What is the maximum age you can start in gymnastics training? My niece wants to enroll in a training school but I am afraid she will not be admitted because of her age. Is there an age limit? Or it depends on how flexible your body is?

it depends on the facility ... a 30 year old could enroll in gymnastics, but they'd be put in the beginner class, most likely with 3-4 year olds ... but again, it depends on the facility and their requirements and guidelines ...