Flexibility is your joint’s ability to through a fullwith less energy.

move, range of motion without pain

Explanation:

The sentence should be representing the description of what flexibility is and in that case, it should be ''Flexibility is your joint's ability to move through a full range of motion without pain and with less energy.

Flexibility is considering flexibility training which is including exercises such as stretching and activities like yoga or Tai Chi. It is important to because of the muscles which must have appropriate length.