Today's Mwod is all bout the Split Jerk.
One of the props we like to use a lot is some kind of elevated surface, like a table or jump box.
The stretching with one leg up on an elevated surface has the unique ability to keep the other leg on the ground, and by extension your back in neutral. I'm always amazed when I see otherwise enlightened athletes horking on their backs to mobilize some other body part. Not cool.
Keep your back in neutral, especially in mobs that potentially bias the athlete into overextension.