I recently learned this from a jailer:
Officers should not wear their handcuffs in the small of their backs in front of the spinal cord. He advised me of a “jailhouse trick” I was unaware of. Prisoners have somehow learned that if they can approach officers/jailers from behind and deliver a strong kick to the handcuff pouch in the small of their back, it can (and often does) inflict a temporary paralysis. It causes the legs to drop out from under you and go numb. After a few minutes you recover but I could not imagine trying to fight without the use of your legs. Stay safe and move your cuffs.