Possible Clues:

• Its report should stimulate athletic progress
• One's report initiates speedy action
• It's quickly run away from when fired
• Reporter at Olympics, perhaps, could make last sprint go with it
• Source of report that gets competitors up and running
• It gets things going with a bang
• Jumping the gun, typically this one
• Gun used in hold-up on the track?
• One providing report in advance of the event?
• Jumping on colt, say, before race I'm fired up