Aerobic endurance refers to

• A. The maximum weight you can lift in a single effort.
• B. The time you can exercise without lactic acid building up in your muscles.
• C. The total distance you can run in a week.
• D. The number of kilometers you can cycle in an hour.

Answer: (B)

Aerobic endurance is the body's ability to sustain exercise for a long period by using oxygen to produce energy. When you work at a moderate pace, your heart and lungs deliver enough oxygen to the muscles, so energy comes mainly from aerobic metabolism. The longer you can keep that effort without lactate building up to fatigue, the greater your aerobic endurance. The option that mentions the time you can exercise before lactate accumulates best captures this idea, because lactate buildup signals a shift toward anaerobic energy and fatigue in prolonged activity. The other statements describe different fitness aspects: maximum weight lifted relates to strength, weekly distance reflects training volume, and cycling speed per hour describes pace or power, not the capacity to sustain aerobic energy over time. Training to improve aerobic endurance typically involves longer, steady activities that stay in the aerobic zone and gradually increase in duration.