It's a hyperbole. Injuries generally cause brain to release endorphins, which in turn releases dopamine, causing addiction. For example, cutting is a common ty

It's a hyperbole. Injuries generally cause brain to release endorphins, which in turn releases dopamine, causing addiction. For example, cutting is a common type of self-mutilation depressed people do. High-intensity exercise arguably also does the same thing - as your body is "microinjured" by strain, your brain releases endorphins to help with the pain, causing effects like "the runner's high".