Duhhh!! All starts are power starts and ,yes, we have to breath. So what?
A two thirds breath intake locked in on the ‘set’ command will ensure a rigid mid section, or core, to prevent loss of power transfer in the chain from arms to feet. In other words the hips will stay parallel (horizontal) and not rotate.
Forcing the breath out between the teeth or with a hissing sound will hold the abdomen under tension through the acceleration phase.
But how long can you hold it? That will depend on your level of aerobic fitness. You may not need to breathe during a 100m sprint, but if you do, try breaking your breaths in to ‘phases’ or zones.
If you expel air rapidly during your start suck in another breath quickly to hold the tension. Over 40m you may need to do this two or three times. Up to the individual.
Once through the acceleration stage use short pants of air while maintaining tight abdominals to keep the pelvis rotated forward.
In martial arts terms this is called ‘breathing behind the shield’.