Application of an integrated metabolic power paradigm in elite soccer

The aims of this thesis were to: 1) to assess whether different frequencies of GPS systems can influence the measure of distance while accounting for different speeds; 2) to determine the differences in energy cost of straight (Cr)- and shuttle-running (Csh) in soccer players vs. marathoner runners by applying di Prampero’s approach; 3) to assess energy cost of straight-running (Cr) in elite professional soccer players in their ecological setting and determine whether changes in Cr can be established; 4) to investigate the average metabolic power (MP) on a soccer-specific test through direct (K4b2, PVO2) and indirect (GPS, PGPS) measurement of O2 consumption by di Prampero’s approach and modifying Minetti’s equation of C; 5) to investigate how different systems of play effect soccer outcomes with special attention to high-intensity; 6) to evaluate the existence of significant correlations between physical and physiological performance data on elite soccer database of matches and training sessions. When reviewing the literature, it became apparent that smaller and smaller margins determine the outcome of a game. As a result, highly scientific processes are being developed to help players, managers and sport scientists gain an understanding and advantage in soccer. Through time-motion analysis it has been observed that players perform a multitude of physical activities, that consist of sprinting, turning, stopping and jumping, and the amount of time spent during these actions. Since the introduction of GPS, there has been a rapid uptake of GPS technology within soccer and numerous studies have examined the validity and accuracy of GPS systems to establish the accuracy of measuring physical data. Although faster GPS systems have been validated for team sports, some doubts continue to exist on the validity and accuracy of these. To address this problem, a pilot study was performed to assess the validity of GPS technology using a laser speed gun by tracking the movement of the ten participants. The GPS system with an increased sample frequency (rate) provided valid means of assessing running speed during rapid acceleration and deceleration that occur during linear runs and runs with tight changes of direction using a 100-Hz laser system. To gain a better understanding about the sport specific demands of soccer, it is important that we establish the determination of energy cost (C) using a valid method. A second pilot study was performed to address this issue and compare C of straight- and shuttle-running in 10 professional soccer players vs. 7 marathoner runners. It was found that straight-running energy cost (Cr) is significantly greater in soccer players, while shuttle running was significantly lower. Therefore, the specificity of the sport plays a major role on the energy cost required for the specific movements required to excel in the given sport. Once the C was established, it appeared that the need to monitor and possibly condition the Cr in soccer players was advisable. Therefore, an up-to-date assessment of Cr in elite professional soccer players in their ecological setting was provided to see whether changes in Cr are different compared to values established previously in literature. A total of seventeen professional players were involved in this study and performed a straight-running energy cost assessment on a UEFA standard grass soccer pitch. From the acquired data, Cr was calculated and compared to previous research. It was found that the Cr of straight-running on a UEFA standard grass soccer pitch is 4.66 J∙kg-1∙m-1 in elite professional soccer players which is different to previous observations. This study provided an up-to-date measure of on-pitch Cr and was employed in the subsequent studies. To truly gain an understanding of the amount of effort during soccer performance it is important to understand and incorporate the concept of di Prampero and Osgnach in relation to energy cost and metabolic power. As a result, a new energetic model for soccer, considering acceleration and deceleration, based on the previous theories of di Prampero et al. (2005) and Minetti et al. (2002). This study looked to establish the average MP of a specific soccer test through direct and indirect measurements of oxygen consumption using di Prampero’s approach while modifying Minetti’s equation of energy cost by testing 13 professional soccer players. The new energy cost equation calculation was derived from findings in the previous study and it was established that metabolic power was slightly underestimated as a result. Once Cr and MP were established, our next study assessed whether specific variables and different formations in soccer can predict performance outcome. What are the differences between the 1st and 2nd half and between formations and what specific variables influence the outcome of results when assessing a team over the course of 19 home games? A decrease in both physical performance (i.e., TDC) and metabolic power (MP) variables are present with almost all formations in the second half. When winning significantly longer distances and distances by speeds more than 16 km·h-1 were covered when compared to losing. Most of the successful teams showed better technical skills variables values than the less successful ones. The selection of the appropriate tactic plays an essential role during every pre-game preparation phase, to ultimately win the game, but little research has been conducted. Therefore, the final study investigated the correlation between the essential parameters analysed during training sessions and during official matches of elite soccer, as well as investigating the ‘functional model’ proposed in training. There were positive correlations between the performance data analysed during the games played in training and locomotor data obtained through video match analysis.