Ekdromoi

The northern Polises began to use a type of hoplite that wore little or no armor called an Ekdromoi, these light hoplites however were not wide spread and the Greek military as a whole did not change. In the period between the end of the Persian Wars and the Peolponnesian War the Greek army went under drastic change: Ekdromoi became wide spread, javelin-throwing troops became commonplace, and mercenaries were beginning to form large parts of the main armies. The hoplites themselves went under changes such as: lighter armor, slightly wider shields, and more practical helmets.

More about them you can read here.