Final answer:
Oxygen is an effective ergogenic aid when it can be breathed during endurance exercise. This helps to increase aerobic respiration and provides more oxygen to the muscles. Breathing oxygen can improve performance in endurance athletes. The correct option is a. can be breathed during endurance exercise.
Step-by-step explanation:
Oxygen is an effective ergogenic aid when it can be breathed during endurance exercise. When oxygen is breathed during exercise, it helps to increase aerobic respiration and provide more oxygen to the muscles. This allows the muscles to perform at a higher level and have more sustained performance.
For example, oxygen can be breathed prior to a football game or on the sideline between plays. By breathing oxygen, athletes can increase the availability of oxygen to their muscles and improve their performance.
This is important for endurance athletes who depend on aerobic metabolism for extended periods of exercise. The correct option is a. can be breathed during endurance exercise.