Full Idea
One should preserve a balance and avoid exercising the mind or body without the other; mathematicians should exercise physically, and athletes mentally.
Gist of Idea
One should exercise both the mind and the body, to avoid imbalance
Source
Plato (Timaeus [c.362 BCE], 88c)
Book Reference
Plato: 'Timaeus and Critias', ed/tr. Lee,Desmond [Penguin 1971], p.118
A Reaction
Excellent, and very modern. Use it or lose it. It suggests that Plato had a fairly holistic view of a human being, and saw mind and body as closely integrated.