**Core Concept**
During high-intensity, short-duration activities, the body rapidly depletes its readily available energy sources, necessitating the breakdown of stored glycogen to meet energy demands. This process is particularly crucial for activities lasting around 1 minute.

**Why the Correct Answer is Right**
The breakdown of glycogen to glucose, facilitated by the enzyme glycogen phosphorylase, is a key mechanism for providing energy during intense, short-duration activities. This process occurs in the liver and muscles, where glycogen is stored. The resulting glucose-1-phosphate is then converted to glucose-6-phosphate and subsequently enters the glycolytic pathway to produce ATP. In the context of a 1-minute activity, the body primarily relies on stored glycogen for energy due to its rapid availability.

**Why Each Wrong Option is Incorrect**
**Option B:** Free fatty acids (FFAs) are a primary energy source during low-intensity, long-duration activities, where the body has sufficient time to oxidize fatty acids for energy. **Option C:** Phosphates, particularly phosphocreatine, are a high-energy compound that rapidly replenishes ATP stores during high-intensity activities. However, they are not the primary source of energy for activities lasting 1 minute. **Option D:** Glucose is a significant energy source, particularly during long-duration activities. However, it is not the primary source of energy during a 1-minute activity, where glycogen stores are more readily available.

**Clinical Pearl / High-Yield Fact**
It is essential to recognize the different energy systems and their corresponding activities. The phosphagen system (phosphocreatine and ATP) is used for high-intensity, short-duration activities (typically < 10 seconds), while the glycolytic system (glycogen and glucose) is used for activities lasting 1-2 minutes.

✓ Correct Answer: A. Glycogen