The complete sentence is this: It is important to avoid ballistic stretches because THEY CAN EXCEED THE STRETCHABLE LIMIT OF THE TISSUE INVOLVED.
The act of stretching helps in relaxation of body muscles. There are many types of stretching and one of them is ballistic stretching. Ballistic stretching involves bouncing and j.erky movements, which use the body momentum to stretch the muscles. This type of stretching is considered risky because it may lead to exceeding the stretchable limit of the muscle involved.