Kicking still....
In choosing stretches, you should examine your needs and the requirements of your activity. For example, if you are a kicker, you need mostly a dynamic flexibility of hips. To increase your range of motion, you need to do dynamic leg raises in all directions.
The principle of specificity states: Flexibility is specific to the speed of movement. Flexibility is also position specific, so static exercises or stretches like splits are not very useful if you want to kick higher (a display of dynamic flexibility). According to Logan and McKinney (1970) the principle of specific adaptation to imposed demands in the case of flexibility means that eventually, either at the end of the first set of dynamic stretches or in other sets, you should stretch at a velocity not less than 75% of the maximal velocity used in your actual skill, a kick, for example.
A common sight in training halls, gyms, dojang, or dojo, is someone standing and holding up the leg. Such standing, while requiring and developing static balance and static strength, is not developing dynamic flexibility nor dynamic strength. It is developing a static active flexibility required from gymnasts but not something that kickers need. Such leg holding requires a strong tension of the muscles on one side of the trunk when the lower back is twisted to this side and pulled forward by the psoas muscle on the same side. This, if done by someone with insufficient lower back strength or any back problem, can lead to lower back strain or intervertebral disc inflammation.
As far as strength is concerned, the specific strength for a kicker is the strength that lets one pack a wallop in a kick, not to hold up a leg! Specific strength for kicking is developed by kicking a heavy bag, kicking into layers of sponge, kicking with bungee cords attached to legs and doing other dynamic exercises similar to kicking. Strength, just like flexibility, is specific to the speed of movement, its angle, and range of motion, and vice versa.
