A person who is running, the main source of energy he will be using in 1st min is:
**Core Concept**
During high-intensity, short-duration activities like running, the body's energy system is primarily driven by anaerobic metabolism, which generates energy without the use of oxygen.
**Why the Correct Answer is Right**
The initial 1-2 minutes of intense exercise, such as running, rely heavily on the anaerobic energy system. This system utilizes stored ATP (adenosine triphosphate) and phosphocreatine (PCr) as energy sources. Phosphocreatine is a high-energy compound that rapidly replenishes ATP stores, allowing for high-intensity muscle contractions. As exercise continues beyond this initial phase, the aerobic energy system, which relies on oxygen to generate energy, becomes more dominant.
**Why Each Wrong Option is Incorrect**
**Option A:** This option is incorrect as it implies the use of fat as the primary energy source during high-intensity exercise, which is not accurate.
**Option B:** This option is incorrect as it suggests that the aerobic energy system is responsible for energy production during the initial minute of running, which is not the case.
**Option C:** This option is incorrect as it implies that the energy source is solely ATP, which is not accurate, as phosphocreatine also plays a crucial role.
**Clinical Pearl / High-Yield Fact**
During intense exercise, the anaerobic energy system can lead to a buildup of lactic acid, causing muscle fatigue and soreness. This is why athletes often experience a "burning" sensation in their muscles during high-intensity activities.
**Correct Answer: A. Phosphocreatine.**