During a 100 m sprint which of the following is used by the muscle for meeting energy demands?
**Core Concept**
The primary energy system used by muscles during high-intensity, short-duration activities like a 100 m sprint is based on the **phosphagen system** and **anaerobic glycolysis**. This system provides immediate energy for muscle contractions.
**Why the Correct Answer is Right**
During a 100 m sprint, the muscle relies heavily on stored **ATP** and **phosphocreatine** for energy, as these can be rapidly mobilized. As the sprint progresses, **anaerobic glycolysis** becomes more significant, breaking down **glycogen** to produce **lactate** and a small amount of **ATP**.
**Why Each Wrong Option is Incorrect**
**Option A:** Incorrect because while **aerobic metabolism** does contribute to energy production in longer events, it's less significant in a very short sprint.
**Option B:** Not the best answer because **fatty acid oxidation** is more relevant to longer-duration, lower-intensity activities.
**Option D:** Incorrect as **protein metabolism** is not the primary source of energy during short sprints.
**Clinical Pearl / High-Yield Fact**
Remember, for efforts lasting less than 10 seconds, like a 100 m sprint, the **phosphagen system** is the primary energy source.
**Correct Answer:** D. ATP and phosphocreatine