a diagnostic golf club system having a diagnostic golf club , an interface means and a computing means is disclosed herein . the diagnostic golf club includes a plurality of sensors , an internal power supply , and a non - volatile memory for capturing data relating to a golf swing . the interface means is capable of transferring data from the diagnostic golf club to the computing means for processing the data and presenting the data in a useful and informative format . the data may be used to determine a shaft flex profile for a particular golfer .