right|thumb|200px|Herodicus.
Herodicus () was a 5th century BC Greek physician, dietician, sophist, and gymnastic master (παιδοτρίβης). He was born in the city of Selymbria, a colony of the city-state Megara, and practiced medicine in various Greek cities including Selymbria, Megara, Athens, and Cnidos. Herodicus believed that exercise and a good diet are key foundations of health, and emphasized the use of both to treat various ailments. His theories are considered the foundation of sports medicine.
History
Herodicus is credited with being the first physician to practice what would become known as therapeutic gymnastics.
Euryphon, a mentor of Herodicus at the medical school of Cnidos, emphasized the importance of diet in maintaining health. He theorized that wastes created through bad digestion spread through the body and caused illness. Herodicus contributed to this theory by adding that proper digestion of food only occurs with subsequent exercise.