Physical Danger
PTs do a lot of heavy lifting—moving patients, manipulating multiple body parts, bending, stooping, squatting, standing. A PT's constant physical activity is extremely taxing and heightens the risk that they themselves will get injured. And a patient could give in to frustration during an inversion on a machine and kick you in the head by mistake (mistake, yeah).
It's important to stay in shape and be very careful and conscientious, because you, too, could end up in the clutches of a PT.