Most people, when running, will naturally breathe with a 2-2 rhythm according to the rhythm of their left-right foot strike. This means they inhale for two foot strikes and exhale for two foot strikes.It works like this: inhale and when the right foot touches the ground, count 1, and when the left foot touches the ground, count 2. From there, exhale, counting 1 when the right foot touches the ground and counting 2 when the left foot touches the ground.
As you begin to fall into the rhythm, your breaths in and out will always fall on the right foot strike. As a result, you will count 2 every time the left foot strikes the ground. This 2-2 pattern means that your diaphragm will bear down on the same side every time; the right side. This will happen because the foot strike will coincide with inhalation and exhalation on the right side only every time.
However, in order to use the diaphragm evenly on both sides, the 3-2 breathing pattern in conjunction with running rhythm was developed. This pattern involves lengthening the inhalation period to three foot strikes, and then exhaling for two foot strikes. This can help prevent injuries arising from greater and repeated impact on one side of the body. This is because the diaphragm and other breathing muscles contract during inhalation and relax during exhalation. Runners can practice this breathing pattern as follows: