Great mobility drills to improve your kicking power and mobility. Featuring the roundhouse kick, but these drills work for other kicks as well!
Powerful kicks come from the hips and the rotation of the core. To develop strong hip musculature, you need to work all the functions of the hips.
Working on strength exercises like lunges is only one aspect of developing strong and functional legs. You also need to spend time to strengthen and mobilize the smaller muscle that are needed in movements like kicks.
Unless your hips are in a good shape, you won't be able to kick and move the legs properly. To kick well, you need sufficient levels of flexibility and strength.
Flexibility is fantastic, but mobility is what will allow you to have the most powerful and athletic legs possible.
Mobility is about having both strength and flexibility - it's about having healthy muscles that are strong in their entire range of motion. This is why a great deal of leg work in Movement 20XX is mostly mobility exercises and active flexibility drills.
Dynamic flexibility drills are good for developing power, but mobility will produce better results in the long term. This is because the legs will become more structurally balanced, stronger and thus harder to injure.
The drills below will dramatically enhance your movement capability and kicking ability. Correct execution (slow tempo, control and mind-muscle-connection) are the keys to progress.
In addition to having strong hip muscles, your core muscles (especially the internal & external obliques) need to be exceptionally strong and mobile. For perfect core training, check out Abs20XX.com
Mobility Drills for Kicks
Leg Raises

Front leg raises (hip flexion) will work the front thigh: quads and hip flexors. Avoid rounding your back. Your hamstrings will also be stretched. The flexibility of your hamstrings can limit the range of motion which is why it's important to mobilize the hamstrings as well.
Side leg raises (hip abduction) will work the glutes and the tensor fasciae latae muscle (side thigh). Keep your core tight - you are supposed to move the leg only and not raise it by flexing your obliques or by rotating the hip. The range of motion is rather small.
Glute Raises

Glute raises can be done standing, on all fours or prone. You can find all the progressions from this video.
Mobile glute muscles play a big part in kicks because they also abduct the hip (side leg raise).
Hip Internal & External Rotation

This is hip internal rotation.
For the roundhouse kick your hip internal rotation needs to be strong. To balance it, you also need to practice hip external rotation. You can find exercises for both hip internal & external rotation from the video.
The most crucial thing is to learn to just rotate the hip - don't do the movement by raising your leg or arching your back. Only the leg should rotate and that's it!
How many times a week and for how long would you suggest doing this?
It depends on the person but 1-2 times per week is plenty