Rhythmic Breathing may simply indicate that you accompany your breathing by mentally including a specific number of counts while inhaling, holding your breath, and/or while exhaling.
For instance, you deeply inhale for four counts, and then hold your breath for three counts before fully exhaling for five counts, and so on. The variations are endless. Box Breathing and Four-Seven-Eight Breathing are examples of Rhythmic Breathing.
Nevertheless, there’s also a specific technique called Rhythmic Breathing that is especially applied in the runner’s world.
The goals of this Abdominal Breathing technique are to increases lung volume, improve awareness and control while you run, help prevent injury, improve running for those with asthma, and help manage muscle cramps, among the other general aims and benefits that are associated with conscious breathing techniques.
In any case, the idea of Rhythmic Breathing for runners is to create a breathing pattern that brings an alternating rhythm between inhaling and exhaling on one side, and your interchanging foot strikes touching the ground on the other side.
To explain this: by using an extended inhaling pattern (compared to the time you exhale) — let’s say three counts for your inhale and two counts for exhaling — you will automatically shift your foot strikes on the ground from one side of the body to the other when exhaling, which creates a better symmetry for the forces “inflicted” on your body.
As it is, if you, for instance, would always land on your right foot while exhaling it would increase imbalance and extra strain for certain body functions and musculature, and subsequently also more risks on fatigue and injury. Thus, the main point of performing Rhythmic Breathing while running is to have the exhalation on alternate foot strikes as you run, and never continually exhale on the same foot strike.