Physical Danger
Paralysis is a real possibility, even if you've done that dismount from the parallel bars a million times before.
Over 25,000 kids and teens find themselves in the ER each year due to injuries from gymnastics (source).
Broken ankles, wrists, legs, backs, head injuries—these are all par for the course when you're talking about hurling yourself in the air and spinning around as if you had wings.