The C3D format does not specify the meaning or interpretation of the events stored in the header section although the original intent of this feature was to allow a small number of human gait related event times to be recorded by any application.  As a result, C3D file may contain a varied number of events and labels.

When used to record gait events the header section can record a maximum of four gait cycles per side (left/right).  While this is generally sufficient for most gait applications, other C3D file users, such as for analog EMG recordings or the entertainment industry, have required more event storage than the C3D header can provide.  This has lead to the development of alternative event storage mechanisms such as the Label and Range section as well as some manufacturer specific implementations.