MONTORING TRAINING IN ELITE SOCCER: A NEW APPROACH BASED ON GPS DERVIED ESTIMATED METABOLIC POWER DATA
Paolo Gaudino · Archivio Istituzionale della Ricerca (Universita Degli Studi Di Milano) · 2014
Introduction: Several studies have previously analysed soccer training sessions and specific drills However, a new method was recently proposed to estimate energy cost and metabolic power from acceleration data together with the evolution of global positioning system (GPS), providing the opportunity to derive a more detailed and accurate description of the physical demands imposed to the player during training. Purpose: The aims of the present investigation were to: i) compare measurements of high-intensity activity when calculated as high running speed or high predicted metabolic power derived from a combination of running speed and acceleration during field-based soccer training sessions; ii) evaluate the agreement between the two methods during soccer small-sided games (SSGs); iii) evaluate whether any bias between the two approaches is dependent upon playing position; iv) examine the extent to which changing the game format (possession play (SSG-P) vs game with regular goals and goalkeepers (SSG-G)) and the number of players (5vs5, 7vs7 and 10vs10) influenced the physiological and physical demands of SSGs. Methods: Data were collected in training during the in-season period from 26 English Premier League and UEFA Champions League outfield players using global positioning system technology. Total distance covered, distance at different speed categories and maximal speed were calculated. In addition, the number of changes in velocity carried out and the absolute maximal values of acceleration and deceleration achieved were reported. By taking into account these parameters besides speed and distance values, estimated energy expenditure and metabolic power were calculated. Finally, high-intensity activity was estimated using the total distance covered at speeds >14.4 km?h-1 (TS) and the equivalent metabolic power threshold of >20 W?kg-1 (TP). Results: Mean training session TS was 478 � 300 m vs 727 � 338 m for TP (p14.4 km?h-1) as well as maximum velocity, acceleration and deceleration increased as pitch dimensions increased (10v10>7v7>5v5; p25.2 km?h-1) speed distances, absolute velocity and maximum acceleration and deceleration were higher in SSG-G than in SSG-P (p7v7>10v10; p<0.001) in both SSG-G and SSG-P. Finally, predicted energy cost and metabolic power were higher in SSG-P compared to SSG-G and in larger compared to smaller pitch areas (p<0.05). Conclusions: The high-intensity demands of soccer training are underestimated by traditional measurements of running speed alone, especially in central defenders, training sessions associated with less high-intensity activity and ?small? SSGs. Estimations of metabolic power better inform the coach as to the true demands of a training session or a particular drill. A detailed analysis of different drills based on metabolic power is pivotal in contemporary football as it enables an in depth understanding of the workload imposed on each player which consequently has practical implications for the prescription of the adequate type and amount of stimulus required during training.