During the 400m world-record performance, which energy system provides the majority of energy?

During the 400m world-record performance, which energy system provides the majority of energy?

• A. Aerobic respiration
• B. Anaerobic glycolysis
• C. ATP-PC system
• D. Protein oxidation

Answer: (B)

The main concept here is how the body fuels a very high‑intensity effort lasting around 40–45 seconds. At such speeds, the demand for ATP is huge and the immediate ATP‑PC system can only supply energy for a short burst, roughly the first 8–12 seconds. After that, to keep the pace, the body relies on anaerobic glycolysis to produce ATP rapidly, even though this process generates lactate and hydrogen ions as byproducts. The aerobic system does contribute, but the rate at which it can produce ATP at maximal sprint intensity is slower than what the muscles need in this moment, so it cannot provide the majority of energy for the entire race. Protein oxidation is not a practical energy source in this context. So, the majority of energy for a 400m world‑record effort comes from anaerobic glycolysis, with smaller contributions from the ATP‑PC system and some input from the aerobic system.

The main concept here is how the body fuels a very high‑intensity effort lasting around 40–45 seconds. At such speeds, the demand for ATP is huge and the immediate ATP‑PC system can only supply energy for a short burst, roughly the first 8–12 seconds. After that, to keep the pace, the body relies on anaerobic glycolysis to produce ATP rapidly, even though this process generates lactate and hydrogen ions as byproducts. The aerobic system does contribute, but the rate at which it can produce ATP at maximal sprint intensity is slower than what the muscles need in this moment, so it cannot provide the majority of energy for the entire race. Protein oxidation is not a practical energy source in this context.

So, the majority of energy for a 400m world‑record effort comes from anaerobic glycolysis, with smaller contributions from the ATP‑PC system and some input from the aerobic system.