Answer:
Quick leg movement.
Step-by-step explanation:
Gymnastics and low-impact aerobics comprehend a wide range of sport activity, which include different type of skill development as strength, balance, flexibility, agility, endurance and coordination.
However, each is a complement of the actual gymnastic activity (which implicates a lot of aerobics), they are trained to develop agility in the athlete, we could say that it's the main skill, because the type of movements in artistic gymnastic, rhythm gymnastic or acrobatics, all they have agility in common, which refers to the ability to move quicker and easier, and that it's mandatory to be successful. That's why Quick Leg Movement is developed skill.