Discriminative ability of the Yo-Yo intermittent recovery test (level 1) in prospective young soccer players

We evaluated the sensitivity of the Yo-Yo intermittent recovery test-level 1 (Yo-Yo IR1) when discriminating among players in varying playing positions and different age categories in youth soccer. One-hundred and six prospective young soccer players, grouped on the basis of chronological age (under-13, under-14, under-15, under-16, under-17, under-18, and under-19) and playing position (center-backs, fullbacks, center midfielders, wide midfielders, and forwards), participated in the study. The players were administered a single Yo-Yo IR1 test at the beginning of the spring season. Analysis of variance revealed significant (F = 25.3; p < 0.001) group differences in Yo-Yo IR1 test performance scores among the observed age categories, and a systematic age-related increase in the Yo-Yo IR1 test performance was evident. Subsequent post hoc comparisons identified a number of significant differences among the selected age categories in Yo-Yo IR1 test performance. Analysis of covariance identified significant differences among playing positions (F = 3.1; p < 0.019) in the Yo-Yo IR1 test performance after controlling for age (F = 135.1; p < 0.001). Subsequent pairwise comparisons of the adjusted Yo-Yo IR1 test performance identified that center-backs had achieved significantly lower (all p < 0.01) performance scores than center midfielders, wide midfielders, and forwards, but not fullbacks. These results could be of practical value to coaches and scientists for further development of talent selection and profiling procedures in soccer, particularly because (a) the endurance performance represents a very important fitness component in selection and profiling of young soccer players and (b) the Yo-Yo IR1 test proved to be valid, reliable, and easily available measurement tool of a player's soccer-specific endurance capacity.     

A test to evaluate the physical impact on technical performance in soccer

The aim of the study was to develop and examine a test for evaluation of the physical and technical capacity of soccer players. Fourteen youth elite (YE) and seven sub-elite (SE) players performed a physical and technical test (PT-test) consisting of 10 long kicks interspersed with intense intermittent exercise. In addition, a control test (CON-test) without intense exercise was performed. In both cases, the test result was evaluated by the precision of the 10 kicks. The players also performed the Yo-Yo intermittent recovery test level 2 (Yo-Yo IR2). For the SE-players, blood samples were obtained and heart rate was measured before, during, and after the PT-test. A muscle biopsy was collected before and after the PT-test. Coefficient of variation for the PT- and CON-test was 11.7% and 16.0%, respectively. The YE-players performed better (P < 0.05) than the SE-players in both the PT-test (16.3 +/- 0.8 (+/-SE) vs. 13.2 +/- 1.3 points) and CON-test (24.4 +/- 0.7 vs. 20.5 +/- 1.6 points) with no difference in the relative PT-test result (PT-test/CON-test: 0.63 +/- 0.03 vs. 0.64 +/- 0.03). Summed performance of the first 5 repetitions was higher (P < 0.05) than for the last 5 repetitions (8.4 +/- 0.6 vs. 6.9 +/- 0.5; n = 20). The YE-players performed better (P < 0.05) than the SE-players during Yo-Yo IR2 (1023 +/- SE vs. 893 +/- SE m). The mean heart rate during the PT-test was 173 +/- 4 b.p.m. (90 +/- 2% of HRmax). Blood lactate, glucose, and ammonia reached 5.6 +/- 0.7, 6.2 +/- 0.6 mmol L(-1), and 76 +/- 11 umol L(-1) at the end of the test, respectively. After the test muscle CP, glycogen and lactate was 52.9 +/- 6.6, 354 +/- 39, and 25.3 +/- 5.9 mmol kg(-1) d.w., respectively. In summary, the PT-test can be used to evaluate a soccer player's technical skills under conditions similar to intense periods of a soccer game.     

Soccer Player Characteristics in English Lower-League Development Programmes: The Relationships between Relative Age,Maturation, Anthropometry and Physical Fitness

The relative age effect (RAE) and its relationships with maturation, anthropometry, and physical performance characteristics were examined across a representative sample of English youth soccer development programmes. Birth dates of 1,212 players, chronologically age-grouped (i.e., U9’s-U18’s), representing 17 professional clubs (i.e., playing in Leagues 1 & 2) were obtained and categorised into relative age quartiles from the start of the selection year (Q1 = Sep-Nov; Q2 = Dec-Feb; Q3 = Mar-May; Q4 = Jun-Aug). Players were measured for somatic maturation and performed a battery of physical tests to determine aerobic fitness (Multi-Stage Fitness Test [MSFT]), Maximal Vertical Jump (MVJ), sprint (10 & 20m), and agility (T-Test) performance capabilities. Odds ratio’s (OR) revealed Q1 players were 5.3 times (95% confidence intervals [CI]: 4.08–6.83) more likely to be selected than Q4’s, with a particularly strong RAE bias observed in U9 (OR: 5.56) and U13-U16 squads (OR: 5.45–6.13). Multivariate statistical models identified few between quartile differences in anthropometric and fitness characteristics, and confirmed chronological age-group and estimated age at peak height velocity (APHV) as covariates. Assessment of practical significance using magnitude-based inferences demonstrated body size advantages in relatively older players (Q1 vs. Q4) that were very-likely small (Effect Size [ES]: 0.53–0.57), and likely to very-likely moderate (ES: 0.62–0.72) in U12 and U14 squads, respectively. Relatively older U12-U14 players also demonstrated small advantages in 10m (ES: 0.31–0.45) and 20m sprint performance (ES: 0.36–0.46). The data identify a strong RAE bias at the entry-point to English soccer developmental programmes. RAE was also stronger circa-PHV, and relatively older players demonstrated anaerobic performance advantages during the pubescent period. Talent selectors should consider motor function and maturation status assessments to avoid premature and unwarranted drop-out of soccer players within youth development programmes.     

Changes in body composition, hormonal status, and physical fitness in 11-, 13-, and 15-year-old Finnish regional youth soccer players during a two-year follow-up

V?nttinen, T, Blomqvist, M, Nyman, K, and H?kkinen, K. Changes in body composition, hormonal status, and physical fitness in 11-, 13-, and 15-year-old Finnish regional youth soccer players during a two-year follow-up. J Strength Cond Res 25(12): 3342-3351, 2011-The purpose of this study was to examine the changes in body composition, hormonal status, and physical fitness in 10.8 ± 0.3-year-old (n = 13), 12.7 ± 0.2-year-old (n = 14), and 14.7 ± 0.3-year-old (n = 12) Finnish regional youth soccer players during a 2-year monitoring period and to compare physical fitness characteristics of soccer players with those of age-matched controls (10.7 ± 0.3 years, n = 13; 14.7 ± 0.3 years, n = 10) not participating in soccer. Body composition was measured in terms of height, weight, muscle mass, percentage of body fat, and lean body weight of trunk, legs, and arms. Hormonal status was monitored by concentrations of serum testosterone and cortisol. Physical fitness was measured in terms of sprinting speed, agility, isometric maximal strength (leg extensors, abdominal, back, grip), explosive strength, and endurance. Age-related development was detected in all other measured variables except in the percentage of body fat. The results showed that the physical fitness of regional soccer players was better than that of the control groups in all age groups, especially in cardiovascular endurance (p < 0.01-0.001) and in agility (p < 0.01-0.001). In conclusion, playing in a regional level soccer team seems to provide training adaptation, which is beyond normal development and which in all likelihood leads to positive health effects over a prolonged period of time.     

Fitness improvements of young soccer players after high volume or small sided games interventions

The main goal was to determine anaerobic and aerobic improvement of young soccer players after six-week high volume (HVT) or small sided games (SSG) training intervention. One hundred and one highly trained youth soccer players (16.2 ± 1.3 years) were divided into SSG (n = 51) and HVT groups (n = 50) and according to age into an under sixteen subgroup (U16), under seventeen subgroup (U17), and under nineteen subgroup (U19). The performance was assessed by Yo-Yo intermittent test, Repeated sprint ability test (RSA), and K-test before and after both training interventions. For U16 the SSG group recorded significant improvements in the K-test (0.64 ± 0.56 s; p = .04) and RSA (0.15 ± 0.43 s; p = .01). For U19 the SSG group recorded the same improvements, in the K-test (0.43 ± 0.57 s; p = .007), RSA (0.21 ± 0.22 s; p = .048), and Yo-Yo test (127.25 ± 17.87; p = .049). HVT improved aerobic performance when the Yo-Yo test was significantly better after intervention at U17 (199.00 ± 111.83 m; p = .030), U19 (88.40 ± 66.38 m; p = .049). In total, the HVT group spent 621 min (56.45 ± 5.01 min) of aerobic training and the Small sided game group spent 291 min (26.45 ± 8.61 min) of small sided games focused on aerobic performance. This study showed that both SSG and HVT training interventions were effective for aerobic improvement for the U19 category, but not for younger players. SSG was identified to be more appropriate to fitness development of soccer players.     

Sprint Conditioning of Junior Soccer Players: Effects of Training Intensity and Technique Supervision

The aims of the present study were to compare the effects of 1) training at 90 and 100% sprint velocity and 2) supervised versus unsupervised sprint training on soccer-specific physical performance in junior soccer players. Young, male soccer players (17 ±1 yr, 71 ±10 kg, 180 ±6 cm) were randomly assigned to four different treatment conditions over a 7-week intervention period. A control group (CON, n=9) completed regular soccer training according to their teams’ original training plans. Three training groups performed a weekly repeated-sprint training session in addition to their regular soccer training sessions performed at A) 100% intensity without supervision (100UNSUP, n=13), B) 90% of maximal sprint velocity with supervision (90SUP, n=10) or C) 90% of maximal sprint velocity without supervision (90UNSUP, n=13). Repetitions x distance for the sprint-training sessions were 15x20 m for 100UNSUP and 30x20 m for 90SUP and 90UNSUP. Single-sprint performance (best time from 15x20 m sprints), repeated-sprint performance (mean time over 15x20 m sprints), countermovement jump and Yo-Yo Intermittent Recovery Level 1 (Yo-Yo IR1) were assessed during pre-training and post-training tests. No significant differences in performance outcomes were observed across groups. 90SUP improved Yo-Yo IR1 by a moderate margin compared to controls, while all other effect magnitudes were trivial or small. In conclusion, neither weekly sprint training at 90 or 100% velocity, nor supervised sprint training enhanced soccer-specific physical performance in junior soccer players.     

Effects of Small-Sided Games vs. Interval Training in Aerobic Fitness and Physical Enjoyment in Young Elite Soccer Players

The purpose of this study was to compare the effects of Small-Sided Games (SSG) vs. Interval Training (IT) in soccer training on aerobic fitness and physical enjoyment in youth elite soccer players during the last 8 weeks of the season. Seventeen U-16 male soccer players (age = 15.5 ± 0.6 years, and 8.5 years of experience) of a Spanish First Division club academy were randomized to 2 different groups for 6 weeks: SSG group (n = 9) and IT group (n = 8). In addition to the usual technical and tactical sessions and competitive games, the SSG group performed 11 sessions with different SSGs, whereas the IT group performed the same number of sessions of IT. Players were tested before and after the 6-week training intervention with a continuous maximal multistage running field test and the counter movement jump test (CMJ). At the end of the study, players answered the physical activity enjoyment scale (PACES). During the study, heart rate (HR) and session perceived effort (sRPE) were assessed. SSGs were as effective as IT in maintaining the aerobic fitness in elite young soccer players during the last weeks of the season. Players in the SSG group declared a greater physical enjoyment than IT (P = 0.006; ES = 1.86 ± 1.07). Coaches could use SSG training during the last weeks of the season as an option without fear of losing aerobic fitness while promoting high physical enjoyment.     

Muscle damage, endocrine, and immune marker response to a soccer match

ABSTRACT: Thorpe, R and Sunderland, C. Muscle damage, endocrine, and immune marker response to a soccer match. J Strength Cond Res 26(10): 2783-2790, 2012-This study represents the first time that muscle damage, endocrine, and immune markers have been measured, together with activity profile, during a competitive soccer match. Seven semiprofessional soccer players participated in a competitive league match. Blood and saliva samples were obtained 1 hour before kick off and immediately postmatch. Global positioning system equipment was used to measure heart rate and activity profile data throughout the match. Percentage increase in creatine kinase (CK) and myoglobin (MYO) concentrations was correlated with the number of sprints performed during the match (r = 0.88, p = 0.019; r = 0.75, p = 0.047, respectively). Creatine kinase increased by 84% (p = 0.17) from prematch to postmatch, whereas MYO increased by 238% (p = 0.05). Players performed 39 ± 18 sprints during the course of the match. Cortisol increased by 78% (p = 0.103), whereas testosterone increased significantly by 44% (p = 0.004). No differences were seen from prematch to postmatch in the testosterone to cortisol ratio, immunoglobulin (Ig) A, IgM, or IgG. Sprinting is correlated with changes in CK and MYO and may therefore be associated with muscle damage in semiprofessional soccer players.     

Effects of including endurance and speed sessions within small-sided soccer games periodization on physical fitness

The main aim of this study was to analyse the effects of including additional speed and endurance sessions during small-sided games (SSG) training periodization on physical fitness in professional soccer players. Sixteen outfield players (age = 25.6 ± 7.6 years) who competed in the First Division of a European League participated in this study. Players were randomly assigned to perform only the SSG periodization (G-SSG group) or to add endurance and speed training contents to the SSG (ES-SSG group). Before and after the 6-week experimental period, a Yo-Yo Intermittent Recovery Test level 1 (YYIR1) and a 40 m sprinting test were performed. Rating of perceived exertion (RPE) was also measured after each training session. The G-SSG group showed a large improvement in the YYIR1 performance (p = 0.018–0.028; ES = 0.521–0.576) after the training programme, whereas no significant changes were observed for the ES-SSG group (p = 0.763–1.000; ES = 0.000–0.014). In addition, no significant differences (p > 0.05, ES = 0.005–361, trivial to small) in sprint performance at 5 and 10 m intervals up to 40 m were observed at post-training in comparison to pre-training evaluation in G-SSG and ES-SSG groups. No significant differences (p > 0.05) between groups were observed at baseline in the YYIR1 test. The 6-week SSG training supported with only six endurance and speed training sessions was no more effective than well-organized SSG alone for improving running endurance in professional soccer players.     

Individual match playing time during the season affects fitness-related parameters of male professional soccer players

The purpose of this study was to analyze the effects of an entire season on physical fitness parameters (PFPs) in male professional soccer players (N = 18). Performance in 5- and 30-m sprint (T5 and T30), countermovement jump (CMJ), agility (T-test), knee extensor (KE) and knee flexor (KF) isokinetic strength, hamstrings/quadriceps strength ratio (H/Q) and bilateral differences (BDs), and Yo-Yo intermittent endurance test 2 (YYIE2) was evaluated in 4 moments (E1-E4) throughout the season. Individual match playing time was quantified. Significant improvements in CMJ and YYIE2 from E1 to E2 were observed (p < 0.05-0.01). The T30 improved from E2 to E3 (p < 0.01). The CMJ decreased from E2 to E3 and E4, and YYIE2 from E2 to E4 (p < 0.05). There were increments in the H/Q ratio and Agility from E1 and E2 to E3 and E4 (p < 0.05-0.01). Significant correlations were found in all evaluation points between different PFPs and between changes in strength parameters and agility, T5 and T30, CMJ, and YYIE2 (p < 0.05-0.001). Influence of individual match playing time was correlated to changes in T5 (E1 to E3; r = -0.705), KE nondominant leg (KEND; E2 to E3; r = 0.786), and KF (E3 to E4; r = 0.575-0.590). The interrelationship between muscle strength (e.g., KE), sprint (e.g., T5), and jump abilities (CMJ) suggests the importance of muscle strength and power training for soccer. This study suggests that the systematic participation of the players in soccer matches favors the increase and maintenance of soccer players KE and KF muscle strength and sprint ability (T5). Thus, given the unique demands of actual match play, coaches should try to incorporate a competitive friendly match in the weekly training cycle of nonstarter players.     

The Effects of a 6-Week Strength Training on Critical Velocity,Anaerobic Running Distance, 30-M Sprint and Yo-Yo Intermittent Running Test Performances in Male Soccer Players

The objectives of this study were to examine the effects of a moderate intensity strength training on changes in critical velocity (CV), anaerobic running distance (D''), sprint performance and Yo-Yo intermittent running test (Yo-Yo IR1) performances. Methods: two recreational soccer teams were divided in a soccer training only group (SO; n = 13) and a strength and soccer training group (ST; n = 13). Both groups were tested for values of CV, D'', Yo-Yo IR1 distance and 30-m sprint time on two separate occasions (pre and post intervention). The ST group performed a concurrent 6-week upper and lower body strength and soccer training, whilst the SO group performed a soccer only training. Results: after the re-test of all variables, the ST demonstrated significant improvements for both, YoYo IR1 distance (p = 0.002) and CV values (p<0.001) with no significant changes in the SO group. 30-m sprint performance were slightly improved in the ST group with significantly decreased performance times identified in the SO group (p<0.001). Values for D'' were slightly reduced in both groups (ST -44.5 m, 95% CI = -90.6 to 1.6; SO -42.6 m, 95% CI = -88.7 to 3.5). Conclusions: combining a 6-week moderate strength training with soccer training significantly improves CV, Yo-Yo IR1 whilst moderately improving 30-m sprint performances in non-previously resistance trained male soccer players. Critical Velocity can be recommended to coaches as an additional valid testing tool in soccer.     

The yo-yo intermittent recovery test in junior basketball players according to performance level and age group

The aim of this study was to evaluate the Yo-Yo Intermittent Recovery Test Level 1 (Yo-Yo IR1) ability to discriminate between elite, subelite junior basketball players, and a group of nonathletic healthy male athletes at 3 different age groups (U-14 to U-17). In a cross-sectional design, 119 age-matched participants spread over 3 groups, elite (n = 46), subelite (n = 42) junior basketball players, and nonathletic healthy male athletes (n = 31), were evaluated over a 5-week period. The participants undertook 2 familiarization trials of the Yo-Yo test performance and 3 test sessions on an indoor basketball court. When controlling for the effect of the participants' body mass, the results showed that elite athletes had a significantly higher Yo-Yo performance compared with the subelite athletes (1,271 ± 385 vs. 861 ± 428 m; p < 0.0017; effect size [ES] 1.0 ± 0.35) and the nonathletic group (1,271 ± 385 vs. 738 ± 345 m; p < 0.0017; ES 1.45 ± 0.38). No statistical differences (p > 0.0017; ES from 0.02 to 0.39) were noted between participants' performance levels across age groups. Typical between-performance levels and -age groups differences in the Yo-Yo IR1 were observed. However, when controlling for the effect of the participants' body mass, this study demonstrates that the Yo-Yo test is accurate only to discriminate elite junior basketball players but cannot be used to differentiate the basketball-specific aerobic performance for age.     

Dietary analysis of young professional soccer players for 1 week during the competitive season

Limited data exist concerning the dietary practices of young professional soccer players that compete within the United Kingdom. Therefore, the purpose of this study was to investigate the nutritional and activity habits of professional male soccer players (n = 10; age: 17 ± 1 years, height: 1.72 ± 0.01 m, mass: 67.5 ± 1.8 kg, estimated maximal aerobic capacity: 57.8 ± 0.9 ml·kg·min) who played for the youth team of a UK-based Championship club. All players recorded their 7-day dietary intake and activity habits during a competitive week that included a match day, 4- training days, and 2 rest days in the first half of the 2009/2010 playing season. The intake of carbohydrates (5.9 ± 0.4 g·kg·d), proteins (1.7 ± 0.1 g·kg·d), and fats (1.5 ± 0.1 g·kg·d) represented 56 ± 1, 16 ± 1, and 31 ± 1% of the mean daily energy intake respectively. The intake of fiber was found to be significantly lower than Recommended Nutrient Intake (RNI) values (67% of RNI, p < 0.001), whereas all other analyzed micronutrients met or exceeded recommended values. A mean daily energy deficit of 788 ± 174 kcal existed because daily energy expenditures exceeded that of intake (3,618 ± 61 vs. 2831 ± 164 kcal, p = 0.001). The mean daily fluid intake was 3.2 ± 0.3 L. Consequently, the nutritional practices of the sampled group of professional youth soccer players were inadequate to sustain optimized performance throughout training and match play. Youth soccer players should therefore seek to ensure that their diets contain adequate energy through increased total caloric intake, while also optimizing the proportion of energy derived from carbohydrates and ensuring that enough fiber-rich foods are consumed.     

Effect of training intensity distribution on aerobic fitness variables in elite soccer players: a case study

The aim of this article was to quantify the distribution of training intensities and its effect on aerobic fitness in professional elite soccer players. Fourteen professional soccer players were observed during the prechampionship training period (6 weeks). Treadmill running speed and heart rates (HRs) at 2 and 4 mmol · L(-1) blood-lactate concentrations were assessed pre and posttraining. Training intensities were categorized using 3 HR zones: low intensity (

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HR 4 mmol · L(-1)). Analysis of the 504 individual training sessions showed that 73 ± 2.5, 19 ± 2.8, and 8 ± 1.4% of the total training time was spent at low, moderate, and high intensity, respectively (p < 0.001). Speed at 2 and 4 mmol · L(-1) significantly improved posttraining (5 and 7%, respectively, p < 0.01). Training spent at high intensity was significantly related to relative speed improvements at 2 mmol · L(-1) (r = 0.84, p < 0.001;) and 4 mmol · L(-1) (r = 0.65, p = 0.001). Players spent almost two-thirds of their training time at low intensities. However, only the time spent at high intensity (>90% of maximal HR) was related to changes in aerobic fitness. These results support the usefulness of the quantification of aerobic training load using HR. Furthermore, it stresses the effectiveness of the high-intensity training in soccer.     

The construct and longitudinal validity of the basketball exercise simulation test

The purpose of this study was to assess the validity of the recently developed Basketball Exercise Simulation Test (BEST). Ten semiprofessional (age, 22.7 ± 6.1 years; height, 189.6 ± 9.5 cm; weight, 86.5 ± 18.7 kg; % body fat, 14.7 ± 3.5%) and 10 recreational (age, 26.6 ± 4.0 years; height, 185.9 ± 7.9 cm; weight, 92.6 ± 8.4 kg; % body fat, 23.8 ± 6.3%) male basketball players volunteered for the study. The participants completed a Yo-Yo Intermittent Recovery Test (Yo-Yo IRT) and BEST trial midway through the playing season. Eight participants (semiprofessional, n = 4; recreational, n = 4) completed an additional Yo-Yo IRT and BEST trial at the end of the playing season. Performance measures from the BEST included sprint decrement (%), mean sprint and circuit time (seconds), and total distance covered (m). Construct validity was calculated using Student's unpaired t-tests to identify the differences in Yo-Yo IRT and BEST performances between playing levels. Longitudinal validity was determined based on the relationship between changes (%) in Yo-Yo IRT1 and BEST performances across the season. Semiprofessional players performed significantly (p < 0.01) better in the Yo-Yo IRT (1,283 ± 62 vs. 636 ± 297 m) and BEST (mean sprint time: 1.45 ± 0.01 vs. 1.65 ± 0.03 seconds; mean circuit time: 18.98 ± 1.79 vs. 22.72 ± 2.01 seconds; sprint decrement: 8.54 ± 0.15 vs. 15.38 ± 0.27%) compared with recreational players. For the group as a whole, a strong relationship was evident between the changes in BEST sprint decrement and changes in Yo-Yo IRT performance (R = -0.815, p = 0.014) across the season. In conclusion, the BEST displayed both discriminative and longitudinal validities and provides a novel match-specific fitness test for basketball players.     

Physical responses of different small-sided game formats in elite youth soccer players

A major use of small-sided games (SSGs) in soccer training is the concomitant development of game-specific aerobic fitness. We hypothesize that the SSG formats of 2 vs. 2, 3 vs. 3, and 4 vs. 4 players reveal game-like intensities and therefore are most adequate to increase game-specific aerobic fitness. Heart rate (HR), percentage of maximum heart rate (HRmax), blood lactate concentration (La), and time-motion characteristics of 17 elite male youth soccer players (aged 14.9 ± 0.7 years, V[Combining Dot Above]O2max 61.4 ± 4.5 ml·kg·min, HRmax 199.6 ± 7.3 b·min) were collected by global positioning systems while performing the SSG formats. Repeated-measures analysis of variance and effect sizes were calculated to demonstrate the differences between SSG formats. Highest physiological responses were obtained in 2 vs. 2 (HR: 186 ± 7 b·min, HRmax: 93.3 ± 4.2%, La: 5.5 ± 2.4 mmol·L) followed by 3 vs. 3 (HR: 184 ± 8 b·min, HRmax: 91.5 ± 3.3%, La: 4.3 ± 1.7 mmol·L) and 4 vs. 4 (HR: 179 ± 7 b·min, HRmax 89.7 ± 3.4%, La: 4.4 ± 1.9 mmol·L). Pronounced differences were found for most physiological parameters and for time spent in the speed zones "walking" (<5.3 km·h), "moderate-speed running" (10.3-13.9 km·h), and "maximum sprinting" (≥26.8 km·h). The findings suggest that all the formats reveal game-like intensities and are suitable for aerobic fitness improvements. However, we found pronounced demands on the anaerobic energy supply in 2 vs. 2, whereas 3 vs. 3 and 4 vs. 4 remain predominantly on an aerobic level and differ mainly in the HR response. We suggest using 3 vs. 3 for soccer-specific aerobic fitness training.     

Comparative study of field and laboratory tests for the evaluation of aerobic capacity in soccer players

The purpose of this study was to evaluate the maximal oxygen uptake (Vo(2)max) values in soccer players as assessed by field and laboratory tests. Thirty-five elite young soccer players were studied (mean age 18.1 +/- 1.0 years, training duration 8.3 +/- 1.5 years) in the middle of the playing season. All subjects performed 2 maximal field tests: the Yo-Yo endurance test (T(1)) for the estimation of Vo(2)max according to normogram values, and the Yo-Yo intermittent endurance test (T(2)) using portable telemetric ergospirometry; as well as 2 maximal exercise tests on the treadmill with continuous (T(3)) and intermittent (T(4)) protocols. The estimated Vo(2)max values of the T(1) test (56.33 ml.kg(-1).min(-1)) were 10.5%, 11.4%, and 13.3% (p < or = 0.05) lower than those of the T(2) (62.96 ml.kg(-1).min(-1)), T(3) (63.59 ml.kg(-1).min(-1)) and T(4) (64.98 ml.kg(-1).min(-1)) tests, respectively. Significant differences were also found between the intermittent exercise protocols T(1) and T(3) (p < or = 0.001) and the continuous exercise protocols T(2) and T(4) (p < or = 0.001). There was a high degree of cross correlation between the Vo(2)max values of the 3 ergospirometric tests (T(2) versus T(3), r = 0.47, p < or = 0.005; T(2) versus T(4), r = 0.59, p < or = 0.001; T(3) versus T(4) r = 0.79, p < or = 0.001). It is necessary to use ergospirometry to accurately estimate aerobic capacity in soccer players. Nevertheless, the Yo-Yo field tests should be used by coaches because they are easy and helpful tools in the training program setting and for player follow-up during the playing season.     

Activity profile of young soccer players during actual match play

This study investigated the activity profile of young soccer players (mean age 11.8 +/- 0.6 years; N = 12) with the aim of providing information for the development of training strategies. Data for movements of each player were obtained using 2 cameras that aimed at the subject throughout the match (Play Controller, Phromos, Italy). Encoders transmitted camera movements to a computer. The collected signals were then converted into distances, times, and speed attained at arbitrarily selected match categories. Players were monitored during official 11 vs. 11 matches (N = 12), with each match consisting of 2 halves, each lasting 30 minutes played on a regular soccer pitch. Mean total match distance amounted to 6,175 +/- 318 m. During the second half, players covered 5.5% less distance (p > 0.05). At speeds between 13.1 and 18.0 km.h(-1), players covered 12% less distance during the second half (p < 0.05). Players stood still 11% of the total time played (3,789 +/- 109 seconds). At speeds faster than 18 km.h(-1), players performed 33 +/- 4 bouts during match play, with a mean time length of 2.3 +/- 0.6 seconds per bout. Mean time interval between two successive maximal sprint bouts was 118.5 +/- 20.5 seconds. Players stood still longer during the course of the second half (229 +/- 76 seconds vs. 173 +/- 61 seconds, p < 0.05). Players tended to play in small areas of the football pitch and spent 9% of the total match time at high intensity. In order to promote a more active space coverage of the young player, at least for the age considered in the present study, the dimensions of the football pitch and the number of players should be reduced.     

Age-related effects on fitness performance in elite-level soccer referees

Elite soccer referees usually achieve the peak of their officiating careers at an average age that is considerably older than that observed in competitive matched soccer players. As ageing has been reported to negatively affect physical performance, the aim of this study was to investigate the effect of ageing on fitness performance in elite-level soccer referees. Thirty-six elite-level soccer referees were grouped into young (Y, n = 12), average (A, n = 14), and old (O, n = 10) groups, according to their age and observed for field test performance (countermovement jump [CMJ], 50-m and 200-m sprints, and 12-minute running for distance). Results showed a significant age effect on CMJ (r = -0.52, p < 0.001), 200 m (r = 0.51, p < 0.001), and 12-minute time trial running (r = -0.52, p < 0.001). Y jumped higher than A and O groups (p < 0.05) and were faster than O over 200 m (p < 0.05). No group effect was observed for 12-minute run and 50-m performance (p > 0.05), respectively. Sixteen of the 36 referees were further examined for selected physiological variables and grouped into 2 equal (n = 8) age groups (young and old, Y1 and O1, respectively). Vo(2)max was higher in Y1 (p < 0.05), but O1 attained performances similar to Y1 running at selected blood lactate speeds (4 mmol L(-1), p > 0.05). Although older referees demonstrated acceptable fitness levels, younger officials should ensure that they develop appropriate levels of aerobic and anaerobic fitness to be able to match the demands placed upon them while refereeing throughout their careers. To promote this, fitness test standards should be age related.     

Match analysis of elite adolescent team handball players

The purposes of this study were to examine the activity profile of elite adolescent players during regular team handball games and to compare the physical and motor performance of players between the first and second halves of a match. Activity patterns (video analysis) and heart-rate (HR) responses (telemetry) were monitored in top national-division adolescent players (18 men, aged 15.1 ± 0.6 years) throughout 6 regulation games (25-minute halves with a 10-minute interval). The total distance covered averaged 1,777 ± 264 m per game (7.4% less in the second than in the first half, p > 0.05). Players ran 170 ± 24 m at high intensity and 86 ± 12 m at maximal speed, with 32 ± 6 bouts of running (duration 2.3 ± 0.3 seconds) at speeds > 18 km·h(-1); they stood still for 16% of the playing time. The mean HR during play was 172 ± 2 b·min(-1) (82 ± 3% of maximal HR). Blood lactate concentrations at the end of the first and second halves were 9.7 ± 1.1 and 8.3 ± 0.9 mmol·L(-1), respectively (difference p < 0.05). We conclude that adolescent handball players cover less distance and engage in fewer technical actions in the second half of a match. This indicates that team handball is physiologically very demanding. The practical implication is that coaches should seek to sustain performance in the second period of a game by modifying playing tactics and maximizing both aerobic and anaerobic fitness during training sessions.