Predation is one of the most pervasive selective pressures affecting predator and prey individual fitness. Minor differences in speed, maximal exertion or endurance during predator-prey encounters may mean success or failure, with potentially fatal consequences. Knowing physical capacities may, for instance, permit a biologist to predict the outcome of an encounter such as that between predator and prey. Yet beyond speed and manoeuvrability, the measurement of such capacities in the wild has remained conspicuously neglected. We retrieved continuous accelerometer data from large herbivore and carnivore species and modelled individual physical abilities of animals in the wild, based on models derived from exercise physiology. We then reconstructed the continuous physiological fatigue state of prey and predators during predation events. This allowed us to relate predator foraging tactics (ambush or cursorial) and prey anti-predator behaviour (e.g. freeze or flight) to different exhaustion levels at successful capture events. We expected prey to reach higher levels of exhaustion than their predators because of thelife-dinner principle, and predators to show different fatigue kinetics depending on foraging tactic. In some prey, escape led to depletion exceeding 90% of anaerobic reserve, precipitating a catastrophic loss of locomotor performance and rendering further escape impossible. Our approach also allows identifying "near-miss" events characterised by high, yet non-maximal, fatigue accumulation, shedding light on ecological situations seldom observablein nature. In translating human exercise science models to free-ranging wildlife, our findings provide original empirical insights into key energetic processes shaping behaviour, predator-prey interactions, and individual variation in fitness.