Relationship between field tests and match running

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The Journal of Sports Medicine and Physical Fitness 2018 March;58(3):256-62 DOI: 10.23736/S0022-4707.17.06651-8

ORIGINAL ARTICLE EXERCISE PHYSIOLOGY AND BIOMECHANICS

Relationship between field tests and match running performance in high-level young Brazilian soccer players Rodrigo AQUINO 1, 2, 3 *, Luiz H. PALUCCI VIEIRA 2, 3, Lucas de PAULA OLIVEIRA 2, Luiz G. CRUZ GONÇALVES 2, Paulo R. PEREIRA SANTIAGO 2, 3, 4 1Center

for Investigation, Education, Innovation, and Intervention in Sports (CIFI2D), Faculty of Sports, University of Porto, Porto, Portugal; 2Rehabilitation and Functional Performance, Faculty of Medicine at Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil; 3Biomechanics and Motor Control Lab (LaBioCoM), University of São Paulo, Ribeirão Preto, Brazil; 4School of Physical Education and Sports of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Brazil *Corresponding author: Rodrigo Aquino, Faculty of Sports, University of Porto, Dr. Plácido da Costa 91, 4200-450, Porto, Portugal. E-mail: [email protected]

A B S T RAC T BACKGROUND: The main aim of this study was to analyze the relationship between field tests and match running performance using computational tracking technology in high-level young Brazilian soccer players. METHODS: Twenty-five young male Brazilian soccer players participated in this study (U-15, N.=13; U-17, N.=12). In the same week, the players were submitted to field tests and actual matches. The field tests were: Maximum Speed (10-30 m), Zig-Zag, Running-based Anaerobic Sprint Test, and Yo-Yo Intermittent Recovery Test Level 1. Additionally, participants performed actual soccer match-play. Match running performance was collected using a fixed video-camera. Subsequently, computerized tracking video-analysis (30 Hz) was utilized to identify each physical performance indicator. Pearson’s correlation and linear regression were used for statistical analysis. RESULTS: The results showed that the majority of field tests were not related to match running performance. The Zig-Zag Test, Running-based Anaerobic Sprint Test, and Yo-Yo Intermittent Recovery Test level 1 seem to be the most specific tests (r=0.41-0.47), however the explanatory powers of these field tests in relation to match running performance were low (R2=17-22%). CONCLUSIONS: Assessment of match running performance should be included in the evaluation periods of young soccer players, together with the most specific tests reported. (Cite this article as: Aquino R, Palucci Vieira LH, de Paula Oliveira L, Cruz Gonçalves LG, Pereira Santiago PR. Relationship between field tests and match running performance in high-level young Brazilian soccer players. J Sports Med Phys Fitness 2018;58:256-62. DOI: 10.23736/S00224707.17.06651-8) Key words: Soccer - Exercise test - Athletic performance.

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hysical performance in soccer has been evaluated in the scientific literature mainly using two approaches. The first refers to field tests, developed to try to simulate efforts similar to the events that occur during the practice, such as the Yo-Yo Intermittent Recovery Test Levels 1 and 2,1, 2 Repeated Sprint Ability,3, 4 Maximum Speed 10-30 m and Agility tests.5 The second is based on assessments of physical performance during an actual game (i.e., match running performance), such by the distances covered at different intensities.6, 7 In recent

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years, some researchers have focused on verifying possible associations between field tests and match running performance,8-11 in search of the selection of field tests which are more specific to the physical demands of an actual match-play. Several studies reported significant correlations between field or laboratory-based tests and match running performance.8-11 Specifically, in professional and young European soccer players significant correlations were found between distances covered at high

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COPYRIGHT 2018 EDIZIONI MINERVA MEDICA RUNNING PERFORMANCE IN BRAZILIAN SOCCER PLAYERS AQUINO

intensity running during an actual match and the YoYo Intermittent Recovery Test Level 1, peak running speed during an incremental field test, and mean sprint time in the repeated sprint ability test.8, 10 However, the majority of these studies used a Global Positioning System (GPS) with low frequency of acquisition (1 or 5 Hz) 9, 11, 12 or observational analysis,10 in which underestimation of the distances covered at high intensity running is expected.13, 14 Thus, the need for research on this issue using more robust methodological technologies (i.e., computational tracking 15) becomes evident. In the Brazilian scenario, to the best knowledge of the authors, there are no studies that have related field tests and match running performance in soccer players. Dellal et al.16 reported that cultural differences in distinct countries, may require adjustment in physical activities according to the particular style of national leagues. In addition, the implementation of scientific evidence on possible relations between field tests and match running performance in young Brazilian soccer players would be of interest for soccer coaches at the time of selecting the tests, to explain the physical capacity of the players with greater specificity and transferability to actual match physical demands. Therefore, the main aim of this study was to analyze the relationship between field tests and match running performance in high-level young Brazilian soccer players using computational tracking technology. Furthermore, we examine the explanatory power of field tests to match running performance during actual matches. According to the methodological differences of the previous studies 9, 10 in relation to the present study, we hypothesized that the majority of field tests are not related to match running performance and the explanatory powers of the field tests are low. Materials and methods Participants Twenty-five young soccer players (mean±SD; age 15.2±1.0 years, height 174.0±8.5 cm, body mass 64.1±7.3 kg, body fat 11.5±2.1%; 11 defenders, 5 wingers, 5 midfielders, 4 strikers) from U-15 (N.=13) and U-17 (N.=12) categories participated in this study. All players were members of a soccer club playing in the São Paulo First Division League; this division is consid-

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ered the leading state-level championship in Brazil.7, 17 The following were adopted as inclusion criteria; experience of at least two (U-15) and four (U-17) years in systemized training and participation in state championships, not presenting any injury, and not being engaged in any additional training (i.e., resistance training) at the time of investigation. Players trained five times a week (~90 minutes per session) and played a tournament once at the end of each week (Saturday). The training sessions were primarily for the development of technical-tactical ability (four times a week, 80% of total time). Physical conditioning was developed once a week (20% of total time) through strength exercises, such as maximum strength (squat, bench press, deadlift), endurance strength (circuit training), and fast strength (plyometric training). The aerobic conditioning was stimulated by the small sided games. This study conforms to the Code of Ethics of the World Medical Association (approved by the ethics advisory board of Swansea University), was approved by the Research Ethics Committee of the Faculty of Medicine at Ribeirão Preto (protocol 710.998/2014), and was conducted in accordance with the Declaration of Helsinki. All participants and their legal guardians signed an Assent and Consent Term respectively, with the objectives and purposes of the study. Procedures A cross-sectional study was designed to associate field tests and match running performance. The assessment protocol of this study was developed at the beginning of the competitive season (February 2016). All players underwent a battery of field tests at 09:00 a.m.: Maximum Speed 10-30 m and Agility tests (Monday); Repeated Sprint Ability test (Wednesday); Yo-Yo Intermittent Recovery Test Level 1 (Friday). In addition, participants played an actual match (09:00 a.m., Sunday). All the evaluations were performed in the same week. Match running performance, such as total distance covered and percentage of total distance at different intensities, was assessed using a computational tracking video-based system, software DVIDEOW (average error approximately 0.3 m and 1%), for determination of positions on the pitch and distances covered, respectively.15, 18

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Field tests Maximum speed and agility To determine the maximum speed, speed tests of 10 m and 30 m were applied.5 The player was positioned behind the output line. After a sign from the evaluator, the player covered a distance of 30 m at full speed to the finish mark. Time was quantified at both distances. Agility was determined by the Zig-Zag test, during which four 5-m accelerations were performed with changes of direction at an angle of 100°.5 The running time in seconds was measured using three pairs (Maximum Speed Test) and two pairs (Agility Test) of photocells Fspeed (FEsystems®, Sorocaba, São Paulo, Brazil). Two attempts were allowed at intervals of 2-3 minutes, in order to consider the best value as the final result. Repeated Sprint Ability To assess the repeated sprint ability of the players, the Running-based Anaerobic Sprint Test was applied.3, 4 The athlete covered six runs with a distance of 35 m at maximum speed, interspersed with a 10-second interval between runs, starting from the stopped position. The running time in seconds was measured using two pairs of Fspeed photocells (FEsystems®). The variables minimum power, peak power, and average power were considered3 and all the values were relativized by body mass (kg). Specific endurance The Yo-Yo Intermittent Recovery Test Level 1 was applied to evaluate the individual’s ability to repeatedly perform intense exercise with a focus on the capacity to carry out exercise to maximal activation of the aerobic system.1, 2, 19 The test consists of 2×20-m shuttle runs at increasing speeds, interspersed with a five second period of active recovery (controlled by audio signals). The test consists of four running bouts at 10-13 km/h (0-160 m) followed by seven runs at 13.5-14 km/h (160440 m). This continues with stepwise 0.5 km/h speed increments after eight running bouts. The distance covered (m) is the test result.

First Division League 2015 (i.e., away match). According to specific rules of the São Paulo Soccer Federation,22 the U-15 match lasted 60 minutes (30’×30’) and the U-17 match lasted 80 minutes (40’×40’); with 15’ for passive recovery between halves for both categories. The matches were played on an official FIFA standard pitch (natural grass; ~105×68 m [length × width]). The daily average temperature was 25 or 77 °F (climate record of the Brazilian Institute of Meteorological Research – IPMet) and the altitude of the match location is 588 m (record of the Brazilian Institute of Geography and Statistics [IBGE)). The two matches were recorded in full by a single digital video camera (GoPro Hero 3+ Black Edition, Woodman Labs Inc., USA) adjusted to an acquisition frequency of 30 Hz in full HD (1920×1080 pixel; NTSC standard), positioned at the highest point in the stadium. An automatic algorithm specific for tracking purposes was applied to correct the radial distortion before video analysis and ensure accuracy of the measurements.20 In the DVIDEOW environment,15, 18, 21, 22 the computational tracking of all player trajectories was obtained by only one examiner to prevent any inter-rater variability, using the tracking of mouse positions method 15 (Figure 1), considering the players position as a projection on the game plan. After tracking, the 2D reconstructed data 23 was exported to the Matlab environment (The MathWorks Inc., Natick, MA, USA), smoothed by a Butterworth low-pass third order digital filter (cut-off frequency 0.4 Hz).15, 18 Thus, by means of specific routines written for this study, the total distance covered (TD), defined by the cumulative sum of distances covered between frames per minute (m) and, maximal velocity (Vmax), defined as maximal instantaneous velocity attained during the match (km/h) were calculated individually. In addition, the percentage of distances covered at eight velocity bands was calculated, based on minor adaptations of previous studies in youth soccer:6, 7, 11, 23, 24 0.00