: an illness that affects a person, animal, or plant : a condition that prevents the body or mind from working normally. : a problem that a person, group, organization, or society has and cannot stop.
a disorder of structure or function in a human, animal, or plant, especially one that produces specific symptoms or that affects a specific location and is not simply a direct result of physical injury.
I'd say it's false. People who are physically active are in better shape and probably won't miss school to things like muscle aches or other health-related issues.