According to Bard (google):
Leonidas of Rhodes was one of the fastest runners in the ancient world. He won 12 Olympic gold medals in the stadion, diaulos, and hoplitodromos, a feat that has never been matched. The stadion was a short race of about 200 meters, the diaulos was a longer race of about 400 meters, and the hoplitodromos was a race in full armor. Leonidas won all three races in four consecutive Olympiads, from 164 to 152 BC.
It is impossible to know for sure how fast Leonidas was, but it is estimated that he could have run the stadion in about 20 seconds and the diaulos in about 40 seconds. These times would have been very fast even by today's standards.
Leonidas's speed was due to a combination of factors, including his natural talent, his training, and his diet. He was said to have trained for hours every day, and he ate a diet that was high in protein and carbohydrates. He was also known for his dedication to his sport, and he was said to be willing to do whatever it took to win.
Leonidas's accomplishments are still celebrated today. He is considered one of the greatest athletes of all time, and his name is synonymous with speed and athleticism.