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Relationship Between Endurance Field Tests and Match Performance in Young Soccer Players

Castagna, Carlo1,2; Manzi, Vincenzo2; Impellizzeri, Franco3; Weston, Matthew4; Barbero Alvarez, José C5

Journal of Strength and Conditioning Research: December 2010 - Volume 24 - Issue 12 - p 3227-3233
doi: 10.1519/JSC.0b013e3181e72709
Original Research
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Castagna, C, Manzi, V, Impellizzeri, F, Weston, M, and Barbero Alvarez, JC. Relationship between endurance field tests and match performance in young soccer players. J Strength Cond Res 24(12): 3227-3233, 2010-The purpose of this study was to examine the relationship between popular endurance field tests and physical match performance in elite male youth soccer players. Eighteen young male soccer players (age 14.4 ± 0.1 years, height 1.67 ± 4.8 cm, body mass 53.6 ± 1.8 kg) were randomly chosen among a population of elite-level soccer players. Players were observed during international championship games of the corresponding age categories and randomly submitted to the level 1 of the Yo-Yo intermittent recovery test (Yo-Yo IR1), the Multistage Fitness Test (MSFT), and the Hoff test on separate occasions. Physical and physiological match demands were assessed using Global Positioning System technology and short-range telemetry (GPS Elite, Canberra, Australia), respectively. Players covered 6,087 ± 582 m (5,098-7,019 m) of which 15% (930 ± 362 m; 442-1,513) were performed as a high-intensity activity. During the first and second halves, players attained 86.8 ± 6.5 and 85.8 ± 5.8% of maximum heart rate (HRmax; p = 0.17) with peak HRs of 100 ± 2 and 99.4 ± 3.2% of HRmax, respectively. Players' Yo-Yo IR1 and MSFT performance were significantly related (r = 0.62-0.76) to a number of match physical activities. However, the Hoff test was only significantly related with sprint distance (r = 0.70, p = 0.04). The Yo-Yo IR1 showed a very large association with MSFT performance (r = 0.89, p < 0.0001). The results of this study showed that the Yo-Yo IR1 and MSFT may be regarded as valuable tests to assess match fitness and subsequently guide training prescription in youth soccer players. The very strong relationship between Yo-Yo IR1 and MSFT suggests their use according to the period of the season and the aerobic fitness level of the players. Because of the association of the Yo-Yo IR1 and MSFT with match physical performances, these tests should be considered in talent selection and development of players.

1San Marino Football Federation (FSGC), Department of Research, San Marino; 2School of Sport and Exercise Sciences, University of Rome Tor Vergata, Rome, Italy; 3Neuromuscular Research Laboratory, Schulthess Clinic, Zurich, Switzerland; 4Department of Sport and Exercise Science, Teesside University, United Kingdom; and 5Faculty of Education and Humanities of Melilla, Department of Physical Education and Sport of the University of Granada, Melilla, Spain

Address correspondence to Dr. Carlo Castagna, castagnac@libero.it.

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Introduction

In youth soccer, aerobic fitness has been reported to be a relevant component of the physiological make-up of the elite-level young soccer player (38-40). Indeed, scientific evidence has shown that aerobic fitness parallel the competitive development of youth soccer players (41,43,44).

Although laboratory aerobic fitness (32) detection is the optimal choice for the determination of reliable results, the procedures involved are time consuming and require highly trained personal (19). Furthermore, laboratory testing requires exercise modes such as linear running that are not soccer specific (2,5,28,41). Consequently, the laboratory assessment of aerobic fitness may result in having doubtful relevance to soccer-specific training. Furthermore, the protocol used may limit players' motivation to testing (2,5,21,27,41).

Field tests are considered as a sustainable alternative of laboratory tests (26,34,41). Recently, a number of field tests have been proposed to assess aerobic fitness in male youth soccer players (7,10,13,26,41). These tests possess a different degree of logical validity as per the exercise mode (i.e., continuous vs. intermittent shuttle running) and for sport-specific skills (i.e., ball dribbling or passing) considered (2,41). However, despite their association with criterion physiological variables of aerobic fitness, only limited evidence was provided for their relationship with game activities (i.e., direct validity) (4). Indeed to the best of our knowledge, only the Yo-Yo intermittent recovery test level 1 (Yo-Yo IR1) has been assessed for direct validity with regard to male youth soccer players (13). Information in this regard would be of interest because direct validity is considered as a necessary prerequisite of a sport-specific field test (4,12,13). Furthermore, knowledge of test redundancy may help strength and conditioning coaches in endurance assessment when dealing with male youth soccer.

As a consequence of the developed reasoning, the possibility to implement a soccer exercise-mode specific field test for the determination of aerobic fitness would be of interest for coaches and soccer strength and conditioning professionals. Therefore, the aim of this study was to examine the relationship between popular endurance-based field-test performance and match physical activities in young male elite-level soccer players. A second aim of the study was to evaluate the practical application of each test.

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Methods

Experimental Approach to the Problem

In this study, the association between match physical performance and endurance performance of young elite-level soccer players was examined using a descriptive correlation design (9). Players' physical load, as time and distance spent in selected match activity categories, was assessed using Global Position System technology (GPS, SPElite, GPsports, Australia). Physiological stress was assessed by monitoring heart rate (HR) during matches (18,20). The endurance performance was tested using 3 popular field tests: the Yo-Yo Intermittent Recovery level 1 test (Yo-Yo IR1) (2,29), the Multistage Fitness test (MSFT) (36), and the Hoff et al. (22) test (Hoff test). The MSFT and Yo-Yo IR1 share the same directional running mode (i.e., shuttle running over 20 m) showing difference in speed progression and exercise form (i.e., continuous vs. intermittent running). Indeed the Yo-Yo IR1 protocol involves a 10-second recovery every 40 m and a higher starting speed (10 vs. 8 km·h−1) compared to the MSFT. However, after the first 2 stages (i.e., 12 km·h−1), the Yo-Yo IR1 considers speed increments of 0.5 km·h−1 until exhaustion as in the MSFT (2,29).

The Hoff test was recently proposed as a valid alternative to shuttle-running tests for endurance assessment in soccer (14,22). This test requires players to cover as much distance as possible during 10-minutes of dribbling a ball over a purpose-built circuit (14) (Figure 1). Recent studies have shown that the Hoff test possesses criterion validity and sensitivity to aerobic fitness development in youth soccer players (14). Despite this, no study has evaluated the reliability and direct validity of the Hoff test, and therefore, the relevance of the Hoff test to soccer is mainly associated with its supposed logical validity (i.e., ball dribbling) (14). To the best of our knowledge, no published study is currently available as per direct validity of the MSFT.

Figure 1

Figure 1

Because the field tests considered in this study are deemed to test the same physiological variable (i.e., aerobic performance), test redundancy was assessed with multiple comparison correlation analysis (45).

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Subjects

Eighteen soccer players (age 14.4 ± 0.1 years, height 1.67 ± 4.8 cm, body mass 53.6 ± 1.8 kg) all members of an elite-level National Youth Soccer Academy (Federazione Sammarinese Giuoco Calcio, San Marino, N = 200) were randomly selected using age and playing role as stratification criteria. The selected players (6 forwards, 6 midfield, and 6 defenders) possessed at least 4 years of experience in soccer training and competition and took part in National and International championships at the time of the investigation. Players trained 3 times a week (∼90 minutes per session) with a competitive match taking place at the end of the week. Training sessions consisted mainly of technical and tactical skill development (75% of the training time). Physical conditioning was performed twice a week and was aimed toward anaerobic and aerobic performance development (1). Anaerobic training consisted of plyometrics and sprint training drills (1), and aerobic fitness was developed using small-sided games (35) and short or long-interval running (27).

Testing procedures were performed during the last stage of the competitive season (April-May 2007). This study was conducted in accordance with the Human and Animal Experimentation Policy Statements of the American College of Sports Medicine. Written informed consent was received from all players and parents after verbal and written explanation of the experimental design and potential risks of the study. Information was presented at the time of consent in a way that was easily understood by the subjects and provided in a language in which the subjects were fluent. As a result, a fair explanation of the procedures to be followed and their purposes, identification of any procedures that were experimental, and description of any and all risks attendant to the procedures was provided to each players and parents or guardians who voluntarily accepted to participate after randomized selection and prior familiarization with the testing procedures. Informed consent was obtained from each of the participants and their parents or legal guardians only after familiarization with the procedures used in this study (i.e., submaximal practice of the field tests and use of GPS during a trial game). To improve internal validity, players were blinded about the work hypothesis informing the aims of this observational study. All players agreed to provide their maximum will effort to perform at their best during all the field tests and competitions considered in this study. Before familiarization, each player and parent or legal guardian was written to and verbally made aware that they were free to withdraw from the study without any penalty for any upcoming reasons. The local Institutional Review Board approved the study.

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Procedures

In this study, the activity profile of the players was assessed using GPS technology. During competitive matches, players wore a GPS device, inserted in a purpose-built back-pack, which enabled speed and distance recording (1 Hz). Players' accelerations were also recorded using a built-in accelerometer that had an operational sampling rate of 100 Hz, to improve the quality of speed detection (GPS, SPElite, GPsports). Validity of the GPS system used has been reported elsewhere (3,16,17,31,33). In a recently published comparative research article (37), the GPS system used in this study provided distances (in match categories similar to this study) that were nearly perfectly (r = 0.90-0.94) the same as those detected with a semiautomatic image-recognition system (25 Hz), which has been validated and widely used for match analysis in professional European soccer (6). Before commencing this observational research study, a quality control measurement was performed with the GPS system of this study on 10 players. No significant bias (p > 0.05) was found between the actual vs. GPS-detected distances (discrete bouts of 10-50 m) at the speed (photocells timing as criterion) considered for the match categories of this study. The magnitude of the difference was in the range of ±1-3%, which was similar to that reported as acceptable for most used match analysis systems currently available (6).

Match activities were determined according to the method of Castagna et al. (8) as follows: (a) standing (ST; 0-0.4 km·h−1); (b) walking (W; 0.4-3.0 km·h−1); (c) jogging (J; 3.0-8.0 km·h−1); (d) medium intensity running (MIR; 8.0-13.0 km·h−1); (e) high-intensity running (HIR; 13.0-18.0 km·h−1); (f) sprinting (SPR; >18.0 km·h−1); and (g) high-intensity activity (HIA; HIR + SPR).

Competitive matches (11 vs. 11, n = 4) were played at the same time of the day (15.30 pm) on a regular sized synthetic-grass soccer pitch over 2 halves each lasting 30 minutes (10-minute interval). Match air temperature and relative humidity were 22.8 ± 1.8° C and 40 ± 9.8%, respectively. To avoid dehydration, players were allowed “ad libitum” drinking. A minimum of 5 and a maximum of 8 players were observed during the same competitive match. Each player was observed for a minimum of 2 and a maximum of 4 competitive matches (within 15-20 days), and physical match performance categories were reported as the mean of the observed games.

Heart rates were monitored using short-range telemetry every second during the matches (GPS Elite, GPSports, Canberra, Australia) and every 5 seconds during the Yo-Yo IR1 (Polar Team-System, Kempele, Finland). Data analyses were performed with dedicated software packages (Team AMS software GPSports and Polar Team-System, respectively).

The Yo-Yo IR1 and MSFT were performed according to the procedures suggested by Krustrup et al. (29) and Castagna et al. (11). The Hoff test was performed following the procedures suggested by Chamari et al. (14). All tests were performed in a random order and on separate occasions (i.e., at least 72 hours apart) within 10-15 days before or after the competitive matches on a grass football pitch. Peak HR attained during the Yo-Yo IR1 was considered as the players' maximal HR (HRmax) as per the Krustrup et al. study (29). The reliability of Yo-Yo IR1 was established in 18 players tested 1 week apart resulting in a coefficient of variation (CV) of 3.8% with an intraclass coefficient of correlation (ICC) of 0.92. The CV and ICC for the MSFT (3.6% and 0.92) and Hoff test (18.2% and 0.68) were assessed in 16 players 1 week apart. Field-test procedures were carried out with air temperature and relative humidity of 21.5±1.2° C and 45 ± 4.3%, respectively.

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Statistical Analyses

Results are presented as mean ± SD (range). Data sets were checked for normality using the Shapiro-Wilk normality test and visual inspection. Differences between 2 variables were analyzed using paired t-tests. The effect size (ES) of the difference between the variables was assessed using Cohen's d (15). A value of d < 0.1, from 0.1 to 0.20, from 0.20 to 0.50, from 0.50 to 0.80, and >0.80 were considered as trivial, small, moderate, large, and very large, respectively. Relationships between variables were assessed using Pearson's product-moment correlation. According to Hopkins (24), the magnitude of correlation coefficients was considered as trivial (r < 0.1), small (0.1 < r < 0.3) moderate (0.3 < r < 0.5), large (0.5 < r < 0.7), very large (0.7 < r < 0.9) nearly perfect (r > 0.9), and perfect (r = 1). Confidence intervals at 95% (95%CI) were provided for the correlation between variables. The significance was set at 0.05. A pilot study performed before this investigation showed that to obtain a power of 0.80 12 players were necessary.

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Results

During the match, players covered 6,087 ± 582 m (5,098-7,019 m) of which 15% (930 ± 362 m, 442-1,513) were performed at HIA. During the second half, players covered significantly less total distance (TD; −3.8%, p = 0.04) and distance at MIR (11%, p = 0.04). No difference between halves was observed for HIA (p = 0.96) and SPR (p = 0.18). Details of match activities are presented in Table 1. During the first and second halves, players attained the 86.8 ± 6.5 and 85.8 ± 5.8% of HRmax (p = 0.17), respectively. Peak HR during the first and second halves was 100 ± 2 and 99.4 ± 3.2% of HRmax, respectively.

Table 1

Table 1

The TD covered during the Yo-Yo IR1, MSFT, and Hoff test was 760 ± 283 m (400-1,320 m), 1,653 ± 367 m (1,040-2,120 m), and 1,059 ± 191 m (666-1,280 m), respectively. Association between field tests and match activities is given in Table 2. The TD was associated (large) with MSFT only. However, the Yo-Yo IR1 and MSFT performances were significantly related (large to very large) to HIA (Figure 2), HIR, and SPR. The Hoff test performance was only related (large) to SPR. The Yo-Yo IR1 performance was significantly correlated (very large) with MSFT performance (r = 0.89, p < 0.0001, 95%CI 0.78-0.93). No significant relationship was found between Hoff test with either Yo-Yo IR1 or MSFT performances.

Table 2

Table 2

Figure 2

Figure 2

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Discussion

This is the first study to test 3 popular field tests (Yo-Yo IR1, MSFT, and Hoff test) for direct validity in male youth soccer players within the same research design.

In this study, Yo-Yo IR1 and MSFT showed large to very large association (Table 2) with several physical match activities that have been demonstrated to be a soccer-specific dependent variable (24,25), thus supporting the direct validity of the Yo-Yo IR1 and MSFT for male youth soccer. However, the Hoff test demonstrated a large association with only the distance covered while sprinting (r = 0.70, p = 0.04, 95%CI 0.63-0.77).

The results of this study are in-line with those of previous studies that examined the direct validity of the Yo-Yo IR1 in male and female soccer players (2). Also, the very large correlation (r = 0.73, p = 0.003, 95%CI 0.68-0.83) found between HIA and Yo-Yo IR1 performances is similar to that reported by Castagna et al. (13) for male young soccer players (r = 0.77, p < 0.001) and by Krustrup et al. (29,30) for adult male (r = 0.71, p < 0.05) and female (r = 0.76, p < 0.05) soccer players. However, in contrast to previous studies, no significant relationship was observed between TD and Yo-Yo IR1 (r = 0.42, p = 0.14, 95%CI 0.31-0.53) (13,29,30).

This study addressed for the first time the direct validity of MSFT and Hoff test in young male soccer players. The MSFT was significantly related to distances covered in several activity categories showing a magnitude of effects ranging from large to very large (24) (Table 2). In contrast to the Yo-Yo IR1, the MSFT performance was largely related to TD (r = 0.62, p = 0.02, 95%CI 0.52-0.72). However, no significant difference (p > 0.05) was found between correlation coefficients of Yo-Yo IR1 and MSFT for the TD covered. This finding may be considered as a consequence of the almost nearly perfect correlation (r = 0.89, p < 0.0001, 95%CI 0.78-0.93) found between MSFT and Yo-Yo IR1 performance in this study.

In light of the finding of this study, the MSFT and Yo-Yo IR1 may be considered as similar tests (i.e., 79% common variance) for young elite male soccer players of the age (14-15 years) considered here. Consequently, the MSFT and Yo-Yo IR1 may be used interchangeably to track the soccer-specific fitness of young male players in field conditions.

Despite having potential for a higher logical validity because it involves ball dribbling throughout the test, the Hoff test showed only a limited association with match activities when compared to MSFT and Yo-Yo IR1. Indeed the Hoff test was only related to the distance covered during the match with sprinting (r = 0.70, p = 0.04, 95%CI 0.68-0.72), with the magnitude of the correlation coefficient being consistent with those reported for the same match activity in the MSFT and Yo-Yo IR1 comparisons. The reason for that limited relevance for soccer shown by the Hoff test is difficult to be explained with this research design. However, the low relative (ICC = 0.68) and absolute (CV = 18.2) reliability reported in this study may suggest a limited application of the Hoff test for the performance assessment of young male soccer players' aerobic fitness.

The main problem with correlation studies is that the value of correlation is sensitive to sample homogeneity (23). However, the generalization of the findings of this study may be warranted by the stratified random sampling undertaken for determining the players' group. Furthermore, the data reported here for Yo-Yo IR1 and MSFT are in line with those found by Castagna et al. (13) and Williford et al. (46) in soccer players of a similar competitive level and age, respectively. Additionally, the average match distance covered by players was similar to that previously reported in studies addressing male youth soccer players of similar characteristics (i.e., age, experience and competitive level) (8,13). Furthermore, similarities with previously published studies on male youth soccer were found for cardiovascular stress (i.e., mean HR) (41). Conservation of HIA between halves was found despite a significant decrement of TD and MIR across halves, a finding in line with those of previously published papers (8,13), thus further supporting the suggested competitive “sparing behavior” reported originally by Castagna et al. (8). As a consequence of these similarities, in terms of physical match performance and field-test performance, the population of male youth soccer players used in this study may be considered as being representative of age, training, and competitive-level soccer players. Consequently, the external validity of the finding of this study is warranted (12).

The findings of this study clearly demonstrate that aerobic performance, as determined by commonly used field tests, is related to physical match performance in young male soccer players. This provides further evidence to the relevance of aerobic fitness per se in male youth soccer (39,40). Consequently, aerobic fitness should be collated in the training strategies attempting to develop the physical preparedness of young soccer players (13,27,41).

The associations resulting between field-test performance and match physical performance demonstrate that the Yo-Yo IR1 and MSFT may be regarded as relevant tests to evaluate endurance in young soccer players. However, the magnitude of the effect although ranging between large to very large according to the definition provided by Hopkins (24), the corresponding ES of the relationship, assumed as coefficient of determination (r2), was above the critical value of 0.50 only in 4 of the 8 significant preplanned correlations (42). Furthermore, the highest value did not reach 60% of shared variance. Although the specificity of this test should be interpreted with caution (i.e., r2 = 0.38-0.58), the direct validity was warranted by the findings of this study (42). It could be speculated that new soccer-specific tests are to be established to more closely describe physical demands of matches. In this regard, field tests should more closely mimic match activity pattern and must thus be based on sound match and time motion analysis procedures (6). Because of the interest and relevance of this issue, future studies are warranted.

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Practical Applications

The results of this study showed that the Yo-Yo IR1 and MSFT being strongly associated (i.e., r = 0.89, p < 0.0001) and similarly related to match physical performance (see Table 2) may be considered as being interchangeable. This peculiarity may suggest the use of these "beep tests" (i.e., audio cue guided tests) depending on the preparation moment of the season. Coaches and strength conditioning professionals may use the MSFT in the first stages of their fitness-training program because its protocol involves lower starting speeds (11). On the other hand, the Yo-Yo IR1 may be implemented when players are more aerobically fit because it considers starting speeds, although repeated for a limited number of bouts and with frequent recovery time (i.e., 10 seconds every 40 m), that very often correspond to the maximal speed attained at exhaustion during the MSFT. An added value of the Yo-Yo IR1 lies in the limited amount of time that is usually required (i.e., 6.21 minutes) in this population of young male soccer players (13). This suggests the Yo-Yo IR1 to be a field test that is easy to implement when limited time can be devoted to testing (i.e., during the competitive season) (2,29).

Interestingly, the Hoff test, although involving an exercise mode relevant to soccer (i.e., ball dribbling) possessed only a limited association with physical match performance (i.e., sprinting) and no significant relationship with the other field tests. However, the emerged association with match sprinting distance was similar to those shown by Yo-Yo IR1 and MSFT (p > 0.05). As a consequence of the required labor time necessary to set up the Hoff test track, the limited number of players that may be reasonably tested with this course at a time and the poor reliability shown by this test in this study, the use of the Hoff test is discouraged.

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Acknowledgments

This project was fully financed by the Federazione Sammarinese Giuoco Calcio (FSCG, San Marino). We would like to thank Emilio Cecchini and Marco Giovannelli for their valuable help in collecting the data and in the organization of the practical aspect of this research. We extend our warm thanks to the enthusiastic availability of all the coaches and players of the FSGC.

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References

1. Bangsbo, J. Fitness Training in Football-a Scientific Approach. Bagsværd, Denmark: HO+Storm, 1994.
2. Bangsbo, J, Iaia, FM, and Krustrup, P. The Yo-Yo intermittent recovery test: A useful tool for evaluation of physical performance in intermittent sports. Sports Med 38: 37-51, 2008.
3. Barbero-Alvarez, JC, Coutts, A, Granda, J, Barbero-Alvarez, V, and Castagna, C. The validity and reliability of a global positioning satellite system device to assess speed and repeated sprint ability (RSA) in athletes. J Sci Med Sport 13: 232-235, 2010.
4. Boddington, MK, Lambert, MI, and Waldeck, MR.Validity of a 5-meter multiple shuttle run Test for assessing fitness of women field Hockey players. J Strength Cond Res 18: 97-100, 2004.
5. Bravo, DF, Impellizzeri, FM, Rampinini, E, Castagna, C, Bishop, D, and Wisløff, U. Sprint vs. interval training in football. Int J Sports Med 29: 668-674, 2008.
6. Carling, C, Bloomfield, J, Nelsen, L, and Reilly, T. The role of motion analysis in elite soccer: Contemporary performance measurement techniques and work rate data. Sports Med 38: 839-862, 2008.
7. Castagna, C, Abt, G, and D'Ottavio, S. Competitive-level differences in Yo-Yo intermittent recovery and 12 min run test performance in soccer referees. J Strength Cond Res 19: 805-809, 2005.
8. Castagna, C, D'Ottavio, S, and Abt, G. Activity profile of young soccer players during actual match play. J Strength Cond Res 17: 775-780, 2003.
9. Castagna, C, Impellizzeri, F, Cecchini, E, Rampinini, E, and Alvarez, JC. Effects of intermittent-endurance fitness on match performance in young male soccer players. J Strength Cond Res 23: 1954-1959, 2009.
10. Castagna, C, Impellizzeri, FM, Belardinelli, R, Abt, G, Coutts, A, Chamari, K, and D'Ottavio, S. Cardiorespiratory responses to Yo-Yo intermittent endurance test in nonelite youth soccer players. J Strength Cond Res 20: 326-330, 2006.
11. Castagna, C, Impellizzeri, FM, Chamari, K, Carlomagno, D, and Rampinini, E. Aerobic fitness and yo-yo continuous and intermittent tests performances in soccer players: A correlation study. J Strength Cond Res 20: 320-325, 2006.
12. Castagna, C, Impellizzeri FM, Rampinini, E, D'Ottavio, S, and Manzi, V. The Yo-Yo intermittent recovery test in basketball players J Sci Med Sport 11: 202-208, 2008.
13. Castagna, C, Impellizzeri, I, Cecchini, E, Rampinini, E, and Barbero Alvarez, JC. Effects of intermittent-endurance fitness on match performance in young male soccer players. J Strength Cond Res 23:1954-1959, 2009.
14. Chamari, K, Hachana, Y, Kaouech, F, Jeddi, R, Moussa-Chamari, I, and Wisløff, U. Endurance training and testing with the ball in young elite soccer players. Br J Sports Med 39: 24-28, 2005.
15. Cohen, J. Statistical Power Analysis for the Behavioral Sciences. Hillsdale, NJ: Lawrence Erlbaum Associates, 1988.
16. Coutts, AJ and Duffield, R. Validity and reliability of GPS devices for measuring movement demands of team sports. J Sci Med Sport 13:133-135, 2008.
17. Edgecomb, SJ and Norton, KI. Comparison of global positioning and computer-based tracking systems for measuring player movement distance during Australian football. J Sci Med Sport 9: 25-32, 2006.
18. Esposito, F, Impellizzeri, FM, Margonato, V, Vanni, R, Pizzini, G, and Veicsteinas, A. Validity of heart rate as an indicator of aerobic demand during soccer activities in amateur soccer players. Eur J Appl Physiol 93: 167-172, 2004.
19. Gore, CJ, ed. Physiological Tests for Elite Athletes. Champaign, IL: Human Kinetics, 2000.
20. Helgerud, J, Engen, LC, Wisløff, U, and Hoff, J. Aerobic endurance training improves soccer performance. Med Sci Sports Exerc 33: 1925-1931, 2001.
21. Hill-Haas, SV, Coutts, AJ, Rowsell, GJ, and Dawson, BT. Generic versus small-sided game training in soccer. Int J Sports Med 30: 636-642, 2009.
22. Hoff, J, Wisløff, U, Engen, LC, Kemi, OJ, and Helgerud, J. Soccer specific aerobic endurance training. Br J Sports Med 36: 218-221, 2002.
23. Hopkins, WG. Measures of reliability in sports medicine and science. Sports Med 30: 1-15, 2000.
24. Hopkins, WG. A Scale of Magnitudes for Effect Statistics. Available at: http://www.sportsci.org/resource/stats/index.html. Accessed March 2009.
25. Iaia, FM, Rampinini, E, and Bangsbo, J. High-intensity training in football. Int J Sports Physiol Perform 4: 291-306, 2009.
26. Impellizzeri, F, Rampinini, E, and Marcora, S. Physiological assessment of aerobic training in soccer. J Sports Sci 23: 583-592, 2005.
27. Impellizzeri, FM, Marcora, SM, Castagna, C, Reilly, T, Sassi, A, Iaia, FM, and Rampinini, E. Physiological and performance effects of generic versus specific aerobic training in soccer players. Int J Sports Med 27: 483-492, 2006.
28. Impellizzeri, FM, Rampinini, E, Castagna, C, Bishop, D, Ferrari Bravo, D, Tibaudi, A, and Wisløff, U. Validity of a repeated-sprint test for football. Int J Sports Med 29: 899-905, 2008.
29. Krustrup, P, Mohr, M, Amstrup, T, Rysgaard, T, Johansen, J, Steensberg, A, Pedersen, PK, and Bangsbo, J. The Yo-Yo intermittent recovery test: Physiological response, reliability, and validity. Med Sci Sports Exerc 35: 697-705, 2003.
30. Krustrup, P, Mohr, M, Ellingsgaard, H, and Bangsbo, J. Physical demands during an elite female soccer game: Importance of training status. Med Sci Sports Exerc 37: 1242-1248, 2005.
31. MacLeod, H, Morris, J, Nevill, A, and Sunderland, C. The validity of a non-differential global positioning system for assessing player movement patterns in field hockey. J Sports Sci 27: 121-128, 2009.
32. Pate, RR and Kriska, A. Physiological basis of the sex difference in cardiorespiratory endurance. Sports Med 1: 87-98, 1984.
33. Portas, M, Rush, C, Barnes, CC, and Batterham, A. Method comparison of linear distance and velocity measurements with global positioning satellite (GPS) and the timing gate techniques. J Sports Sci Med 6(Suppl. 10): 7, 2007.
34. Rampinini, E, Bishop, D, Marcora, SM, Ferrari Bravo, D, Sassi, R, and Impellizzeri, FM. Validity of simple field tests as indicators of match-related physical performance in top-level professional soccer players. Int J Sports Med 28: 228-235, 2007.
35. Rampinini, E, Impellizzeri, FM, Castagna, C, Abt, G, Chamari, K, Sassi, A, and Marcora, SM. Factors influencing physiological responses to small-sided soccer games. J Sports Sci 25: 659-666, 2007.
36. Ramsbottom, R, Brewer, J, and Williams, C. A progressive shuttle run test to estimate maximal oxygen uptake. Br J Sports Med 22: 141-144, 1988.
37. Randers, MB, Mujika, I, Hewitt, A, Santisteban, J, Bischoff, R, Solano, R, Zubillaga, A, Peltola, E, Krustrup, P, and Mohr, M. Application of four different football match analysis systems: A comparative study. J Sport Sci DOI: 10.1080/02640410903428525 (ahead of print). 2010.
38. Reilly, T. An ergonomics model of the soccer training process. J Sports Sci 23: 561-572, 2005.
39. Reilly, T, Bangsbo, J, and Franks, A. Anthropometric and physiological predispositions for elite soccer. J Sports Sci 18: 669-683, 2000.
40. Reilly, T, Williams, AM, Nevill, A, and Franks, A. A multidisciplinary approach to talent identification in soccer. J Sports Sci 18: 695-702, 2000.
41. Stølen, T, Chamari, K, Castagna, C, and Wisløff, U. Physiology of soccer: An update. Sports Med 35: 501-536, 2005.
42. Thomas, JR, Nelson, JK, and Silverman, J. Research Methods in Physical Activity (5th ed.). Champaign, IL.: Human Kinetics, 2005.
43. Vaeyens, R, Lenoir, M, Williams, AM, and Philippaerts, RM. Talent identification and development programmes in sport: Current models and future directions. Sports Med 38: 703-714, 2008.
44. Vaeyens, R, Malina, RM, Janssens, M, Van Renterghem, B, Bourgois, J, Vrijens, J, and Philippaerts, RM. A multidisciplinary selection model for youth soccer: The Ghent Youth Soccer Project. Br J Sports Med 40: 928-934, 2006.
45. Vincent, WJ. Statistics in Kinesiology. Champaign, IL: Human Kinetics, 1995.
46. Williford, HN, Scharff-Olson, M, Duey, WJ, Pugh, S, and Barkdale, JM. Physiological status and prediction of cardiovascular fitness in highly trained youth soccer athletes. J Strength Cond Res 13: 10-15, 1999.
Keywords:

association football; fitness assessment; match analysis; team sports; intermittent exercise

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