Baker, McCormick & Robergs 2010, Interaction among skeletal-muscle energy systems

Review of muscle bioenergetics: ATP is resupplied by three interacting systems, the phosphocreatine (ATP-PCr) system for immediate high-power efforts of seconds, anaerobic glycolysis for hard efforts of roughly tens of seconds to a couple of minutes, and oxidative phosphorylation for everything sustained. The systems operate simultaneously and blend continuously by intensity and duration rather than switching on and off; distance running is overwhelmingly oxidative. Strong.