It is often seen that some beginners run 100 meters and breathe like cows, which will increase the contraction of chest muscles, but it is not conducive to performance.
Most high-level athletes run in one breath (100m without breathing). From the appearance, their mouths and noses also have the action of "breathing". In fact, that action is "virtual", that is to say, the air inhaled by the mouth and nose action is exhaled directly without going through the lungs, but this is only a subconscious action made by facial muscles to relax, and there is no "breathing" effect.