Gold Standard or Fool’s Gold? The Efficacy of Displacement Variables as Indicators of Energy Expenditure in Team Sports

Abstract

Over recent decades, the use of player tracking technology to monitor physical work output has become established practice in many team sports. Early tracking systems were manual in nature, relying on subjective assessments and arbitrary classifications of movement intensity. Poor spatial and temporal resolution meant that only gross displacement measures could be used to infer energy demands. However, the advent and evolution of automated systems, with higher sampling rates and improved accuracy, have enabled data collection to occur on a mass scale, and served as a catalyst for extensive research into the demands of team sport activity, including comparisons between different groups of athletes, and the effects of various interventions on performance. The inherent assumption with this research is that, based on steady-state models where energy cost is independent of speed, total distance and average speed are indicative of the amount and rate of work done, respectively. This assumption could be justified if the activity was performed at a constant speed in a straight line. However, team sport movement involves continual changes in both speed and direction, both of which increase energy cost. Accordingly, new models have emerged that incorporate both speed and acceleration to determine metabolic power. This provides a more complete measure of energy expenditure in intermittent activity, and is potentially more suitable than displacement variables for research into the demands of team sports.

Quantification of in-season training load relative to match load in professional Dutch Eredivisie football players

“…Currently, energy expenditure is underestimated, even when measured with a highly accurate LPM system, and most likely even more when using GPS (Stevens et al 2015). Moreover, although energy expenditure would potentially be a better indicator of total workload than distance covered (Polglaze et al 2016), in the present study estimated energy expenditure provided very similar information as total distance covered during training (Pearson's correlation = 0.99).…”

Metabolic Power in Team Sports - Part 1: An Update

“…In recent years, thanks to the advances in player-tracking technology (e. g., Global Positioning System -GPS) in our knowledge of the energetics of accelerated and decelerated running, it has become possible to: (i) estimate the time course of the instantaneous metabolic power requirement of any given player, and (ii) infer therefrom the time course of actual O 2 consumption. Hence, (iii) overall energy expenditure and metabolic power, as well as the aerobic and anaerobic fractions thereof, can be assessed for any given time window of a soccer drill or match [2,4,5,13,14].…”

Comparing Maximal Mean and Critical Speed and Metabolic Powers in Elite and Sub-elite Soccer

“…Utilising such absolute and generic measures, however, ignores the cost of changing speed, which is a prominent action in soccer and can be the most physiologically demanding locomotor activity [12]. Therefore, true estimations of physiological cost require calculating the sum of all displacements relating to acceleration [3,12,13]. As a result, integrating metabolic power (P met ) data, which accounts for acceleration (and deceleration) and instantaneous speed, may provide a more appropriate and comprehensive assessment of variable-speed and non-linear intermittent sport demands for each athlete [3].…”