Question

the 100 - meter dash is a quick and short run requiring explosive speed. on completion of the dash, the runners will continue to breathe hard for several seconds to minutes even though they are no longer running. which of the following is the best explanation for why this is so?
the runners use of stored oxygen, glucose, and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.
since the exercise was mostly aerobic exercise, the runners bodies have not yet realized the run is over.
slow oxidative fibers are recruited last and have only started to work at completion of the run.
the runners fast oxidative muscles are so slow to utilize oxygen, they only begin aerobic respiration by the time the run has finished.

Explanation:

During intense exercise like the 100 - meter dash, the body uses stored oxygen, glucose, and creatine phosphate. After the exercise, the body needs to replenish these stores. This replenishment process (such as converting lactic acid back to glucose in the Cori cycle) requires oxygen. So, runners continue to breathe hard to take in more oxygen for this replenishment.

• Option 2: The 100 - meter dash is an anaerobic exercise (not aerobic), so this option is incorrect.
• Option 3: Slow oxidative fibers are more active in endurance activities, not in a short - burst 100 - meter dash.
• Option 4: Fast oxidative muscles are not slow to utilize oxygen. In fact, they can use both aerobic and anaerobic pathways, but the main reason for continued heavy breathing is the replenishment of stores, not this.

Answer:

The runners' use of stored oxygen, glucose, and creatine phosphate is being replenished and this requires a prolonged increase of oxygen intake.