When the reflex occurs the flexors in the withdrawing limb contract and the extensors relax, while in the other limb the opposite occurs.

An example of this is when a person steps on a nail, the leg that is stepping on the nail pulls away, while the other leg takes the weight of the whole body.

Another example of a crossed extensor reflex is when someone violently grabs your arm, the arm that is grabbed retracts towards the body while the other arm moves towards the attacker for protection.