For a 400-meter sprint, which energy systems contribute to rapid ATP resynthesis?

• A. Aerobic system
• B. ATP-PCr system
• C. Lactic acid system
• D. ATP-PCr system and lactic acid system

Answer: (D)

During a 400 m sprint, the body relies on quick, non-oxidative energy pathways to resynthesize ATP. The phosphagen system provides immediate ATP for the very start of the effort, but its stores are exhausted within roughly 10 seconds. To sustain the race, anaerobic glycolysis (the lactic acid system) kicks in, rapidly producing ATP without oxygen and generating lactate as a byproduct. This pathway can sustain high-intensity work for the duration of the sprint, up to about a minute. The aerobic system does provide some energy, but it operates too slowly to be the main source of rapid ATP resynthesis in this event. Therefore, both the ATP-PCr system and the lactic acid system best explain rapid ATP resynthesis in a 400 m sprint.