Influencia de la superficie de juego en el rendimiento de los jugadores de fútbol y rugby / influence of sports surface on soccer and rugby players’ performance

Abstract

ABSTRACT Collective sports like soccer and rugby have traditionally been played on natural grass which moreover is considered the most quality surface for playing sports. However, this sort of pavement is associated to high maintenance costs and limited hours of use. Thus, both amateur and base sports usually have to look for other surfaces. In the case of soccer, up to XXI Century most facility enabled for non-professional level opted for dirt pitches. At present, the newest artificial turf systems of third generation have achieved the mechanical properties of natural grass surfaces, becoming a real alternative either to natural grass pavement or dirt field. Since the acceptance of artificial turf for sports practice by the Fédération Internationale de Football Association (FIFA) and the World Rugby (WR), artificial turf fields have expanded exponentially for practising either football or rugby. The main advantage of artificial turf systems is a high economic return compared to natural surfaces, and a higher quality of play than dirt pavements. Despite the qualitative improvement of these synthetic systems and their increasing use, many athletes remain reluctant to them; arguing that they have a higher rate of injury, greater fatigue and affects the development of the game. Therefore, artificial turf systems not only have to keep improving their performance, but they have the challenge to prove that they have achieved the same performance than natural grass surfaces, demonstrating that they do not limit the players’ performance or increase the risk of suffering an injury. On the other hand, beach sports are growing even in non-coastal areas. For that reason, several authors have started to study how sand surfaces affect the physical and physiological responses of players. Contrary to the remaining surfaces, sand has a very high impact reduction causing athletes to modify their running technique. Moreover, these impact reduction capacity together with a greater capability to dissipate the energy makes the speed of sprints much lower than in the rest of pavements. This difference in the movement kinetics results in greater metabolic demands and higher physiological responses of players (higher lactate levels in blood and greater peak heart rate). For that reason, more and more authors propose the use of this surface either for rehabilitation of athletes or for improving their fitness. In the current Doctoral Thesis, there are enclosed six different studies that assess the influence of sports surface on physical and physiological responses of athletes when performing their sports modality. The objectives of these studies are: 1) to evaluate the influence of game surface and pitch size on the movement profile in sub-elite female soccer players during small sided games of four aside; 2) to evaluate the influence of game surface and pitch size on the physiological responses, fatigue and perception in sub-elite female soccer players during small sided games of four aside; 3) to analyse the metabolic power demands of various small sided games on possession play without goal-keepers, played on three different surfaces; 4) to analyse the influence of the game surface on amateur soccer player’s physical and physiological responses using a soccer simulation protocol; 5) to assess the influence of the game surface on physiological patterns and neuromuscular responses of soccer players during a soccer simulation protocol that incorporates repeated sprints and nonlinear actions at maximum speed; 6) to discover the influence of sand and natural grass on muscle parameters in female rugby players after an induced fatigue test. The sample of studies 1, 2 and 3 was composed of sixteen female soccer players from the Spanish Second Division (19.56 ± 1.97 years old). Players were gathered into four teams of players each based on coaches’ criteria. Each team played three different small-sided games of different pitch size (400 m2; 600 m2; 800 m2) on the three selected surfaces (natural grass, artificial turf and dirt). The small-sided games were played without goalkeeper and both team and matches were always the same. Each small sided game last 4 minutes and was played twice on each surface. In study 1, time motion of players (speed, total distance, accelerations, etc.) on each SSGs was recorded through a global positioning system (GPS) designed for sports practising (Spi Pro X, GPSports, Canberra, Australia). Moreover, sprint actions (actions over 18 km/h) were analysed in detail (maximum acceleration, maximum speed, total distance, duration). In study 2 a heart rate monitor was used for assessing the physiological responses of players (Polar Team System, Kempele, Finland). Outcomes of heart rate were obtained either in beats per minute (b.p.m) or based on the maximum heart rate of each player (%HRmax). Before and after each small-sided games, participants performed two counter-movement jump. Also, players assessed the quality of each surface through a perception questionnaire using a visual analogue scale (VAS). Finally, in study 3, the GPS devices were used for estimating the metabolic load (absolute [KJ] and relative [KJ/kg]) of each small-sided games. Likewise, it was estimated the rate of energy consumed per second (W/kg), the total distance covered at 20 W/kg or more (m) and the maximum distance that players could have run with the total energy consumed if they ran at a constant speed. The sample of the studies 4 and 5 was composed of sixteen amateur players (22.17 ± 3.43 years old) In this case players performed the first three bouts of a soccer simulation protocol on two different surfaces (natural grass and artificial turf) whose mechanical properties were assessed (impact reduction, vertical deformation and energy return). The soccer simulation protocol was designed for replicating the physical and physiological demands of soccer matches. In study 4, the physical patterns of soccer players on each surface (sprint time. Non-linear sprint time, speed) were recorded through a photocell system (Microgate, Bolzano, Italy) and GPS devices (HPU, GPSports, Australia). The physiological responses were monitored by means of heart rate monitors (Polar Team System, Kempele, Finland). In study 5, it was assessed the physiological load of the soccer simulation protocol through monitoring the heart rate. The performance of players in a counter-movement jump was recorded before and after the soccer simulation protocol, as well as the response of the rectus femoris and biceps femoris to an electrical stimulus. This last test was performed by means a tensiomyography equipment (BMC Ltd., Ljubljana, Slovenia). Finally, study 6 is focused on rugby. In this case, fifteen female amateur players (23.4 ± 4.42 years old) performed a repeated sprint test on a natural grass pavement and a sand surface. The physical performance of the test was collected through the photocell system and GPS devices used in the study 4; while the muscular responses of biceps femoris and rectus femoris to an electrical stimulus either before or after the repeated sprint test were recorded through the tensiomyography test. Lastly, the explosive capacity of participants’ lower body was assessed through a counter-movement jump. The main conclusions of these studies are 1) the physical response of female soccer players is higher on artificial turf than ground. In the most intense small sided games, natural grass provides greater external load than artificial turf. Moreover, when the dimensions of the space are too large, the external load stagnates or even decreases. 2) Female soccer players consider that artificial turf does not reduce the quality of the game compared to natural grass, rejecting the use of dirt for playing soccer. The natural surfaces produce a greater internal load in the players than artificial turf during soccer practice. In contrast, pitch size can be used for controlling the intensity of the small-sided games as bigger pitches entails higher physiological responses. However, if the pitch size increases too much the physiological responses decrease. 3) Playing on dirt reduces the metabolic power of small-sided games; being natural grass the most suitable surface for obtaining the higher metabolic response. Likewise, if pitch sizes increase too much the metabolic demands of the small-sided games do not improve. 4) The mechanical variability between natural grass and artificial turf is not high enough to affect the physical and physiological performance of amateur football players to the same stimulus. However, these differences do slightly affect the performance in turns and changes in direction. 5) The mechanical response of artificial grass differs from that of natural grass. However, the physiological and muscular response of amateur soccer players to the same stimulus are not affected by such mechanical variability. 6) The sand surface produces greater fatigue in the rectus femoris of the rugby players than the natural grass after a repeated sprint test.