Final answer:
Cycling is an efficient method of aerobic exercise due to its reliance on oxygen, improvement of cardiovascular endurance, and engagement of multiple muscle groups.
Step-by-step explanation:
Aerobic exercise, such as cycling, is deemed an efficient method of aerobic exercise due to several factors. First, aerobic exercise uses oxygen to meet energy demands during exercise, making it reliant on the aerobic energy-generating process. Second, cycling at a moderate level of intensity over a relatively long period of time helps improve cardiovascular endurance. Finally, cycling primarily involves the leg muscles, but also engages other major muscle groups such as the abdominals, chest, and arms, making it a full-body workout.