What you should say is elastic rope. The applicable age of general elastic rope is 10-50 years old. Too small or too large is unacceptable.

Generally speaking, children can exercise speed and endurance from the age of ten, absolute strength from the age of thirteen and absolute strength from the age of fifteen. However, people's muscles begin to age slowly from the age of 40, and after the age of 50, muscle aging is accelerated, and various functions of the body are also problematic.