It is worth repeating that, “Yesterday's food should have passed both gastric and hepatic digestion, and also intravascular digestion, —the time for the next meal now approaching … it is better to choose a time for exercise when one is not hungry, and when one is hot and moist rather than cold and dry. But the best time is when the state is. between the two. Exercise in a man of hot and dry temperament may lead to illness, and he will benefit by avoiding it at such a time...”
http://data.nur.nu/Kutub/English/Avicenna_Canon-of-Medicine_text.pdf