J. Paul Getty Museum, MS Ludwig IX 6, f. 2r
If you will, walk daily somewhere morning and evening. And if the weather is cold, if you can, run on [an] empty stomach or at least walk rapidly, that the natural heat may be revived… If you cannot go outside your lodgings, either because the weather does not permit or it is raining, climb the stairs rapidly three or four times, and have in your room a big heavy stick like a sword and wield it now with one hand, now with the other, as in a scrimmage, until you are almost winded. This is a splendid exercise to warm one up and expel noxious vapors through the pores and consume other superfluities. Jumping is a similar exercise. Singing, too, exercises the chest. And if you will do this, you will have healthy limbs, a sound intellect and memory, and you will avoid rheum.
Peter of Fagarola, Letter to his sons (trans. Lynn Thorndike)
Too cold for running outside? No problem – your mock swordplay and singing will definitely impress the other gym-goers.