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Analysis of the distance covered by Brazilian professional futsal players during official matches a
a
Murilo José De Oliveira Bueno , Fabio Giuliano Caetano , Tiago a
a
Julio Costa Pereira , Nicolau Melo De Souza , Gustavo Damasceno a
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c
Moreira , FáBIO Yuzo Nakamura , Sergio Augusto Cunha & Felipe a
Arruda Moura a
Laboratory of Applied Biomechanics, State University of Londrina, Londrina, Brazil b
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Physical Education Department, State University of Londrina, Londrina, Brazil c
Laboratory of Instrumentation for Biomechanics, University of Campinas, Campinas, Brazil Published online: 16 Sep 2014.
To cite this article: Murilo José De Oliveira Bueno, Fabio Giuliano Caetano, Tiago Julio Costa Pereira, Nicolau Melo De Souza, Gustavo Damasceno Moreira, FáBIO Yuzo Nakamura, Sergio Augusto Cunha & Felipe Arruda Moura (2014) Analysis of the distance covered by Brazilian professional futsal players during official matches, Sports Biomechanics, 13:3, 230-240, DOI: 10.1080/14763141.2014.958872 To link to this article: http://dx.doi.org/10.1080/14763141.2014.958872
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Sports Biomechanics, 2014 Vol. 13, No. 3, 230–240, http://dx.doi.org/10.1080/14763141.2014.958872
Analysis of the distance covered by Brazilian professional futsal players during official matches
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´ DE OLIVEIRA BUENO1, FABIO GIULIANO CAETANO1, MURILO JOSE TIAGO JULIO COSTA PEREIRA1, NICOLAU MELO DE SOUZA1, ´ BIO YUZO NAKAMURA2, GUSTAVO DAMASCENO MOREIRA1, FA SERGIO AUGUSTO CUNHA3, & FELIPE ARRUDA MOURA1 1
Laboratory of Applied Biomechanics, State University of Londrina, Londrina, Brazil, 2Physical Education Department, State University of Londrina, Londrina, Brazil, and 3Laboratory of Instrumentation for Biomechanics, University of Campinas, Campinas, Brazil (Received 7 November 2013; accepted 21 August 2014)
Abstract The purpose of this study was to measure and characterise the distances covered by Brazilian professional futsal players. The trajectories of 93 players during five matches were obtained using an automatic tracking method. The distances covered were analysed for different game conditions: over the entire game and during the times when the ball was out of play and in play separately. When the entire game was considered, the results showed that there was a reduction in the total distance covered per minute from the first [median ^ IQR (interquartile range): 97.9 ^ 16.2 m/min] to the second half (median ¼ 90.3 m/min; IQR ¼ 12.0), and when only the in-play time was considered (first half: 136.6 ^ 17.2 m/min; second half: 129.2 ^ 16.7 m/min). The percentage of distance covered in the standing and walking velocity range was higher in the second half than in the first when considering the entire game (30.8% and 28.0%, respectively) and during the in-play time (19.3% and 16.2%, respectively). In conclusion, this study verified that futsal players reduced the physical performance during the second half.
Keywords: Kinematics, automatic tracking, activity profile, in-play time, out-of-play time
Introduction The implementation of recent technological advancements has enabled the use of automatic tracking procedures using videogrammetry (Figueroa, Leite, & Barros, 2006a, 2006b; Liu et al., 2009) to obtain information regarding the positions of players in team sports on a pitch as a function of time. These procedures have been used in official competitions for several sports (primarily for football) for the purpose of quantifying various physical, technical, and tactical variables (Barros et al., 2007; Dellal et al., 2011; Moura et al., 2013; Moura, Martins, Anido, Barros, & Cunha, 2012). Correspondence: F.A. Moura, Laboratory of Applied Biomechanics, Sport Sciences Department, State University of Londrina, Av. Gil de Abreu e Souza, 2335, Unidade 1121, Esperanc a, CEP 86058-100 Londrina, Brazil, E-mail: [email protected] q 2014 Taylor & Francis
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Some of the physical demands related to competition have been evaluated by quantifying the total distances covered by players during a match, the distances covered in specific ranges of velocities, and the time spent in each velocity zone. By quantifying a match in this manner, the physical demands of a given sport may be characterised to help coaches better plan specific training sessions (Barros et al., 2007) and track player fatigue, which is thought to impair performance by transiently reducing the intensity of the match after the most intense periods and/or during the second half (Mohr, Krustrup, & Bangsbo, 2003). Unlike the substantial number of studies that have quantified the physical demands of several sports (particularly football), there are few studies that have analysed futsal matches. In previous studies, activity profiles during futsal matches were analysed for Spanish National League professionals (Barbero-Alvarez, Soto, Barbero-Alvarez, & Granda-Vera, 2008; Castagna, D’Ottavio, Granda Vera, & Barbero Alvarez, 2009), Thai players (Makaje, Ruangthai, Arkarapanthu, & Yoopat, 2012) and Australian players (Dogramaci, Watsford, & Murphy, 2011). In spite of the international success of elite-standard Brazilian futsal players, their kinematic characteristics during participation in the National League have not been investigated. These data would be extremely valuable because 9 of the 14 players who were the champions of the last FIFA Futsal World Cup played in the Brazilian League during 2012. Of the previous studies, only Barbero-Alvarez et al. (2008) analysed official matches. It is well accepted that competitiveness can influence motion characteristics (Dogramaci et al., 2011) and possibly induce bias in the interpretation of the physical demands of nonofficial or friendly matches. Furthermore, there is also an important methodological consideration in the aforementioned futsal studies that should be highlighted. According to the rules of futsal, the clock is stopped when the ball is out of play. Although studies in other sports (e.g. Fernandez-Fernandez, Sanz-Rivas, Fernandez-Garcia, & Mendez-Villanueva, 2008; Sarro, Misuta, Burkett, Malone, & Barros, 2010) have analysed players’ physical activity profiles during periods when the ball was out of play and in play, this procedure is often ignored in futsal. This consideration is relevant because an analysis of the entire game that ignores match interruptions may underestimate the real physical demands during the inplay phase. Characterising players’ kinematics as a function of the match situation (i.e. in play and out of play) during official matches can help coaches better estimate the physical profile of futsal competitions and to formulate training drills to help players address the real physical challenges of the sport. Therefore, the purpose of this study was to measure and characterise the distances covered by Brazilian professional players during official matches. In addition, we aimed to compare the work rates between the first and second halves to detect possible decreases in performance, as has been previously found for other leagues (e.g. BarberoAlvarez et al., 2008). We hypothesised that there would be a decrease from the first to the second half in the distance covered by the players and in the percentage of distance that was covered in high velocity ranges.
Methods Participants and procedures The experimental design consisted of a cross-sectional study of an elite male professional futsal competition. The study was approved by the Ethics Committee at the State University of Londrina. Five official matches in the 2012 Brazilian First Division League were filmed using two digital cameras (30 Hz) that were fixed at elevated positions in the gymnasium. Each
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camera covered roughly three quarters of the court with an overlapping region (Figure 1A). The images were transferred to computers and were synchronised by identifying common events in this overlapped region, such as a kick by a player. Then, the players’ positions as a function of time were obtained by means of an automatic tracking system. The trajectories of 93 players (four of these players were champions of the last FIFA Futsal World Cup; mean age ¼ 26 ^ 4 years, height ¼ 1.75 ^ 0.06 m, and mass ¼ 73.0 ^ 7.8 kg) were obtained using the DVideo software automatic tracking system (Figueroa et al., 2006b). The average error for the determination of player position was 0.098 m, and the average error for the distance covered was 0.8%. The two automatic procedures of segmentation (Figure 1B) and tracking (Figure 1C) generated players’ positions as a function of time over the entire match. Before the matches, we obtained the coordinates of 16 control points on the court, which were defined relative to the coordinate system associated with the court. The corresponding projections of these points in the image were determined using the DVideo software.
Figure 1. Camera images with overlapping regions (A) and the results of the segmentation process (B) and tracking (C).
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The homography parameters of the image–object transformation were then calculated based on the direct linear transformation method, and the players’ two-dimensional coordinates were obtained relative to the pitch’s coordinate system. Finally, players’ trajectories were filtered with a Butterworth third-order low-pass digital filter with a cut-off frequency of 0.4 Hz.
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Kinematic data analysis The distance covered by each player was calculated as the cumulative sum of the displacement between two consecutive frames. The total distance covered by each player was normalised against the length of time the player participated in the match. In addition, the percentage of the distance covered was computed in the following velocity ranges (Castagna et al., 2009): V1 # 6.0 km/h (standing and walking); 6.1 , V2 # 12.0 km/h (low-intensity running); 12.1 , V3 # 15.4 km/h (medium-intensity running); 15.5 , V4 # 18.3 km/h (high-intensity running); and V5 . 18.4 km/h (sprinting). To more accurately characterise the activity profile during the futsal match, the variables were analysed over the entire game time and during periods when the ball was out of play and in play. Statistical analysis The distances covered by the players and the percentages of the distance covered in each velocity range were expressed as the medians and interquartile ranges (IQRs). Before each analysis, Kolmogorov– Smirnov test verified whether the data were normally distributed. A significance level of p , 0.05 was used for all statistical analyses. Because a normal distribution was not found in all situations, a non-parametric test for the following analyses was adopted; a Wilcoxon rank-sum test compared the values for distance covered obtained for the first and second halves, and the percentages of the distance covered in each range of velocity for both halves. All statistical procedures were performed using MATLABw software (6.0, MathWorks, Inc., Natick, MA, USA). Results Figure 2 shows an example of the accumulated distance covered by the outfield players during the first half of a match during in-play and out-of-play conditions. A considerable portion of the distance covered by the players was performed when the ball was out of play. The median (IQR) value of the total distance covered by the player was 3,133.2 (2,248.5) m for the entire game and 2,133.9 (1,424.4) and 1,028.5 (807.8) m for the in-play and out-of-play phases, respectively. The distance covered during the entire game in the first half (median ¼ 1,710.6; IQR ¼ 888.3 m) was not significantly different (p ¼ 0.43) from that in the second half (median ¼ 1,635.9; IQR ¼ 1,089.2 m). Furthermore, there was considerable inter-individual variability in the total and partitioned distances (Figure 2), and it appeared to be a result of different playing times due to unlimited substitution in futsal. Table I presents the values of distances covered (m/min) by the players during the entire game and during the in-play (M ^ SD: 47.9 ^ 3.2% of the total match duration) and out-ofplay periods. The statistical analysis showed a decrease in the distance covered per minute in the second half compared with the first half when considering the entire game and the in-play period only. Figure 3 shows examples of the individual histograms of velocity in the different playing conditions that were found for four players. There was a tendency towards a greater distribution among the higher velocity values during the in-play periods, whereas the velocity distribution was concentrated at lower values during the out-of-play periods.
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Figure 2. Accumulated distance covered by professional futsal players during the first half of a match differentiated by in-play and out-of-play periods.
Table II confirms the typical pattern in Figure 3 by presenting the percentage of the total distance covered by players in the different velocity ranges. From the first half to the second half, significant increases in the percentages of distance covered by players in the standing and walking velocity range were observed for the entire game and for the in-play condition, and significant decreases in the percentages of distance covered in medium- and high-intensity running for the same conditions. For out-of-play periods, however, a significant increase in the high-intensity running velocity range from the first half to the second half was observed.
Discussion and implications The purpose of this study was to perform a kinematic analysis during official futsal matches of the Brazilian League to quantify the distance covered by the players and the percentage of Table I. Total distance covered (m/min). Condition In play Out of play Whole game
First half
Second half
p
136.6 (17.2) 58.8 (10.4) 97.9 (16.2)
129.2 (16.7)* 56.8 (14.8) 90.3 (12.0)*
0.01 0.21 ,0.01
Note: Values in median (IQR). *Significantly different from the first-half value (p , 0.05).
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Figure 3. Velocity histogram examples for professional futsal players during the first half of a match distinguished by the in-play and out-of-play periods.
this distance covered in different velocity ranges. The variables were distinguished by “whole game”, “in-play”, and “out-of-play” conditions; then, the first halves were compared with the second halves. The players investigated in this study covered less distance per minute considering the entire game for both halves than the players investigated in a study by Castagna et al. (2009), who covered 121 m/min. Castagna et al. (2009), however, analysed simulated futsal matches with four sets of 10 min each, interspersed with 5-min recovery periods. In this protocol (i.e. Table II. Percentage of the distance covered in velocity ranges (%). Condition
Velocity ranges
In play
Standing and walking Low-intensity running Medium-intensity running High-intensity running Sprinting Standing and walking Low-intensity running Medium-intensity running High-intensity running Sprinting Standing and walking Low-intensity running Medium-intensity running High-intensity running Sprinting
Out of play
Whole game
Note: Values presented in median (IQR). *Significantly different from the first half value (p , 0.05).
First half
Second half
p
16.2 (5.7) 41.9 (5.3) 20.1 (4.2) 10.3 (3.5) 10.1 (6.1) 52.4 (11.9) 33.1 (8.0) 8.1 (5.9) 2.1 (2.4) 1.5 (2.8) 28.0 (6.1) 39.0 (5.0) 16.4 (3.4) 8.0 (2.4) 7.6 (4.3)
19.3 (8.3)* 42.1 (5.4) 17.8 (5.1)* 9.6 (3.4)* 9.9 (5.0) 55.4 (15.2) 32.9 (11.1) 8.7 (5.5) 3.1 (3.2)* 1.7 (3.0) 30.8 (6.7)* 38.7 (4.0) 15.4 (3.4)* 7.5 (2.0)* 7.2 (2.7)
,0.01 0.69 ,0.01 ,0.01 0.49 0.72 0.44 0.55 ,0.01 0.29 ,0.01 0.92 ,0.01 ,0.01 0.32
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not in accordance with official futsal rules), athletes may maintain a higher level of activity because of the shorter work periods, which allows them to cover greater distances. Our results for distance covered were also less than those of Barbero-Alvarez et al. (2008), who obtained mean values of 118.4 m/min (first half) and 110.5 m/min (second half) in Spanish players. Surprisingly, teams from less successful countries such as Australia and Thailand also appeared to outperform the Brazilian teams (Table III). With respect to football, different values for distance covered by players from several leagues and levels were found in the literature (Carling, Bloomfield, Nelsen, & Reilly, 2008) and were partly dependent on players’ fitness levels (Mohr et al., 2003). Thus, it is feasible that in futsal, different leagues present specific physical requirements. Recently, it has been reported that National League-level futsal players in Brazil covered approximately 1,500 m in the Yo-Yo Intermittent Recovery Test, level 1 (Oliveira, Leicht, Bishop, Barbero-Alvarez, & Nakamura, 2013; Soares-Caldeira et al., 2014). Players from the ´ lvarez highest national level in Spain were able to cover 2,600 m in the same test (Barbero-A ´ lvarez, 2003). Nevertheless, the maximal oxygen consumption in Brazilian & Barbero-A futsal players (, 60 ml/kg/min) (Milanez et al., 2011; Pedro, Milanez, Boullosa, & Nakamura, 2013) was not substantially different from the values obtained from their highlevel European counterparts (Alvarez, D’Ottavio, Vera, & Castagna, 2009). Therefore, it appears that the Brazilian players are less fit in specific on-field intermittent tests compared with European players, which may partially explain the lower work rate found during the matches. We also verified a significant decrease in the distance covered per minute by the players from the first half to the second half, which corroborates the findings of Barbero-Alvarez et al. (2008). This result confirms our initial hypothesis that there is a decrease in the players’ physical performance. Although futsal rules permit unlimited substitutions, this reduced performance may be attributed to changes in physiological conditions (such as reduction in glycogen stores, thermal stress, and dehydration) during the game (Barbero-Alvarez et al., 2008). However, this output may be related to an increased stability of the players’ collective and individual behaviours over the match, as reported previously for football (Duarte et al., 2013). The previous literature reports reduced distances covered from the first half to the second half for Brazilian football players (Barros et al., 2007); however, this response had not yet been reported in the literature for Brazilian futsal players. We also separately analysed the variables for the in-play and out-of-play periods to characterise the activity profiles of futsal players during different match conditions. A considerable distance was covered during the out-of-play periods (Figure 2 and Table I). During these periods (which consisted of more than 50% of the total match duration), athletes perform activities that should be considered by coaches in planning and prescribing physical training for the sport. Although the distance covered per minute provides relevant information about the physical demands of futsal matches, it is also important to report intensity profiles, which identify at which velocities the players covered these distances. Previous studies had analysed the intensity of team sports by classifying the distance covered in different velocity ranges (Barros et al., 2007; Hartwig, Naughton, & Searl, 2011; Povoas et al., 2012), and some of these studies have addressed futsal matches (Barbero-Alvarez et al., 2008; Castagna et al., 2009; Dogramaci et al., 2011; Makaje et al., 2012). The velocity ranges from Castagna et al. (2009) were adopted in this study because they represent a classification based on futsal players’ incremental tests with physiological measures of metabolic transitions, according to the authors. This procedure has been endorsed by studies on soccer players, but individual analyses should be tested in futsal in the future.
Spanish
Spanish Australian Thai Brazilian
Barbero Alvarez et al. (2008)
Castagna et al. (2009) Dogramaci et al. (2011) Makaje et al. (2012) Present study
b
a
Values presented as M ^ SD. Distance presented as metres. c Distance presented as m/min. d Values presented as mean (confidence intervals). e Values presented as median (IQR).
Nationality
Source
8 18 30 93
10
n
Simulated Simulated Simulated Official
Official
Match characteristic a,b
2,496.1 ^ 1,024.9 118.4 ^ 13.0a,c – – – 1,710.6 (888.3)b,e 97.9 (16.2)c,e
First half
Total 4,313.2 ^ 2,138.6a,b 117.3 ^ 11.6a,c 121.0 (105.0– 137.0)c,d 4,277.0 ^ 1,030.0a,b 5,087.0 ^ 1,104.0a,b 3,133.2 (2,248.5)b,e
2,595.7 ^ 932.0 110.5 ^ 9.0a,c – – – 1,635.9 (1,089.2)b,e 90.3 (12.0)c,e a,b
Second half
Distance covered
Table III. Distance covered by futsal athletes from different nationalities.
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When the entire game is considered, the players presented a tendency towards greater percentages of distance covered at low velocities, which is similar to findings of previous studies (Castagna et al., 2009; Dogramaci et al., 2011; Makaje et al., 2012). Furthermore, there was a significant increase in the percentage of distance covered in the walking velocity range and a significant decrease in the percentage of the distance covered in the highintensity running range from the first half to second half, as reported in the literature for Spanish matches (Barbero-Alvarez et al., 2008). However, a comparison of the percentage values presented in our study with the results of the study by Barbero-Alvarez and colleagues is impractical due to differences in the velocity range classifications. The percentage of the distance covered in different velocity ranges during in-play and outof-play periods were also computed in this study. This criterion was chosen because futsal matches have many game interruptions. Thus, we questioned whether analysing these variables only for the entire game would underestimate the intensity required when the ball is in play. Indeed, this underestimation is clearly noticed when analysing Table I, which visually demonstrates a greater distance covered per minute in working game clock periods compared with whole game. Similarly, Table II shows a greater percentage of distance covered in the high-intensity running and sprinting velocity ranges for the in-play condition compared with the values found when the entire game is considered. In addition, a significant increase in the high-intensity running percentage was found during the out-ofplay periods from the first half to second half, which may be attributed to players’ choices in the second half to perform a greater number of set attacking piece plays from corner kicks, kick-ins, or free kicks with high-velocity running immediately before the moment that the ball is in play. This result is also notable because it shows that even when the ball is not in play, futsal matches can require substantial physical efforts from players. Conclusion The purpose of this study was to characterise the distance covered by Brazilian professional futsal players and its intensity in different velocity ranges, using an automatic tracking method. The results showed that the distances covered per minute during the in-play and whole game conditions decrease from the first half to the second half. In addition, the percentage of the distance covered in the standing and walking range of velocity increased from the first half to the second half, when the whole game and in-play conditions were considered. Because futsal rules allow unlimited substitutions, coaches may consider a greater number of substitutions during the match to prevent decreased physical performance. Acknowledgement The authors gratefully acknowledge the contribution of Mauricio Moura during the manuscript preparation. Funding This research was financially supported by the Fundac a˜o Arauca´ria [grant number 185/2013]. References Alvarez, J. C., D’Ottavio, S., Vera, J. G., & Castagna, C. (2009). Aerobic fitness in futsal players of different competitive level. Journal of Strength and Conditioning Research, 23, 2163 – 2166. doi:10.1519/JSC. 0b013e3181b7f8ad
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Sarro, K. J., Misuta, M. S., Burkett, B., Malone, L. A., & Barros, R. M. (2010). Tracking of wheelchair rugby players in the 2008 Demolition Derby final. Journal of Sports Sciences, 1–8. doi:10.1080/02640410903428541 Soares-Caldeira, L. F., Alves de Souza, E., Hugo de Freitas, V., Franzoi de Moraes, S. M., Leicht, A. S., & Nakamura, F. Y. (2014). Effects of additional repeated sprint training during pre-season on performance, heart rate variability and stress symptoms in futsal players: A randomized controlled trial. Journal of Strength and Conditioning Research. doi:10.1519/JSC.0000000000000461
Sports Biomechanics Publication details, including instructions for authors and subscription information: http://www.tandfonline.com/loi/rspb20
Analysis of the distance covered by Brazilian professional futsal players during official matches a
a
Murilo José De Oliveira Bueno , Fabio Giuliano Caetano , Tiago a
a
Julio Costa Pereira , Nicolau Melo De Souza , Gustavo Damasceno a
b
c
Moreira , FáBIO Yuzo Nakamura , Sergio Augusto Cunha & Felipe a
Arruda Moura a
Laboratory of Applied Biomechanics, State University of Londrina, Londrina, Brazil b
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Physical Education Department, State University of Londrina, Londrina, Brazil c
Laboratory of Instrumentation for Biomechanics, University of Campinas, Campinas, Brazil Published online: 16 Sep 2014.
To cite this article: Murilo José De Oliveira Bueno, Fabio Giuliano Caetano, Tiago Julio Costa Pereira, Nicolau Melo De Souza, Gustavo Damasceno Moreira, FáBIO Yuzo Nakamura, Sergio Augusto Cunha & Felipe Arruda Moura (2014) Analysis of the distance covered by Brazilian professional futsal players during official matches, Sports Biomechanics, 13:3, 230-240, DOI: 10.1080/14763141.2014.958872 To link to this article: http://dx.doi.org/10.1080/14763141.2014.958872
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Sports Biomechanics, 2014 Vol. 13, No. 3, 230–240, http://dx.doi.org/10.1080/14763141.2014.958872
Analysis of the distance covered by Brazilian professional futsal players during official matches
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´ DE OLIVEIRA BUENO1, FABIO GIULIANO CAETANO1, MURILO JOSE TIAGO JULIO COSTA PEREIRA1, NICOLAU MELO DE SOUZA1, ´ BIO YUZO NAKAMURA2, GUSTAVO DAMASCENO MOREIRA1, FA SERGIO AUGUSTO CUNHA3, & FELIPE ARRUDA MOURA1 1
Laboratory of Applied Biomechanics, State University of Londrina, Londrina, Brazil, 2Physical Education Department, State University of Londrina, Londrina, Brazil, and 3Laboratory of Instrumentation for Biomechanics, University of Campinas, Campinas, Brazil (Received 7 November 2013; accepted 21 August 2014)
Abstract The purpose of this study was to measure and characterise the distances covered by Brazilian professional futsal players. The trajectories of 93 players during five matches were obtained using an automatic tracking method. The distances covered were analysed for different game conditions: over the entire game and during the times when the ball was out of play and in play separately. When the entire game was considered, the results showed that there was a reduction in the total distance covered per minute from the first [median ^ IQR (interquartile range): 97.9 ^ 16.2 m/min] to the second half (median ¼ 90.3 m/min; IQR ¼ 12.0), and when only the in-play time was considered (first half: 136.6 ^ 17.2 m/min; second half: 129.2 ^ 16.7 m/min). The percentage of distance covered in the standing and walking velocity range was higher in the second half than in the first when considering the entire game (30.8% and 28.0%, respectively) and during the in-play time (19.3% and 16.2%, respectively). In conclusion, this study verified that futsal players reduced the physical performance during the second half.
Keywords: Kinematics, automatic tracking, activity profile, in-play time, out-of-play time
Introduction The implementation of recent technological advancements has enabled the use of automatic tracking procedures using videogrammetry (Figueroa, Leite, & Barros, 2006a, 2006b; Liu et al., 2009) to obtain information regarding the positions of players in team sports on a pitch as a function of time. These procedures have been used in official competitions for several sports (primarily for football) for the purpose of quantifying various physical, technical, and tactical variables (Barros et al., 2007; Dellal et al., 2011; Moura et al., 2013; Moura, Martins, Anido, Barros, & Cunha, 2012). Correspondence: F.A. Moura, Laboratory of Applied Biomechanics, Sport Sciences Department, State University of Londrina, Av. Gil de Abreu e Souza, 2335, Unidade 1121, Esperanc a, CEP 86058-100 Londrina, Brazil, E-mail: [email protected] q 2014 Taylor & Francis
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Some of the physical demands related to competition have been evaluated by quantifying the total distances covered by players during a match, the distances covered in specific ranges of velocities, and the time spent in each velocity zone. By quantifying a match in this manner, the physical demands of a given sport may be characterised to help coaches better plan specific training sessions (Barros et al., 2007) and track player fatigue, which is thought to impair performance by transiently reducing the intensity of the match after the most intense periods and/or during the second half (Mohr, Krustrup, & Bangsbo, 2003). Unlike the substantial number of studies that have quantified the physical demands of several sports (particularly football), there are few studies that have analysed futsal matches. In previous studies, activity profiles during futsal matches were analysed for Spanish National League professionals (Barbero-Alvarez, Soto, Barbero-Alvarez, & Granda-Vera, 2008; Castagna, D’Ottavio, Granda Vera, & Barbero Alvarez, 2009), Thai players (Makaje, Ruangthai, Arkarapanthu, & Yoopat, 2012) and Australian players (Dogramaci, Watsford, & Murphy, 2011). In spite of the international success of elite-standard Brazilian futsal players, their kinematic characteristics during participation in the National League have not been investigated. These data would be extremely valuable because 9 of the 14 players who were the champions of the last FIFA Futsal World Cup played in the Brazilian League during 2012. Of the previous studies, only Barbero-Alvarez et al. (2008) analysed official matches. It is well accepted that competitiveness can influence motion characteristics (Dogramaci et al., 2011) and possibly induce bias in the interpretation of the physical demands of nonofficial or friendly matches. Furthermore, there is also an important methodological consideration in the aforementioned futsal studies that should be highlighted. According to the rules of futsal, the clock is stopped when the ball is out of play. Although studies in other sports (e.g. Fernandez-Fernandez, Sanz-Rivas, Fernandez-Garcia, & Mendez-Villanueva, 2008; Sarro, Misuta, Burkett, Malone, & Barros, 2010) have analysed players’ physical activity profiles during periods when the ball was out of play and in play, this procedure is often ignored in futsal. This consideration is relevant because an analysis of the entire game that ignores match interruptions may underestimate the real physical demands during the inplay phase. Characterising players’ kinematics as a function of the match situation (i.e. in play and out of play) during official matches can help coaches better estimate the physical profile of futsal competitions and to formulate training drills to help players address the real physical challenges of the sport. Therefore, the purpose of this study was to measure and characterise the distances covered by Brazilian professional players during official matches. In addition, we aimed to compare the work rates between the first and second halves to detect possible decreases in performance, as has been previously found for other leagues (e.g. BarberoAlvarez et al., 2008). We hypothesised that there would be a decrease from the first to the second half in the distance covered by the players and in the percentage of distance that was covered in high velocity ranges.
Methods Participants and procedures The experimental design consisted of a cross-sectional study of an elite male professional futsal competition. The study was approved by the Ethics Committee at the State University of Londrina. Five official matches in the 2012 Brazilian First Division League were filmed using two digital cameras (30 Hz) that were fixed at elevated positions in the gymnasium. Each
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camera covered roughly three quarters of the court with an overlapping region (Figure 1A). The images were transferred to computers and were synchronised by identifying common events in this overlapped region, such as a kick by a player. Then, the players’ positions as a function of time were obtained by means of an automatic tracking system. The trajectories of 93 players (four of these players were champions of the last FIFA Futsal World Cup; mean age ¼ 26 ^ 4 years, height ¼ 1.75 ^ 0.06 m, and mass ¼ 73.0 ^ 7.8 kg) were obtained using the DVideo software automatic tracking system (Figueroa et al., 2006b). The average error for the determination of player position was 0.098 m, and the average error for the distance covered was 0.8%. The two automatic procedures of segmentation (Figure 1B) and tracking (Figure 1C) generated players’ positions as a function of time over the entire match. Before the matches, we obtained the coordinates of 16 control points on the court, which were defined relative to the coordinate system associated with the court. The corresponding projections of these points in the image were determined using the DVideo software.
Figure 1. Camera images with overlapping regions (A) and the results of the segmentation process (B) and tracking (C).
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The homography parameters of the image–object transformation were then calculated based on the direct linear transformation method, and the players’ two-dimensional coordinates were obtained relative to the pitch’s coordinate system. Finally, players’ trajectories were filtered with a Butterworth third-order low-pass digital filter with a cut-off frequency of 0.4 Hz.
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Kinematic data analysis The distance covered by each player was calculated as the cumulative sum of the displacement between two consecutive frames. The total distance covered by each player was normalised against the length of time the player participated in the match. In addition, the percentage of the distance covered was computed in the following velocity ranges (Castagna et al., 2009): V1 # 6.0 km/h (standing and walking); 6.1 , V2 # 12.0 km/h (low-intensity running); 12.1 , V3 # 15.4 km/h (medium-intensity running); 15.5 , V4 # 18.3 km/h (high-intensity running); and V5 . 18.4 km/h (sprinting). To more accurately characterise the activity profile during the futsal match, the variables were analysed over the entire game time and during periods when the ball was out of play and in play. Statistical analysis The distances covered by the players and the percentages of the distance covered in each velocity range were expressed as the medians and interquartile ranges (IQRs). Before each analysis, Kolmogorov– Smirnov test verified whether the data were normally distributed. A significance level of p , 0.05 was used for all statistical analyses. Because a normal distribution was not found in all situations, a non-parametric test for the following analyses was adopted; a Wilcoxon rank-sum test compared the values for distance covered obtained for the first and second halves, and the percentages of the distance covered in each range of velocity for both halves. All statistical procedures were performed using MATLABw software (6.0, MathWorks, Inc., Natick, MA, USA). Results Figure 2 shows an example of the accumulated distance covered by the outfield players during the first half of a match during in-play and out-of-play conditions. A considerable portion of the distance covered by the players was performed when the ball was out of play. The median (IQR) value of the total distance covered by the player was 3,133.2 (2,248.5) m for the entire game and 2,133.9 (1,424.4) and 1,028.5 (807.8) m for the in-play and out-of-play phases, respectively. The distance covered during the entire game in the first half (median ¼ 1,710.6; IQR ¼ 888.3 m) was not significantly different (p ¼ 0.43) from that in the second half (median ¼ 1,635.9; IQR ¼ 1,089.2 m). Furthermore, there was considerable inter-individual variability in the total and partitioned distances (Figure 2), and it appeared to be a result of different playing times due to unlimited substitution in futsal. Table I presents the values of distances covered (m/min) by the players during the entire game and during the in-play (M ^ SD: 47.9 ^ 3.2% of the total match duration) and out-ofplay periods. The statistical analysis showed a decrease in the distance covered per minute in the second half compared with the first half when considering the entire game and the in-play period only. Figure 3 shows examples of the individual histograms of velocity in the different playing conditions that were found for four players. There was a tendency towards a greater distribution among the higher velocity values during the in-play periods, whereas the velocity distribution was concentrated at lower values during the out-of-play periods.
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Figure 2. Accumulated distance covered by professional futsal players during the first half of a match differentiated by in-play and out-of-play periods.
Table II confirms the typical pattern in Figure 3 by presenting the percentage of the total distance covered by players in the different velocity ranges. From the first half to the second half, significant increases in the percentages of distance covered by players in the standing and walking velocity range were observed for the entire game and for the in-play condition, and significant decreases in the percentages of distance covered in medium- and high-intensity running for the same conditions. For out-of-play periods, however, a significant increase in the high-intensity running velocity range from the first half to the second half was observed.
Discussion and implications The purpose of this study was to perform a kinematic analysis during official futsal matches of the Brazilian League to quantify the distance covered by the players and the percentage of Table I. Total distance covered (m/min). Condition In play Out of play Whole game
First half
Second half
p
136.6 (17.2) 58.8 (10.4) 97.9 (16.2)
129.2 (16.7)* 56.8 (14.8) 90.3 (12.0)*
0.01 0.21 ,0.01
Note: Values in median (IQR). *Significantly different from the first-half value (p , 0.05).
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Figure 3. Velocity histogram examples for professional futsal players during the first half of a match distinguished by the in-play and out-of-play periods.
this distance covered in different velocity ranges. The variables were distinguished by “whole game”, “in-play”, and “out-of-play” conditions; then, the first halves were compared with the second halves. The players investigated in this study covered less distance per minute considering the entire game for both halves than the players investigated in a study by Castagna et al. (2009), who covered 121 m/min. Castagna et al. (2009), however, analysed simulated futsal matches with four sets of 10 min each, interspersed with 5-min recovery periods. In this protocol (i.e. Table II. Percentage of the distance covered in velocity ranges (%). Condition
Velocity ranges
In play
Standing and walking Low-intensity running Medium-intensity running High-intensity running Sprinting Standing and walking Low-intensity running Medium-intensity running High-intensity running Sprinting Standing and walking Low-intensity running Medium-intensity running High-intensity running Sprinting
Out of play
Whole game
Note: Values presented in median (IQR). *Significantly different from the first half value (p , 0.05).
First half
Second half
p
16.2 (5.7) 41.9 (5.3) 20.1 (4.2) 10.3 (3.5) 10.1 (6.1) 52.4 (11.9) 33.1 (8.0) 8.1 (5.9) 2.1 (2.4) 1.5 (2.8) 28.0 (6.1) 39.0 (5.0) 16.4 (3.4) 8.0 (2.4) 7.6 (4.3)
19.3 (8.3)* 42.1 (5.4) 17.8 (5.1)* 9.6 (3.4)* 9.9 (5.0) 55.4 (15.2) 32.9 (11.1) 8.7 (5.5) 3.1 (3.2)* 1.7 (3.0) 30.8 (6.7)* 38.7 (4.0) 15.4 (3.4)* 7.5 (2.0)* 7.2 (2.7)
,0.01 0.69 ,0.01 ,0.01 0.49 0.72 0.44 0.55 ,0.01 0.29 ,0.01 0.92 ,0.01 ,0.01 0.32
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not in accordance with official futsal rules), athletes may maintain a higher level of activity because of the shorter work periods, which allows them to cover greater distances. Our results for distance covered were also less than those of Barbero-Alvarez et al. (2008), who obtained mean values of 118.4 m/min (first half) and 110.5 m/min (second half) in Spanish players. Surprisingly, teams from less successful countries such as Australia and Thailand also appeared to outperform the Brazilian teams (Table III). With respect to football, different values for distance covered by players from several leagues and levels were found in the literature (Carling, Bloomfield, Nelsen, & Reilly, 2008) and were partly dependent on players’ fitness levels (Mohr et al., 2003). Thus, it is feasible that in futsal, different leagues present specific physical requirements. Recently, it has been reported that National League-level futsal players in Brazil covered approximately 1,500 m in the Yo-Yo Intermittent Recovery Test, level 1 (Oliveira, Leicht, Bishop, Barbero-Alvarez, & Nakamura, 2013; Soares-Caldeira et al., 2014). Players from the ´ lvarez highest national level in Spain were able to cover 2,600 m in the same test (Barbero-A ´ lvarez, 2003). Nevertheless, the maximal oxygen consumption in Brazilian & Barbero-A futsal players (, 60 ml/kg/min) (Milanez et al., 2011; Pedro, Milanez, Boullosa, & Nakamura, 2013) was not substantially different from the values obtained from their highlevel European counterparts (Alvarez, D’Ottavio, Vera, & Castagna, 2009). Therefore, it appears that the Brazilian players are less fit in specific on-field intermittent tests compared with European players, which may partially explain the lower work rate found during the matches. We also verified a significant decrease in the distance covered per minute by the players from the first half to the second half, which corroborates the findings of Barbero-Alvarez et al. (2008). This result confirms our initial hypothesis that there is a decrease in the players’ physical performance. Although futsal rules permit unlimited substitutions, this reduced performance may be attributed to changes in physiological conditions (such as reduction in glycogen stores, thermal stress, and dehydration) during the game (Barbero-Alvarez et al., 2008). However, this output may be related to an increased stability of the players’ collective and individual behaviours over the match, as reported previously for football (Duarte et al., 2013). The previous literature reports reduced distances covered from the first half to the second half for Brazilian football players (Barros et al., 2007); however, this response had not yet been reported in the literature for Brazilian futsal players. We also separately analysed the variables for the in-play and out-of-play periods to characterise the activity profiles of futsal players during different match conditions. A considerable distance was covered during the out-of-play periods (Figure 2 and Table I). During these periods (which consisted of more than 50% of the total match duration), athletes perform activities that should be considered by coaches in planning and prescribing physical training for the sport. Although the distance covered per minute provides relevant information about the physical demands of futsal matches, it is also important to report intensity profiles, which identify at which velocities the players covered these distances. Previous studies had analysed the intensity of team sports by classifying the distance covered in different velocity ranges (Barros et al., 2007; Hartwig, Naughton, & Searl, 2011; Povoas et al., 2012), and some of these studies have addressed futsal matches (Barbero-Alvarez et al., 2008; Castagna et al., 2009; Dogramaci et al., 2011; Makaje et al., 2012). The velocity ranges from Castagna et al. (2009) were adopted in this study because they represent a classification based on futsal players’ incremental tests with physiological measures of metabolic transitions, according to the authors. This procedure has been endorsed by studies on soccer players, but individual analyses should be tested in futsal in the future.
Spanish
Spanish Australian Thai Brazilian
Barbero Alvarez et al. (2008)
Castagna et al. (2009) Dogramaci et al. (2011) Makaje et al. (2012) Present study
b
a
Values presented as M ^ SD. Distance presented as metres. c Distance presented as m/min. d Values presented as mean (confidence intervals). e Values presented as median (IQR).
Nationality
Source
8 18 30 93
10
n
Simulated Simulated Simulated Official
Official
Match characteristic a,b
2,496.1 ^ 1,024.9 118.4 ^ 13.0a,c – – – 1,710.6 (888.3)b,e 97.9 (16.2)c,e
First half
Total 4,313.2 ^ 2,138.6a,b 117.3 ^ 11.6a,c 121.0 (105.0– 137.0)c,d 4,277.0 ^ 1,030.0a,b 5,087.0 ^ 1,104.0a,b 3,133.2 (2,248.5)b,e
2,595.7 ^ 932.0 110.5 ^ 9.0a,c – – – 1,635.9 (1,089.2)b,e 90.3 (12.0)c,e a,b
Second half
Distance covered
Table III. Distance covered by futsal athletes from different nationalities.
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When the entire game is considered, the players presented a tendency towards greater percentages of distance covered at low velocities, which is similar to findings of previous studies (Castagna et al., 2009; Dogramaci et al., 2011; Makaje et al., 2012). Furthermore, there was a significant increase in the percentage of distance covered in the walking velocity range and a significant decrease in the percentage of the distance covered in the highintensity running range from the first half to second half, as reported in the literature for Spanish matches (Barbero-Alvarez et al., 2008). However, a comparison of the percentage values presented in our study with the results of the study by Barbero-Alvarez and colleagues is impractical due to differences in the velocity range classifications. The percentage of the distance covered in different velocity ranges during in-play and outof-play periods were also computed in this study. This criterion was chosen because futsal matches have many game interruptions. Thus, we questioned whether analysing these variables only for the entire game would underestimate the intensity required when the ball is in play. Indeed, this underestimation is clearly noticed when analysing Table I, which visually demonstrates a greater distance covered per minute in working game clock periods compared with whole game. Similarly, Table II shows a greater percentage of distance covered in the high-intensity running and sprinting velocity ranges for the in-play condition compared with the values found when the entire game is considered. In addition, a significant increase in the high-intensity running percentage was found during the out-ofplay periods from the first half to second half, which may be attributed to players’ choices in the second half to perform a greater number of set attacking piece plays from corner kicks, kick-ins, or free kicks with high-velocity running immediately before the moment that the ball is in play. This result is also notable because it shows that even when the ball is not in play, futsal matches can require substantial physical efforts from players. Conclusion The purpose of this study was to characterise the distance covered by Brazilian professional futsal players and its intensity in different velocity ranges, using an automatic tracking method. The results showed that the distances covered per minute during the in-play and whole game conditions decrease from the first half to the second half. In addition, the percentage of the distance covered in the standing and walking range of velocity increased from the first half to the second half, when the whole game and in-play conditions were considered. Because futsal rules allow unlimited substitutions, coaches may consider a greater number of substitutions during the match to prevent decreased physical performance. Acknowledgement The authors gratefully acknowledge the contribution of Mauricio Moura during the manuscript preparation. Funding This research was financially supported by the Fundac a˜o Arauca´ria [grant number 185/2013]. References Alvarez, J. C., D’Ottavio, S., Vera, J. G., & Castagna, C. (2009). Aerobic fitness in futsal players of different competitive level. Journal of Strength and Conditioning Research, 23, 2163 – 2166. doi:10.1519/JSC. 0b013e3181b7f8ad
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