Indirect calculation of metabolic power in soccer: a critical analysis of a popular model

INTRODUCTION: The Global Positioning System (GPS)-based metabolic power model for soccer, proposed by di Prampero and applied by Osgnach, rests on a fixed energy cost (EC) of running of 4.6 J·kg-1·m-1 and a biomechanical equivalence between accelerated level and constant-speed uphill running. SOURCES OF DATA: A narrative review was conducted via PubMed, Scopus, and Web of Science using terms like metabolic power, EC of running, GPS soccer, sprint biomechanics, equivalent slope, and running economy (2005-2025). AREAS OF AGREEMENT: Running EC is relatively speed-independent across submaximal velocities typical of football (~6-18 km·h-1). The geometric principle underlying the accelerated-to-inclined running equivalence is accepted, and GPS metabolic power provides a useful metric for relative load comparisons. AREAS OF CONTROVERSY: A universal fixed EC ignores interindividual variability (~20%), fatigue, surfaces, and drag. The equivalence model has vector orientation inconsistencies, employs the imprecise term 'equivalent mass', and derives its postural reference from sprint-start conditions unrepresentative of match-play accelerations (~2-4 m·s-2). Validation studies show systematic underestimations of 29%-85% relative to indirect calorimetry. Refinements exist but remain unimplemented in most commercial platforms. GROWING POINTS: Individually calibrated EC values, inertial measurement unit integration, and hybrid models combining GPS kinematics with cardiorespiratory data are promising. Force-velocity profiling offers a biomechanically grounded alternative for individual sprint characterization. AREAS TIMELY FOR DEVELOPING RESEARCH: Priorities include calorimetric validation under match conditions; player-specific EC models incorporating fatigue, surface, and role; implementing model updates in commercial software; and comparing alternative load metrics for injury-risk prediction.