Since this is not my area of expertise, I searched Google under the key words "importance flexibility training" to get these possible sources:
https://www.google.com/search?client=safari&rls=en&q=flexibility+importance+in+sports&ie=UTF-8&oe=UTF-8&gws_rd=ssl#q=importance+flexibility+training
In the future, you can find the information you desire more quickly, if you use appropriate key words to do your own search. Also see http://hanlib.sou.edu/searchtools/.
http://www.hackcollege.com/blog/2011/11/23/infographic-get-more-out-of-google.html
Explain how sprinters use flexibility.
Explain how javelin throwers use flexibility.
Explain how gymnasts in floor routines use flexibility.
2 answers
Runners use flexibility to run faster and sprint. Javelin throwers use flexibility so the y can throw better. Gymnastics people use flexibility so they can do splits, cartwheels and many cool body stunts