The best way to ease the apprehension of a 3-year-old child before/during a PE is to:

This is done by making the child feel very comfortable with the whole process and ensuring he participates and hold some parts of the tools used in the exercise.

He can also be given some toys to play within order to distract him from the main action as him seeing some medical equipment could make him nervous as a result of previous experiences with them.

Lots of caution should also be taken and interactions will help to ease and brighten the mood of the child

answer; did not understand that the act was wrong because she/he was suffering from a mental illness;