 and 0.40 Hz [HF], in normalized unit) were calculated. One-way ANOVA showed that both morning/evening aerobic interval training protocol significantly increased the parasympathetic cardiac tone POST-12h (p<0.05) which returns to baseline level POST-24h. Un-paired t-test detected significant difference in PRE aerobic training in LnRMSS (p=0.049), LnSDNN (p=0.043), HF n.u. (p=0.021), showing that in evening conditions subjects have an increased parasympathetic activity. In POST-12h subjects that trained during the evening have an increased LnRMSS (p=0.043), LnSDNN (p=0.032), HF n.u. (p=0.024), maybe due to a reduced recovery. No differences in POST-24h both in sympathetic and parasympathetic activity were detected. The 4x4 protocol seems to influence the parasympathetic tone in the same way both in morning and evening conditions. On the other hand, in PRE conditions people that train in the evening showed an increased parasympathetic cardiac tone. Because soccer players have often to train twice a day during the season, with morning and evening training sessions, monitoring HRV is a useful and non-invasive method to detect the effects of high intensity interval training, with the aim to facilitate a more efficient planning and manipulation of training sessions.
A genetic-based algorithm for personalized resistance training in soccer players
Authors: Suraci, B., Jones, N., Kiely, J., Pickering, C., Collins, D., de Lorenzo, D., Grimaldi, K.
Summary: Resistance training leads to increases in maximal running speed, acceleration, jumping abilities, force in kicking, tackles and headers and reduces the risk of injuries in soccer players. Association studies have identified dozens of genetic variants linked to training responses and sport-related traits. However, no intervention studies utilizing the idea of personalized training based on athlete’s genetic profile have been carried out, especially in soccer. Here we propose an algorithm that allows achieving greater results in response to high- or low-intensity resistance training program by predicting an athlete potential for the development of power and endurance qualities with a panel of 15 performance-associated gene polymorphisms. These polymorphisms are located within the genes primarily involved in the regulation of muscle fibre type composition and muscle size, cytoskeletal function, muscle damage protection, metabolism, circulatory homeostasis, mitochondrial biogenesis, thermogenesis and angiogenesis. Soccer players (n=39) completed an eight-week high- or low-intensity resistance training program, either matched or mismatched to their individual genotype. The high-intensity resistance training program consisted of ten sets of two reps over the eight-week study. The low-intensity resistance training program consisted of three sets of ten reps for first two weeks, three sets of fifteens reps for the next three weeks and three sets of twenty for the last three weeks. Two variables of explosive power and aerobic fitness, measured by the countermovement jump (CMJ) and aerobic 3-min cycle test (Aero3), were assessed pre and post 8 weeks of resistance training. DNA samples of athletes were genotyped for the ACE I/D, ACTN3 R577X, ADRB2 Gly16Arg and Gln27Glu, AGT M235T, BDKRB2 rs1799722 C/T, COL5A1 rs12722 C/T, CRP rs1205 A/G, GABPB1rs7181866 A/G, IL6 -174 C/G, PPARA rs4253778 G/C, PPARGC1A G482S, TRHR rs16892496 A/C, VDR rs1544410 A/G, VEGFA rs2010963 G/C gene polymorphisms by real-time PCR. The percentage power/endurance genotype score (P/E) ratio was determined for each athlete. Following the training intervention, players from the matched group (i.e. high-intensity trained with power genotype or low-intensity trained with endurance genotype) have demonstrated significantly greater (P<0.0001) performance changes in both tests compared to mismatched group (i.e. high-intensity trained with endurance genotype or low-intensity trained with power genotype). CMJ improved by 7.1% in the matched group, compared to 2.4% in the mismatched group. Improvements in Aero3 were 7.7% in the matched vs 1.9% in the mismatched group. Our results indicate that matching the individual’s genotype with the appropriate training modality leads to more effective resistance training. The developed algorithm may be used to guide individualized resistance-training interventions.
Sugar and micronutrient intake within elite youth British soccer players: the nutritional transition from schoolboy to fulltime soccer player
Authors: Naughton, R., Drust, B., O'Boyle, A., Morgans, R., Abayomi, J., Davies, I.G., Morton, J.P., Mahon, E.
Summary: It is recommended that soccer players consume a diet high in carbohydrate to augment performance. However, growing evidence suggests there is a link between high free-sugar intake (>5% total energy intake (TEI)) and some metabolic diseases (1). Additionally, recent data has found that soccer players are at risk of oral caries, which was linked to free-sugar intake (2). Little is currently known about the free-sugar intake within elite British youth soccer players and, consequently, their risk to adverse health conditions. We therefore tested the hypothesis that elite British youth soccer players consumed above the current UK DRV (5% TEI) for free-sugars. Players from an English Premier League academy under (U) 18 (n = 13); U15/16 (n = 25); U13/14 (n = 21)] completed a 7-day food diary over a training period in which no competitive games took place. Upon analysis, using dietary analysis software (Nutritics Ltd, Ireland), these data were compared to the current UK DRV for free-sugar via a t-test. Intakes between squads was analysed using a one-way ANOVA. All data are expressed as means (SD), statistical significance p < 0.05. The U13/14s (TEI, 10.0 17.7%) and U15/16s (TEI, 11.2 30.0%) both consumed higher amounts of free-sugar in comparison to the UK DRV of TEI 5% (P < 0.01), conversely, the U18s (TEI, 5.1 12.7%) were no different from the DRV. Furthermore, the free-sugar intake of the U18s was significantly lower than that of the U13/14s and U15/16s (P < 0.01). Our data provides novel evidence on the free-sugar intake across a range of ages within an elite youth British soccer academy. It would appear that there is a shift in nutritional habits from when a player transitions to fulltime (U18s) from schoolboy (U13-U16s). However, it may be put forward that as the tested population are athletes they may have need for a higher carbohydrate intake in comparison to the UK DRV, which may lead to higher free-sugar intake than the general population. Further research is needed to establish if there is any health risk to this population as a result of an increased free-sugar intake (>5% TEI).
Beetroot juice supplementation improves exercise performance in soccer players
Authors: Nyakayiru, J., Jonvik, K.L., Trommelen, J., Pinckaers, P.J.M., Senden, J.M.G., van Loon, L.J.C., Verdijk, L.B.
Summary: Dietary nitrate supplementation has previously been shown to enhance exercise performance in moderately-trained endurance athletes. Recent work also suggests increases in repeated sprint and/or intermittent high-intensity exercise performance following nitrate supplementation, relevant for team-sports. We assessed the effects of 6 days of nitrate supplementation on high-intensity intermittent type exercise performance in trained soccer players. Thirty-two trained soccer players (23±1 y; 2nd and 3rd Dutch amateur league) participated in a double-blind, randomized, placebo-controlled cross-over experiment. Following a familiarization trial, all subjects participated in 2 separate test-days in which intermittent exercise performance was assessed using the Yo-Yo intermittent recovery level 1 test (Yo-Yo IR1). Test days were preceded by 6-days of concentrated nitrate-rich beetroot juice ingestion (140 mL; providing ~800mg nitrate/day; BRJ), or a nitrate-depleted beetroot juice (PLA), with the last supplemental bolus being ingested 3 h prior to performing the Yo-Yo IR1 test. A single blood sample was collected ~2.5 h after ingestion of the last supplemental bolus to determine pre-exercise nitrate and nitrite concentrations. Supplementation periods were separated by 1 week washout. The primary outcome was distance covered in the Yo-Yo IR1 test. Additionally, heart rate (HR) was measured continuously throughout the test, and ratings of perceived exertion (RPE) were assessed using the Borg-20 scale. All data were analyzed using paired samples t-tests. Plasma and saliva nitrate and nitrite concentrations represent preliminary data from n=24. Data are presented as mean ± SEM. Plasma nitrate and nitrite concentrations were significantly increased following 6 days of BRJ supplementation (836±44 μM and 581±45 nM) when compared to the PLA trial (72±5 μM and 165±14 nM; both P<0.001). Distance covered in the Yo-Yo IR1 test was 3.4±1.3% greater with BRJ (1623±48 m) when compared to PLA (1574±47 m; P=0.027). Mean HR was significantly lower with BRJ vs PLA (172±2 vs 175±2; P=0.014). Peak HR (190±1 vs 191±1), and RPE (17.3±0.4 vs 17.6±0.3) did not differ between BRJ and PLA. Six days of beetroot juice supplementation increases plasma nitrate and nitrite concentrations and improves performance during an intermittent type exercise task in soccer players.
Mental fatigue impairs soccer-specific performance
Authors: Smith, M., Marcora, S., Lenoir, M., Badin, O., Merlini, M., Deprez, D., Zeuwts, L., Coutts, A.
Summary: Anecdotal reports from soccer players and coaches suggest that mental fatigue impairs soccer performance. However experimental investigations of this claim are limited. Therefore, two randomised, crossover investigations were conducted to assess the impact of mental fatigue on soccer-specific physical, technical, and decision-making performance. Players completed a 30-min Stroop task (mental fatigue treatment), or 30 min of an emotionally neutral control, prior to tests of soccer-specific performance. Study 1 assessed the impact of mental fatigue on physical and technical performance of 20 well-trained soccer players during 15-min, 5 vs. 5 small-sided games (SSGs). Physical performance was assessed using 15-Hz GPS units, and technical performance was assessed using video-based notational analysis. Heart rate (HR) and ratings of perceived exertion (RPE; CR10) were also recorded during the SSGs. Study 2 utilised videos of simulated play to assess the impact of mental fatigue on soccer-specific decision-making, and visual search behaviour in 12 well-trained soccer players. Decision-making skill was assessed using response time and accuracy, while visual search behaviour was assessed via search rate, fixation location, and fixation order. A progressive magnitude-based approach was used to assess chances of differences between conditions being trivial or true (greater than the smallest worthwhile change; 0.2 × the between-subjects SD). Players reported higher levels of mental fatigue following the Stroop task than the control treatment in both studies, while no clear differences in motivation existed. Mental fatigue had unclear effects on most physical performance variables in Study 1, despite a possibly lower HR (mental fatigue = 85 ± 5%HRmax; control = 86 ± 4%HRmax; ES = -0.28), and likely higher RPE in the mental fatigue condition (mental fatigue = 6.8 ± 1.4; control = 6.2 ± 1.6; ES = 0.39). In contrast, mental fatigue impaired both offensive and defensive technical performance during the SSGs (positive involvements: mental fatigue = 70 ± 10%; control = 63 ± 9%; ES = -0.73). In Study 2, mental fatigue very likely reduced soccer-specific decision-making accuracy (mental fatigue = 81 ± 6%; control = 86 ± 4%; ES = -0.89) and likely increased response time (mental fatigue = 768 ± 134 ms; control = 685 ± 156 ms; ES = 0.49), despite minimal differences in visual search behaviour. These findings support anecdotal reports that mental fatigue impairs soccer-specific performance. Soccer clubs may benefit from assessing pre-match routines, to ensure players are not mentally fatigued prior to competition, and are advised to identify and implement strategies that may attenuate the negative impact of mental fatigue on performance. In this respect, coaches could utilise short SSGs to train technical performance under mentally fatigued conditions, without compromising physical training loads.
The determination of energy costs during soccer matches: comparative analysis between measured and calculated energy expenditure
Authors: Venzke, J., Nardiello, D., Platen, P.
Summary: The metabolic demands of soccer and other team sport players have been a subject of research for many years. However, there is no method for estimating the energy costs (EC) during official matches. A new mathematical approach1 can be used to calculate metabolic loads during a match. Using this method it might be possible to determine EC from velocity and acceleration data measured by global positioning system (GPS) or comparable technology. The aim of the study was to validate the new mathematical approach for the determination of metabolic demands by comparing the results of the mathematical analysis against the direct measurement with spirometry (SM) during a soccer match. 22 healthy soccer players from the 5th German League agreed to participate in a simulated soccer match with a playing time of 90 min and a regular halftime break (15 min). 8 of the subjects (24.4±2.1 y, 183.3±6.9 cm, 82.6±8.0 kg) wore a portable GPS system (GPI-Sports, 5 Hz) for the determination of accelerations and decelerations and velocities, and additionally a portable SM system. GPS and SM data were recorded simultaneously to compare direct vs. indirect determination of EC. The match was separated into four quarters to acquire an accurate analysis. Data was analyzed by means of a paired t-test and Pearsons chi-squared test. EC determined by the mathematical approach underestimated directly determined EC by approximately 25% and was significantly lower compared to the directly determined EC (1030±287 vs. 779±171 kcal, 2p<0.05 for directly measured and calculated EC, respectively). The correlation between the calculated and directly measured EC was highly significant for the total game (R =0.88), the two halves (R1st =0.85, R2nd =0.96), and the last two quarters (R3rd =0.97, R4th =0.91) (2p <0.01). Data showed that the determination of EC of a soccer match based on acceleration and velocity data using a new mathematical approach seems to be possible and valid however the results still underestimate the real energy costs. Correction factors are required for an even better approximation to the real EC, including corrections for movements with the ball, passing the ball, shots, jumps, and taking into account different ground conditions. Further studies will result in nearly exact estimation of EC of soccer matches and will help to optimize training loads.
Metaboreflex and perfoamnce in elite female soccer – effects of inspiratory muscle training
Authors: Archiza, B., Andaku, D.K., Caruso, F.R., Ricci, P.A., Bonjorno Jr, J.C., Oliveira, C.R., Phillips, S.A., Arena, R., Borghi-Silva, A.
Summary: Inspiratory muscle training (IMT) is an established way to improve strength (S) and endurance (E) of inspiratory muscles. It has been extensively studied and used as an important tool in sports performance, mainly for those aerobic in nature. The objectives of this study are to test the effects on metaboreflex and exercise performance in a professional athlete cohort. Eighteen professional female soccer players were recruited and underwent a cardiopulmonary exercise test. Subjects were randomized to placebo (PG) and IMT (IMTG) groups. Subsequently, they underwent tests of lung function, S and E of inspiratory muscles, constant high-load exercise testing (CLET) and repeated-shuttle-sprint ability test (RSSA). Near-infrared spectroscopy assessed oxygenation ([oxyHb] and [tHb]) of respiratory (intercostals) and peripheral (vastus lateralis) muscles during CLET and blood samples were taken to analyze lactate concentration ([L]). After 6-weeks of IMT [30 inspiratory efforts, twice/day, 5 days/week, IMTG training at 50% of maximal inspiratory pressure with load adjustments every week], subjects were reevaluated. There were significant improvements observed in the IMTG following IMT: 1) gain of inspiratory muscles S (19.45 ± 10.91 %) and E (53.06 ± 32.51 %); 2) greater exercise tolerance (P<0.05) and reduced [L] over time (P<0.05) in CLET; 3) [oxyHb] of intercostals muscles was higher (from -8.66 ± 4.96 to -1.94 ± 8.50 umol/cm) while [tHb] was also higher in the vastus lateralis (from 2.21 ± 5.60 to 5.56 ± 7.21 umol/cm), and; 4) soccer performance inferred by RSSA was better after IMT (P<0.05). Recent evidence shows that IMT could affect lactate recovery, indicating that respiratory muscles are capable of lactate clearance, reducing [H+] and metabolites (Brown et al., 2009). This could explain the increased exercise tolerance and improved athletic performance (Nicks et al. 2009). Likewise, blunted metaboreflex’ responses were observed post-IMT only in the IMTG, indicating an increase of [oxyHb] and [tHb] in respiratory and peripheral muscles, respectively, in accordance with previous study (Witt et al., 2007). We conclude that IMT is an important and effective strategy to enhance exercise performance in professional women soccer players.
Development of physical and sports specific performance of youth soccer players for the period of one season.
Authors: Hofer, C., Wirth, K., Haller, A.
Summary: The purpose of this study is to reveal possible developments between two performance groups within the same team for the period of one season. It has already been shown that jumping and sprinting abilities can be increased through strength training interventions (Wirth et al., 2011). The aim of this study is to disclose how one different training session influences sports motoric and soccer specific performance parameters although training and match volume keeps the same. The subjects (n=15; age= 9.17 ? 0,28; sex= 14 m, 1 w) played all for the same team, but participated in different training sessions (2 groups). Once a week the training of the high performance group members was replaced by a session at a performance centre (LAZ) and they were selected by talent scouts of the Austrian Football Association (OEFB). Performance parameters were analysed for Drop Jumps (DJ) from various heights (16,24 and 32 cm), Squat Jumps (SJ), Countermovement Jumps (CMJ), Sprints (10 and 30 Meters), a soccer specific version of the Illinois Agility Tests (IA) and for the Loughborough soccer passing test (LSPT) over 12 weeks (autumn season). Data was analysed with a two-way analysis of variance (ANOVA) with post hoc Test Bonferroni by using the statistics software SPSS (Version 20.0). The study indicated a significant (p<0.05) decrease in sprint performance of both groups over 10 and 30 meters. Regarding repeated measurement factors no interactions for any parameter between the groups has been found over the period of the season. Due to no significant varying development of both groups, the one different training session of the high performance group has no influence on the development of the measured performance parameters. Regarding declining sprint times, environmental influences like variable temperature, minimal discrepancies of the light barrier system positioning or the possible error created by the design of the light barrier system (one sensor system) can not be ruled out.
Physical and technical performance of elite youth soccer players during international tournaments: Influence of opponent quality and team success
Authors: Varley, M., Gregson, W., McMillan, K., Bonnano, D., Stafford, K., Modonutti, M., Di Salvo, V.
Summary: This study investigated the positional differences in physical performance of elite youth footballers across two international club tournaments and the influence of team success and opponent quality on team physical and technical performance. Match performance observations were collected using a semi-automated multi-camera tracking system across two elite under-17 international club tournaments from all players and teams (n=1,457 individual cases). To investigate if the exclusion of substituted players influenced the physical performance profile, data of only players who completed a full game and data of all players were analysed in relative (m.min-1) terms. Teams were classified based on their final tournament rank as top (1-4 rank), middle (5-8 rank) and bottom (9-12 rank). Technical performance measures were expressed in absolute terms and relative to the time the team was in possession of the ball. Positional differences in physical performance and the influence of team success and opponent quality on team match performance were identified using a generalized linear mixed model. Positional differences were similar to that observed in elite senior players. Full game players experienced a clear reduction in relative very-high speed running distance in the 2nd half, however when all players were analysed there were no clear reductions. Top ranked teams performed a greater number of absolute and relative shots and shots on target than bottom teams (Effect Size = 0.67 to 0.82). Passing and organising variables had unclear effects between team rankings. Top ranking teams performed a greater number of relative tackles than bottom and middle teams (ES; 0.44 to 0.70). When playing against top ranking opponents the number of absolute shots and shots on target, shot conversion and passing accuracy were lowest compared to playing against middle and bottom opponents (ES; -0.86 to -0.31). Discussion: In an elite youth tournament setting, opponent quality has a greater influence on match performance than team success. Practitioners should account for these contextual factors when analysing match performance data to assist in their match preparation. Finally, match analysis should include full game players and all players to avoid to understand the influence of substitutes on team physical performance.
Neuromuscular, biochemical, performance and perceptual responses following a self-paced soccer match simulation
Authors: Tofari, P., Kemp, J., Cormack, S.
Summary: A soccer match is characterised by high-intensity, intermittent running, including directional changes, rapid accelerations and decelerations, resulting in both biological and psychological disturbance. Match simulations used to assess responses in a controlled environment lack ecologically validity due to external pacing. Recently, an ecologically valid and reliable self-paced protocol has been developed using a non-motorised treadmill (NMT). The aim was to assess the neuromuscular, biochemical, performance and perceptual responses to that protocol. Twelve male team-sport athletes (24.5±3.9 y, 76.8±5.1 kg, VO2peak 52.3±4.0 ml•kg-1•min-1) performed a self- paced 90-min match simulation on a NMT. Match running performance and the following variables were collected Pre-, Half-time (except blood), Post-, 2-h post-, and 1-4 days post-match: - Quadriceps function via a maximal voluntary contraction and magnetic stimulation assessing central (voluntary activation) and peripheral (potentiated twitch torque) fatigue. - Endocrine response (testosterone and cortisol), oxidative stress (uric acid) and muscle damage [creatine kinase (CK)] - Countermovement jump, squat jump (SJ) and isometric mid-thigh pull (IMTP) performance. - Rating of perceived exertion and self-report wellness questionnaire. Statistical analysis included magnitude of change calculations between time points compared to pre-match using effect size statistics (±90% CL) and regression analysis. Participants covered 12445.8±768.7m at 87.1±3.2% maximal HR, similar to actual match observations. Central and peripheral fatigue was evident at Half-time (-0.38±0.46 and -0.79±0.30, respectively) and persisted post-match. SJ height was reduced at Half-time (-0.42±0.31) and persisted until Day 4. Perceptual fatigue and soreness peaked at Day 1 (-0.92±0.88 and -1.49±0.76, respectively), as did CK (123.4±70.8%). Significant relationships arose between numerous variables, including high speed running and soreness (r=0.65), very high speed running and potentiated twitch torque (r=-0.78) and IMTP F.kg-1 Pre with change in CK (r=-0.58 to -0.81). The current protocol allowed detection of central and peripheral fatigue at half time, which has not been previously reported, and this magnitude of change was not increased post-match. Similar to previous work, there was disturbance to numerous systems, generally returning to baseline in 3 days. Relationships exist between activity profile and perceptual and neuromuscular variables, and higher maximal lower-body strength resulted in less muscle damage post-match. The findings warrant further investigation into the role of central and peripheral fatigue in regulating second half performance and potential interventions to minimise any negative impacts.
Resistance training status and effectiveness of low frequency resistance training on upper-body strength and power in soccer players
Authors: Hertzog, M., Rumpf, M.C., Hader, K.
Summary: Soccer is classified as a contact/collision sport with many player-to-player duels. Winning these duels, shielding the ball or fending off an opponent requires upper-body strength and power. Therefore, the purpose of the study was, a) to examine upper-body strength and power changes in elite soccer players with different resistance-training (RT) status, b) to investigate if the RT status influences performances throughout an entire competitive season. Twenty-eight elite young male soccer players (age 18 ± 1 years, height 178 ± 5 cm, body mass 71 ± 7 kg) participated in this study and were divided into a trained (TG; n=14) and a novice (NG; n=14) group, according to their RT status (Rhea et al., 2003). Both groups performed the same upper-body RT once a week besides the soccer-specific team training over 30 weeks. Maximal strength was assessed via one repetition maximum (1RM) for bench press (BP) and bench row (BR) before (T1), after 10 weeks (T2) and the competitive season (T3). Maximal power (MP) was assessed in the BP exercise only. Results At T1, TG presented significant and moderately greater 1RM in BP (+9.9 ± 10.2%; effect size, ES=1.0) and MP (+14.0 ± 13.1%; ES=1.1) than NG. There was no between-groups difference in 1RM for BR. At T2 and T3, both groups showed significant improvements in the 1RM. The magnitude of changes was small (TG; +5.9 ± 2.6%; ES=0.3-0.4) and large (NG; +11.7 ± 3.2%; ES=0.9-1.3) at T2 and increased to moderate (TG; +13.4 ± 3.1%; ES=0.7-0.9) and very large (NG, +20.6 ± 3.8%; ES=1.8-2.1) at T3. There is no change in MP at T2 and moderate improvement at T3 (+13.0 ± 5.8%; ES=1.1) for NG. TG presented a significantly small decrement at T2 (-11.6 ± 3.9%; ES=0.4) and small improvement at T3 (+7.7 ± 4.9%; ES=0.3). At T2 and T3, there was no between-groups difference in 1RM while MP remained moderately greater for TG. The players with less RT experience presented a greater rate of improvement in maximal strength after 10 weeks only (Kraemer et al., 2004), notwithstanding a low RT frequency; while maximal power was not affected positively over the same time. One RT session per week is considered as an effective frequency for muscular strength and power maintenance (ACSM, 2009), however our results show that RT throughout a competitive season may elicit substantial improvement in upper-body maximal strength and power regardless of players’ RT status.
Isokinetic strength qualities that differentiate rapid deceleration performance in academy male youth soccer players
Authors: Harper, D.J., Jordan, A., Wilkie, B., Liefeith, A., Metcalfe, J., Thomas, A., Kiely, J.
Summary: Decelerating (DEC) is just as frequent as accelerating in contemporary soccer match play (Russell et al., 2014). Recent evidence suggests that lower body eccentric strength directly improves the ability of a player to produce and tolerate braking forces (Spiteri et al., 2014). The aim of the present study was to identify if measures of isokinetic strength can differentiate performance of a rapid DEC maneuver. Nineteen (n=19) academy youth soccer players (age: 16.7+1yrs; height: 175+8.4cm; body mass: 69.1+7.5kg; body fat: 9.5+3.9%) participated in the study. Tests included: isokinetic dynamometer (Cybex International Inc., New York, USA) strength profiling of quadricep (Q) and hamstring (H) peak concentric (con) and eccentric (ecc) torque (both dominant [kicking leg] and non-dominant legs) assessed at slow (60°/s) and fast (180°/s) angular velocities. Functional H:Q ratios representative of knee flexion (Hcon:Qecc) and extension (Hecc:Qcon) was also calculated; 30m linear sprint time (with 5m, 10m and 20m splits) was recorded using a single beam timing system (Witty, Microgate, Italy) and rapid DEC quantified using time to stop (TTS) and distance to stop (DTS) determined following a 20m maximal acceleration (within 5% threshold of best 20m linear sprint time) using video analysis (Dartfish, Fribourg, Switzerland) captured from a 50Hz video camera (Panasonic HDC-HS900, Japan). 10, 20 and 30m sprint times had moderate to large correlations with fast con peak Q and H torque. Slow velocity con peak H torque in dom leg had moderate to large correlations with 10, 20 and 30m sprint times. No significant correlations were found for peak con strength in either Q or H for DEC performance (TTS and DTS). Slow velocity ecc peak Q torque and time to peak torque was significantly correlated to DEC TTS. No significant correlations were found for fast ecc strength parameters in Q or H for either sprint or DEC performance. Sprint and DEC performance had no significant correlations. Players with superior sprint speed can produce high peak con forces in both Q and H at fast velocities. DEC seems to be a unique movement skill requiring specific ecc strength qualities. Interestingly, in this study slow velocity ecc strength of the Q seems to be critical for production of braking forces and reducing the time spent DEC. In conclusion this study highlights the need for careful consideration to developing specific strength qualities needed for DEC alongside those more commonly known for sprinting and accelerating.
The relationship between pre-season workload indicators and changes in the Yo-Yo intermittent recovery test in professional soccer
Authors: Jaspers, A., Brink, M.S., Frencken, W., Helsen, W.F.
Summary: In pre-season, a main objective is to develop aerobic fitness to prepare for the competitive season. Workload monitoring can aid in maximizing training adaptations. However, it remains unclear which workload indicators best relate to changes in fitness in professional soccer . Therefore, the aim was to examine the association between workload indicators and changes in the Yo-Yo intermittent recovery test. During the first 2 weeks of pre-season, both external (total distance, distance covered in velocity zones (15-20 km/h, 20-25km/h and >25km/h) and PlayerLoadTM) and internal (sRPE multiplied by duration) training and match load were collected in 15 professional soccer players (mean age ± SD: 22,2 ± 3,6 years). A submaximal Yo-Yo intermittent recovery test level 1 (sYYIRT1; a duration of 8 minutes and 58 seconds, up to 8 repetitions at 15 km/h) was performed at baseline and 2 weeks thereafter. Cumulative workloads over 2 weeks as well as in the week preceding the second sYYIRT1 were related to relative changes in average heart rate over the last 60 second (HRex) of sYYIRT1. Pearson correlations were used to assess relations. A significant lower average heart rate (p < 0.01) was observed during the second sYYIRT1 (167,9 ± 7,7 beats/min) compared to the first test (179,8 ± 8,2 beats/min). More distance covered in velocity zone 15-20 km/h in the week preceding the second sYYIRT1 was related to a negative percentage change in HRex (r = -0.64, p < 0.05). Other indicators were not significantly related to changes in HRex. Distance covered in velocity zone 15-20 km/h in the week preceding the second sYYIRT1 is related to improvements in fitness during pre-season. The Yo-Yo test performance is positively related to distance covered above 15 km/h in professional matches . A similar type of workload (15-20 km/h) in turn appears to result in a beneficial stimulus for the physical capacity in intermittent exercise. Careful planning of distance covered in the 15-20km/h velocity zone should be considered to optimize training regimes during pre-season.
Time-motion analysis in elite soccer players: small-sided games vs. match performance
Authors: Riboli, A., Rampichini, S., Limonta, E., Cè, E., Venturelli, M., Esposito, F.
Summary: Video-analysis and global positioning system (GPS) are used to determine players’ loads and drills during soccer activities. Small-sided games (SSGs) are generally utilized as skill-based conditioning drills, the workload intensity of which is a crucial feature. The aim of the study was to compare the equivalent distance (ED, i.e., the distance that a given player would have run, given the actually measured overall energy expenditure, had he been running at constant speed throughout the whole match) (di Prampero et al., 2015) determined during SSG in different pitch dimension with average ED during official matches (EDmatch). For this approach, the interchangeability of video analysis and GPS during SSGs is a crucial issue and was also assessed (Buchheit et al., 2014). Twenty-five elite soccer players (Italian Serie A) performed a total of 1033 and 1532 observations for collective possession plays (SSG-P) and SSGs with goalkeeper (SSG-G), respectively. SSGs were evaluated by GPS (10 Hz; accelerometer: 100 Hz, 16G Tri-Axis). For each player, a median of 39±14 SSG-P (mean ± SD) and 57±17 SSG-G were examined on different pitch dimensions. Each drill was normalized per meter covered in one minute (m·min-1) and area per player (m2⋅player). In addition, thirty-nine official matches (18±9 observations per player) were monitored by semi-automatic multiple cameras. Lastly, a typical training session with SSGs was monitored with both GPS and video-analysis to assess the interchangeability of the two methodologies. A small typical error of the estimate (TEE: 0.07, 95% confidence intervals: 0.04/0.13) and a higher correlation (r2=0.99, P<0.001) were found between ED calculated from GPS and video-analysis. A correlation (r2=0.788, P<0.001) between ED and area per player was found only for SSG-P. The regression line in SSG-P crossed EDmatch at an average area of 95±8 m2⋅player with a smaller dimension (36±1 m2⋅player) for central defenders (CD) than other roles (P<0.05). A small TEE and a higher correlation permitted a comparison between GPS and video-analysis with these technologies. Due to a lower tactical and higher physical involvement than in SSG-G, ED increased with area per player and induced average EDmatch only during SSG-P, with a less area per player in CD. These findings may contribute to better assess workloads using SSG-P with respect to match intensity for each role.
Criterion validity of the Loughborough soccer passingtest in elite youth soccer
Authors: Serpiello, F.R., Cox, A., Oppici, L., Hopkins, W.G., Varley, M.C.
Summary: Successful passing is a key component of skilled performance in football, particularly for elite youth players. Owing to the difficulty of assessing passing performance in a controlled environment in games, field tests have been developed to isolate the measurement of this skill. The Loughborough Soccer Passing Test (LSPT) is commonly used to assess passing performance under time pressure. The test is reliable and displays discriminant validity in youth soccer. Here we report its criterion validity with such athletes. Twenty-five players from the U18 state representative team (age 15.1 ± 0.6) performed the LSPT. The first eight games of the season were then recorded and coded for passing ability using a custom-made coding window from commercially-available software (SportsCode, Hudl). Data were coded according to two scenarios. The first reflected overall success rate for all passes within a game. The second scenario represented a high-quality passing situation and passes were included only when they met all the following criteria: the player had performed ≤3 touches before the pass, the pass lead to a scoring opportunity or forward movement of a team-mate, the pass occurred across halves or in the opponent’s half, and pass direction was forward or sideways. Inter-rater agreement was assessed for overall passing success rate using Cohen’s kappa. Criterion validity of the LSPT scores was assessed as the correlation between the players’ mean passing score and their LSPT score. The validity correlation coefficient was then adjusted to take into account the error of the criterion using the intraclass correlation coefficient (ICC) for the mean passing score in 8 games. Inter-rater agreement kappa was 1.00. The ICC for 8-game reliability was 0.67 for overall passing success and 0.75 for the high-quality situation. Overall validity of the LSPT compared to the criterion was very poor for both time-only LSPT (corrected r=0.59) and LSPT total time (corrected r=0.58). Validity of the LSPT compared to the criterion in the high-quality passing scenario was impractical for both time-only LSPT (corrected r=0.32) and LSPT total time (corrected r=0.18). This study demonstrated for the first time that the LSPT does not have criterion validity in Australian elite youth football. Despite the strong reliability and discriminant validity, attention must be paid to the interpretation of the test result, as it does not accurately represent in-game passing performance.
Relative acceleration as a new indicator of game intensity in soccer
Authors: Sonderegger, K., Rumo, M., Tschopp, M.
Summary: Intensity in team sports has been commonly measured on the basis of distances covered in different speed zones. It was recently noted that the problem with this approach is that short acceleration does not contribute to game intensity because the required speed is not achieved. Relative acceleration accounts for these short-term actions and may be therefore a more valid indicator of game intensity. During 14 official games, 90 positional datasets were collected from 69 elite junior players (mean age, 17.0 ± 0.6 y) of the highest and 91 datasets from 69 sub-elite junior players (mean age, 17.9 ± 0.9 y) of the second highest national U18 championship levels, using the Local Position Measurement System. Based on the raw acceleration and speed data, each acceleration peak was identified as a single action. For each action, the relative acceleration was calculated as a ratio between the acceleration of the action and the maximum possible acceleration, dependent of the initial running speed, which was determined in a sprint test conducted prior to the games. All actions were classified into four intensities based on the relative acceleration and the initial running speed. The number of high-, moderate-, low-, and very low-intensity actions were then compared with commonly used speed zones (high-speed running [HSR] > 19.8 km∙h-1 and sprinting [S] > 25 km∙h-1). Differences between the two performance levels were determined by calculating the effect sizes (ES). Elite junior players had more of high- (84 vs 66), moderate- (90 vs 82), and low- (183 vs 176) intensity actions. The difference is larger in high- (ES, 0.91) than in moderate- (0.48) and low- (0.28) intensity actions. The number of high-intensity actions yields a larger ES than the commonly used indicators of game intensity such as distances covered in high-speed zones (HSR: 522 vs 431 m; ES, 0.50; S: 111 vs 76 m; ES, 0.51). Comparison between the elite and sub-elite players for specific positions yielded a larger ES when number of high-intensity actions rather than common speed zones were used, except for fullbacks (central midfield: ES of 1.38 vs 0.52 [HSR]/0.09 [S]; centre back: ES of 0.68 vs 0.48/0.31; forward: ES of 1.47 vs 0.52/-0.03; wide midfield: 0.64 vs -0.89/0.28; fullbacks: ES of 0.87 vs 1.22/1.88). The differences in game intensity between elite and sub-elite junior soccer players is larger when expressed by number of high-intensity actions calculated with relative acceleration than by commonly used speed zones. The difference can be explained by the fact that using relative acceleration to determine intensity results in taking high accelerations from low initial running speeds as well as lower accelerations from high initial speeds into account. Therefore, the new indicator proposed here removes the bias introduced by the commonly used speed zones.
COGNIFOOT - Assessing the cognitive-motor performance of soccer players: objective measurements vs coaches’ evaluation
Authors: Taube, W., Chassot, S., Cheneviere, X., Hicheur, H.
Summary: The cognitive-motor performance, defined here as the capacity to rapidly use sensory information and transfer it into efficient motor output, represents a major contributor to performance in almost all sports, involving soccer. The difficulty is to assess this complex cognitive-motor performance in a standardized and quantitative manner while preserving the ecological validity of the tested tasks. For this purpose, we used a high-technology system (COGNIFOOT, patent pending) which combines a visual environment simulator fully synchronized with a motion capture system. With this device, objective real-time measurements of several parameters such as response time and kicking accuracy were done in a large (10 x 8 meters – length x width) turf-artificial grass playfield on which players could execute real soccer skills. Fourty-six (46) young elite soccer players aged between 11 and 16 years who all belonged to the U12-U13-U14-U15-U16 categories of the same youth soccer academy were tested. Each player had to shoot the ball as fast and as accurately as possible towards a 0.2 meters-diameter visual target projected onto a large screen (4 x 3 meters – width x height) located 5 meters in front of him/her (a short pass situation). The response times were computed as the delay between the appearance of the visual stimulus and the initial movement of the ball, thus, including a motor preparation phase. The response times were found to decrease with increasing age of the players (on average from 1100 ms to 1020 ms for the U12 and U15-U16 categories, respectively) while the kicking accuracy increased linearly with age indicated by smaller spatial errors (from 45 to 29 cm for the U12 and U15-U16 categories). These data were converted into 5 point-scales in order to compare them with the judgement of the coaches, who also used a 5 point-scale to evaluate the reactiveness and the kicking accuracy of their players, respectively. The global cognitive-motor performance indices computed from these two types of evaluations were highly correlated when considering every single age category. However, coaches’ more subjective evaluations across age groups were not consistent and failed to detect the age effect measured via the COGNIFOOT system. The functional implications of these findings for talents identification will be discussed together with the potential interest of this new type of sport technology for testing/training the cognitive-motor performance.
Age related effects on Yo-Yo test performance and heart rate analysis on Turkish soccer referees
Authors: Kızılet Bozdogan, T., Kızılet, A., Erol, M.
Summary: Referees are responsible apply the rules for such as played on lounge area and sport large areas and while maintaining the compliance with the rules of players. Moreover, during the match play for the success of the referee, they must maintain competences to meet the physical and physiological demands and the competence to make decisions under intense pace for high level (Helsen and Bultynck ,2004). Also elite soccer referees, because of their careers later in life manage more high level match, it is more important that their physical and physiological competence. In several studies (Castagna, et al.,2005) regarding of game action profile of football referees and physiological effect on the evaluation of the game, ıt is reported that the referees are done an average of 2200 meters high intensity running in a match. This results are explained that the importance of running distance on YO-YO IRL1 test performance during to their all career and also it reveals the importance of performing at a high level until the end of the their years (Weston, et al.2010). The aim of this study was to investigate the effect of ageing on fitness performance on elite-level soccer referees. 131 elite level and national soccer referees (age range 27–45 years) are participated in study. All referees are performed YO-YO IRL1 (Yo-Yo Intermitent Test Recovery Level 1) (Bangsbo, et al.,2008). All polar datas are recorded every each 1 seconds ( HRload, MaxHR, Mean HR and After 1 minute recovery) ( polar team system, Polar eloctro, Finland). Data are presented as mean and SD. Comparisons between more than 2 means were performed using one-way analysis of variance. Post hoc testing was carried out using Tukey’s test. Relations between variables of interest were detected using Pearson’s correlation coefficient (r) (p <0.05). Advancing age, it is seen that all physical and physiological results are development. İt is reported that there is statistically significant difference in HRmax and HRmean (p=0.00), but there is no statistically significant difference HRload (p= .874) and after 1 minute recovery heart rate ( p= .541). (p<0.05). On YO-YO IRL1 test running distance is better on elderly referees than young, average ve old referees but it is not seen statistically significant difference (p=.88). According to correlation analysis, there is negative correlation between body fat and YO-YO IRL1 test (r= -341) (p<0,05). Physiological values are better when they are advancing age. So it reveals that the importance of involve in systematic training program when they are younger. Thus, aerobic and anaerobic be able to meet demands for a match at a younger age.
Diagnostic of the high-energy system in female soccer
Authors: Wördehoff, A., Meinerz, S., Heine, O., Knigge, H.
Summary: Despite of several diagnostic tools in sport, test results do not determine team line-up. There are obviously factors influencing match performance that cannot be measured yet. Nevertheless, diagnostics are essential for systematic training and its evaluation. In female soccer, a lack of money is responsible for insuffiecient testing. A sprint test with changes in direction is a typical test for team sport attendees and does not require an expensive setup. The aim of the current study was to modify a common sprint test setup by adding information about the speed profile. This could allow assumptions about the demands on the energy system and lower limb strenght. 26 female soccer players (playing in second or third German league) participated voluntarily in this study. As pretests, a field level test protocoll, a treadmill ramp test protocoll and a Counter-Movement-Jump (CMJ) were conducted. After a warm-up the participants performed an 80 m sprint with two changes in direction of 180 degrees. A LAVEG laser gun was used to gauge the speed profile and the alactice time was determined based on the model of Heck and Schulz (2002). Further parameters measured were heart rate, blood lactate concentration, maximal velocity and interims of the sprint. The analysis showed a correlation between the interims of the sprint and the generated W/kg in the CMJ. A linear regression showed that at least 30 % of the variance of the sprint interims could be explained by the generated W/kg. In addition large differences between the alactic time could be observed. The influence of the physical precondition seems to play a significant role concerning the sprint performance. Adapting a common sprint test protocol could easily help diagnosticians to get more information at lower expenses. Future research may enable scientists to identify different types of athletes concerning especially the use of the energy system. Therefore they could provide more appropriate training recommendations for coaches.
Sequencing effects of balance and plyometric training on physical performance in youth soccer athletes.
Authors: Chaouachi, A., Hammami, R., Granacher, U., Behm, D.G.
Summary: While there seems to be an advantage for including balance exercises within strength or power training programs (Chaouachi et al. 2014), it is not known whether the sequencing of balance and plyometric training has additional training benefits in youth. The objective was to examine the effect of sequencing balance and plyometric training on the performance of 12-13-years-old athletes. Based on a similar study (balance and strength) conducted with young adults (Bruhn 2006), it was hypothesized that balance training prior to plyometric training would provide greater gains in balance, power, sprint and agility performance. Twenty-four young elite soccer players trained twice per week for eight weeks either with an initial four weeks of balance training followed by four weeks of plyometric training (BPT) or four weeks of plyometric training proceeded by four weeks of balance training (PBT). Testing was conducted pre- and post-training and included medicine ball throw, horizontal and vertical jumps, reactive strength, and leg stiffness, agility, 10, 20, 30-m sprints, Standing Stork-balance and Y-Balance-Test. Results indicated that BPT provided significantly greater improvements with reactive strength index, absolute and relative leg stiffness, triple hop test and a trend for the Y balance test (p=0.054) compared to PBT. While all other measures had similar changes for both groups, the average relative improvement for the BPT was 22.4% (d=1.5) versus 15% (d=1.1) for the PBT. BPT effect sizes were greater with 8 of 13 measures. Behm et al. (2008) recommended that balance training should precede plyometric training since balance and coordination are immature in children, and balance is essential for optimal performance and the prevention of athletic injuries. Bruhn et al. (2006) suggested that in young-adults, balance training could have a preconditioning effect on subsequent resistance training. The present study provides experimental data corroborating this recommendation. Since the adolescent growth-spurt can adversely affect balance, coordination, and movement patterns, initially implementing balance training can improve anticipatory postural adjustments and motor coordination, possibly decreasing the likelihood of injuries from unstable landings and positions. Based on the present findings, it would be more effective for coaches and fitness conditioning professionals to institute at least four-weeks of initial balance-training prior to plyometric training for their youth-athletes. The balance training should progress from less demanding stationary activities to more complex dynamic balance activities. Such a program should enhance the subsequent plyometric training adaptations.
Warm-ups work! Examining the time-course of changes in muscle temperature and contractile function following the pre-match warm-up in soccer and the use of passive heating
Authors: Marshall, P.W.M., Cross, R., Lovell, R.
Summary: We were interested in examining the time-course of changes in quadriceps muscle contractile function and voluntary drive around a soccer specific warm-up, and how any changes contributed to measures of rate of force development as an experimental measure of muscle power. Moreover, considering the links between muscle temperature (Tm) and mechanisms of power output, we examined the effect of a ‘cool-down’ period commensurate with that observed in the EPL prior to match-play on measures used. Finally, we tested whether a passive heating garment applied after the warm-up would have any effect on measures we performed. Ten amateur soccer players performed two experimental sessions that involved performance of a modified FIFA 11+ soccer specific warm-up, followed by a 12.5 minute rest period where participants were required to either wear normal clothing or a passive electrical heating garment was applied to the upper thigh muscles. Assessments around the warm-up and cool down included measures of maximal torque, rate of torque development, vastus lateralis muscle temperature (measured at a depth of 4cm), and electrically evoked measures of quadriceps contractile function and voluntary activation (10Hz and 100Hz doublet stimulation of the femoral nerve). Tm was increased after the warm-up by 3.2 ± 0.7 °C (p<0.001). Voluntary and evoked rates of torque development increased after the warm-up between 20 to 30% (p<0.05), despite declines in both maximal voluntary torque and voluntary activation (p<0.05). Application of a passive heating garment in the cool-down period after the warm-up did not effect variables measured. While Tm was reduced by 1.4 ± 0.4°C after the rest period (p<0.001), this value was still higher than pre warm-up levels. Voluntary and evoked rate of torque development remained elevated from pre warm-up levels at the end of the cool-down (p<0.05). The soccer specific warm-up elevated muscle temperature by 3.2°C and was associated with concomitant increases of between 20 to 30% in voluntary rate of torque development, which seems explained by elevations in rate dependent measures of intrinsic muscle contractile function. Application of a passive heating garment did not attenuate declines in muscle temperature during a 12.5-minute rest period.
An evaluation of resistance training programmes in an elite soccer academy and it’s effects on the development of isometric strength
Authors: Brownlee, T., O’Boyle, A., Morgans, R., Morton, J., Erskine, R., Drust, B.
Summary: Muscular strength is a desirable attribute in soccer players of all ages. The aim of this study was to evaluate the training completed by English Premier League soccer players in an academy over an 8-week period and to determine whether such training increased isometric strength compared to a control group. Training for 184 elite soccer players from under 9 (U9) to under 21 (U21) was recorded over an 8-wk period. Data was examined to establish distribution of training time in soccer training, matches, non-resistance training athletic development activities and resistance training. From that group 155 elite and 93 control participants completed two isometric mid-thigh pull tests 8-wks apart. Isometric strength was expressed as both absolute and allometrically scaled (force * body mass 0.66). Total training time progressively increased between the U9 (268 ± 25 min/wk) and U14 (477 ± 19 min/wk) age groups with only a small proportion of training time (3 ± 18%) consisting of training focussed on solely improving physical attributes. Total training time was then subsequently reduced from the U14 to the U15 (266 ± 77 min/wk) age groups, with no differences in training duration for any groups between U15 and U21 (P > 0.05). When the U15 to U21 squads (the only players who completed resistance training) were compared no difference in session duration was observed (P > 0.05). No main effect for peak isometric force (PF) between elite (1617.10 ± 611.15 N) and control (1535.69 ± 624.83 N) groups was present (P = 0.087). For allometrically scaled force (RF) a main effect was noted with the elite cohort (118.29 ± 21.96 N) being stronger than controls (109.69 ± 27.91 N) though no interaction between group and maturity status was observed (P = 0.167). Following 8 weeks of training no changes were seen in either group for PF (at 8 wk elite group 1580.12 ± 632.55 N; control group 1496.38 ± 555.51 N) or RF (elite group at 8 wk, 119.12 ± 23.43 N; control group at 8 wk, 110.89 ± 25.75 N) (P > 0.05). These data examine training practices and isometric strength throughout an English Premier League soccer academy compared with a matched control group. They suggest that training practices evaluated here do not elicit increases in isometric strength. This is likely a result of the focus of training time on technical development. This data can provide practitioners with baseline isometric strength data and training data for comparisons across teams.
The development of standardized protocol for monitoring heart rate recovery in soccer players
Authors: Orme, P, Anderson, L., Morgans, R., Morton, J.P., Drust, B.
Summary: Physiological monitoring during the recovery process following elite soccer performance has been an area of considerable interest over recent years. The aim of this study was to develop a standardised exercise protocol for use in the calculation of heart rate recovery (HRR) that can be integrated into a training strategy used by an elite team. Furthermore, this study attempted to evaluate the reliability of the HR response to the protocol as well as compare the protocol to specific physical loads completed during the recovery period following soccer match play. Three exercise protocols (1-6x60m 6ms 10:20s; 2-6x80m 5ms 16:14s; 3-6x60m 5ms 12:8s) were tested for reliability of HR response and suitability with regards to soccer training loads. Nine male competitive soccer players (Mean±SD: age 17±0.6 years, height 1.7±0.9m, body mass: 63±9.0kg) took part in the study. All subjects completed one trail of each protocol on each of 5 data collection days (3 familiarisation trials and 2 testing sessions). Trials completed on each data collection day were separated by 30 min of seated rest. HR and GPS data was collected throughout all trials (duration, total distance, peak speed, %MAXHR, HRR at 1 min post exercise). Data were analysed using standard error of measurement (SEM) and coefficient of variation (CV) for reliability assessment and by the use of paired t-tests to compare the physical loads completed in the protocol and by players during actual recovery training sessions. There were no significant differences (P<0.05) between previous soccer recovery activities completed in training (duration– 3min, distance– 399m, peak speed– 4.7ms, %MAXHR– 74%) and the exercise protocols developed in this study (duration– 4min, distance– 406m, peak speed- 5.3ms, %MAXHR– 86%). All protocols elicited a %MAXHR above 80% (protocol 1–82.5%, protocol 2–85.5%, protocol 3–89.5%). CV and SEM were lower for both HRR and %MAXHR for protocol 2 (HRR CV=9.95%, HRR SEM=2.14% - %MAXHR CV=2.57%, %MAXHR SEM=2.19%) compared with protocol 1 (HRR CV=21.99%, HRR SEM=5.74% - %MAXHR CV=4.08%, %MAXHR SEM=3.36%) and 3 (HRR CV=40.41%, HRR SEM=10.41% - %MAXHR CV=2.62%, %MAXHR SEM=2.33%). This study developed a protocol (6x80m 5ms, 16:14s) that is suitable for use as a real world monitoring tool during the recovery period following soccer match play. The developed protocol presented CV and SEM data to suggest that this protocol is suitable for use to detect changes in the HR response.
The Effect of Static Stretching on Muscle Recovery Following Competitive Soccer Matches
Authors: Pooley, S., Spendiff, O., Allen, M., Moir, H.
Summary: Static stretching (SS) is a recovery intervention often used in elite football for assisting in the reduction of muscle soreness post-exercise, and in research as a control for comparing alternative recovery interventions. However, its effects on elite young footballers has received little attention, and therefore the aim of this study was to assess the effects of static stretching on muscle recovery following competitive soccer matches in elite young footballers. Participants used in this study were recruited from a professional football academy from the Premier League. Participants were male (16 ± 1 years) and of elite standard. Using a controlled cross-over design, participants completed a total of 6 competitive soccer matches followed by one of two recovery interventions (static stretching or passive recovery). The recovery interventions were conducted immediately following completion of competitive soccer matches. The static stretching protocol was administered comprising 7, 15 second stretches on lower body muscles whilst the passive recovery protocol comprised 10 minutes passive seating. Assessments used to measure muscle damage were taken before, within 30 minutes after, and 48hours post match and consisted of muscle oedema, Creatine Kinase (CK) assessment, countermovement jump (CMJ) height and perceived muscle soreness. To maintain control, players were excluded from individual games if they failed to complete a minimum of 80% of the competitive soccer match. When comparing the effects of recovery interventions over time, results showed that competitive soccer matches had a significant effect on markers of muscle damage, with almost all indicators showing significant differences for pre and immediately-post competitive match for recovery interventions, with only gastrocnemius oedema assessment showing no significant difference. Additionally, significant differences between pre- and 48 hours post-exercise assessments were found in perceived soreness, CK values and CMJ height. When comparing the effects of recovery interventions between conditions, the only difference observed was between CK which demonstrated improved levels of recovery in the static stretching group at 48 hours following exercise. The findings from this study demonstrate that competitive soccer matches provide strenuous exercise, inducing muscle damage which may have detrimental effects on future performance. This is demonstrated by the reduction in CMJ performance and elevation in CK and muscle soreness at 48 hours post-exercise. Furthermore, there is limited evidence to suggest that a static stretching protocol would assist in the reduction in muscle damage post-exercise, with only CK showing improved effects. The improved effects of static stretching on CK are unclear, however may be linked to the idea that static stretching assists in the removal of muscle oedema following exercise. Additionally, it may be possible that due to the elite standard of participants, they have a heightened level of CK removal post-exercise.
Does mental imagery have positive effect on closed motor skills in tennis, field hockey and soccer?
Authors: Hegazy, K.1,2, Jekauc, D.3,4, Woll, A.1
Summary: Research has shown that preparatory imagery, or using imagery immediately before a performance, can improve performance in strength tasks and muscular endurance tasks (Vealey & Greenleaf, 2006). In addition, combining imagery with relaxation is more effective. Few studies have addressed the efficacy of mental imagery to improve precision on closed motor skills (Coelho et al., 2007; Hegazy, 2012). Therefore, the aim of this study was to analyze the effects of mental training on precision in tennis serve, field hockey hit and soccer penalty kick. The intervention used an experimental design with a pre- and posttest. The experimental groups received both technical practice and mental training units including imagery and relaxation exercises on the court for a total of four weeks. The control groups received only technical practice for the same time period. A total of 156 subjects from Germany and Switzerland, aged between 14 and 35, were divided into 60 in tennis (35 male, 25 female), 54 soccer male and 42 field hockey male and one female all amateur athletes with a high skill level. The dependent variable was measured by a hit ratio of a precision test for tennis serve, field hockey hit and soccer penalty kick. In this test, each player played 20 attempt aimed at a target area. The results of ANOVA with repeated measurements showed a highly significant interaction effect between time and group in tennis (F1, 55 = 22.6; ETA2 = .29) and field hockey (F1, 41 = 19.9; ETA2= .33). However, in soccer the interaction effect was not significant (F1, 52 = 3.71; ETA2 =.67). This improvement of precision, in the intervention group in comparison to the control group, demonstrates the effectiveness of positive imagery on closed motor skills in tennis and field hockey. The effect of the intervention can be seen as large (Cohen’s d > 1.00) in both games. For tennis, the intervention group improved their performance in the precision task by 4.1 hits in 20 trials, whereas, the control group improved only by 1.0 hits. For field hockey, the intervention group improved their performance in the precision task by 2.7 hits in 20 trials, whereas the control group decreased their performance by 0.4 hits in 20 trials. However, in soccer, the difference between the intervention and the control group was not significant.
12-Week Recreational Soccer Training Improved Health Profile of Type 2 Diabetes Patients more than Running and Diet Alone – a Brazilian Study
Authors: Sousa, M., Fukui, R., Krustrup, P., Silva, M.E.R.
Summary: Among Latin America countries, Brazil has the highest number of people with Type 2 Diabetes (T2D) estimated in 12.1% in São Paulo state (Borges et al., 2014). Lifestyle modification has been demonstrated to prevent outcomes, particularly coronary heart disease, and induce remission of early T2D. Therefore, we aimed to investigate the impact of recreational soccer combined with a caloric restricted diet on health profile of untrained Brazilian T2D patients vs. running training. Sixty (n=60) untrained Brazilian T2D patients aged 47-74 years were randomized into a soccer+diet group (SDG; n=19), a running+diet group (RDG; n=19) and a diet group (DG; n=22). Training sessions were held for 40 min, 3 times per week for 12 weeks. Dual-energy X-ray, treadmill testing, and fasting blood samplings were performed before and post 12 weeks. Maximal oxygen uptake increased only in the training groups (P<0.05) while a decrease (P<0.05) was observed in DG after 12 weeks. Systolic blood pressure reduced (P<0.05) only in the SDG from 128.2±3.2 to 124.2±2.2 mmHg after 12 weeks, with no changes in diastolic blood pressure for any of the groups. HBA1c decreased (P<0.05) by ~10% in all groups after 12 weeks. In all groups, bone mineral density increased (P<0.05) by ~0.02 g/cm2, fat mass decreased (P<0.05) by ~ 3 kg, and lean body mass was not altered ~64 kg (P>0.05). For SDG and RDG, respectively, baseline triglycerides, total cholesterol and VLDL-cholesterol were reduced by 24.8% (37.3±1.9 mg/dL), 12.5% (22.2±0.2 mg/dL) and 24.3% (7.3±1.8 mg/dL); 27.9% (50.6±4.4 mg/dL), 10.4% (21.4±0.5 mg/dL) and 28.0% (10.2±0.8 mg/dL). LDL-cholesterol was lowered (P<0.05) only in the SDG by 15.4% (16.4±1.3 mg/dL), while HDL-cholesterol was unaltered (P>0.05) in all groups after 12 weeks. Regarding between-group differences, SDG improved more (p<0.05) in baseline fasting lipids than RDG and DG during the 12-week intervention period. Soccer training lowered systolic blood pressure, which may reflect a better muscle capillarization and vascular structural adaptations (Krustrup et al., 2009). In addition, lower LDL-cholesterol levels suggests greater increased fat oxidation rate post-training (Pachalis et al., 2011) due to the multiple intense actions during soccer training stimulating musculoskeletal and cardiovascular adaptations better than running training. Recreational soccer training plus diet resulted in large benefits on health profile of T2D, and appear to better prevent cardiovascular issues than running plus diet and diet alone.
Examining the association between lower-limb muscle complaints and muscle function in soccer players.
Authors: Wakefield, K.J., Whalan, M.D., Lovell, R., Sampson, J.A.
Summary: Lower-limb power, flexibility and hamstring strength are risk factors for time-loss injury; however, Fuller’s 2006 consensus statement highlights injury as any physical complaint. This study therefore examined the hypothesis that muscle complaints will negatively correlate with lower limb flexibility, power and hamstring strength. 19 semi-professional soccer players (Male, 24 ± 3.1 yrs, 75.5 ± 9.5 Kg, 178.7 ± 6.0 cm) were recruited. Lower-limb power was assessed during 3 counter-movement jumps (Kistler portable force platform, CH-8408 Winterthur, Switzerland). Flexibility assessments of the hamstrings, quadriceps, calves and groin were performed using goniometry. Hamstring strength was assessed via maximum isometric (prone, 30° knee flexion) and isokinetic (prone, 0-135° concentric/eccentric knee flexion 60°/S) dominant limb contractions. Muscle complaints were recorded weekly (frequency), allocated a numerical value from 0-3 (based on reduction of participation) and summed to calculate a severity score (Clarsen et al., 2013). Pearson’s correlations (r2) were performed with significance set at p≤0.05. 174 muscle complaints with a severity score of 190 were recorded. Hamstring complaints (47) were negatively associated with quadriceps flexibility (r2=0.34; p=0.0086). Groin complaints (15; r2=0.43; p=0.0023) and their severity (25; r2=0.32; p=0.0114) were negatively correlated with adductor flexibility. No other relationships were observed. Flexibility measures were most associated to the frequency and severity of muscle complaints. The direct association between groin complaints and poor adductor flexibility is consistent with existing time-loss-groin injury reports (Ekstrand & Gillquist, 1982). Poor quadriceps flexibility has been shown to increase torque on the hamstring muscles during the late swing phase of sprinting, increasing hamstring injury risk (Gabbe et al., 2005). The effect of which could explain the indirect association we observed between hamstring complaints and poor quadriceps flexibility. In contrast to previous work, hamstring muscle strength assessments were not correlated with hamstring complaints. In summary, the results support a groin flexibility screening process to detect and prevent adductor injury.
Skeletal maturation associated with lower limb muscle flexibility in highly trained young soccer players
Authors: Materne, O., Farooq, A., Chamari, K., Johnson, A., Greig, M., McNaughton, L.
Summary: Flexibility has been shown to be a key factor for performing football-specific tasks (Garcia-Pinillos et al., 2015) in youth soccer. Yet, the understanding of changes in lower limb muscle flexibility during maturation, remain limited. This study examined the relationship between skeletal age and the flexibility of the lower limb muscle groups in young elite Qatari soccer players. It was hypothesized that skeletal maturity status influences the flexibility of the lower limb muscles. 188 youth soccer players (Mean: age: 14.4±1.5 years; weight: 50.7±10.9 kg; height: 162.5±10.7 cm) were measured in pre-season screening over six consecutive years in six different age groups (U13 to U18). Flexibility of eight muscle groups (quadriceps, hamstrings, adductors, hip flexors, gastrocnemius, soleus, hip medial-, and hip lateral- rotators) were bilaterally and consistently measured using a reliable method (Fourchet et al., 2012). Skeletal age (SA) was estimated by an experienced observer using the Fels method. Linear mixed model analysis was used to compare the flexibility with maturity status (SA minus chronological age: Late (L): > - 1 year; Normal (N): +/-1 year; Early (E): < 1 year) within each age group. Data from 852 limbs for each muscle group were available for analysis. Flexibility of all lower limb muscle groups decreased significantly with age. Substantial variations within identical age categories but different maturity status were reported, e.g. Quadriceps (U16: E: 128.2±0.9˚ > N: 132.7±1.3˚ > L: 141.7±4.5˚, p<0.05); Gastrocnemius (U16: E: 11.4±0.7˚ > N: 14.7±0.9˚, p<0.05); Soleus (U16: E: 28.5±0.8˚ > N: 33.7±1.1˚ > L: 39.5±3.9˚, p<0.05); Medial rotator (U16: E: 49.2±1.6˚ > N: 54.9±1.6˚, p<0.05); Hamstring (U14: E: 65.9±1.3˚ > N: 67.8±1.3˚ > L: 83.7±5.1˚, p<0.05); Adductor (U15: E: 57.1±0.9˚ > N: 60.1±0.8˚ > L: 71.1±3.6˚, p<0.05); Lateral rotator (U15: E: 36.4±1.2˚ > N: 37.7±1.2˚ > L: 49.7±4.9˚, p<0.05). Hip flexors did not show any substantial difference between the maturity status in any age group. This study revealed that lower limb muscle flexibility changes through skeletal maturation and appeared to be muscle group dependent. Such information will enhance the understanding of lower limb flexibility changes during maturation, and will help youth soccer academies to initiate appropriate developmental strategies.
Evaluation of Dextrose Prolotherapy Injections in Soccer Players with Chronic Groin Pain
Authors: Eroglu, A., Sarı, A.
Summary: Groin pain is a very common problem in soccer. Among male soccer players, the incidence of groin pain is estimated at 10% to 18% per year( Holmich P et al) . The most common causes of chronic groin pain in soccer players are adductor strain and osteitis pubis. One important disease to consider in the differential diagnosis of groin pain in athletes is osteitis pubis: a painful, inflammatory process involving the pubic symphysis and its surrounding structures such as the pubic rami, cartilage, musculotendinous and ligamentous structures of the pelvis(Batt ME at al 1995;William PR et al2000). Our study is that chronic, overuse-related, and performance-limiting osteitis pubis in soccer players can be treated effectively using dextrose prolotherapy, despite failure of nonsurgical treatment for a minimum of 6 months. Most patients were referred by the orthopedic surgeon and team physician of the regional soccer team Turkey. Twenty patients were soccer players and 3 were regional endurance athletes. Dextrose prolotherapy injection sessions at occurred between three weeks (0-3-6 weeks). The solution used was a combination of 20% dextrose and 1% jetokain simplex. It was prepared by mixing 10mL of 1% preservative- and epinephrine-free jetokain simplex with 10mL of 20% dextrose solution in a 20mL syringeat pubic rim on either side of the symphysis pubis in 1-cm intervals, covering the pectineus origin and pyramidalis insertion, external oblique insertions, and the superior pelvic rim. A pretreatment visual analog scale (VAS) for pain with exercise was administered, and each subject was asked to fill out the Nirschl Pain Phase Scale (NPPS) to determine his functional impairment level.
Effects of dimple on a soccer ball flight
Authors: Hong, S., Asai, T.
Summary: It has been reported that the aerodynamic force applied to the ball changes in accordance with the number of panels and their orientation, consequently changing the flight trajectory (Goff et al., 2014; Hong & Asai, 2014; Hong et al., 2015). However, as the shapes on the surface of a soccer ball are a combination of various forms of panels and complicated seams, the influence that these shapes have on the aerodynamic force acting on the soccer ball is mostly unclear. Hence, in this study we aerodynamically studied the shape of the panels and the surface design (presence or absence of dimples). In this study, we introduced dimples on the surface of a soccer ball and examined their effect on the aerodynamic forces acting on the ball using a wind tunnel. We targeted three types of soccer balls in this study, namely, a soccer balls constructed from 32 panels, 12 panels and 6 panels, all of which are made out of the same material (leather). In addition, for each type of soccer ball, we constructed a type with dimples (dimple width of 3 mm and depth of 1 mm) and a type without dimples, making a total of six types of soccer balls. We then studied and measured the effect of the number of panels and the presence or absence of dimples on these six types of soccer balls using a wind tunnel experiment and revealed the aerodynamic characteristics. The drag coefficient of soccer balls with dimples in the supercritical region, the soccer ball with 32 panels had the smallest drag value of approximately 0.10 (Re = 2.3×10⁵) whereas the soccer ball with 12 and 6 panels had a value of approximately 0.15 (Re = 2.1×10⁵) and 0.17 (Re = 2.1×10⁵). However, for the case of soccer balls without dimples, the soccer ball with 32 panels had a drag coefficient value of approximately 0.13 (Re = 3.5×10⁵) and the soccer ball with 2 and 6 panels had a value of approximately 0.12 (Re = 3.5×10⁵) and 0.12 (Re = 3.4×10⁵). Furthermore, in a wind speed of 30 m/s, the variations in the lift and side force in the case of a soccer ball with 32 panels without dimples were 2.5 N and 2.6 N, respectively. Likewise, the dimple soccer balls with 32 panels were 1.3 N and 1.7 N, respectively. The presence or absence of dimples on the surface of a soccer ball greatly varied the drag working on the ball. From this, it is plausible that, in the speed range used during a pass and a long kick, soccer balls with dimples have the possibility of flying faster, whereas, in the speed range used during powerful shots, soccer balls without dimples have the possibility of flying faster. In addition, during the flight of a soccer ball, horizontal motion is believed to be more stable for soccer balls with dimples than for soccer balls without dimples.
Fatigue and recovery of neuromuscular function after a simulated soccer match
Authors: Thomas, K., Dent, J., Howatson, G., Goodall, S.
Summary: Soccer match-play induces transient and on-going decrements in physical function that persist for up to 72 hours post-game (Nedelec et al., 2012; Minnet & Duffield, 2014). There are frequent congested periods in the competitive schedule that require multiple games per week, separated by as little as 48 hours. Consequently, understanding and managing fatigue and the associated recovery post-match is an important consideration. Previous work has characterised the recovery of peripheral function after a soccer match, but there is sparse data on the recovery of neuromuscular function (Rampinini et al., 2011). The aim of the study was to assess the fatigue and recovery of neuromuscular, physical and perceptual responses following a simulated soccer match. Fifteen semi-professional male soccer players completed a 90 min simulated soccer match. Pre-, immediately-post and at 24, 48 and 72 h participants completed a battery of tests. Maximum voluntary force (MVC) and twitch responses to femoral nerve stimulation during isometric knee-extensor contractions and at rest were measured to assess central (voluntary activation, VA) and peripheral (quadriceps potentiated twitch force, Qtw,pot) fatigue. Creatine kinase (CK) was analysed from capillary blood samples as a humoral index of muscle damage. Countermovement jump (CMJ), reactive strength index (RSI) and sprint performance (10 & 20 m) were assessed to profile the recovery of physical function, alongside perceptual markers of recovery (active & passive soreness, fatigue). Simulated soccer match play elicited decrements in MVC that remained unresolved at 72 h (P = 0.01). Qtw,pot declined by 13% post-match (P < 0.001) and remained depressed until 72 h post. VA was reduced by 8% post-match and remained below baseline at 72 h (P = 0.049). CK was elevated post-match and remained elevated at 72 h post (P < 0.001). CMJ performance remained depressed at 72 h (P < 0.01), RSI was decreased at 48 h (P < 0.01) but recovered by 72 h, and sprint performance recovered by 24 h. Perceptual markers of fatigue were elevated until 48 h post (P < 0.01) and had recovered by 72 h. Simulated soccer match-play induced significant fatigue that was both central and peripheral in origin. The loss in maximal voluntary force was not restored by 72 h post-match, and was accompanied by persistent central fatigue. The similar time-course recovery of neuromuscular function, jump performance and perceptual markers of fatigue indicates these tools might be useful as indices of fatigue and recovery in soccer players.
Practical impact of modern performance analysis in football
Authors: Lames, M.
Summary: The advent of new technologies and the interest of media in enhanced reports have advanced football to the most analysed sports in Europe. This development was accompanied by the hope for improvements in football practice as well as competition analysis. Meanwhile, some critical opinions gave rise to a ’practical impact debate’ with controversial positions. A basic reason for the failure of performance analysis research to provide hints for practical improvement is the applied research strategy. There are fundamental differences between the applied basic research and applied research, that would in fact be needed to generate practical impact. Some basic requirements for a practice oriented research program in performance analysis are: Adaptation of qualitative methods to arrive at sound interpretations of player behaviour. Integration of background information (tactics, preparation, opponent, situation) for assessing the quality of actions. Interpretation of results from basic research only as background information for practical analyses. Development of a new generation of game analyses that make use of the new data available and aim at assessing constructs on a higher tactical or physiological level oriented at the information needs of practice. Investigation of football from the aspect of emergency and contingency for a better understanding of its nature.
Female fans of men’s football – socialization, motivation and circumstances of life
Authors: Pfister, G.
Summary: Football is an invention by men for men, and today, the majority of players and fans are men. There is an abundance of literature on football and fandom; however, gender is mostly not an issue in these publications. Research about female football supporters and fans is very limited. Based on gender concepts, socialization theories as well as on approaches to circumstances of life, this contribution addresses women and their (lack of) interest in men’s football. The main questions refer to the numbers of female supporters and their patterns of football consumption. The sources of information are user data of mass media, results of a survey about football fans in a number of European countries (conducted by members of the FREE project) and the results of an interview study with female fans. A specific focus of this article is on the minority of female supporters who attend football games. How do they become fans, adapt to a ‘man’s world’ and integrate football in their everyday lives? What are their roles in the ‘male environment’ of the game and its fans?
The results of a survey and the statements of interviewees revealed that female fans have to cope with a measure of sexism, and that they often adopt the men’s perspectives in order to be accepted as ‘authentic fans’. Other women reacted on men’s domination in the football stadium by founding women only fan groups that seem to allow them to find their own way to be women and fans.
Supporter culture – for whom? Women’s perception of football arena culture in sweden
Authors: Radmann, A.
Summary: Football supporter culture has been studied and analysed since the 1960s from historical, economic, sociological, cultural and psychological perspectives. Important questions within the field have been who the football supporters are, what influences them, how they can be understood, whether they are violent or well behaved, and what kind of identities are developed within the football supporter culture on a local, regional, national or international level. Most studies on football supporters have focused on men and on men´s supporter culture and research on female fandom is lacking. This study has a different focus, as female supporters in a Swedish context will be studied. The aim is to map out and analyse female supporters’ views of their situation in Swedish football supporter culture. Of special interest is the question of whether female supporters express the same ideas on gender specific codes within the supporter culture as the male supporters. Interviews with 18 female supporters from Swedish clubs are analysed. The interviews last between one to two hours and are recorded and transcribed. Life stories from four females presented in two different books on supporter culture are used too. The theoretical framework is based on Erving Goffman’s dramaturgical perspective, and Judith Butler’s notion of performative gender. In the interviews and the life stories of the female supporters, three themes emerge in women’s description of their football fandom: restrictions, respect and freedom.
Gender positions in School sport: Floorball and Soccer
Authors: Larneby, M.
Summary: In Sweden, organized team sports performed during leisure time are mainly separated for boys and girls. As Messner (2002) argues, this often reproduces traditional gender hierarchies within sport, in which boys are favored and girls undervalued. In sport schools, however, mixed-sex training groups are as common as separated groups. Anderson (2009) discusses that mixed-sex team sports may effectively reduce gender stereotypes, because men and women need to cooperate. Therefore, it is of interest to study mixed-sex and separated team sport groups at a sport school. The aim of this study was to explore and discuss young people’s construction and display of gender in floorball and soccer groups at a sport school, and in what way gendered power relations were exercised. An ethnographic approach was used to access voices, attitudes and actions on and off the floorball and soccer lessons (cf. Ennis & Chen 2012). Young teenagers attending floorball and soccer lessons at a sport school (7th to 9th grade) were observed and 21 one of them interviewed. Lorber’s (1994) theory of gender as a social institution was used to analyze and interpret their expressions and actions, attitudes and notions of sport. “Boys are better than girls” was the hegemonic discourse in the training groups. The mixed-sex floorball setting seemed to actualize an unquestioned need to dichotomize and construct distinct groups of boys and girls. However, the floorball girls emphasized that they empowered themselves by improving their athletic skills together with boys. Though being recognized by the boys, they were also patronized in various ways. The floorball boys reproduced an orthodox masculinity and similarly challenged this masculinity by most often appreciating the girls as skilled training peers. The soccer girls experienced a verbal patronizing as the soccer boys frequently told them that “girls are rotten soccer players”, though never having trained together. The soccer boys weren’t as reflective as the floorball boys, instead maintaining that “boys are better than girls” and that a mixed-sex setting was evidently inacceptable. Although the boys and girls constantly emphasized differences due to gender, they strove towards a uniform level of skills and ideal way of play–to be fast, tough, strong and technical. Gender seemed to lose significance in this common strive for similarity, still they continued to compare each other with boys as the norm. Therefore, gendered power relations set an agenda based in a notion underlining that “boys’ way to play” is the ideal.
The effects of self-reported menstrual cycle phase on physical football performance
Authors: Julian, R., Hecksteden, A., Meyer, T.
Summary: Despite the increasing scientific interest surrounding female football, gender-specific aspects of physiology, e.g. the menstrual cycle, remain largely unexplored (Datson, 2014). This is despite the known influence of the involved hormones on relevant aspects of exercise physiology and energy metabolism (De Jonge 2003). Therefore, the aim of the study was to investigate the effects of menstrual cycle phase on football specific performance. Sixteen sub elite female football players (19.4 ± 3.0 y, 164.8 ± 6.8 cm) participated in the current study. Prior to testing all participants completed a menstruation diary for a minimum of 6 months. Females who had a cycle phase < 25 days or > 30 days were excluded. The phases of the menstrual cycle were determined by counting backwards from subsequent menses, and were then controlled using the onset of the following menses. Testing time-points were established as Follicular Phase (FP) day 5-7 and Luteal Phase (LP) day 21-22, where greatest hormonal variations are known to occur (Reilly, 2010). A battery of football specific performance tests was implemented (endurance capacity (Yo-Yo IE1), sprinting performance (3 x 30m) and explosive lower limb power (CMJ)). Data was collected in the early evening and training load was kept consistent for the 48 hours prior to testing. All measures were conducted outside on artificial turf under similar weather conditions. Magnitude based inferences indicated a possibly harmful effect in the LP for Yo-Yo performance. For all other performance variables, a most likely negligible effect was suggested. Standard null hypothesis testing indicated a tendency towards significance in Yo-Yo IE1 performance (p=0.065) between phases. No significant differences in CMJ (p=0.544) or 3x30m sprint at any distance splits (0-5m, p=0.787; 0-10m, p=0.786; 0-30m, p=0.772) were found. The results suggest a possible reduction in endurance capability for female footballers, indicated by a decline in Yo-Yo IE1 performance. Further investigation is needed to corroborate this influence of menstrual cycle on performance and to establish the underlying mechanisms. Furthermore, although lab based performance appears to be reduced, the effects of menstrual cycle phase on game specific scenarios is warranted within future research on this topic.
Effects of recreational football performance once a week on cardiovascular risk factors in middle-aged men. A randomized controlled trial design
Authors: Beato, M., Impellizzeri, F.M., Coratella, G., Schena, F.
Summary: It is well established that there is a strong relationship among physical activity, cardiovascular diseases and mortality. International guidelines recommend at least 150 minutes per week of moderate intensity aerobic training in order to achieve health benefits. Considering the lack of time the major barrier to active life style, the same benefits could be achieved also with lower amount of the recommended training volume. Regular recreational football training induces lowering blood pressure, heart rate at rest, fat percentage, maximal aerobic power (VO2max) and LDL cholesterol (Bangsbo et al., 2014; Krustrup et al., 2013). Despite the popularity and wide diffusion of this sport, no one has investigated the effect of one session per week on cardiovascular risk factors. This study analysed the effect of 1-hour football session per week on middle-aged men. This study used a randomised controlled trial design. Participants were randomized between Football Group (FG) and Control Group (CG). FG performed supervised recreational football training (5-a-side futsal match) on 36 x 18.5 meters synthetic indoor once per week (1 hour) over 3 months. After 12 training weeks, VO2max and maximal aerobic speed (MAS) improved in FG respectively of 4.4% (p = 0.002) and 5.95% (p = 0.01). SBP and MBP improved respectively of 2.5% (p = 0.04) and 2.2% (p = 0.044) in FG, while DBP didn’t change during protocol period (p > 0.05). CG didn’t show any meaningful variation over the training period. Anthropometric and blood parameters did not change in both FG and CG during the study. This study is the first examining the effect of 1-hour recreational football session per week on cardiovascular risk factors. Recreational football activity produces health benefits improving VO2max and blood pressure parameters in middle-aged men. This study may have important implications on the prevention of cardiovascular disease and for designing health programs.
Half-time re-warm up with repeated bouts of exercise improves subsequent intermittent exercise performance in football referees
Authors: Yanaoka, T., Yamagami, J., Hasegawa, M., Kidokoro, T., Kashiwabara, K., Min, D.K., Miyashita, M.
Summary: The previous review suggested that an active continuous half-time re-warm up is effective for attenuating the reduction of physical performance (Yiannis, 2014). In addition, the review suggested that more research is needed to investigate the effect of different frequencies of exercise during the half-time on subsequent physical performance (Yiannis, 2014). Moreover, there was no literature to investigate the effects of the re-warm up on blood metabolites including creatine kinase (CK), a marker of muscle damage. Therefore, the purpose of the present study was to examine the effects of a re-warm up with repeated bouts of running exercise (RWR) during the half-time period on subsequent intermittent exercise performance and blood metabolites. Ten male referees (22 ± 1 years, 173.6 ± 5.8 cm and 67.2 ± 6.4 kg) were required to complete two trials (i.e., Control (seated rest) and RWR) administered in a randomised counterbalanced order. The two trials consisted of the Loughborough Intermittent Shuttle Test (LIST), half-time and Yo-Yo Intermittent Recovery Test level 1 (Yo-Yo test) periods. In the half-time period, participants either rested on the chair (Control) or RWR for 15 min. The RWR protocol consisted of repeating 2.15 min of a passive recovery, followed by 2.15 min of running at 70% of HRmax for 13 min. The re-warm up started 1 min after the start of the half-time period and ended 1 min before the start of the Yo-Yo test period. Yo-Yo test performance, plasma glucose, serum fatty acids (FFA), serum triglyceride (TG), blood lactate (BLa), plasma CK, the rating of perceived exertion (RPE), mean heart rate (HR) and maximal heart rate (HRmax) were analysed. For the distance covered during the Yo-Yo test, the RWR trial was higher than the control trial (3094.6 ± 102.9 vs 2904.4 ± 133.1 m, p < 0.05). Circulating concentrations of glucose, FFA, TG, BLa and CK did not differ between the RWR and control trials. RPE during the half-time period, but not after Yo-Yo test period, was higher than the control trial. Mean HR and HRmax during Yo-Yo test did not differ between the RWR and control trials. The present findings indicate that RWR improves subsequent intermittent exercise performance and do not affect blood metabolites response (i.e., circulating concentrations of glucose, FFA, TG and BLa). These findings suggested that energy substrates may not be a factor to improve subsequent intermittent exercise performance at least in our study. Moreover, the present study showed that RWR do not affect concentrations of CK.
Reliability of a novel posterior limb isometric muscle test in football players
Authors: Alcaraz, P.E., Abedin-Maghanaki, A., Matinlauri, A., Freitas, T., Toscano, F.J., Martínez-Ruiz, E., Mendiguchia, J., Cohen, D.D.
Summary: Fatigue and strength deficits are important predisposing factors for hamstring strains (1). McCall et al (2) demonstrated the reliability of a posterior lower limb test performed on a portable force platform as a practical tool to monitor posterior limb isometric peak force (PL-IPF) in team sport athletes. They also showed that this test performed in two supine positions, was sensitive to match induced fatigue in footballers. However, evidence suggests that hamstring fatigue following simulated football is greatest close to full knee extension (3) and the majority of hamstring strains are thought to occur to the biceps femoris in an extended position (1). Therefore, we aimed to determine the reliability of a test which assesses PL-IPF in such a position. Fourteen semi-professional male football players were tested twice, on consecutive weeks. PL-IPF was measured with two tests, both performed in a standing position with the tested leg positioned on a portable force platform at 90° hip flexion and 20° knee flexion (90:20). The non-tested leg, upper back and head were positioned against a wall and the arms were either (i) crossed on chest, palms placed over the contralateral acromion (AC); or (ii) next to trunk against the wall, elbows fully extended and palms in pronated position (AW). There was no effect of test protocol or leg on PL-IPF. Differences between repeated trials displayed trivial or small effect sizes in both positions and in both dominant (DOM) and non-dominant (NON) legs; AW-DOM; CV=12.4%, ICC=0.63, p=.044. AW-NON; CV=12.2%, ICC=0.82, p=.002. AC-DOM; CV=14.5%, ICC=0.71; p=.018. AC-NON; CV=9.2%, ICC=0.90; p=.001. Both versions of the 90:20 showed good-to-high reliability with the AC position slightly superior. In all conditions, except for the AW-DOM, CV´s were close to 10% and ICC´s to 0.75, qualifying values often used to define a variable as reliable (4). The 90:20 can be considered a reliable means to rapidly assess PL-IPF with the biceps femoris in an extended position. Further research should evaluate the capacity of the 90:20 to detect post-competition fatigue and to compare muscle activation in the 90:20 versus supine tests (2).
Impact of a strength training program on footballer’s VO2max
Authors: Ibo, B.J., Chevalier, J., Comtois, A.S.
Summary: There is considerable variation between football players’ BMI and players of other sports such as rugby, hockey or American football. Nonetheless, that contrast is dwindling when it comes to body fat percentage and cardiorespiratory capacity. Many football specialists still believe that hypertrophy will alter footballers’ efficiency. However, players from the aforementioned sports succeed in their respective disciplines. The main purpose of this study is to put elite footballers through a resistance training program and demonstrate that this type of training is not deleterious to the footballers’ VO2max. The second objective is to verify hypertrophic gains while examining the impact of the program on the players’ other attributes. The study was conducted on the U-19 players from the academy of professional football club Asec Mimosas; 20 subjects participated in the study (N = 20). A total of seven tests were performed to measure various components: BMI, Body fat percentage, VAMEVAL test, 30m dash, RSA, Illinois test and broad jump test.The experimental design consisted of a single group, with pre and post measures. All results are reported as standard deviation (SD). Results were compared using a paired Student’s T test and accepted as significant at P<.05. The idea was to develop a 45 to 60 minute in-season training protocol that required minimal equipment. It was also essential that the program involved a majority of various muscle groups. Hence the implementation of functional movement training program followed twice a week. The program was divided into 3 circuits. Circuit 1: Bench Press, DB Rows and Side Plank. Circuit 2: Squats, Hip Thrust, and Pullups. Circuit 3: Deadlift, Overhead Press and Plank. Players performed 3 sets of 5 to 10 reps. BMI (p=.0001) from 20.7± 1.6 to 21± 1.6 kg/m²; Body fat percentage (p=.0001) from 9.8± 1.4 to 8.2± 1.2 %; Lean body mass (p=.0001) from 57.5± 5.7 to 59.5± 6.1 kg; 30m sprint (p=.0001) from 4.22±0.1.to 3.98± 0.2 s.; RSA (p=.0001) from 4.46±0.2 s. to 4.25± 0.2 s; Broad jump (p=.009) 2.31± 0.1 to 2.45 ± 0.2m; Illinois test (p=.001) from 15.69±0.1s to 15.16 ± 0.1s.; VO2max from 58.78 ±0.6 ml/mn/kg to 59.6 ±0.6 ml/mn/kg. The findings suggest that resistance training is not deleterious to footballers’ VO2max. For this reason, once elite players reach VO2max standards, it is necessary to implement a good in-season resistance training program that will help improve VO2max, lean body mass, body fat percentage and other footballers’ important qualities such as speed, RSA, agility and leg .
Comparative anthropometric and physical characteristics of youth football players at the various stages of an international football talent screening and selection program
Authors: Price, A., Peltola, E., Varamenti, E., Bourdon, P., Cable, T.
Summary: This study compares the baseline anthropometric and physical performance characteristics of youth football players at the various levels of a four-stage international humanitarian football talent screening and selection project (Aspire Football Dreams) which aims to inspire hope in children in developing countries. Over the past 9 years, ~4.6 million boys from 19 developing countries across Africa, Asia and Latin America have registered for the project. This study includes data from the first 4 years of the project (2007-2010) as it takes a minimum 4 years to progress to Stage 4. Players were categorised based on the highest selection stage they achieved; Stage 1 - Country Finals (n=1823), Stage 2 - World Finals (n=49), Stage 3 – Educational and Sports Development Scholarship (n=64), Stage 4 -Professional Contract (n=20). Player progression was decided by a panel of coaches/staff based on a myriad of factors including technical, tactical, physical, psychological measures and predicted future potential. Only a limited number of players progress at any stage and they could opt to drop out at any time. Minimum age to progress to Stage 4 is 18 years old. Three anthropometric (height, seated height and body mass) and three physical performance measures (counter movement jump (CMJ) using a KMS jump mat, 40 m sprint with 10 m splits to assess peak velocity (m/s) using an electronic timing gate system, and a 20 metre multi stage shuttle run test) were assessed on all players during Stage 1. These measures were used for all subsequent analyses. ANOVA analysis showed that players that progressed to Stage 3 were significantly (p ≤ 0.05); taller (167.5 vs. 171.1 cm), heavier (55.8 vs. 59.0 kg), faster (40 m sprint – 5.67 vs. 5.43 s), more powerful (CMJ – 37.1 vs. 39.9 cm) and displayed greater endurance (20 m Shuttle score – 11.55 vs. 12.45 level) than those players who did not progress beyond Stage 1. Those players selected to Stage 4 failed to show any significant differences from the other stages which is likely due to the relatively low number of players (n=20) progressing to this stage. These results suggest anthropometric and physical performance characteristics play an important role in the earlier stages of the selection program (Stages 1 to 3). However when it comes to the selection of players for a professional contract at Stage 4, other non-physical measures (i.e., technical skills, tactical understanding, personality, attitude etc.) become equally if not more important.
Revealing parameters that influence game flows in football using jordan network
Authors: Saito, Y., Kimura, M., Ishizaki, S.
Summary: Sometimes the change of game balance in football games is discussed based on the idea of game flows (Alister et al., 2005), however, the quantitative definition has not been clarified. The aim of this study is reveal features that influences game flow factor by constructing and analyzing the game flow models. We use play-action data and game flow data in this study. The play-action data include time series data such as coordination of the ball, the players who play the ball, the type of the play-actions, (e.g. pass, shoot and dribble) and so on. The game flow data are two dimensional vectors represented advantage of both home teams and away teams. Either zero or one are assigned to each element in the vector, for example, if the home team gains an advantage, and in contrast, the away team loses it, the vector becomes (1, 0) and via versa. In order to construct the game flow models, we chose Jordan neural network. The Jordan network is a class of artificial neural networks whose inputs at the time include one of outputs at the time . Since, in football games, the game flows should be closely related to the prior situation, the Jordan network should be suitable to model game flows. We trained network using the play-action data that have over 900 parameters as the input and the game flow data as the output. Afterwards, we applied the sensitivity analysis to the game flow model and revealed parameters that contribute to the game flows. In our experiments, we constructed the game flow model using data of Urawa Reds’ (a club of Japan Professional Football League (J-League)) five games and applied the model to other five games to predict their game flows. Moreover, we applied the sensitivity analysis to the game flow model. We confirmed that the predicted game flows were well explained in the real game situations. This suggests that the constructed game flow model was relevant to predict game flows in Urawa Reds’ games. Sensitivity analysis of the obtained neural network shows the frequencies of Makino and Moriwaki handling the ball in front court varying from 0 to 1 cause the large difference of the values of Urawa Reds game flow around 0.97. This shows Urawa Reds’ superiority was influenced on whether Makino and Moriwaki, defenders in Urawa Reds, played at the higher position than other games or not. The frequencies that Makino and Moriwaki played at the higher position precisely represent the frequencies that they contributed Urawa Reds’ attacks. Urawa Reds is a team with the highest ball possession rate in J-League and it often makes attacks with many of the players. From these reasons, it was reasonable results that Makino’s and Moriwaki’s attacks influenced on Urawa Reds’ game flow.
When girls are empathic and norm-enforcing than boys on the football field?
Authors: Van Lange, P.A.M.
Summary: A key revolution in the past three decade is the enormous growth in women’s football. This raises intriguing questions that include and go beyond the evolution of sex differences. How are women and men different, when they are playing soccer? Being more emphatic in general, might we, for example, see young female football players exhibit greater empathy on the field? If so, how? And when do girls and boys differ corrective behaviors by showing disapproval of one another’s fouls? Such knowledge should ultimately help us generate new solutions to enduring problems in soccer, such as violence in and around the field. In total, 107 children (55 boys, 52 girls, age 10-18) participated in a web-based experiment. They were asked to imagine themselves at the soccer field being in control of the ball when another player falls on the ground. Using a within-participants design, we manipulated location (distant or close to the other team’s goal) and team of fallen player (own or other team). We assessed the extent to which participants thought they would quickly stop to look how the fallen player was doing, which served as our measure of empathy. Also, we examined the likelihood of girls and boys “openly disapproving ” of a foul enacted by a player of their own versus the other team. All participants exhibited greater empathy when the other player fell on a location farther away from the other team’s goal, and when the player was from the own team. Most interestingly, boys and girls differed in one key aspect: At midfield, boys and girls were about equally empathic, but closer to the goal of the other team (when scoring is a clear possibility) boys were far less empathic than girls. Disapproval of fouls also uncovered intriguing differences. Reportedly, while girls were about equally likely to show disapproval when against player of their own versus the other team, boys were far more likely to do so when the foul was conducted by a player from the other (versus own) team. When do sex differences in football become manifest? We find that when scoring becomes a real possibility (when the distance to the goal is small), girls still enact empathy while boys move on to continue playing. This finding is consistent with the notion that men more than women are oriented on pursuing a single goal rather than multiple goals. We also find differences in showing fault disapproval. While boys are clearly biased in favor of their own team, girls are about equally “corrective” towards players of their own and the other team. The latter finding is important, because it is possible that showing disapproval of especially unnecessary fouls (e.g., at the midfield) by own team players may often help the team to win – and to win by proper means.
Development and Validation of a Proxy for Gaze Behaviour Measurement in Football
Authors: Oppici, L., Panchuk, D., Serpiello, F.R., Farrow, D.
Summary: Wearable, head-mounted eye trackers are widely used in sport-psychology research to assess eye movements and provide insights into perceptual-cognitive changes underpinning the development of sport skill. Where possible, the assessment of eye movements should take place in the performer’s natural environment as decision making and attentional processes are constrained by the environmental cues the performer is responding to. However, quick head movements and ground impact in dynamic tasks, such as football games, affect the reliability in detecting eye features, limiting the evaluation of gaze location. We developed a new approach to deal with this issue and validated a method that uses head orientation as a proxy for gaze measurement in football. A window, using gaze coordinates, was designed to derive the gaze location in the absence of point-of-gaze references and validated against the gold standard point-of-gaze method. Forty-eight youth football players performed 6 v 6, small-sided games on a modified pitch. The raw gaze coordinates on the x- and y-axes of 6 players were plotted to analyse the dispersion of gaze. Two standard deviations from the mean were used to capture the majority of gaze behaviour (95.44%) and in turn develop an empirical coding window to classify the gaze in two gaze regions of interest, described as player-directed or ball/ground-directed. To validate the new method, footage collected from the eye tracker of 12 players were coded frame-by-frame using the empirical window and compared to the standard point-of-gaze coding. Results: The overall agreement between the two methods was 90%. However, this rate of agreement does not account for the agreement expected by chance. Cohen’s kappa value, which corrects for this, was 0.64 (p<0.001). Furthermore, the distribution of the categories in the data was skewed as 2830 belonged to one category and 597 belonged to the other. The kappa value was influenced by this prevalence issue and the adjusted-kappa (PABAK) was 0.80, indicating substantial agreement between the two methods. Discussion: Locomotor activities, in general, create noise in gaze data and this new coding method, using a window derived from gaze location coordinates, is a valid approach to overcome potential issues when assessing eye movements in dynamic tasks, such as football small-sided games. Researchers operating in the field may use this approach when dealing with poor quality data and it may encourage researchers to perform their experiments in participant’s natural environments.
Defensive balance in elite football: making reliable observations
Authors: Schulze, E., Meyer, T.
Summary: It has been found that teams show anti-phase coordination during goal-scoring opportunities in elite football (soccer; Moura et al., 2016). These contrasting movements can be interpreted as a perturbation of the defensive team’s balance in relation to the offensive one. The concept of defensive balance has been introduced before and deemed crucial for the efficacy of playing styles (Tenga et al., 2010). The aim of this study was to determine the reliability of expert observations of defensive balance to possibly extract patterns within successful attacking sequences. Ten performance analysts, coaches, and scouts (7±5yrs of experience with match analysis) analysed five clips involving goal-scoring opportunities in matches between different elite international teams in a randomised order. The defensive balance within the defending team was rated in 1s-intervals on a 5-point scale. A slope of every four consecutive log-transformed ratings was calculated to determine the time window where defensive balance was disturbed most strongly (SLP). After every clip, participants also had to indicate which second they deemed decisive during the attacking sequence (SEC). Agreement was calculated as the percentage of ratings corresponding to the mode, the most reported rating for one variable, and statistically tested with a paired samples T-test. Ratings of defensive balance in 1s-intervals agreed by 58.2±3.8% between participants. The conversion of these ratings led to an agreement of 52.0±23.9% for SLP. A tendency towards a significantly higher agreement was found compared to SEC (36.0±11.4%; P=0.08). By including those ratings within 1s of the mode, the agreement of SLP and SEC increased to 70.0±14.1% and 50.0±18.7%, respectively. This allowance did not significantly change the agreement within methods (P=0.07&P=0.14), however the agreement within SLP was significantly higher than that within SEC after allowing for a 1s-variance (P=0.05). The method that used the second-by-second ratings of defensive balance and transformed those into a slope describing the change in balance over a 4s-window (SLP), proved to be more reliable when allowing a 1s-deviation from the mode compared to a self-selected time frame (SEC). This shows that the concept of defensive balance requires more than merely subjective ratings of experts. The strong agreement within SLP could enable indicating what player actions are most detrimental to a team’s defensive balance. This might provide useful information towards improving team performance and the quality of opposition scouting.
Development and Validation of a Proxy for Gaze Behaviour Measurement in Football
Authors: Oppici, L., Panchuk, D., Serpiello, F.R., Farrow, D
Summary: Wearable, head-mounted eye trackers are widely used in sport-psychology research to assess eye movements and provide insights into perceptual-cognitive changes underpinning the development of sport skill. Where possible, the assessment of eye movements should take place in the performer’s natural environment as decision making and attentional processes are constrained by the environmental cues the performer is responding to. However, quick head movements and ground impact in dynamic tasks, such as football games, affect the reliability in detecting eye features, limiting the evaluation of gaze location. We developed a new approach to deal with this issue and validated a method that uses head orientation as a proxy for gaze measurement in football. A window, using gaze coordinates, was designed to derive the gaze location in the absence of point-of-gaze references and validated against the gold standard point-of-gaze method. Methods: Forty-eight youth football players performed 6 v 6, small-sided games on a modified pitch. The raw gaze coordinates on the x- and y-axes of 6 players were plotted to analyse the dispersion of gaze. Two standard deviations from the mean were used to capture the majority of gaze behaviour (95.44%) and in turn develop an empirical coding window to classify the gaze in two gaze regions of interest, described as player-directed or ball/ground-directed. To validate the new method, footage collected from the eye tracker of 12 players were coded frame-by-frame using the empirical window and compared to the standard point-of-gaze coding. Results: The overall agreement between the two methods was 90%. However, this rate of agreement does not account for the agreement expected by chance. Cohen’s kappa value, which corrects for this, was 0.64 (p<0.001). Furthermore, the distribution of the categories in the data was skewed as 2830 belonged to one category and 597 belonged to the other. The kappa value was influenced by this prevalence issue and the adjusted-kappa (PABAK) was 0.80, indicating substantial agreement between the two methods. Discussion: Locomotor activities, in general, create noise in gaze data and this new coding method, using a window derived from gaze location coordinates, is a valid approach to overcome potential issues when assessing eye movements in dynamic tasks, such as football small-sided games. Researchers operating in the field may use this approach when dealing with poor quality data and it may encourage researchers to perform their experiments in participant’s natural environments.
Changes in lower limb muscle activity in soccer players with Functional Ankle Instability during a diagonal single-leg drop
Authors: Κunugi, S., Masunari, A., Miyakawa, S.
Summary: Ankle sprain is one of the most common injuries in soccer players. Functional ankle instability (FAI) is residual symptom often develop as a result of ankle sprain. Patient with FAI has postural control deficits at ankle joint. Time to stabilization (TTS) that is used to evaluate the postural control is the time it takes for an individual to regain to single-leg stability after landing. Reduction in peroneus longus (PL) activity was accompanied by inverted position of the ankle joint from pre landing period (Delahunt et al. 2006). This can cause that patient with FAT take longer TTS than healthy people (Ross et al. 2005). However, peroneus brives (PB) activity is not clear during landing period. Twenty-one male collegiate soccer players participated in this study. They were classified into 2 groups using Cumberland ankle instability tool Japanese version (CAIT-J)(Kunugi et al. 2016). 11 FAI group (age 18.2 ± 04 years, CAIT-J 21.0 ± 3.1) and 10 control group (age 18.7 ± 0.8 years, CAIT-J 30.0 ± 0.0) were instructed to land from a box of 30-cm high into anterolateral direction, stabilize as soon as possible, and remain as motionless as possible in a single-leg stance for 20-s. We calculated TTS mediolateral (TTSML) using a force plate. We recorded the muscles activity from the PL, PB, tibialis anterior (TA), gastrocnemius medialis (GM) during drop landing. Data relating to the period 500-ms pre-initial contact (IC) and 500-ms post-IC were analyzed to compare to difference between FAI and healthy group using independent two-sided t-test. α was set at 0.05. There was significant difference for TTSML between FAI group (mean 4626.3 ± 347.4-ms) and control group (mean 4282.1 ± 282.4-ms). Reduction in PL, PB, and TA activity was founded in FAI group during the time 1-ms–11-ms post-IC, from 214-ms–31-ms pre-IC, and 68-ms–85-ms post-IC, respectively (p< .05). Male collegiate soccer players with FAI had postural control deficits and low muscle activity in PL, PB, and TA during single-leg landing. This reduction in muscle activity may be caused by proprioceptive deficit at ankle joint. It is clear that PB activity has reduced in participants with FAI during pre-IC.
Head impact mechanisms during practice for soccer junior athletes
Authors: Osullivan, D.
Summary: Since the high number of deaths (suicides) and debilitating head injuries in American Football there has been a lot of attention both by the media and by researchers for
head injuries in sport. However, soccer is reported to be responsible for the largest number of head impacts and highest concussion rates among females (Gessel et al., 2007). Only recently the
technology to measure head impact mechanisms during practice and competition is available and so there is a dearth of data regarding the magnitudes and frequency of head impacts in soccer for all
genders and levels. Therefore the purpose of this study was to measure the head impact characteristics of junior boys during soccer practice. Using the xPatch (Biosystems Inc.) head impact data
(peak linear acceleration (PLA), peak rotational acceleration (PRA), peak rotational velocity (PRV) and Head injury Criterion (HIC) 15ms) were collected over ten training sessions. Ten junior
boys aged between 8 and 12 years of age participated after their parents/ guardians signed the University Hospital approved IRB consent form. Data from the sensor was then backed up on the
Biosystems cloud and their proprietary software Impact Management System software was used to output the impact severity related variables. Non-parametric Krushall-Wallis tests were used to
investigate the differences in the sessions and among the participants. During the ten sessions, there were a total of 501 impacts recorded, averaging out at 90 impacts per 100 minutes. The
averages and standard deviations for PLA, PRA, PRV and HIC were 17.8±10.3g, 3168 ± 2442deg/s2, 16.1 ± 10.6deg/s, 11.4 ± 34.2. The most impacts were located at the back of the head (45.5%),
followed by the side (33.7%)), front (19.9%) and top (0.9%). According to the PLA guidelines by King (2014) 96.2% were classified as low severity (10-39g), 3.3% medium severity (40-69g), and 0.4%
as high severity (<70g). With the exception of a few impacts (2 impacts) the magnitudes recorded in this study were not classified as a high severity. However, because of the high frequency of
head impacts in soccer, it is important for those participating and their medical support staff to be aware of the risks associated with repetitive impacts. Future research is needed to maintain
a longitudinal design to assess the effects of repetitive low impacts.
Aorrtic root dimension in soccer players
Authors: Olm, T., Baskin, K., Herde, K.
Summary: Cardiac adaption to different sports has been extensively described. However the potential effect of top-level training on the aortic root dimension (AO) remains less investigated. At same time the frequency of cases of pathological dilatation of AO in top-athletes has been increasing. The aim of this study is to assess echocardiographic characteristics in order to elucidate aortic adaption in different age groups of soccer players. The subjects were 247 soccer players of the best clubs of Estonia. In the first group (n=149) the average age was 19.1±1.24 and in the second group (n=98) 25.3±3.12 years. The test battery included anthropometrics, ECG, and treadmill test and BLa concentration, VO2max, anaerobic threshold were recorded. The echocardiography was performed using GE Vivid E/9. The t-test and Pearson product moment correlation coefficients were calculated. Means: Group 1 (n=149): Age (y) 19,1 ± 1,24; BSA (m2) 1,95 ± 0,12; AO (mm) 29,2 ± 2,30; AO/BSA (mm/m2) 15,0 ± 1,34. Group 2 (n=98): Age (y) 25,3 ± 3,12; BSA (m2) 1,99 ± 0,11; AO (mm) 31,0 ± 2,18; AO/BSA (mm/m2) 15,6 ± 1,13. Sport-specific adaptive cardiac structural changes are still under debate. D`Andrea et al. (2010) concluded that the AO diameter was significantly greater in strengh-trained athletes (n=245) than in endurance athletes (n=370). At the same time Pelliccia et al. (2010) assessed athletes of 28 different sports disciplines (n=1300) and showed that the AO dimension was explained by weight, height, left ventricular mass (LVM) and age, with type of sports training having a significant but lower impact. The mean AO was greater (32.2±2.7 mm) than in our soccers and 1.3% of athletes had an enlarged AO (over 40 mm). In our investigation the greatest AO is 37 mm in both age groups. Correlation analysis shows that statistically significant correlations between AO and other indices are similar in both groups. AO has the strongest correlation with LVM, moderate relationship with left atrial dimension and significant but surprisingly low correlation with age. We can conclude that in soccer players sports-specific influence on the aortic root dimension occurs early and progresses moderately, being part of the symmetric remodeling of heart.
Scaling of Defensive Tactical Performance from Tracking Data of Soccer Game
Authors: Matsuoka, H., Mishio, S., Naomoto, H., Kumagai, S., Ando, K., Nishijima, T.
Summary: Game analysis using tracking data in soccer has become popular in the world. However, soccer defensive tactical performance (SDTP) measurements has not analysed sufficiently. The purpose of this study was to construct SDTP variables by using tracking data of a soccer game. An official game of J-league in 2015 season in Japan was analysed to measure SDTP. The SDTP variables with content validity were consisted from pressing defence (PDF), retreat defence (RDF) and shoot defence (SDF), using the causal-effect analysis and Delphi method with five experts qualitatively. The SDTP variables were measured from x-y coordinates of all field players during ball lost through ball gain or opponents shoot extracted from the tracking data. Total number of SDTP was 102 plays in a game (44 in PDF, 37 in RDF, and 21 in SDF). PDF and RDF were defined as successful defence, and SDF was defined as unsuccessful. SDTP variables were analyzed using descriptive statistics. Binomial logistic regression analysis was used to analyse the effective correlation of SDTP variables to defensive performance (successful or unsuccessful). The statistical significant level P< .05 was set. SPSS 22 (SPSS Inc., Chicago, USA) was used for analysis. Distance between ball and the 1st and the 2nd defenders (DFs) at the beginning of defensive play, distance covered by from FW player, distance covered by bottom DF player from the beginning to the end of defensive play, velocity and position of final DF line which distance from own goal line from the beginning to the end of defensive play, area of front five players and area of back 5 players at the end of defensive play were investigated as SDTP variables by Delphi method. Distance between ball and the 1st defender (odds ratio (OR) = 1.502, p= .41), and the 2nd DF (OR = .672, p= .49) at start of defence, distance covered by FW player (OR = .844, p= .48), distance covered by DF player (OR = 1.428, p= .007), and position of final DF line (OR = 1.600, p= .004) were correlated with the defensive performance, respectively. The distance between ball and the 1st and the 2nd DFs at the start of defensive play is a key factor of defensive tactical play. Available of the 1st DF to reduce the opponent attacking speed is one of key component of defensive tactical skill of soccer (Suzuki & Nishijima, 2007). The distance covered by FW and DF, and position of final DF line directly relate with control of opponent attack such as decreasing opponent attacking space. In conclusion, these SDTP variables are statistically valid to use for defensive performance analysis in soccer games.
The movement speed of during the game in amputee soccer
Authors: Maehana, H., Iguchi, Y., Miyamoto, A., Horiike, T., Koshiyama, K., Yoshimura, M.
Summary: Amputee soccer activities are comprised of varying explosive movements like forward and backward shuffles, runs at different intensities and sustained forceful contractions to control the ball against defensive pressure1). As with soccer player, which had less time with the ball, players should had spent a lot of time to move. However, there is no indication of the movement speed in amputee soccer. It is possible to evaluate the performance by creating an index of the movement speed. Appropriate training plan is devised by evaluating a performance. The present study was aimed to evaluate the measured performance of the movement speed during the game in amputee soccer players. Twelve male amputee soccer players with unilateral lower limb amputees participated in this study voluntarily. In amputee soccer, matches are played between teams of seven players using bilateral crutches. Wearing a prosthetic device is not allowed during match play. The match is played in two equal periods of 25 minutes each. The half time interval must not exceed 15 minutes. The size of the coat is a 70m × 50m.To measure the movement speed during the game based on the above official rules. Match activity data were collected using the GPS (15Hz). The average of the total distance was significant longer in the first half compare with the second half (1721.8m vs. 1398.4m, p<0.05). The movement distance with Walking (0.4-5.0km/h) was longest in both the first half and the second half. The movement distance was significant higher in the first half compare with the second half in Moderate intensity Running (8.0-13.0km/h) (584.6m vs. 421.6m, p<0.05). During the game had a higher rate to move below 13km/h. No significant difference between the first half and the second half was observed in Maximum speed, frequency of High intensity Running and distance per one time of High intensity Running. Below-knee amputation had 0.9km/h faster maximum speed, and 30cm longer in distance per one time of High intensity Running compared with Above-knee amputation. The finding of the present study was suggested that high percentage to move in the following 13km/h during the game, and there was the influence of limb length difference of the remaining portion in the amputation level.
The effect of muscular strength and strength asymmetry on jumping height among soccer players
Authors: Misjuk, M., Rannama, I., Zusa, A.
Summary: The game of soccer involves frequent one-sided activities, which may lead to muscle strength asymmetries between two legs (Kellis et al., 2001). Bilateral muscle asymmetries may reduce performance and increase injury risk (Fousekis et al., 2010). There are many studies that investigate relationship between muscle strength and jump height, but there is lack of studies that investigate relationship between muscle strength asymmetries and jump height. The purpose of this study is to investigate relationship between knee flexors/extensors strength, strength asymmetries and vertical jump height. The 17 male soccer players of Estonian Premium League teams (22.6±3.9yrs, 182.7±7.1cm, 79.4±9.6kg, soccer experience 15.9±4.0 yrs) performed countermovement jump (CMJ) and countermovement jump with arm swing (CMJA) in Kistler force plate. The jump height was calculated with impulse method. Knee extensors (EX) and flexors (FL) peak torque (PT) was measured with an isokinetic dynamometer Humac Norm (USA). Concentric actions were measured at angular velocity of 60, 180 and 300°/s, and eccentric (ECC) actions at angular velocity of 60°/s. The hamstring quadriceps (H/Q) ratio and absolute bilateral asymmetry index (ASI) between dominant (D) and non-dominant (ND) legs were computed (ASI=100*(D-ND)/0.5*(D+ND)). The forward stepwise regression analyses were made between both jump height values and relative EX and FL PT (N/kg), H:Q ratio and ASI of EX and FL PT in different testing speeds. The regression model for CMJ height: CMJ=10.49+22.82×EX300-0.199×FL300ASI (p<0.01, adjusted R square =0.74). The regression model for CMJA height: CMJA=21.3+21.9×EX300-0.393× EX300ASI-0.218×FL300ASI (p<0.01, adjusted R square =0.76). Results on current study are in line with previous study by Lehance et al (2009) that knee EX strength is strongly correlated with CMJ height, but the current study foundthese strong correlations at lower angular velocity. The main finding of this study is negative relationship between CMJ height and knee EX and FL strength asymmetry measured in high testing speed, it supports modelling based findings of Yoshioka et al (2011).
The effects of PHV on physical performance on young soccer players
Authors: Bellistri, G., Oddo, A., La Torre, A., Muratore, M., Sforza, C.
Summary: In youth soccer academy categories are organized into annual age groups in order to provide similar competition level and age specific training program (Deprez et al, 2012). Several studies (Figueiredo et al, 2009) have shown better performance in strength, power, speed and endurance in relation to a faster biological maturity in the same age group. Talent identification is often based on physical capacities and so there is the risk that players who are physically less mature may be deselected but not on the basis of their adult potential. No studies evaluated a possible correlation between age of peak height velocity (APHV) and physical capacities. The aim of this study was to examine the relationship between APHV and physical capacities in young soccer players. Methods. 158 young soccer players (8-16 years old) were recruited in this study. Players had their APHV indirectly estimated by the leg length, height and weight using equation from Mirwald et al (2002): Maturity off set = –9.236 + 0.0002708 × (leg length × sitting height) – 0.001663 × (decimal age × leg length) + 0.007216 × (decimal age × sitting height) + 0.02292 × (weight/height ratio). Counter movement jump (CMJ), agility (Illinois test modified for young players), linear sprint performance (5, 10, 20 m), balance (Y balance test, YBT) and flexibility (Sit and reach test, S&R) were evaluated to determine the players’ physical capacities. Relationships between APHV and physical variables were evaluated using Pearson’s product-moment correlation. The magnitudes of the correlations were considered as trivial (<0.1), small (0.1-0.3), moderate (0.3-0.5), large (0.5-0.7), very large (0.7-0.9), nearly perfect (>0.9) and perfect (1.0) in accordance with Hopkins et al (2009). Statistical significance was set at P<0.05. Results. All physical variables were significantly correlated with APHV. Very large magnitude correlations were observed between APHV and linear sprint performance on 5, 10 and 20 meters (P<0.001, r=-0.71; P<0.001, r=-0.82; P<0.001, r=-0.86, respectively), large magnitude correlations were observed between APHV and agility test (P<0.001, r=-0.56), S&R (P<0.001, r=0.55) and CMJ (P<0.001, r=0.52), moderate magnitude correlation was found between APHV and YBT (P<0.001, r=0.38). Our results indicated correlations between APHV and physical performance in young soccer players and so the physical capacities should be evaluates in relation to individual biological maturation for talent identification and in order to program appropriate training in groups with a great variability of APHV.
Differences in anthropometric characteristics between children soccer players – today and eighteen years ago
Authors: Gusic, M., Molnar, S., Smajic, M., Markovic, L., Maksimovic, D., Marinkovic, D.
Summary: The aim of this study was to determine significant differences in some anthropometric characteristics between children soccer players aged 7-10. Over the last two decades, percentage of overweight and obese children is rapidly growing (Podstawski and Boryslawski, 2012), which made many researchers, doctors and sociologists to feel the need of exploring the various possibilities of preventing this negative tendency, by collecting and analyzing a specific bit of information that aids in understanding growth and maturation. This study was conducted on the entity of 150 male subjects aged 7-10 divided into two groups: 90 soccer players measured at present and 60 soccer players measured 18 years ago. A t-test was used for comparison of 9 anthropometric variables: height, weight, BMI, knee diameter, circumference and skin folds of upper and lower leg. Based on compared data, significant differences (p<.01) were found in 8 variables where the group that was measured at 1997.had significantly lower values than group measured at 2015. The only variable that had no significant differences was: lower leg skin fold. It appears that, at present, children spend less time practicing sports or physical activities, while they devote more time to activities such as watching television and playing video games (Vicente-Rodriguez et al., 2003). Sedentary lifestyle and badly programmed diet combined with physical exercise will result in changes of bodily composition (Prskalo et al., 2015.), which will mostly reflect on the quality of life of an individual. The importance of similar research topics (secular, longitudinal studies) has great interests for the global community, all in a cause of understanding variations of population’s growth and maturation through time. It is yet to find out if synergy of factors such as nutrition, a specific type of physical activity or sociology-cultural factors has a predictive influence on referent dynamics of growth and maturation. Secular trend in height has stopped in many developed countries while weight has continued to increase (Malina, 2014) resulting in increase in overweight and obese.
Sex differences in chosen cytokine concentrations following an exercise stress in soccer player
Authors: Pokora, I., Zebrowska, A., Kochanska-Dziurowicz, Z.
Summary: The production of cytokines in response to exercise is directly linked to the duration, intensity of exercise, the number of muscle fibers recruited and the fitness level of subjects. Recently, researchers have suggested there are sex differences in the immune response to exercise (Northoff et al., 2008, Gillum et al., 2011). It is recognized that women have more brisk immune responses than men and that woman’s immune responses are influenced by sex hormones (Timmons et a., 2006). Female sex hormones fluctuate during the menstrual cycle and one would expect that in women immune responses to exercise may depend on the phase of the menstrual cycle. This study investigated whether there are any gender and menstrual phase related differences for physiological strain and whether the cytokine alterations to exercise stress are different in male and female soccer players. 12 men (M) and 15 women (W) completed an incremental intensity running test to exhaustion. Women were tested during the follicular (F) and luteal (L) phase of the menstrual cycle. All subjects trained football for about 8 years and underwent medical evaluations at the same point of the pre-season training process. Before exercise body mass and body composition were determined. During exercise oxygen uptake (VO2), heart rate (HR) and tympanic (Tty) temperature were continuously recorded. Before and at the end of exercise a physiological strain index (PSI) was calculated. In the blood samples collected before and following exercise the selected cytokine levels (IL-1 beta, TNF-alpha and IL-6), AlAT, AspAT activity and sex hormones (estradiol-E and progesterone-P only in women) were determined. There were significant gender differences in subjects’ characteristics. The VO2max, PSI and maximal power (Wmax) were significantly higher in M than W. Despite higher Ttymax in M, the rise of Tty/min, delHR, HRmax were similar in both groups. The analysis of blood samples showed there are significant gender differences in IL-1beta, AlAT and AspAT activity. There were no significant differences in TNF-alpha and IL-6 cytokine responses to exercise between the M and W. There were significant menstrual phase-related differences for PSI, Wmax, E level and AlAT, AspAT activity in women. There are gender and menstrual phase related differences in the physiological strain to exercise, however in relation to the PSI women have more visible cytokine responses to exercise than men. Women in the luteal phase demonstrated a slightly greater pro-inflammatory cytokine response to exercise than in the follicular phase.
Peak torques and hamstring to quadriceps ratio in professional soccer, futsal and basketball players
Authors: Parpa, K., Michaelides, M.
Summary: Quadriceps (Q) and hamstrings (H) muscle strength inadequacies and imbalances has been shown to be associated with increased risk of lower extremity injury in athletes. A reduced (0.75 or less) hamstring to quadriceps ratio (H/Q ratio) may put athletes at a higher risk for lower extremity injuries. The purpose of the present study was to examine the peak torques of the Q and H muscles and their torque-ratio (H/Q) in professional soccer, futsal and basketball players. In addition, differences between the limbs were examined. Seventy six participants (football n: 44, futsal n: 16, basketball n: 16) were evaluated using an isokinetic dynamometer. Peak torque and H/Q ratios were evaluated at both 60 degrees/s and 300 degrees/s. It was found that basketball players produced significantly greater torques (at 300degree/s) in both the right and left Q compared with the football and futsal players [F =7.37, p<0.05 and F =7.25, p<0.05 for right and left Q respectively]. In addition basketball players demonstrated significantly greater toques for hamstrings compared to the other 2 groups [F =5.98, p<0.05 and F =5.55, p<0.05 for right and left H respectively]. No significant differences were observed in H or Q torques or H/Q ratio among the players of different sports. Finally, no significant differences were observed between the right and left limbs among the players with mean values being less than 10% in all groups. It is concluded that basketball players have stronger quadriceps and hamstring muscles only when tested at faster speeds. Also, based on the H/Q rations and the absence of asymmetries these professional players do not seem to be at an increased risk for injuries. Isokinetic evaluation of the lower extremities may provide the coaching team with valuable evidence regarding potential asymmetries between Q and H that may progressively contribute in performance deterioration and increase the risk of muscle injuries development. Possible asymmetries may be eliminated by incorporating the appropriate training into the habitual exercise routines of professional athletes.
Leukocyte alteration in response to a soccer game
Authors: Devrnja, A., Barišić, V., Bašić, M., Matković, B.R.
Summary: Soccer is one of the most popular modern sports played by men and women all around the world. It is estimated that players cover approximately 8 to 13 km per game, including different intensities of movement: walking, moving backwards, jogging, running and sprinting. During the game soccer players experience a number of short accelerations and deccelerations at near maximal or even maximal intensities that could represent an important source of muscle damage and inflammation. The aim of the study was to determine the effect of soccer game on changes in leukocyte subpopulations in young soccer players. 44 male field players aged 16 to 18 years, members of two soccer teams competing on junior national level, volunteered to participate in this research. All subjects signed informed consent. The study was carried out in accordance with and approved by the Research Ethics Committee of Faculty of Kinesiology University of Zagreb. 30 minutes before and immediately after the game (2 x 45min) blood samples were taken and leukocyte numbers were determined. Focus X2 was used to analyze player on-field activities. Statistical computations were performed using Statistica for Windows software. Total absolute number of leukocytes increased significantly from 5271 to 9465x10^9/L. Compared with circulating numbers at rest before the game increased number of neutrophils, eosinophils and monocytes were determined, while the number of lymphocytes significantly decreased. Significant differences were determined among the changes according to the player’s position. The changes in total leukocyte numbers and all leukocyte subpopulations were identified. The similar changes were observed for all positions of players, but the level of changes was different. In goalkeepers the changes were not significant which is in accordance to their lower load during the game. More pronounced differences were present for defenders and midfield players. These large increases in total number of leukocytes and especially in segmented neutrophils from pre-match to post-match are in agreement with other studies observing muscle damage changes in soccer players during the game. The correlation with distances covered was noticed.
Kinetic analysis of pelvis horizontal rotation of angled instep kicking in soccer
Authors: Inoue, K., Nunome, H.
Summary: Previous study illustrated that matured instep kick included appreciable pelvis counter-clockwise rotation and that motion was induced by torques mainly due to ground reaction force (Inoue et al., 2014). However, mechanical factors that induce the pelvis rotation have not been revealed when players kick the ball to varied angles. This study aimed, therefore, to clarify the kinetic aspects of the pelvis rotation when players kick the ball towards angled directions. Nine male soccer players performed maximum instep kicks towards three angled directions (15, 45 and 75 deg.). Their motions and ground reaction forces were recorded by a motion capture system at 500 Hz. Angular velocity and torque vectors regarding the support leg and the pelvis were calculated, and then the components that induce the pelvis rotation on the horizontal plane were extracted. An increase of the angle of kicking direction led to a significant (p<0.05) increase of the range of the pelvis rotation. With increasing the kicking angle, the higher hip joint torques of the support leg were observed. The angular impulses due to the hip joint torques were systematically and significantly (p<0.05) increased with an increase of kicking direction angle. The ranges of foot segment rotation (ROM) of the support leg were also systematically emphasized with an increase of the kicking direction angle while the torques for the foot rotation were small to be negligible in all the kicking directions. Scurr & Hall (2009) reported that soccer players displayed a greater pelvic rotation when using a wider approach angle. Levanon & Dapena (1998) argued that the pelvic rotation has a role to face the anterior half of the thigh (kicking leg side) onto the target direction. In this study, we succeeded in illustrating how the kinetic background changes when players kick the ball to angled directions. Inoue et al. (2014) already demonstrated that the interaction torque due to ground reaction force is the main drive in producing the pelvis rotation in normal straight instep kicking. We accumulated additional knowledge about the emphasized pelvis rotation when the ball was kicked to angled directions. The pelvis rotation was emphasized in response to the increased kicking angles. The hip joint torque (angular impulse) of the support leg was the kinetic factor systematically corresponded to the change of kicking directions. Thus, it can be assumed that the hip joint torque of the support leg is responsible for the increased pelvic rotations. Likewise, we observed the foot rotation was increased with an increase of the kicking angles. However, this motion was not accompanied by the action of the torque. Hence, it is most likely that the foot rotation is passively induced by some other factors such as partial friction of the floor acting on the foot segment.
The influence of acute dietary nitrate supplementation on performance during a soccer specific treadmill protocol
Authors: Peters, G., Henderson, K., Stone, M.
Summary: Research shows that dietary nitrate supplementation (DNS), reduces the O2 cost of walking and running (Lansley et al. 2011) Further research suggests that DNS reduced the O2 cost of low intensity exercise, and enhanced tolerance to high intensity exercise (Bailey et al. 2009). Field based research has shown that DNS improves intermittent running performance by around 3.8% when time to fatigue is assessed (Wylie et al. 2013). However no studies so far have examined the effect of acute DNS on the physiological responses to high intensity interval exercise (HIIE). Therefore the aim of the study is to show the effects of DNS on high intensity intermittent running. Participants visited the Human Performance Laboratory (HPL) four times. The first visit was a maximal oxygen uptake (V ̇O2max) test, to volitional fatigue. Following a pilot session, the participants then performed two exercise tests 10 days apart, in a doubly blind randomised crossover design. Participants ingested a 70 ml shot of Beetroot juice (BRJ) containing 0.4 g (4mmol) of dietary nitrate, or 70ml placebo (PL) 60 min prior to an intermittent treadmill protocol. At time of submission, seven participants completed study. Mean Oxygen uptake (V ̇O2) was 36.6 and 36.2 ml.kg.min-1 between BRJ and PL respectively. Mean blood lactate concentrations are 4.89 and 5.76 mmol.L-1 for BRJ and PL respectively. Mean blood glucose concentrations are 4.38 and 4.46 mmol.L-1 for BRJ and PL respectively. Perceptual responses are 13 v 12 for BRJ and Pl respectively. Early results suggest that acute dietary nitrate supplementation reduces the perceptual effort of high intensity exercise, despite no changes in oxygen consumption. Blood lactate and glucose also show no differences between BRJ and PL respectively. Further data to be collected to ensure type I or II errors are not made.
Does a Paleolithic diet influence performance or metabolic parameters and is it suitable in everyday life of young soccer players? – A pilot study
Authors: Oertzen-Hagemann, V., Eibl, A., Platen, P.
Summary: A balanced and healthy diet is essential for elite athletes and thus it is for soccer players. Nevertheless many investigations show that the eating patterns of young soccer players are largely inadequate. To satisfy energy needs and optimize performance a modification seems to be necessary. A paleolithic diet (PD) is assumed to be associated with positive health due to its exclusion of processed food products. The aim of the present study was to investigate whether a PD is compatible for young German soccer players and to evaluate metabolic parameters at rest and during endurance exercise. 17 young soccer players (age: 14.4±0.5 years; body mass: 64.8±6.5 kg; height: 173.5±6.5 cm, fat mass: 10.8±1.2 %) completed two test trials, separated by a 4-week intervention period. The intervention group (PG) ate a paleolithic diet based on the lifestyle conditions more than 10.000 years ago preferring minimally processed food, wild fruits, vegetables and different animal food. The control group (CG) was instructed to follow their normal diet. Between the test trials all participants completed a nutrition diary and underwent identical training protocols. The test days started with venous blood sampling to determine lipid profile, glucose, electrolytes, urea and uric acid, and anthropometric measurements followed by different exercises, such as sprints, jumps and an incremental step test on a treadmill for the determination of VO2max. Furthermore, they completed the 30-15 intermittent fitness test during their training sessions one day later. Additionally, an interview was performed for the determination of compliance and possible side effects. Because of illness, injury, incompatibility or an insufficient level of compliance with the intervention guidelines, five participants did not complete the study or were excluded from statistical analysis. Weight (PG: pre 65.6±5.8 kg vs. post 64.9±5.6 kg; CG: pre 61.6±7.0 kg vs. post 61.7±6.4 kg), fat mass (PG: pre 10.5±0.8 % vs. post 9.9±1.0 %; CG: pre 10.2±1.4 % vs. post 10.7±1.5 %) and metabolic blood parameters remained unaffected by the dietary intervention. Performance parameters like sprint time, jump height and endurance performance showed no significant differences within and between groups, as well as metabolic parameters during exercise. However, 4 out of 9 participants reported gastrointestinal discomfort during the paleolithic diet intervention, two complained about having headaches and two about a loss of concentration or sleeping problems. To summarize, a 4-week paleolithic diet did not affect performance or metabolic parameters during rest or exercise in young football players, but caused symptoms of discomfort in the majority of them.
Using external and internal parameters of effort in monitoring the training of junior III football players
Authors: Marinescu, G., Ticală, L.D., Dulceață, V., Petre, A.T., Buzărnescu, M., Rădulescu, A., Dreve, A., Tătaru, T., Sima, D., Mănescu, D.C.
Summary: To achieve remarkable performances during a match, it is not enough to have the motivation and desire to succeed, but it is also necessary to understand the concept of total training, which claims that man is an indivisible whole and each exercise has a global impact on all components of performance (Brunet-Guedj E. et al., 2006). During a football game, metabolic systems are exerted as follows: 70% aerobic system, 15-20% anaerobic lactacid system and 10-15% anaerobic alactacid system (Cazorla G., 2002). It should be mentioned that, for reaching a steady state of maximal oxygen consumption (VO2max), this one goes through several intermediate stable states which are encompassed in the concept of VO2 DRIFT. Coaches should avoid the serious error of working in the slow component of VO2max (Wilmore J.H. et al., 2008). The research sample was made up of 18 athletes registered at School Sports Club 1 of Bucharest and born in 1998. Athletes were subjected to two tests (1st testing - 12.08.2014 and 2nd testing - 12.02.2015). The tests used were: 5-minute endurance test and 240-meter shuttle test. Data collection was achieved using GPSports equipment and SPI IQ software. The obtained reports provide data about the following items: covered distance, travel speed, acceleration speed, maximal aerobic velocity (MAV), VO2max, heart rate etc. and their evolution. In the 5-minute endurance test, 1st testing, the arithmetic mean for relative VO2max is 54.9%, while in the 2nd testing, the arithmetic mean has increased to 58.6%; the difference between the two tests is 3.7%, which shows a progress between tests as regards higher aerobic capacity. The use of 5-minute endurance test and calculation of maximal aerobic velocity (MAV) etc. provide information regarding the exercise capacity level of athletes and their limits. Scientific monitoring of training reveals important data about the body’s response to specific stimuli and helps coaches to conduct preparation according to the structure and components of periodization.
Effects of high-intensity interval training during the transition period in football players sub-19
Authors: Romero Moraleda, B., Martos Varela, S., da Silva García-Riego, R., Gallardo, J., Jiménez, V., de la Torre, P., Porcel, D., Paredes Hernández, V.
Summary: Currently exists a growing interest in the application of high-intensity interval training (HIIT) in football (Buchheit et al. 2013). HIIT has shown eficience to improve performance variables in team sports (Iaia et al. 2009). However, little research has been reported regarding the effects of HIIT on performance after winter transition period in football. Therefore, the aim of this study is to compare the effects on performance versus traditional training HIIT during the winter transition period in football players U19. A total of 40 players (20 players U19 of premier league and 20 players of second league) of 17.8±0.4 and 16.8±0.4 years respectively performed a program of 3 sessions during the week of winter transitional period (7 days). The HIIT group, performed a high-intensity interval training that consisted of 5 repetitions of 15 seconds at 140% of your Maximum Aerobic velocity (VAM) followed by a period of 45 seconds at 60% VAM, plus 5 core exercises (2x30’’). NO-HIIT group, performed 30 minutes of continuous running at 60% of maximum heart rate. The training sessions were monitored with Runtastic mobile application and a training log. The performance were measured before and after the transition period: countermovement jump test (CMJ) using MyJump, squat power test by SmartCoach and body composition variables (body mass and fat percentage). Student’s test was performed to analyze the differences for independent variables with software SPSS v.20 for Macintosh. The change percentage for the power in half squat (p=0.05) and CMJ (p=0.03) was significantly negative for NO-HIIT group. After the transitional period, both groups showed significant intra-group increases for fat percentage (HIIT group: 6.37±7.9; NO-HIIT group: 3.80±5.75; p=0.01 and 0.02 respectively). The main finding of the study was that HIIT group obtained favorable results for power variables. A similar study showed that football players achieved to maintain the values of VO2max during the transitional period, with a lower density of HIIT sessions (Slettalokken et al. 2014). Other studies have shown the effectiveness of HIIT training versus continuous training for both VO2max and power variables in young players (Sperlich et al 2011;. Pilianidis 2013 et al.). These results could show that intermittent high intensity training can be a useful method and recommended to maintain or even improve variables such as average power in squat and CMJ during the transitional period. The HIIT group showed significantly favorable results for the half squat and power CMJ compared with NO-HIIT group. The fat percentage was significantly increased in both groups.
Epidemiology of female collegiate football team injuries for two years
Authors: Oda, K., Ogaki, R., Murakami, K., Yamaguchi, T., Tajahashi, Y., Kurosawa, T, Miyakawa, S.
Summary: Football is played worldwide by more than 265 million players, of whom 26 million are female players (Astrid et al., 2007). The popularity of female football players in Japan has been rising since the winning of FIFA World Cup championship in 2011. The number of population continues to increase every year and exceeds approximately 30,000 today. Football requires physical contact, and therefore associates with a large number of injuries in both sexes. Injuries in male football have been the subject in many studies. However, the number of reports regarding female football injuries in adults is low and epidemiologic date in Japanese collegiate female football players is very rare. The aim of this study was investigating the injuries in Japanese female collegiate football players in two season (2014-2015) using definitions established by the Federation International de Football Association (FIFA). A total of 32 female collegiate football players (mean height = 159.3 ± 7.1 cm, mean weight = 57.0 ± 7.3 kg) participated in the study. We investigated the injured situation (game or practice, contact or non-contact), type of injury (traumatic or overuse), location, severity, days until return to play, and a month that the injury occurs. Injuries were classified into the following three categories according to FIFA severity. Overall, 76 injuries were documented in 25 players (78.1%). 82.9% of injuries were traumatic and 17.1% were overuse injuries. 31.6% of injuries were occurred during games and 68.4% were during practices. 36.2% of injuries were caused by the contact play and 65.8% were non-contact play. Most injuries (85.5%) were located in the lower extremities with affecting thigh (32.9%), ankle (23.4%), and knee (17.1%). The days taken until return to play with injuries during game and practice were 46.9±69.4 and 17.1±19.8 respectively. April was the predominant month for injuries (25.0%). As with other studies, our results show that the most injuries occurred in lower extremity. However, the days taken until return to play was longer in our study than its other studies (K. Söderman et al 2001). The results suggest that, in addition to the rehabilitation that focuses on early recovery, reducing severity of injuries by applying the preventive intervention of lower extremity injuries is the crucial strategy to shorten the return to play in female football players.
Brain Information Processing of Football Players during Decision Making
Authors: Matsutake, T., Natsuhara, T., Tabei, Y., Nakayama, M., Asai, T.
Summary: In soccer, there are many situations in which decision making for instantaneous judgments is required. The main research method in this area has been measuring the Reaction Time (RT) and visual search behavior (Ando et al., 2001; Montes-Mico et al., 2000). It has been argued that RT is an elapsed time from the perceived stimulus to the action, and visual search behavior involves cognitive behavior. For that reason, only analyzing these two indicators, will not produce adequate considerations for how soccer players process information during decision making. The purpose of this study, therefore, was to clarify the differences in information processing process of football players with different performance level. Participant were college football players who were winners of the all Japan university top level (n = 5; Expert) and 5 graduate students with no football experience (n = 5; Novices). They used a decision making task (Soccer version). Electroencephalography (0.5–100 Hz) was recorded with Ag/AgCl electrodes from 5 scalp locations: Fz, Cz, Pz, C3, C4. Trials with eye blinks, eye movements and response errors were excluded from analysis (±80 mV).EMG-RT is the time from stimulus onset to the appearance of the electromyogram (EMG). EMG-RT is a valid indicator of programming time. the electrode is mounted the surface of the gastrocnemius lateral head. P300 was identified at the latency and from the polarity to induced latent, latency and amplitude were also measured. In all of the participants of the experiments and the tasks, P300 has been confirmed. EMG-RT has appeared before the P300 latency in all participants. Expert had a significantly shorter RT and EMG-RT than Novices in the task. The result of this study identified the trend that EMG-RT has appeared before the P300. The human brain always predicts the future and it changes the behavior by calculating the consistency of the results. Rather than to predict and evaluate by a command from the brain, it can be evaluated from the receiving sensation (Seth, A. K. , 2013). This is called the interoceptive inference, and it has attracted attentions in recent years. The results of this study, did not agree with the results of previous studies on the ERP and EMG. For that reason, it can be considered that it is likely to be associated with the interoceptive inference. In future studies, number of participants need to be increased for more reinforced considerations.
Effects of creatine supplementation on sprint performance in youth, elite football players
Authors: Horne, S., Simpson, A.J., Sharp, P., Farrier, G., Sharps, R., Kippelen, P.
Summary: Creatine is a highly popular food supplement in football (Waddington et al., 2005). Whilst a wealth of data exists on the ergogenic effects of creatine supplementation in senior players, limited data are available in youth players. Therefore the aim of this study was to examine the effects of a standard, 8wk course of oral creatine monohydrate (CM) supplementation on sprint performance in youth, elite football players. Fifteen U18 (age 16 to 18 yr), male, Football Academy players followed a randomised, double-blind, placebo-controlled, parallel-group trial during the early competitive season. Players ingested 0.3 g/kg/d of CM (n=7) or placebo (PLA, n=8) during a 1wk loading phase, followed by 5 g/day of CM or placebo during a 7wk maintenance phase. Pre- and post-supplementation participants underwent body composition assessment (via body mass and sum of 8 skinfold thicknesses) and performed a repeated-sprint ability (RSA) test (Rampinini et al., 2009). In a subgroup of 10 outfield players (4 on CM and 6 on PLA), GPS data were obtained during match play in the period leading to the supplementation period and in weeks 4 to 8 of the supplementation period. Key index of sprint performance was % of overall match distance covered at >19 km/h (Osgnach et al., 2010). Data are presented as mean +/-SD, compared by RM-ANOVA. Body mass did not significantly change over the course of supplementation in either group. A small but significant (P=0.007) decrease in skinfold thickness was observed post-supplementation, with no group difference (-7+/-4% in CM and -5+/-8% in PLA). RSA did not significantly improve post-supplementation (mean RSA time pre- vs post-supplementation: 7.57+/-0.18 vs 7.52+/-0.22 sec in CM; 7.44+/-0.30 vs 7.24+/-0.18 sec in PLA). Sprint performance during competitive match play did not significantly differ pre- to post-supplementation, or between groups (overall match distance covered at >19 km/h: pre 4.8+/-0.7 and post 5.6+/-1.6% in CM vs pre 7.3+/-2.8 and post 7.2+/-2.9% in PLA). In youth, elite players 8wk of CM supplementation did not induce muscle mass gain beyond that observed with training alone. Further, CM did not significantly improve sprint performance. Thus these findings cast doubt about the effectiveness of CM as an ergogenic aid in youth, elite football.
Effects of mental and physical fatigues on football players’ in-game behaviours
Authors: Coutinho, D., Gonçalves, B., Wong, D.P., Travassos, B., Sampaio, J.
Summary: This study aimed to identify the effects of mental and peripheral physical induced fatigues on football players’ in-game behaviours. Ten Under-15 players performed a Gk+5v5+Gk small-sided game (SSG) on a 30x20m pitch based 3 bouts of 6 minutes each, and performed under three different conditions: i) physical fatigue condition (PF), induced by performing a repeated change-of-direction; ii) control condition (CTR), in which players performed the SSG without any previous activity; c) mental fatigue condition (MF) using a 30 minutes computerized version of the Stroop task. Time-motion variables and players’ positional data were gathered using global positioning systems (5 Hz). Positional data were used to compute tactical-related variables such as team’s stretch index, distance between players’ dyads and synchronization of longitudinal and lateral displacements of players’ dyads. When compared with CTR condition, players under PF condition was likely to lower the number high-intensity accelerations by ~33% (Cohen’s d: 0.5±0.5) and possibly lower the ratio of high distance covered by ~38% (Cohen’s d: 0.3±0.5). From the tactical perspective, the distance between players’ dyads in PF was very likely lower compared to CTR. Also in PF, player’s spent likely ~7% more time synchronized in longitudinal displacements than in CTR and most likely ~14% more than in MF (Cohen’s d: 0.7±0.3). The teams’ stretch index were very likely and most likely lower in MF than in PF and CTR, respectively. Although players spent less time synchronized in MF, the distance between players’ dyads showed a very likely more predictable pattern (i.e., lower approximate entropy values) in MF than in PF (Cohen’s d: -0.4±0.2) and possible more than CTR. Applying a physical stimulus previously to tactical tasks may be used to promote an increase in players’ longitudinal displacements synchronization and optimise the in-game physical performance, since dyads become more coupled. The induced mental fatigue decreased the team dispersion and the time that players’ spent synchronized in longitudinal displacements. This self-organized behaviour may be linked with the increased perception of mental fatigue, that encouraged team contraction and as consequence of higher proximity between players might decreased the need to stay synchronized with the surrounding teammates. Therefore, induced mental fatigue seems to change the way of how players perceive the environmental information. Overall, coaches may use both situations to promote variability in players’ tactical behaviours, and consequently, provide wide adaptive environments.
Relationship between mechanical stress and injury around the hip joint due to kicking action in Football.
Authors: Murakami, K.
Summary: In this study, we therefore analyzed the association between kick-induced mechanical stress (stress distribution) and the clinical findings of injuries around the hip joint that are known to be related to kicking actions in football. We selected 5 healthy football players, They perform the inside kick, instep kick, and infront kick 3 times each for right-footed. A three-dimensional motion analysis device was used to record their motion and measure the duration between maximum hip extension (MHE) and ball impact (BI). The motion analysis software, nMotion (nac, Japan) , was used to calculate stress between hip joints and the angle of the hip joint in each kicking motion. In addition, the bone strength analysis software Mechanical Finder (RCCM, Japan) was used to analyze the computed tomography and magnetic resonance imaging data of each subject to develop a finite-element model consisting of the right ilium, sacrum, and femur. Then, stress between hip joints calculated in dynamics analysis was input as a load value into the finite-element model for the stress analysis. At the time of BI, kicking actions produced a high-stress area in the pubic ramus compared with other areas. This value was an equivalent stress value generated in the area of interest (30 mm3) in the pubic ramus. Stress generated in the superior and inferior rami of the pubic bone was 3.52 and 2.94 MPa for the inside kick, 7.15 and 5.40 MPa for the instep kick, and 4.47 and 3.33 MPa for the infront kick, respectively. The high-stress area on BI was the same area where groin pain syndrome (pubic bone marrow edema) occurs in the clinical examination of football-related hip joint injury and where stress fractures occur in pubic bone rami. Furthermore, in the BI-related area of interest (pubic rami), the values of equivalent stress generated by the inside kick, instep kick, and infront kick in the superior and inferior rami were approximately 3 times, 5 and 4 times, and 3 and 2 times the stress created in the same area by standing by one leg (1.53 and 1.47 MPa in the superior and inferior rami), respectively. The analysis system that integrates motion dynamics into the body structure revealed the relationship between the clinical symptoms of the hip joint and previously reported kick-related injuries around the hip joint.
The effects of isokinetic hip flexion and extension training for men’s university football players
Authors: Miyagi, O., Kumagai, T.
Summary: The studies about hip muscular strength have been reported that the muscles iliopsoas was active during the entire kicking motion and the mean ball velocity related significantly with hip flexion strength of the kicking leg and hip extension strength of the supporting leg. So this study was designed to clarify the effect of isokinetic hip flexion and extension training over eight weeks training and to examine the change in mean ball velocity by kick, jump height, and sprint speed before and after training for men’s football players. The Subject were sixteen university football players. The team had trained 12 to 15 practice hours per week and played at least one soccer game per week. There were divided into 2 groups (training group, control group), and measured isokinetic hip Flex/Ext strength at 3 angular velocities (60, 180, 300deg/sec), mean ball velocity by kick, jump height (Squat jump: SJ, Counter movement jump: CMJ), and 30m sprint speed before and after training. Training group did isokinetic hip flexion and extension training. BIODEX SYSTEM 3 was used for training and measurement of muscular strength. Training intensity was 180deg/sec of angular velocity. Training was conducted 3 days per week, 3 sets per day, and 10 repetitions per set for 8 weeks. As a result, the changes of isokinetic hip Flex/Ext strength were indicated as follows. Isokinetic hip extension strength at 180, 300 deg/sec was significantly improved with training. And isokinetic hip Flex/Ext strength at all angular velocities tended to improve. Mean ball velocity by kick and jump height was significantly improved. Although sprint speed shows no improvement, it tended to improve within after 15m. It suggested that improvement of hip extension strength affected improvement of mean ball velocity and jump height. These results suggested that hip extension strength is important for mean ball velocity and jump height.
The Relationship between Coach Feedback and Self-Perceived Sport Competence in Collegiate Male Football Players
Authors: Ambe, H., Murase, K.
Summary: Coach feedback significantly contributes to players’sport competence associated with intrinsic motivation. However, limited research has examined this relationship with observation in real sport-coaching settings. Therefore, the purpose of this study was to investigate the relationship between coach feedback and players’self-perceived sport competence in actual coaching contexts. One coach and 23 players of a male university soccer club participated in this study. The coach’s feedback to the players was recorded for 10 weeks using VTR and, subsequently, categorized into seven domains: 1) positive, 2) negative, 3) instructive, 4) questioning, 5) organizing, 6) friendly, and 7) other. Both before and after receiving coach feedback, players were asked to complete a questionnaire, which consisted of 10 subscales: (1) pass and control decision-making, (2) speed, (3) dribble skill, (4) physical strength, (5) endurance, (6) defense skill, (7) leadership, (8) motivation, (9) long kick skill, (10) heading skill. A significant relationship between soccer players’self-perceived competence and coach feedback was found. The results reveal that frequency of positive feedbacks, such as praise and encouragement, are negatively associated with pass and control decision-making as well as dribble skill. The results further indicate that collegiate male soccer players tend to draw on self-comparison and other internal processes more than positive coach feedback to evaluate their competence. Alternatively, a positive association between negative feedback, such as scold, and pass and control decision-making competence was also found. In competitive sports setting, the coach and players would share their common goal as a victory. In this case, players who received negative coach feedback understand the coaches’intent behind that. As a result, negative coach feedback seems to improve players’self-perceived competence in pass and control decision-making areas.
Monitoring of a football team during a competitive season by measuring serum myosin isoforms
Authors: Cussó, R., Carmona, G., Cadefau, J.A., Solanas, J.L., Revuelta, G., Maestro, A., Guerrero, M.
Summary: We developed an ELISA methodology sandwich type to improve the medical diagnosis of the professional sports men muscle damage. The new technic was applied to obtain basal values of a reference population and to monitor a team players during a football season. 49 reference volunteer and 27 male professional football players from the Sporting of Gijon Club participated in this study. In the case of players, blood was obtained at the pre-season and at different time-points along the season. In ELISA test monoclonal anti myosin fast and slow antibodies tapissed a polystyrene plate. The calibration curve was performed with purified pork myosin. To close the sandwich ELISA, the polyclonal rabbit antibody was added. Plates were incubated with an anti-anti rabbit antibody linked to peroxidase and TMB substrate for the luminescent reaction of the peroxidase. The absorbance was read at 450 nM wavelength. The calibration curve shows a very good linearity. The intra-assay coefficient of variation was assayed using three different samples low, medium and high values. CV is below 11% for Fast myosin and below 6% for Slow myosin. Linearity for Fast myosin was 80% and for the Slow myosin 90%. Comparing the results of the football team with reference population we observe that our players move below the normal average respect to Fast myosin and above the normal average respect to Slow myosin. In the competitive pre-season there is not increase in serum but at the beginning of season both types of fiber are damaged but not in the same magnitude, as the ratio indicated, due to the tactic and training conducted by the team. The new ELISA assay has greater speed, sensitivity and reproducibility that the Western Blot and shorten the result time from 48 to 4 hours, allows for processing 26 samples at the same time and it is more economic. Values for Fast myosin in the reference population shows no differences between sex and age. Significant differences were found of Slow myosin from older group (45-66) compared to younger (20-44). It may be caused by their lifestyle, which must be more sedentary at maturity, or loss of muscle into mature persons. Moreover, tracking myosin isoforms during a season of racing in a soccer team offers new insight into the state of the fast and slow fibers relating it to the possible significance of sarcomere damage that can occur during different phases of training and competition.
Caffeine supplementation has no effect over performance in young elite football players
Authors: Mackay, K., Díaz-Castro, F., Peñailillo, L., Zbinden-Foncea, H.
Summary: Caffeine has been used as an ergogenic aid in sports performance for at least two decades (Tarnopolsky et al 2010). Studies have hypothesized that due to its stimulant properties on the central nervous system it can be used as an enhancing aid which may improve athletic performance and decrease muscle fatigue. The aim of this study was to observe the effect of the consumption of caffeine on performance in young elite football players before, throughout a 45 min match and after, simulating the end of the first half of a match and observe their performance status for the second half. In a randomized single-blind design, the players (16.4 ± 0.5 years, 69.1 ± 7.5 kg, 175.6 ± 6.6 cm, 13.7% ± 3.0 % body fat) recruited from the national junior chilean team, were given either a capsule of 3 mg · kg1 b.w. of caffeine or placebo (dextrose) 60 min prior to the match. Match activities was assessed with a GPS system and 5 m (acceleration), 15 m (flying time), and 20 m (maximal velocity) sprints and an agility test was measured with timing gates and photocells before and 5 minutes after the 45 min match. Heart rate was monitored throughout the 45 min game. No differences (P >0.05) was observed between the caffeine and placebo group regarding total distance covered (4850.6 ± 231 vs. 4976 ± 386.4 m), sprint number (143.2 ± 10.8 vs. 161.4 ± 22.0), repeated sprints (143.2 ± 11.1 vs. 153.9 ± 24.1), maximal heart rate (198.9 ± 6.7 vs. 197.6 ± 8.0), high intensity zones (zone 5 and 6: 280.5 ± 34.5 vs. 237.6 ± 60.5 m and 178.7 ± 65.6 vs. 157.6 ± 59.1 m, respectively). Acceleration, flying time, maximal velocity, and the agility test showed no differences between groups, before or after the match (P >0.05). Caffeine administration did not show an ergogenic effect in young elite football players for acceleration, flying time, velocity, agility, or any match activities. Our study is in agreement with the results observed by Pettersen et al. 2014, where no effects in performance was observed in young football players after the consumption of caffeine. Our results conclude that the consumption of 3 mg · kg1 b.w. caffeine has no effect in preserving performance after 45 min of a football match.
A study on process of career formation in Japanese football players
Authors: Uemukai, K., Inaba, K., Iida, Y.
Summary: There are some studies related to the career development of athletes in Japan had been carried out so far, however they are mostly based on sport psychology and sport policy. In the field of sport sociology, accumulated studies include “socialization to/by sports”, sociological study of school club activities, history of career development focusing on difficulties that athletes face and a discussion on their second career among others. Iida(2012) had conducted quantitative as well as qualitative researches of J-League academy players and their parents by focusing on their career formation and process. On the other hand, there are not many teams for girls and it is not easy for them to continue playing football after junior high school. Furthermore, there is no option available to become a professional even after they continue their football career up to a high level, so the options to play at a university compared to the male players are not enough either. That means female players have to build their career among unclear and limited options. What kind of impact does this environmental difference bring to the career development process? This study develops from the questions and interests in Iida’s discussion and expands the subject to female football players to find out its characteristics and challenges in comparison with male football players in Japan. The content of questionnaire includes: when and why they started to play football; factors to carry on this career; background details and reasons for joining their current team; what they think of their current environment that they play football in; what they think of their future as footballers; and any factors or persons that affected their decisions when their environment changed. 212 University female football players provided valid data. Almost subjects in this study started to play when they were in a lower grade of elementary school and belonged to local club rather than junior high-school team. This result reflects an issue of girls’ football in Japan, which lacks the system of “club activities” at school after they move on to a junior high school. Furthermore, one of the reasons to choose their high school is because that was a school with a strong football team but only less than 20% of the students talked to their coach about their choice of school and a great number of them consulted their mothers. Similar responses applied to their consultation on their future careers. Considering some preceding studies of male football players, similar research showed that coaches made more of a presence in consulting on the contrary, so it seems to be necessary to further examine the background of this result.
Comparison of different evaluation methods of professional soccer players’ physical and physiological characteristics
Authors: Bizati, Ö., Muniroglu, S., Koz, M.
Summary: The aim of this study is determination of the most suitable and fastest method to measure the physical and physiological capacities of soccer players by comparing labratory and field tests with software supported non-invasive method (SSNM) relatively new approach. First of all all players were joined the antropometric measurements (height, weight, fat), SSNM measurements and VO2max measurements. Secondly, lactic asid tests were applied. Thirdly, Aerobic capacity (Yo-yo IR1) test was completed. And finally, anaerobic capacity (Sprint, Sprint Fatigue-Power Maintanence) test were completed. Repeated measures of ANOVA was used to analysis of variable within the triple groups to learn the statistical differences. Paired-Samples t test was used to investigate the differences between binary groups measurements, and coorelation was used to investigation of relationships. As a result of the measurements, 2mmol HR values and Aerobic threshold maintanence values obtained from the SSNM measurements, 4mmol HR values and Yo-yo IR1 HR values, VO2max HR values and Yo-yo IR1 HR values, VO2max HR values and 4mmol HR values, 4mmol threshold running speed values and Yo-yo IR1 running speed values, SSNM VO2max values and VO2max values, SSNM VO2max values and Yo-yo IR1 VO2max values were similar. But there were differences between SSNM anaerobic threshold HR values and 4mmol HR values, VO2max HR values and Yo-yo IR1 HR values, SSNM anaerobic threshold running speed values and 4mmol threshold running speed values, SSNM anaerobic threshold running speed values and Yo-yo IR1 running speed values. Subjects’ running speeds awere determined as 15.42±0.99 km/h for 4 mmol level, and 13.65±0.93 km/h for SSNM. There are similar resulted studies in literatüre, 4 mmoll running speed is 15.9±0.9 km/s (Kunduracıoglu et al, 2007), 15.9+2.6 km h‐1 (Berthoin et al., 1994). Subjects’ Direct VO2 max value was determined as 53.53±2.69 ml/min/kg and SSNM VO2 max value was determined as 53.74±3.90 ml/min/kg. Luhtanen et al., (2007) explained the VO2 max of soccer palyers is 53.5 ml/min/kg to investigate the heart rate variability at a tournaments. Rampinini at al (2005) was determined VO2 max of players as 53.3±4.2 ml/min/kg at training to determine the physiological load from HR. There is similarity between this study’s VO2 max values and studies of Luhtanen et al., (2007) and Rampinini at al (2005).
Load characteristics of soccer games in PE classes from the viewpoint of improvement in physical fitness
Authors: Tsuda, R.
Summary: The majority of studies on ball games in PE classes have focused on techniques and tactics, factors determining skill levels (Griffin et al., 1997). However, under the current Japanese physical education curriculum, it has been necessary to enhance physical fitness even in sport and dance exercises (Mext, 2008). From this point, it is important to examine the load characteristics of ball games in terms of physical fitness. The purpose of this study was to examine the effect of differences in pitch area and player number, ball, and rule of soccer games on characteristics of the games from the viewpoint of improvement in physical fitness. Experiment 1：Pitch area and player number. Twenty male junior high school students participated in the present study. They played four types of games with changing the size of pitch area and player number. (Game A : 30m×20m, 5 players per team ; Game B：45m×30m, 5players per team ; Game C : 45m×30m, 10 players per team, Game D : 60m×40m, 10 players per team). The number of ball contacts, ratio of appearance time each movement speed, and distance covered during the game were measured. As a results, Small-group games might be improve technique, and the games with large pitch area per player might be available for improvement in anaerobic power. Experiment 2：Types of ball, Sixteen male junior high school students participated in the present study. They played two types of 4vs4 games with changing the ball. (Game A : futsal ball ; Game B : football). The number of ball contacts, distance covered and heart rate during the game were measured. As a results, there was no significant difference in the number of ball contacts, distance covered and heart rate during the game between game A and B. Experiment 3：Rule modifications. Eighteen male junior high school students participated in the present study. They played three types of 4vs4 games with changing the rule. (Game A : free game ; Game B : pass game；Game C : man to man game). The number of ball contacts, ratio of appearance time each movement speed, and distance covered during the game were measured. As a results, the pass game would be the most effective in developing techniques, and the man to man game might be available for improvement in anaerobic power and aerobic endurance. These results suggest that the load characteristics of soccer game from the viewpoint of improvement in physical fitness differ greatly when the pitch area and player number, types of ball and rule modifications of games are changed.
Intake of macro-and micronutrients among Hungarian soccer players
Authors: Dobak, Z., Biro, M., Nyakas, C.
Summary: In sport nutrition one of the general concepts is that the varied natural diet spontaneously consumed may cover the needs. However the nutritional requirement of different sport types, the actual changes in body composition, the nutritional defects especially in micronutrients may require to use of specified nutrition. In competitive sport, hydration and supplements have also a distinguished role for maximal performance. The aim was to examine professional Hungarian soccer players’ macro- and micronutrients intake, eating habits, body composition in general and according to the different training cycles (training-, rest- and match days). Based on that personal dietary advises were also aimed to formulate. Twenty seven elite athletes aged between 18-30 years were included from a single soccer team. The participation was anonym and voluntary. Dietary analysis software (NutriComp®) recorded the athletes’ three-day dietary diary in relation to their exercise cycles (training, rest and competition days). We performed body composition measurement with InBody device 230®. The data analysis was performed using SPSS software package including paired t-test. On the training day the average energy intake was 38.5 kcal/kg/day, at rest day 36.2 kcal/kg/day, and at match day it amounted to 40.3 kcal/kg/day. The evaluation of averaged three-day dietary diary revealed that energy intake remained significantly (p<0.05) below the desired value (adjusted to the present quantified sporting activities it was 50 kcal/kg/day). The vitamin D, iron, calcium intake was below the recommended RDA values defined for the adult population (calcium 741 mg/day, iron 13.7 mg/day, vitamin D 3.5 mg/day). On average, soccer players consumed variable kinds of supplements daily which did not include vitamin D or calcium products. On training day one-fifth of the soccer player energy intake came from protein, and the rest came from fat and carbohydrates in about the same ratio (42% carbohydrates, 37% fat, 20% protein intake, 1% other). There was no significant difference in carbohydrates consumption between training and match days. High fat diet was typical among the Hungarian professional soccer players in each training cycle period. On match day the most attention was payed to increase protein intake on expense of fat intake. Appropriate energy intake is only possible with a well-balanced macronutrient consumption meeting the enhanced energy requirement. In our survey a negative energy balance characterized each training cycle. Defective food habits and incorrect diet throughout the training cycle may degrade performance. The micronutrient dis-balance especially attracts attention and call for the importance of individual and targeted intervention regarding nutrition supplements. In addition, defining lifestyle factors disturbing or supporting nutrition would be also helpful for explanation.
The use of gol scale to measure perceived exertion in soccer
Authors: Polito, L.F.T., Figueira Junior, A.J., Zanetti, M.C., Bocalini, D.S., Marquezi, M.L., Lino, J., Nunes, H.R., Ponciano, K., Montenegro, C.G.P., Brandão, M.R.F.
Summary: The peripheral signals integration from the muscles and joints and also the central signals from ventilation have their integration in the somatosensory cortex, enabling general or local perception of effort. Despite the Rate of Perceived Exertion usually used to estimate the internal training load and monitoring the exercise, few instruments have been developed and validated for specific sports. This study aimed to analyze the preliminary evidences of validation of a scale for soccer players named Gol Scale. The new scale has been developed in two phases. In the first phase the cartoons of the scale were drawn based on the theoretical construct of perceived exertion. The final version of the scale is composed by six cartoons that show different grades of effort (1: low effort to 6: exhaustion). To ensure the representativeness of the cartoons they were validated by judges (nine PhD professors: physiologists, sports trainners and sports psychologists). In the second phase 13 soccer players (18.8 ± 0.77 years old, stature 177 ± 8.0 cm, body mass 70.8 ± 7.53 kg, % body fat 13.42 ± 3.19, lean mass 60.49 ± 4.75 kg and fat mass 9.60 ± 3.19 kg) were evaluated by a 3 minutes progressive protocol up to exhaustion with 1-minute recovery between stages. The Borg Scale 6-20, The Cavasini Scale, The cartoon Gol Scale, Heart Rate (HR), Percentage of Heart Rate (%HR) and Blood Lactate Concentration ([La]) were immediately determined after each stage. Pearson’s correlations coefficients were used. The level of significance was .05. We found significant correlation between the Gol Scale and Borg Scale 6-20 (r = 0.92, p<0.05), Cavasini Scale (r = 0.92, p<0.05), %HR (r = 0.88, p<0.05), HR (r = 0.82, p<0.05), and [La] (r = 0.66, p<0.05). A recent theoretical model explain that perceived exertion is associated to the increase of corollaries stimuli to motor impulses. The intensification of motor impulses generated by the central nervous system for the movement executions would be the main factor responsible for the increased of the RPE. These results showed that the Gol Scale is a promissory instrument for measuring perceived exertion.
External load assessment during small sided games in soccer: influence of pitch size and goalkeeper presence
Authors: Modena, R., Togni, A., Fornasiero, A., Savoldelli, A., Pellegrini, B., Schena, F.
Summary: Several studies aimed to analyze the time motion characteristics using speed thresholds and the physiological responses (1) in soccer small sided games (SSGs). Recently the global position systems technology (GPS) allows to quantify the players acceleration (3). In this study we quantified external load during SSGs with different pitch sizes and with or without goalkeeper (GK) by using acceleration data as novel methodology. 12 amateur soccer players took part in the study during in-season period. A total of 91 drills were monitored in 4 conditions: 2 SSGs in a 30x20 m field with (S-GK) and without GK (S) and 2 SSGs in a 40x30 m field with (L-GK) and without GK (L). Every 4–players SSGs lasted 4 x 4 minutes with 3 minutes of recovery and during these each player wore a GPS device (Viper, StatSport, UK). Differences between SSGs format were assessed for total distance covered (TD) and distance covered in six different speed zones (D): walk, jogging, medium, high and very high speed and sprinting. Also we considered the total number of accelerations (ACC) and decelerations (DEC) phases and those performed in different intensity zones. Every difference were assessed using one-way ANOVA with Bonferroni adjusted 95% confidence intervals. The results are shown as mean difference [95% CI’s]. The total distance covered (TD) was higher in L-GK and L (470.8 [462 – 478.6] m and 467.3 [455.3 – 479.2] m respectively) than in S-GK and S (372.6 [364 – 381.3] m and 410.5 [402.8 – 418.1] respectively) (p < 0.001). TD is also higher in S than in S-GK (p < 0.001). The number of both ACC and DEC was higher in L-GK (51.8 [50.6 – 53.0] and 48.1 [47.0 – 49.3] respectively) than other SSGs (p < 0.001) while in L there was the lowest number of ACC and DEC (47.2 [45.9 – 48.5] and 45.4 [44.1 – 46.7] respectively) (p < 0.001). No significant differences between L and S-GK were found. Furthermore, we found several differences among SSGs format in acceleration activities distribution. In agreement with previous study higher TD were measured in larger pitch size, however the GK influences TD only in small pitch. The differences found in accelerations profile can help coaches to propose the correct muscular load and acceleration patterns using SSGs with different rules.
Analysis of performance in different agility tests in young soccer players
Authors: Perri, E., Massari, M., Trecroci, A., Iaia, F.M., Alberti, G.
Summary: Agility, described as the ability to perform quick runs with directional changes, is an important component of soccer performance (Sheppard J.M. et al. 2006). Agility is a complex capacity (Young W.B. at al. 2002) and further information are needed to better elucidate its reproducibility and the different skills affecting performance during sprint/ agility tests. Therefore, the aim of the present study was to: i) determine the reliability of three different sprint/agility tests; ii) examine any existing relationships among the tests and iii) analyse their physical characteristics. Ten young soccer players from the same professional team (16.9±0.3 years; 178.7±4.8 cm; 68.8±5.6 kg) were involved in the study. The participants carried out two testing sessions separated by one week. Each testing day included three trials of following three tests: 1) 20-m straight sprint 2) Sprint with 90° turns and 3) Sprint with 90° turns dribbling with the ball (Sporis G. et al. 2010). Performance was measured using photoelectric cells (Optojump, Microgate, BZ, Italy), and GPS (Qstarz 15 Hr, Italy). Only the best trial was considered and the following parameters analysed: time, maximal speed (MS), mean power (MP), mean power in change of direction (CODMP). A significant difference in performance time between Sprint and Agility with ball in test-retest was 3.2±0.1 vs 3.1±0.1s (p<0.01), 9.1±0.4 vs 8.9±0.5 (p<0.01), respectively. The coefficients of variation between the test-retest were: 1.8 ± 1.3, 2.8 ± 1.9% and 2.3 ± 1.0% for Sprint Agility and Agility with ball, respectively. No correlation in performance time were observe between 20-m Sprint and Agility (r=0.11 p>0.05), Sprint and Agility with ball (r=0.33 p>0.05) as well as Agility and Agility with ball (r=0.16 p>0.05). No differences (p>0.05) were noted in CODMP between Agility and Agility with ball25.9±1.7 vs 24.2±2.0 W*kg-1 (p>0.05). Significant differences (F=966.5 p<0.001) in MP were shown between 20 m sprint vs agility (p<0.001), 20-m sprint vs agility with ball (p<0.001) and agility vs agility with ball (p<0.001). A variation was observed in performance time between the test-retest indicating high sensitivity and the need of a familiarization period when performing sprint/ agility tests. The pronounced differences in MP together with the absence of relationships found among the three different tests suggest that different abilities upregulate performance during sprint, agility and agility with ball.
Training load and subsequent wellness undertaken by an elite soccer goalkeeper: a case study report
Authors: Malone, J., Jaspers, A., Helsen, W., Frencken, W.G.P., Brink, M.S.
Summary: The role of a goalkeeper is a unique but often overlooked position in soccer. Whilst the training load practices of outfield players has been examined in detail (Malone et al. 2015), such information in goalkeepers in relatively unknown. Therefore, the purpose of the present study was to quantify the training load undertaken by an elite professional goalkeeper. One male international elite goalkeeper participated in this study. Training load data was collected over an 8 week period during the in-season phase (two mesocycles) using a global positioning system (GPS) device, heart rate and session rating of perceived exertion (S-RPE). The following parameters were exported and analysed from the software: duration, total distance covered, average speed (total distance/total duration), high speed distance (> 5.5 m/s), high acceleration and deceleration efforts (> 3 m/s2), PlayerLoadTM and average heart rate. Data was assessed in relation to the number of days prior to a match (MD-). In addition, the subsequent total wellness was assessed using an adapted questionnaire from Hooper et al. (1995). Duration, total distance, PlayerLoadTM and session-RPE were highest on MD-2, but remained similar across the remaining training days. Total wellness scores were highest on MD-3 (mean 21 au), but remained similar across the training microcycles (mean 17-18 au). There was no significant relationship between training load measures and the subsequent wellness response across all MD- days (P > 0.05). This exploratory case-study provides novel data about the training load undertaken by a goalkeeper towards matches. The data suggest there is a limited relationship between training load measures and subsequent wellness in goalkeepers. Previous work has found large correlations between such measures (Buchheit et al. 2013) using parameters applicable to the athlete’s role (e.g. high speed distance covered in Australian Rules Football). The lack of relationship in the present study may be due to the lack of position-specific training load parameters we can currently measure in the applied context. Future work should look to utilise current wearable technology to generate goalkeeper-specific parameters in order to fully understand the loading profile at the elite level.