You not only need flexibility but muscle strength. In order to practice this, you can do following exercises: 1.) hold straight as high as you can then swing it higher, do this 50 times each leg. 2.) hold straight for 10 seconds each leg, once you get better, 20 seconds and so on. 3) kick as high as you can then hold 3 seconds, and this 10 times (or more if you can). 4.) just lift knee as high as you can and then push knee higher, don't ever put your knee don't. Do this 100 times each leg.
- hold straight as high as you can then swing it higher, do this 50 times each leg.
- hold straight for 10 seconds each leg, once you get better, 20 seconds and so on.
- kick as high as you can then hold 3 seconds, and this 10 times (or more if you can)
- just lift knee as high as you can and then push knee higher, don't ever put your knee don't. Do this 100 times each leg.
These exercises will help develop the muscles of your upper thigh which are needed to help keep your front kick for a few seconds.
