How can I improve leg flexibility? I’ve heard that it's hard for a person like me (older than 25 years) to gain flexibility.
It is always more difficult to do physical things as you age; not impossible, just more difficult. Stretch every day. Do not bounce; perform a stretch and hold it for a minute or so. You are not actually stretching anything; you are not making anything thing longer, you are relaxing. When you perform a stretch, the muscles tighten. What you are trying to do is train the muscles to relax when you stretch; so do not concentrate on stretching but instead concentrate on relaxing. Stretch the entire body for overall speed and flexibility, but, to perform better kicks, concentrate on stretching the body and legs in positions that are used when performing the kicks. Use a yoga book or website to find stretches that will best benefit the areas you want to stretch.