Poor hip extension, poor alignment, poor rotary stability and over-reaching . These are all VERY common faults in sprint mechanics that are hard to fix with a simple cue. So what do you do when your athletes exhibit any of the listed symptoms? You fill in the gaps with the proper drills.
The Single-leg rock and the Half-kneeling Knee-lift are two of my favorite drills to throw into a warm up to help alleviate some of the aforementioned flaws. At first they appear to be arbitrary movements, not corresponding with traditional training means. But, when the processes of the movements are taken in you can see how they will have quite an impact on running mechanics or general mobility issues.
Single Leg Rock Progression
Lumbo-pelvic disassociation, rotary stability and increased joint centration, all rolled into one. This is a great drill that I've started using for many of our athletes who have trouble with unilateral lower-body work. As you can see in the video, it has many different benefits and really drives home reflexive hip stability.
Half-kneeling Knee Lift Progression
This is great for teaching hip extension, anterior core stability, proper alignment and even coordinating the sequencing of them all together (though I accidentally swing my arms wrong in the video... no one's perfect, don't judge me). It's also east to progress as you can see in the video.