What counts as the start of an athlete's movement for a false start?

After assuming a full and final starting position, an athlete must not commence their start until the report of the gun. If, in the Starter's judgement, they do, it is a false start. The commencement of the start is:

• Crouch start: any motion that includes or results in one or both feet losing contact with the foot plate(s) of the blocks, or one or both hands losing contact with the ground.
• Standing start: any motion that results in one or both feet losing contact with the ground.

Also:

• If the Starter determines that an athlete initiated a movement before the gun that was not stopped and continued into the commencement of their start, it is also a false start.
• Any other motion is not the commencement of the start, but may bring a disciplinary warning or disqualification.
• Generally no false start is charged if the athlete has not lost contact with the ground or foot plates, for example if they raise and then lower their hips.
• In standing starts, accidental over-balancing may be called "unsteady" rather than a false start, and an athlete pushed or jostled over the line should not be penalised.
• When a World Athletics certified Start Information System is in use, an acoustic signal (reaction time under 0.100 second) tells the Starter or Recaller of a possible false start, and if the gun was fired there is a recall.

Source: World Athletics Technical Rules (C2.1, edition last modified 1 July 2026), Rule 16.