I am a kick boxer. Should I train my hamstrings with resistance, or will they become sort and I will lose my flexibility? PDF Print E-mail
 
This is another myth that leads many athletes to injury.
Strengthening the hamstrings and the adductors are of great importance, and it will not affect your flexibility if you train the right way.
If you kick high and your muscles are not strong enough on the extreme position you risk injury.
The best method to achieve super flexibility and be able to kick high without warm up is by isometric stretching.
Isometric stretches, not only stretch your muscles but also they strengthen them at the extreme position, thus allowing you to do splits safely and avoid injuries.
To learn more about an effective method of isometric stretching read Top coach Thomas Kurz great book "Stretching scientifically" and see the relevant video below: