An article of footwear includes an upper member and a sole structure, with a sensor system connected to the sole structure. The sensor system includes a plurality of sensors that are configured for detecting forces exerted by a user's foot on the sensor. The sensor system also includes a port that is configured to receive a module to place the module in communication with the sensors. The port includes a housing with a chamber configured to receive the module and an interface engaged with the housing and having at least one electrical contact exposed to the chamber. Additional retaining structure and interface structure may be included.