Today's talented youth field hockey players, the stars of tomorrow? Gemser, Marije

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1 University of Groningen Today's talented youth field hockey players, the stars of tomorrow? Gemser, Marije IMPORTANT NOTE: You are advised to consult the publisher's version (publisher's PDF) if you wish to cite from it. Please check the document version below. Document Version Publisher's PDF, also known as Version of record Publication date: 2005 Link to publication in University of Groningen/UMCG research database Citation for published version (APA): Elferink-Gemser, M. T. (2005). Today's talented youth field hockey players, the stars of tomorrow? a study s.n. Copyright Other than for strictly personal use, it is not permitted to download or to forward/distribute the text or part of it without the consent of the author(s) and/or copyright holder(s), unless the work is under an open content license (like Creative Commons). Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim. Downloaded from the University of Groningen/UMCG research database (Pure): For technical reasons the number of authors shown on this cover page is limited to 10 maximum. Download date:

2 Chapter IV Multidimensional performance characteristics and performance level in talented youth field hockey players: A longitudinal study Elferink-Gemser, M.T., Visscher, C., Lemmink, K.A.P.M., and Mulder, Th. Journal of Sports Sciences (pending minor revisions) Acknowledgements: This study has been supported by a grant of the Dutch National Olympic Committee NOC*NSF. The authors thank all players, trainers, and staff of the field hockey clubs HC s Hertogenbosch and HC Rotterdam for their cooperation.

3 Abstract To reveal performance characteristics, which may have power for predicting future elite field hockey players, we made a comparison between 30 elite and 35 sub-elite youth players in terms of anthropometric, physiological, technical, tactical and psychological characteristics measured on three occasions, each separated by a time interval of one year. Mean age of the players on the first measurement was 14.2 years (sd = 1.1). Repeated measures analyses of covariance with factors of performance level and measurement, and with age as a covariate, showed that the elite players scored better than the sub-elite players on technical and tactical variables. Female elite youth players also scored better on interval endurance capacity, motivation and confidence. Future elite players seem to excel in tactical skills by the age of 14 already. They also stand out in specific technical skills and develop these together with the interval endurance capacity better than sub-elite youth players in the two subsequent years. It will be interesting to follow these players until they reach elite status in adulthood to verify these conclusions. 50

4 Chapter I II III IV V VI VII VIII 4.1 Introduction Field hockey is an important sport in the Netherlands. The high level of Dutch field hockey players is recognised world-wide. To reach elite level, players have to start their intensive and time-consuming training at an early age (Alabin et al., 1980; Hahn, 1990). According to Ericsson et al. (1993) and Ericsson (1996), expert performance is the end result of an individual s prolonged efforts to improve performance, and since engagement in deliberate practice is not inherently motivating, commitment from the performers is required. Notwithstanding the efforts of many players, only a few will become successful in the end. What is it that characterises the ones who succeed? This question forms the background for the present paper in which it is attempted to deliver some preliminary answers to this intriguing question. A number of studies have focused on performance-related characteristics of elite field hockey players. Unique requirements of the game include dribbling the ball and moving quickly in a semi-crouched posture (Reilly and Seaton, 1990). Analysis of the physiological cost and energy expenditure of playing hockey has placed it in the category of heavy exercise (Ghosh et al., 1991; Reilly and Borrie, 1992; Boyle et al., 1994; Lothian and Farrally, 1994; Aziz et al., 2000). Two decades ago, Hargraeves (1984) already showed high VO 2 max values for British Olympians, and Withers et al. (1977) did the same for Australian nationals. The intermittent running, accelerating and decelerating increases the overall effort needed in field hockey (Patel et al., 2002). Researchers who focus on talent development in sports often acknowledge that a worldclass performance is the result of several factors (Deshaies et al., 1979; Régnier, 1993; Pienaar et al., 1998; Reilly et al., 2000). According to Williams and Reilly (2000), research should adopt a multidisciplinary approach to identify talent. Burwitz et al. (1994) also recommend interdisciplinary performance-related sports science research. Thereby, Atkinson and Nevill (2001) have argued that more research should involve sports-specific dependent variables. We applied a multidisciplinary design in a recent study on talented Dutch field hockey players. It was shown that a combination of technical, tactical and psychological characteristics distinguished best between elite and sub-elite youth players (Elferink-Gemser et al., 2004). In most previous research, a cross-sectional rather than longitudinal approach has been applied. However, to improve understanding of the factors that contribute to expert performance, players should be monitored over a prolonged period of time (Williams and Reilly, 2000). The goal of the present study is to reveal performance characteristics, which may have power for predicting future elite field hockey players. Within the pool of talented players, a comparison has been made between elite and sub-elite youth players in terms of 51

5 anthropometric, physiological, technical, tactical and psychological characteristics measured on three occasions, each separated by a time interval of one year. Questions to be answered are: On which performance characteristics do elite youth players score better than their subelite counterparts? How do elite and sub-elite youth players develop their performance characteristics over a period of two years, and is there a difference between elite and sub-elite youth players concerning this development? 4.2 Methods Participants One hundred and twenty-six talented field hockey players in the age-bracket (mean age = 13.9, sd = 1.3) participated in a cross-sectional study on the relation between multidimensional performance characteristics and performance level (Elferink-Gemser et al., 2004). All participants were part of a talent development program of a field hockey club of national prestige, and were playing at the highest level for their age category. Within this group, a distinction was made between 38 elite and 88 sub-elite youth players. In contrast to sub-elite players, elite players train and play in a youth selection team of the Dutch Field Hockey Association (KNHB). From the initial 126 field hockey players, 85 were tested again one year later (t 2 ), and after two years (t 3 ) 65 players were tested for the third time. Table 4.1 presents the number of participants at t 1, t 2 and t 3 divided by performance level and gender. Thirty players left the study because they were no longer part of the talent development program. They continued playing field hockey but fell back to club performance level. Reasons for players who were still playing on a national level for leaving the study were not being able to attend the measurements because of illness or injuries or because of lacking time or transportation. Table 4.1. Number of participants at t 1, t 2 and t 3 classified by performance level, gender and number of players that left the study. Female players Male players Players that left the study Elite Sub-elite Elite Sub-elite Elite Sub-elite Club level Measurement t 1 n = t 2 n = t 3 n =

6 Chapter I II III IV V VI VII VIII The proportion of female and male participants on the three measurements was about the same. Two female and three male players of the total group (n = 65) were elite players at t 1 but sub-elite at t 3. One female player was sub-elite at t 1 but elite at t 3. The other players remained either elite or sub-elite from t 1 through t 3. Table 4.2 displays the general characteristics of the participants concerning age, field hockey experience, training hours and match play frequency. Table 4.2. Mean (sd) scores of general characteristics at t 3 concerning age, field hockey experience, training hours and matches per week for talented youth field hockey players classified by gender and performance level. Female youth players Elite players n = 15 Sub-elite players n = 18 Male youth players Elite players n = 15 Sub-elite players n = 17 Age (years) Field hockey experience (years) Field hockey training (hours per week) Total training (hours per week) Matches per week (1.01) (1.28) (1.00) (1.08) 8.43 (2.19) 9.06 (1.69) 8.87 (1.51) 8.80 (2.31) 5.13 (1.65) 4.28 (1.70) 5.18 (0.57) 4.70 (0.31) 8.37 (3.91) 5.64 (2.31) 8.15 (3.64) 7.94 (3.85) 1.07 (0.26) 1.00 (0.00) 1.17 (0.36) 1.00 (0.00) 53

7 Procedure All players were informed about the procedure of the study before giving their informed consent to participate. The clubs and trainers gave their permission for this study. The procedures were in accordance with the standards of the local medical ethics committee of the University of Groningen. The players completed the tests at the end of the competitive field hockey season (t 1 ), at the end of the season (t 2 ) and at the end of the season (t 3 ). Ambient temperature, humidity and wind conditions were documented. Measurements for each player took place according to five categories of performance characteristics: anthropometric, physiological, technical, tactical and psychological. Field tests were executed on synthetic field hockey playing surfaces (water-based pitches). The employed test procedures are described in detail elsewhere (Elferink-Gemser et al., 2004). Anthropometric characteristics Anthropometric measurements were length (m), body mass (kg) and percentage of body fat. The latter was estimated by means of leg-to-leg bioelectrical impedance (BIA) analysis (Valhalla BIA, Valhalla, Inc., San Diego, CA). This method proved to be reliable for measuring body fat percentage, and results correlated highly with body fat percentage as measured with underwater weighing and dual energy X-ray absorptiometry (Nunez et al., 1997). Physiological characteristics All players performed three field tests to determine four physiological characteristics. These characteristics included peak shuttle sprint performance, repeated shuttle sprint performance, slalom sprint performance and interval endurance capacity. In all tests, players had to carry their hockey stick. Peak shuttle sprint and repeated shuttle sprint performance were measured by means of the Shuttle Sprint and Dribble Test (ShuttleSDT), in which players had to run three 30-m sprints with 180-degree turning points. Each 30-meter sprint consists of 5 m toand-fro, directly followed by 10 m to-and-fro. Peak shuttle sprint performance is indicated by the time covered in the fastest of three 30-m sprints, whereas repeated shuttle sprint performance is the total time covered by all three 30-m sprints. Reliability proved to be satisfactory in young field hockey players (Lemmink et al., 2004a). Slalom sprint performance was measured using the Slalom Sprint and Dribble Test (SlalomSDT), in which players have to sprint 30 m in a zigzag fashion with twelve 120- degree turns around cones placed 2 m apart from each other. Reliability for this test was supported (Lemmink et al., 2004a). Interval endurance capacity was measured with the Interval Shuttle Run Test (ISRT) (Lemmink et al., 2000; Lemmink and Visscher, 2003). The 54

8 Chapter I II III IV V VI VII VIII ISRT is a field test that contains intervals at a work-rest ratio of 2:1, turning points at 20 m and an increasing running velocity. The number of fully completed 20-m runs is recorded as the test score. In previous research, this test has proven to be reliable and sensitive for differences in performance level (Lemmink, et al., 2000; Lemmink et al., 2004b; Lemmink et al., 2004c). Technical characteristics All players performed two field tests to determine three technical characteristics. These characteristics included peak shuttle dribble performance, dribble performance in a repeated shuttle run and performance in a slalom dribble. Peak shuttle dribble performance as well as dribble performance in a repeated shuttle run were measured using the ShuttleSDT; performance in a slalom dribble was measured using the SlalomSDT. Players now had to keep control over the ball while performing the tests. Reliability of the dribbling part of both the ShuttleSDT and the SlalomSDT has been supported in young field hockey players (Lemmink et al., 2004a). Tactical characteristics The trainers evaluated the tactical characteristics of their players. For this purpose, each of the 12 trainers filled out the Tactics in Sports questionnaire in order to give their opinion about three tactical characteristics of each player: general tactics, tactics for possession of the ball and tactics for non-possession of the ball. The trainers were instructed to compare each player with the top players in the same age category. In a previous study this questionnaire has proven to be reliable and sensitive for differences in performance level (Elferink-Gemser et al., 2001; 2004). Psychological characteristics All players filled in a sports-specific questionnaire: the Dutch Youth Version of the Psychological Skills Inventory for Sports (PSIS) (Mahoney et al., 1987; Elferink-Gemser et al., 2004). The PSIS was developed for directly assessing an athlete s psychological skills relevant to athletic training and exceptional performance. It assesses the level of motivation, confidence, anxiety control, mental preparation, team emphasis and concentration. This questionnaire has proven to be reliable in previous research (Bakker, 1995; Companjen and Bakker, 2003). 55

9 Data analysis All data were analysed for male and female players separately using SPSS 10. According to the five categories of performance characteristics (anthropometric, physiological, technical, tactical and psychological), mean scores and standard deviations were calculated on measurements 1, 2 and 3 for the four different subgroups based on performance level (elite and sub-elite youth players) and gender. Repeated measures analyses of covariance were used to examine group differences based on performance level together with differences in performance characteristics over time. Age was considered as covariate. The statistical techniques provide comparisons of the subgroups over time, taking into account the possible influence of age. In the between-subjects analysis, a performance-level effect shows differences in average scores on measurements 1, 2 and 3 between elite and sub-elite players. In the within-subjects analysis, a measurement effect shows differences between scores on the three measurements. An interaction effect between performance level and measurement reveals differences between elite and sub-elite players that change as a function of time. An alpha of 0.05 was adopted for all tests of significance. 4.3 Results Table 4.3 presents mean scores and standard deviations of the multidimensional performance characteristics for talented youth female field hockey players on the three measurements classified by performance level. Table 4.4 provides the same information for talented youth male field hockey players. 56

10 Table 4.3. Mean scores (sd) of anthropometric, physiological, technical, tactical and psychological characteristics for talented youth female field hockey players on measurements 1, 2 and 3 classified by performance level. Female elite players n = 15 Female sub-elite players n = 18 t 1 t 2 t 3 t 1 t 2 t 3 Anthropometric characteristics Length (m) Body mass (kg) % Body Fat Physiological characteristics Peak shuttle sprint performance 30m (s) Repeated shuttle sprint perf. 3x30m (s) Slalom sprint performance 30m (s) Interval endurance capacity (runs of 20m) Technical characteristics Peak shuttle dribble performance 30m (s) Dribble perf. in rep. shuttle run 3x30m (s) Performance in a slalom dribble 30m (s) Tactical characteristics General tactics (1-6) Tactics (possession of the ball) (1-6) Tactics (non-possession of the ball) (1-6) Psychological characteristics Motivation (1-5) Confidence (1-5) Anxiety Control (1-5) Mental Preparation (1-5) Team Emphasis (1-5) Concentration (1-5) 1.61 (0.08) (7.75) (6.11) 9.00 (0.30) (0.93) (0.85) (12.08) (0.58) (1.75) (1.78) 4.17 (1.10) 4.19 (0.80) 3.87 (0.65) 4.65 (0.31) 3.68 (0.63) 3.89 (0.48) 2.18 (0.53) 3.54 (0.41) 3.59 (0.41) 1.64 (0.07) (7.18) (5.66) 8.64 (0.33) (0.88) (0.56) (14.98) (0.46) (1.58) (2.00) 3.97 (0.93) 3.97 (0.72) 3.59 (0.52) 4.57 (0.37) 3.27 (0.24) 3.94 (0.48) 2.24 (0.74) 3.52 (0.44) 3.65 (0.53) 1.66 (0.05) (6.42) (5.94) 8.63 (0.26) (0.81) (0.71) (17.16) 9.72 (0.46) (2.26) (1.18) 4.07 (0.59) 4.18 (0.60) 3.91 (0.37) 4.41 (0.48) 3.68 (0.48) 3.81 (0.67) 2.34 (0.68) 3.53 (0.55) 3.52 (0.53) 1.67 (0.05) (7.09) (7.11) 9.08 (0.45) (1.51) (1.20) (17.32) (0.66) (2.64) (2.72) 3.14 (0.90) 3.63 (0.66) 3.75 (0.71) 4.08 (0.55) 3.37 (0.55) 3.92 (0.51) 1.91 (0.58) 3.54 (0.65) 3.64 (0.59) 1.68 (0.05) (7.33) (5.85) 8.78 (0.40) (1.36) (0.97) (12.51) (0.81) (3.47) (1.55) 3.27 (1.03) 3.44 (0.86) 3.55 (0.66) 4.32 (0.60) 3.17 (0.41) 3.89 (0.39) 2.19 (0.64) 3.52 (0.38) 3.64 (0.60) 1.69 (0.04) (6.65) (6.15) 8.72 (0.44) (1.35) (0.96) (16.46) 9.99 (0.87) (2.87) (2.07) 3.67 (0.91) 3.69 (0.75) 3.73 (0.64) 4.10 (0.56) 3.21 (0.56) 3.90 (0.38) 2.00 (0.66) 3.44 (0.35) 3.52 (0.47)

11 Table 4.4. Mean scores (sd) of anthropometric, physiological, technical, tactical and psychological characteristics for talented youth male field hockey players on measurements 1, 2 and 3 classified by performance level. Male elite players n = 15 Male sub-elite players n = 17 t 1 t 2 t 3 t 1 t 2 t 3 Anthropometric characteristics Length (m) Body mass (kg) % Body Fat Physiological characteristics Peak shuttle sprint performance 30m (s) Repeated shuttle sprint perf. 3x30m (s) Slalom sprint performance 30m (s) Interval endurance capacity (runs of 20m) Technical characteristics Peak shuttle dribble performance 30m (s) Dribble perf. in rep. shuttle run 3x30m (s) Performance in a slalom dribble 30m (s) Tactical characteristics General tactics (1-6) Tactics (possession of the ball) (1-6) Tactics (non-possession of the ball) (1-6) Psychological characteristics Motivation (1-5) Confidence (1-5) Anxiety Control (1-5) Mental Preparation (1-5) Team Emphasis (1-5) Concentration (1-5) 1.66 (0.06) (8.15) 9.20 (2.23) 8.63 (0.40) (1.20) (0.70) (27.76) (0.68) (1.89) (1.28) 4.33 (0.90) 4.64 (0.83) 4.44 (0.72) 4.52 (0.24) 3.94 (0.70) 4.08 (0.44) 2.34 (0.68) 3.46 (0.43) 3.41 (0.64) 1.72 (0.06) (7.71) 7.55 (2.09) 8.61 (0.41) (1.12) (0.91) (18.94) 9.38 (0.41) (1.55) (1.13) 4.27 (0.70) 4.13 (0.62) 4.09 (0.68) 4.28 (0.50) 3.51 (0.43) 3.88 (0.91) 2.56 (1.24) 3.48 (0.56) 3.42 (0.85) 1.76 (0.08) (8.03) 7.83 (1.56) 8.18 (0.29) (0.90) (0.54) (19.14) 9.06 (0.40) (1.18) (0.94) 4.17 (0.79) 4.09 (0.65) 4.08 (0.50) 4.20 (0.47) 3.70 (0.79) 3.34 (1.07) 3.07 (1.28) 3.42 (0.38) 3.15 (1.01) 1.69 (0.08) (10.80) 9.51 (4.64) 8.58 (0.35) (1.44) (0.71) (22.19) 9.91 (0.66) (2.41) (2.33) 3.65 (0.79) 3.71 (0.61) 3.90 (0.48) 4.30 (0.46) 3.93 (0.61) 4.01 (0.51) 2.13 (0.60) 3.55 (0.43) 3.88 (0.70) 1.74 (0.08) (9.95) 8.78 (5.30) 8.61 (0.41) (1.55) (0.60) (28.85) 9.49 (0.77) (2.55) (1.83) 2.94 (0.83) 3.16 (0.75) 3.26 (0.60) 4.20 (0.61) 3.35 (0.35) 3.88 (0.57) 2.46 (0.58) 3.52 (0.50) 3.65 (0.56) 1.77 (0.07) (9.28) 8.65 (4.50) 8.18 (0.36) (1.22) (1.00) (26.07) 9.36 (0.64) (2.51) (1.70) 3.21 (0.59) 3.22 (0.82) 3.31 (0.70) 3.88 (0.64) 3.71 (0.72) 3.95 (0.55) 2.45 (0.42) 3.54 (0.46) 3.73 (0.48)

12 Chapter I II III IV V VI VII VIII Talented youth female field hockey players We found a significant main effect on performance level. Elite players performed better than sub-elite players on physiological, technical, tactical and psychological characteristics. Elite players performed more runs on the interval shuttle run test [F (1,30) = , p < 0.01]. They were also faster in the peak shuttle dribble [F (1,30) = 3.146, p < 0.05], repeated shuttle dribble [F (1,30) = 4.536, p < 0.05] and slalom dribble [F (1,30) = 4.064, p < 0.05], with higher scores on general tactics [F (1,30) = 8.133, p < 0.01] and tactics for possession of the ball [F (1,30) = 4.719, p < 0.05]. Finally, elite players were more motivated [F (1,30) = 6.840, p < 0.01] and had more confidence [F (1,30) = 4.509, p < 0.05] than sub-elite players. Concerning the development of the performance characteristics in two years, a significant main effect on measurement was found on anthropometric, physiological, technical and tactical characteristics. From measurements 1 through 3, players were taller [F (1,29) = , p < 0.01) and heavier [F (1,29) = 7.864, p < 0.01]. They improved on repeated shuttle sprint performance [F (1,29) = 4.248, p < 0.05] and interval endurance capacity [F (1,29) = 6.546, p < 0.01], becoming faster in the peak shuttle dribble [F (1,29) = 5.626, p < 0.01] and attaining higher scores on general tactics [F (1,29) = 7.941, p < 0.01]. We found an interaction effect between performance level and measurement on interval endurance capacity [F (1,29) = 2.600, p < 0.05]. In contrast to sub-elite players, elite players showed an increase in the number of runs on the interval shuttle run test, especially from the second to the third measurement (Figure 4.1A). We also found an interaction effect on slalom dribble performance [F (1,29) = 3.178, p < 0.05]. Elite players improved more than sub-elite players (Figure 4.1D). Finally, we found an interaction effect for confidence [F (1,29) = 3.065, p < 0.05]. Scores for confidence on the second measurement were lower than on the first measurement for both elite and sub-elite players. In contrast to the sub-elite players, whose scores remained relatively stable from t 2 to t 3, the confidence scores of the elite players on t 3 were back to the level of measurement 1. No other interaction effects were found, indicating that the development from t 1 through t 3 in test scores is similar for elite and sub-elite players. 59

13 Number of runs Interval endurance capacity Female elite Female sub-elite Male elite Male sub-elite A Time (s) Peak shuttle dribble performance B 40 t1 t2 t3 9 t1 t2 t3 Time (s) Dribble performance in a repeated shuttle run C t1 t2 t3 Measurement Time (s) Performance in a slalom dribble D t1 t2 t3 Measurement Figure 4.1. Performances of the talented youth field hockey players on the three measurements. Talented youth male field hockey players As with female players, we found a significant main effect on performance level in male players. Elite players were faster than sub-elite players in the peak shuttle dribble [F (1,29) = 2.914, p < 0.05], repeated shuttle dribble [F (1,29) = 2.988, p < 0.05] and slalom dribble [F (1,29) = 8.306, p < 0.01] (Figures 4.1B, 4.1C, 4.1D). Compared to sub-elite players, elite players scored better on general tactics [F (1,29) = , p < 0.01], tactics for possession of the ball [F (1,29) = , p < 0.01] and tactics for non-possession of the ball [F (1,29) = , p < 0.01]. Sub-elite players scored better than elite players on concentration [F (1,28) = 6.264, p < 0.01]. A significant main effect on measurement has been found for anthropometric, physiological, technical and psychological characteristics. From measurements 1 through 3, players were taller [F (1,28) = 5.802, p < 0.01], heavier [F (1,28) = 3.752, p < 0.05] and had less body fat [F (1,28) = 3.400, p < 0.05]. They improved on peak shuttle sprint performance [F (1,28) = 3.623, p < 0.05], repeated shuttle sprint performance [F (1,28) = 9.693, p < 0.01], slalom sprint [F (1,28) = 2.875, p < 0.05], interval endurance capacity [F (1,28) = 5.915, p < 0.01] and slalom dribble [F (1,28) = 2.635, p < 0.05]. Scores on anxiety control decreased from measurements 1 through 3 [F (1,27) = 3.678, p < 0.05]. 60

14 Chapter I II III IV V VI VII VIII We found an interaction effect between performance level and measurement for interval endurance capacity [F (1,28) = 3.699, p < 0.05]. Both elite and sub-elite players improved with about 12 runs from t 1 to t 2. From t 2 to t 3, sub-elite players did not improve in contrast to elite players, who ran on average over 20 more runs (Figure 4.1A). We also found an interaction effect for anxiety control [F (1,27) = 6.647, p < 0.01]. From t 1 through t 3, elite players scored lower in contrast to sub-elite players, whose scores remained relatively stable. 4.4 Discussion This study deals with talented youth field hockey players in the Netherlands. At the end of the competitive season we measured 126 players in the age-bracket, all part of a talent development program of a field hockey club of national prestige. Most of today s top performers played in a youth selection team when they were younger. We divided the players into elite and sub-elite youth categories on the basis of membership in an extra selection team of the Dutch Field Hockey Association (KNHB) in the , and/or seasons. During this study, there was only one player that shifted from sub-elite to elite. Therefore, it appears that to develop a successful field hockey career, a youth player has to be part of an extra selection team of the KNHB around the age of 14 already. This, however, is no guarantee for success, since there are more shifts from elite to sub-elite (n = 5) and from sub-elite to club level (n = 30), making it clear that in a period of two years more than 25% of the players could not meet the expectations. It is obviously very hard to predict who will ultimately reach elite status in adulthood, especially in a team sport. Unlike individual sports, in which there is a unidimensional performance criterion like time, distance or height, a performance in team sports depends on the combination of numerous mini-performances of the player and his team-mates (Régnier et al., 1993). Due to a lack of objective performance measurements, players therefore have to convince the scout, trainer or coach of their talent. Over the years, many researchers have attempted to get a grip on the rather vague concept of talent in studies that concentrated on music (Sloboda et al., 1994a,b; Krampe and Ericsson, 1996; Howe et al., 1998) and sports (Starkes and Deakin, 1984; Starkes, 1987; Helsen and Pauwels, 1993; Starkes et al., 1994; Helsen and Starkes, 1999). However, the suggestion that talent provides a basis for predicting excellence is not supported by the current evidence (Helsen et al., 2000). To justify early identification and selection of talented young athletes, it seems crucial to gain more insight into the characteristics of tomorrow s stars. One way to do so is by adopting a multidisciplinary, longitudinal approach in which talented youth players are followed over time until some of them reach elite status in adulthood. 61

15 In our study, 65 players who have been considered as talented for at least three consecutive years were followed and measured on three occasions. Both female and male elite youth players scored better than the sub-elite players on technical and tactical variables. In the female group, elite players also scored better on interval endurance capacity, motivation and confidence than sub-elite players, whereas the sub-elite male players had higher scores on concentration than the elite male players. Hence, the results clearly show that relevant variables to distinguish between elite and sub-elite players do not stem from a single domain of performance characteristics. This is in line with a study of Nieuwenhuis et al. (2002) in which successful and less successful female field hockey players were compared. They concluded that the successful year-old player passes the ball more accurately over a distance, is faster in covering a short distance, has a broader humerus and femur, and experiences the competitive situation more positively. Our results show that maintaining speed while dribbling a hockey ball is important at the elite level. These findings are consistent with other studies. Reilly and Bretherton (1986) reported better dribbling control in elite versus county field hockey players, and Keogh et al. (2003) mentioned better scores for regional representative players in contrast to club-level players while dribbling a hockey ball through an agility course. Top-level coaches also confirmed the importance of technique in field hockey (Van Rossum and Gagné, 1994). It follows that tactical skills performing the right action at the right moment seems crucial for a successful career in field hockey. Our results are in line with other studies showing that skilled players outscore less skilled ones on tactical elements (Williams et al., 1993; Williams and Davids, 1995; Enns and Richards, 1997). However, we are aware that the tactical skill variables in our study do not specify exactly the underlying processes that enable players to perform the right action at the right moment. In the absence of a practical, reliable and valid instrument to measure tactical skills, we used the opinion of the trainer to gain insight into each player s general tactics, tactics for possession of the ball and tactics for nonpossession of the ball. Because we were unable to measure tactical skills directly with the player, results may have been confounded. Trainers work with the players throughout the season during training and match play, and know which players belong to an extra selection team of the KNHB. They might therefore be inclined to grade those players higher than the sub-elite players. However, the trainers in this study were highly qualified and considered as experts in the field, and their opinion was considered as valuable. Except for the interval endurance capacity in female players, we found no differences in anthropometric or physiological characteristics between both performance groups. In contrast, according to Keogh et al. (2003), measures of body fat percentage and short-duration sprinting speed are useful for distinguishing between field hockey players of different ability. 62

16 Chapter I II III IV V VI VII VIII However, in their study they compared regional representative players with local club-level players, and not players who were playing at the national level as was the case in our study. Evidently, differences between players at the elite level are less related to physical and physiological characteristics (Elferink-Gemser et al., 2004). Also Franks et al. (1999) could not discriminate either between young soccer players at the highest level on the basis of their physical and physiological profiles. In the female group, elite youth players scored higher on motivation and confidence than the sub-elite players; we did not find such results in the male group, where on average all players had high scores on motivation and confidence. It seems that in talent identification and development, psychological characteristics are more important for female than for male youth players. When comparing the scores on confidence of the male and female youth players, it appears that the elite female players had scores similar to those of the male players, whereas the sub-elite female players had lower scores. Other studies show that male players have on average higher confidence scores than females (Cox and Liu, 1993; Sewell and Edmondson, 1996), but it seems that this gender difference on confidence cannot be applied at the elite level. We found interaction effects showing a different development over time for both performance groups. Compared to sub-elite youth players, elite youth players improved more on interval endurance capacity and slalom dribble performance. The improvement of the interval endurance capacity is consistent with the TOYA study of Baxter-Jones et al. (1993; 1995). They studied the development of aerobic power in young soccer, swimming, gymnastics and tennis athletes in the 8-16 age-bracket. Results showed that VO 2 max increased significantly with pubertal status in males. In our study, male youth players increased their number of runs on the Interval Shuttle Run Test from the first through the third measurement. Although we did not take any maturity measures, we do not expect significant differences between elite and sub-elite players concerning maturation based on a similar development of their length, body mass and body fat percentage. Nevertheless, one cannot rule out that the most mature children were performing best at this age. Baxter-Jones et al. did not show a significant increase in VO 2 max in the latter stages of puberty in females. In our study, female sub-elite players increased their score on the ISRT (4 runs) only slightly, whereas the female elite players were able to increase their ISRT score with 20 runs on average from the first through the third measurement. To sum up, elite youth players seem to either score better than sub-elite youth players on performance characteristics by the age of 14 and subsequently remain better in the following two years, or they have similar scores to the sub-elite youth players on the first measurement but develop these characteristics better in the next two years (ages 14-16). Since at the first 63

17 measurement both elite and sub-elite youth players were active in field hockey for an average of over 6 years, these findings are not likely to be caused by a difference in active field hockey experience. However, elite players did seem to train more frequently than sub-elite players at the age of 14, even at 16. This concerns both specific field hockey training and general training. These findings are in line with the study of Ericsson et al. (1993), who proposed a model of expertise based on deliberate practice. They argued that practice is the only determinant of expertise. However, another explanation could be that the elite youth players have inherited a more favourable genetic profile for success in field hockey. According to Howe (1998), a talent originates in genetically-transmitted structures and hence is at least partly innate. Probably both nature and nurture are essential. In a study of Starkes et al. (1996), coaches of elite figure skaters acknowledged the role played by talent, but stated that even the most talented athletes must practice hard to succeed. Until the middle of the 20th century, it was possible to become an international athlete without belonging to a nation s group of most-talented individuals (Bouchard et al., 1997). Today, the level of competition has increased to the point that only those athletes who combine their talent with intensive training are potentially able to reach elite status. In conclusion, in field hockey future elite players seem to excel in tactical skills by the age of 14 already. They also stand out in specific technical skills and develop these together with their interval endurance capacity favourably in the subsequent two years, and show high levels of motivation and confidence. To verify these conclusions, it will be interesting to follow these players until they reach elite status in adulthood. 64

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