Which energy system predominates once the anaerobic threshold is exceeded?

• A. Aerobic system
• B. Anaerobic system
• C. Immediate energy system
• D. Circulatory energy system

Answer: (B)

Pushing past the anaerobic threshold means your muscles aren’t getting enough oxygen to meet the energy demand with aerobic metabolism alone, so the body relies more on anaerobic glycolysis to rapidly generate ATP. This anaerobic energy system uses glucose without the need for oxygen, producing ATP quickly but also lactate as a byproduct, which is why lactate levels rise at higher intensities. The immediate energy system (ATP-PC) powers very short bursts and isn’t the main contributor at these intensities, while the aerobic system is still active but can’t supply all the needed energy by itself. The circulatory energy system isn’t a standard energy pathway for this purpose. So the predominant energy source beyond the anaerobic threshold is the anaerobic energy system.