This picture is of a detail of a Byzantine ivory in the Bargello Museum in Florence. It’s from the 5th century CE. In the whole piece, an emperor stands above this scene of the chariot races in the hippodrome in Constantinople. He’s embraced by an allegorical figure representing, I think, a city. You can see four teams of four-horse chariots zooming around the track, which is marked by the ‘spina’ or ‘spine’ at the ends of which are the metae or turning posts (they resemble bowling pins). At the end, the emperor declares a winner. If you look closely at the chariot drivers, their torsos are hatched with horizontal lines, indicating the cords they wrapped around their tunics to keep them from fluttering in the wind but also helped protect their ribs if they had an accident.